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Many thanks to SWLing Post contributor, Ferruccio Manfieri (IZ1096SWL), who shares this report and excellent photo tour from a visit to the Museo Marconi in Bologna, Italy in 2018.
A visit to Museo Marconi in Villa Griffone, Pontecchio, Bologna
by Ferruccio Manfieri (IZ1096SWL)
Bologna, in Northern Italy, is renowned to be the seat of the oldest University in Europe and in the world (the Alma Mater Studiorum) and its historic, artistic and culinary heritage. From a scientific perspective, Bologna is the birthplace of Guglielmo Marconi as well as the place of his first experiments in transmission.
The inventor, born in Bologna on April 25th, 1874, was the son of an Italian father (Giuseppe, a wealthy landowner) and an Irish mother (Annie Jameson, of Jameson’s Whiskey family). At the age of 20, Marconi began to conduct experiments in radio waves, building much of his own equipment in the attic of his home at the Villa Griffone in Pontecchio (in the Bolognese countryside).
Marconi received his final resting place in Villa Griffone Mausoleum, an enterred crypt hosting his porphyr sarcophagus. The building was donated to the Guglielmo Marconi Foundation in 1941 after the death of the inventor (on the 20th of July 1937).
Sadly, Villa Griffone and the Mausoleum suffered heavy damages from WWII bombings and pillages and were patiently rebuilt in post-war years. Today, Villa Griffone is reborn as a hub of research and divulgation activities, hosting Guglielmo Marconi Foundation, the Marconi Museum, a library and two research groups on communication systems.
On the 26th of april 2019 I visited with my family the Museum hosted in the original building (a short trip from Bologna, 20 minutes by public transport)
Villa Griffone and the Marconi Mausoleum
The visit began with a nice stroll in the Villa gardens, home with the nearby hill of the Celestini of the first long-range and not in line of sight transmission experiment in 1895. Marconi managed to send signals over a distance of 2 km, beyond a hill situated between the transmission equipment (to which he had added a grounded vertical antenna) and the reception apparatus (characterised by an extremely sensitive coherer).
Villa Griffone gardens and “Hill of Celestini”
We were in the very spot Marconi was when he transmitted his three signals to the receiver operated by his brother and the gardener behind the hill. Nearby, the replica of eight meter wooden pole with the attached metal boxes used as antenna.
Marconi’s first “long range” antenna – replica
This experiment in universally aknowledged as the birth of radio transmission (and, by the way, the rifle shot used as a confirmation of the reception was the very first QSL…).
Our valent host and guide to the visit was the Director of the Museum, Barbara Valotti, who thoroughly described us (with knowledge, passion and communication skills) the historical framework of Marconi’s biography and works. A more engineering oriented and hands-on visit to the working replicas laboratory was subsequently hosted with passion and knowledge by Adriano Neri I4YCE.
In the Auditorium Dr. Valotti showed us two videos on the first transmission experiment and on the Republic incident in 1909, on of the first application of Marconi radiotelegraphy in an incident at sea, whose success (no lives were lost in the aftermath of the collision thanks to the coordination of rescue efforts via radiotelegraphy) gave a boost of popularity to radiotelegraphy and to the engineer, eventually leading to the Nobel prize in physics later that year.
A frame of the “Republic” video
This part of the visit emphasized his interest in real technological applications of his inventions and their commercial potential. Marconi was a “modern” mix of engineer (with an unhortodox, non-academic formation) and entrepreneur, ready to see the new potential applications of technologies in the society. Interestingly, Dr. Valotti underlined that the main focus of Marconi research was always the point-to-point trasmission and not the broadcast.
Hanging on the ceiling of the auditorium, a replica of the kite used by Marconi to lift an emergency antenna in the first transoceanic transmission from Poldhu to St Johns Newfoundland in 1901.
Yacht “Elettra” – memorabilias
The visit continued to the “silkworm room”, the original room (once used to breed silkworms) where Marconi held his laboratory and performed his experiments. The room was full of instruments replicas to show the laboratory as in the young Marconi years.
“Silkworm room” – Marconi’s first laboratory (original place, instrument replicas)
“Silkworm room” – Marconi’s desk (replica)
It was also possible to replicate the main experiments with educational working replicas.
Marconi transmitter – educational replica
Headphone and coherer used in the first transoceanic transmission (replicas)
The second phase of the visit was a more engineering-oriented explanation of the principles of radio telegraphy conducted by Adriano Neri I4YCE in a didactic laboratory on working replicas of the main epoch instruments.
Experiment table with working replicas: coherers, a wire decoder, a Marconi receiver
Instruments in the educational laboratory
With passion and competence, Mr. Neri explained us in a simple way (there were some very interested young people in the group) the cable telegraphy principles and the sequence of experiments and discoveries that led Marconi to his inventions.
In a detailed and fascinating exposition we saw applications of a Morse writer, the induction coil, the coherer and the first Marconi spark transmitter, all assembled in the end to transmit in the room some morse signals in the air.
Live demonstration of signal transmission by Adriano Neri . Against the wall a Marconi spark transmitter (note the antenna and ground plates), on the table: a Marconi receiver (with a coherer) connected with a Morse writer.
The laboratory, as the whole museum, hosts a huge number of working replicas (a wonderful collection in itself, handmade by Maurizio Bigazzi with rigorous standards of adherence to the original designs and, if possible, reuse of original parts) and some original equipment.
Ship wireless telegraph room – working replica
A last section of the museum is devoted to radio communication during the war (showing a WWI airplane-ground communication system) and radio broadcasting, with original sets of great interest like a 1923 Marconiphone (still working, we had a live demonstration receiving RAI programs) and a Ducati radio (the same Ducati company of motorbikes, based in Bologna).
WWI plane radio and ground receiver
1923 Marconiphone, working original set
Ducati radio
We spent all the morning in the Museum with great fun and interest from all the family.
I highly recommend a visit to the Museum for the place, its significance in the history of radio transmission and the competent and passionate exposition of the historical and technical themes related to Guglielmo Marconi.
A wealth of information (also in english) can be found of the Guglielmo Marconi Foundation website (www.fgm.it).
A detailed gallery of the Museum can also be found on the new Museum website (www.museomarconi.it)
Many thanks to SWLing Post contributor, Dan Robinson, for the following guest post and review:
Sangean v Tecsun in the Battle of Late Shortwave Era Portables: The ATS909x2
by Dan Robinson
Some years ago – actually more than a decade – I decided to give Sangean a shot at winning me over in the shortwave portable category.
I had and still do use numerous portables with a bias toward the classic SONY, Panasonic, and Grundig sets. The ones that made an impression stayed, often in multiples, as anyone can see if they visit the radio shack here in Maryland.
These include, for those interested: the Panasonic RF-B65, SONY ICF-SW77, ICF-2010, ICF-PRO80, ICF-7600D, ICF-7700, ICF-SW1000T, ICF-SW55, ICF-SW100s, ICF-SW07, Grundig Satellit 500, to which were added in more recent times the Toshiba RP-F11, XHDATA D-808, and Tecsun portables ranging from the PL-365 and new PL-368 to the PL-880, PL-990x, H-501x, and S-8800.
Sangean has generally not been on that list. There’s a good reason – I just never considered Sangean to be competitive when it comes to portables, though they did have some excellent larger sets such as the ATS-803A that made the first forays into multiple bandwidth options.
My last experience with Sangean was with the ATS-909. I liked the looks and capabilities of that receiver, and even went to the point of having mine modified by Radio Labs. But those mods were underwhelming, in my view, and the original 909 always seemed to me to be deaf when using the whip antenna.
That issue continued unfortunately with the 909x. Some of you may have seen a video I did a few years ago in which I set a 909x against a SONY SW-07 and Panasonic RF-B65. This was done barefoot with only the whip antennas, but near a window. In short, the other two radios wiped the floor with the 909x.
It took a surprisingly long time for Sangean to update the 909x with the 909×2, during which companies asked valid questions about the need for further development of world band portables.
Eton turned the market on its head when it introduced the still superb E1/XM which competed with the very end of SONY portable production, and co-designed with R.L. Drake added such superb features as Passband Tuning and three selectivity positions.
Meanwhile, Tecsun plugged away, introducing an impressive array of portables including the PL-600 series, then the 880 and now the 990x and H-501 portables.
So, now the 909×2 is here and with its 073 firmware upgrade has become a bit of a holy grail for portable receiver users. There have been a number of excellent reviews, including Dave Zantow’s deep dive, and some others here on SWLing Post.
I’m going to give you my impressions, using the really detailed Zantow review as a base. I received my 909×2 from Amazon just today – it is a 073 firmware which confirms that new supplies have the upgrade.
SENSITIVITY ON WHIP
First, let’s get the elephant in the room out of the way. Although I have not undertaken detailed technical testing of the 909×2 – nor do I have the equipment to carry this out – it does seem that Sangean may have finally tackled this crippling flaw that rendered the old 909x nearly useless when using it only on the whip. I’ll undertake further testing and comparisons with some of my other portables to confirm this. The whip antenna itself is robust – solid and long, something that Tecsun could take note of.
AIR BAND
Inclusion of air band on this radio is a major selling point for those interested in this type of monitoring. My initial tests showed the 909×2 to be quite sensitive and useful – I managed to pick up no fewer than five airport comms frequencies in my area here in Maryland.
SELECTIVITY / AUTO-BANDWIDTH
The 909×2 really shines with FIVE available selectivity options that are easily selectable in shortwave mode. It would have been nice to be able to actually see the values of each filter as one scrolls through, but that’s a minor point. Think about it – in shortwave AM mode, this is the number of selectivity positions that one finds on such power house communication receivers as a Drake R8. Amazing that we now have that in a portable. On the negative side, I find the auto-bandwidth feature on the 909×2 to be nearly useless, as useless as the similar feature found on Tecsun receivers. The automatic switching is distracting and annoying. My advice to users: forget this, and stick with manual bandwidth control. My advice to Sangean – I wish they had left this feature out but given us multiple bandwidths in SSB.
LCD AND BRIGHTNESS
Sangean hits it out of the park with this multi-stage lighting for the display. Simply superb and the kind of quality we could only hope for from other manufacturers.
MAIN TUNING / DETENT CONTROL
I found the detents on the old 909x to be annoying – indeed, modifications have been available that could remove this feature. But Sangean being Sangean, the detent wheel remains in the 909×2 and it is not a deal killer.
AUDIO QUALITY
The radio retains the excellent audio of the 909x – I am not sure the 909×2 exceeds what one hears from a Tecsun 990x or H-501x but it’s right up there and competitive.
POWER SUPPLY
As others have noted, thanks to Sangean for sticking with AA cells. Together with internal charging when using Ni-Mh cells this is a major selling point. On the other hand – competitor Tecsun went a step farther with its H-501x which though it uses 18650 lithium batteries, has dual batteries, one of which can be held in standby, and switchable charging. That’s a design feature that you really have to respect.
VARIABLE RF GAIN
Again, as noted by others Sangean retained the extremely useful thumb wheel RF gain control. This is an excellent feature.
KEYPAD
Another home run for Sangean when it comes to the keypads on the 909×2, which can be compared in this respect to the Tecsun H-501x which itself improves upon the 990x when it comes to front panel control. Time will tell, however, and we shall see if the keys on these radios hold up in heavy use.
UP/DOWN SLEWING
These controls which sit outside the circular main tuning knob are excellent, and reminds one of the slewing buttons on the SONY 7600GR, SW1000T and SW100.
S-METER / DISPLAY
RSSI and SN Digital Signal Strength Information are provided on the beautiful 909×2 display. This is an improvement over the Tecsun signal strength/SNR meters that I wish would be redesigned, if in fact Tecsun has any intention of future modifications to their portables.
NO SOFT MUTING
Thank goodness we don’t have to deal with the annoying soft muting issue that is still seen in some other portables (the XHDATA D808 comes to mind along with the Eton Executive). Soft muting quite simply ruins a listening session and it’s baffling that any manufacturer still puts it in.
NEGATIVES (I AM IN TEARS)
OK, close all airtight doors and prepare to dive! Here are the negatives I see with the 909×2. I held off obtaining one of these radios because I knew there would be issues. And I was disappointed enough in the past with the 909x and 909 before it that I had almost decided not to go for it.
SIGNS OF LONGWAVE RECEPTION PLAGUED BY CROSS-MOD FROM MEDIUMWAVE
On my particular unit – it remains to be seen whether this is true for others – long wave seems to be near useless. The band is filled with mediumwave stations bleeding through. Turning down the RF obviously helps but I still hear AM stations here in the DC area, when I am in LW mode.
SSB PERFORMANCE
ALERT FOR SANGEAN AND ALMOST A DEAL BREAKER – as mentioned in the Zantow review, and in other comments I have seen on the 909×2, the drop in level from AM to LSB is a killer negative.
This is less noticeable in MW. But if you are in shortwave and have turned your volume up on any particular station, say a strong one such as Greece on 9,420 kHz or Spain, or an AM station, and you then switch to LSB it is like you have almost lost the signal. This simply needs to be fixed. Level on USB seems fine and acceptable, but LSB on shortwave requires immediate upwards adjustment of volume, only to have to reverse the process when returning to AM mode. I find this problem to be sufficiently serious that I would recommend against obtaining a 909×2 until Sangean finds a way to fix it. This issue is on the same level of BAD as the still unsatisfactory SYNC mode in all three of Tecsun’s shortwave portables. In fact, I may return the 909×2 I obtained and wait until a fix for this emerges.
Example Video
In this video, I demonstrate the extent of the problem as seen on this particular unit of the 909×2, which carries a serial number dk201043181.
Dave Zantow says his unit does not have this issue, so there is a possibility this is due to unit to unit variation. As you can see, with a strong signal such as 12,160 kHz — switching from AM to LSB instantly reduces listenable level, and signal as measured on the 909×2 drops to zero bars or near zero. In USB, the reduction is less severe. Regardless, having to perform adjustments with main volume just to struggle to hear any signal in SSB is a bit ridiculous. This kind of thing is not seen on the Tecsun H-501x or 990x though as Dave correctly points out, Tecsun receivers are not exactly great performers in SSB. On Tecsun receivers, there is a slight processor pause while the receiver makes the switch into LSB or USB, without the sharp reduction in listenable level.
CALIBRATION ISSUES WITH NO WAY TO ADJUST
Imagine my joy when I first began using the x2. Initially, it seemed to be smack on frequency – I tried this on WMAL, the powerhouse local AM station here in the DC area, and then again with stronger stations on shortwave, such as 12,160 kHz. Ah, I said to myself, Sangean has some decent QC and paid attention. About 30 minutes later, however, what I found matches the Zantow review. Stations are consistently low of the tuned/displayed frequency by as much as 300 Hz. The reason this is so disappointing is that I feel Sangean could have taken a clue from Tecsun and provided a re-calibration function (unless it exists and we aren’t being told about it). On Tecsun radios, the re-calibration capability is the major counter-punch to poor synchronous mode – in my view, one can live with flawed SYNC on a 990x or H-501 or PL-330 as long as you can adjust and at least have zero beat or close to it across frequencies. At the same time, as Zantow points out, no one should be expecting TCXO level performance from portables such as these. However, it is a bit disappointing that after all these years and redesign of the 909x to add some really nice features, they’re still landing up to 300 Hz from a tuned frequency. On the other hand, is this really any worse than one would see from an off-tuned SONY ICF-2010? No, and adjusting those older receivers required surgery.
CONCLUSIONS
I really like the 909×2. There simply is something about this design that Sangean knew was a winner when it first arrived on the market years ago, so it’s not surprising that Sangean stuck with it. It’s clear that some hard thinking went into the step up from the old 909x, notably the larger LCD, addition of finer step tuning to make SSB easier, the robust antenna and the still pretty darn good audio through the wonderful speaker. The 909×2 is a radio that you can imagine guests would comment on if it were sitting on your coffee table – it just looks THAT GOOD.
But then here in 2021, so does a Tecsun H-501x LOOK THAT GOOD. As I noted above, where the Tecsuns fall down – with their still challenged synchronous mode – they make up for with the ability to re-calibrate.
That is a huge feature and one that Sangean struck out on, though surely Sangean designers had to know the 909×2 would appeal both to listeners and to hobbyists with obsessions about frequency accuracy.
To repeat, I really (really) like the 909×2. But another area where the receiver strikes out is the problem with sharp reduction in LSB mode. Seriously – you have to crank the volume control up to at least 50 percent to hear ANYTHING when you’re in LSB, whereas USB requires going only up to about 30 percent. Then when you’re completing your carousel back to AM, you have to be sure not to still have the audio up at 50 percent or more to avoid blowing your speaker.
Again, as I said above, the calibration/drift issue on the 909×2 can be lived with. The problem with LSB, in my opinion, cannot or should not be tolerated. So, the question is, do you want to purchase a 909×2 now that still has that LSB audio issue, or wait a while until Sangean gets its act together?
These and other earthshaking questions are before us here in 2021. We have some of the best portables ever made by anyone in a time of sharply declining shortwave use, but they each have their flaws.
I don’t usually do a star rating or RECOMMEND / NOT RECOMMEND for radios. This time, I am going to make an exception and it links directly to the issue of the LSB problem on the 909×2. These radios simply should not have been allowed to enter the market with this being as serious a problem as I think it is. For that reason, I honestly cannot recommend a Sangean 909×2 until this is corrected.
Many thanks to SWLing Post contributor, Dan Robinson, for the following guest post and review:
Tecsun PL-368: Large Receiver Features In Smaller Vertical Handheld
by Dan Robinson
It was back in 2020 that the first photos surfaced online of the PL-368 – posted on Facebook by someone attending the electronics fair in Shanghai, China.
Photos showed the successor to the PL-360/365 receivers – and also the PL-990, successor to the PL-880, as well as the new king of the hill for Tecsun, the larger dual speaker H-501.
Things looked promising, and it was pretty exciting. Tecsun designers upgraded the PL-365 which had become a favorite of preppers and SWLs, but which was hobbled by the lack of a keypad, to the re-named PL-368.
The PL-365 and PL-360 before it were plagued by the problem of being overly sensitive to the touch – when holding the radio, reception was fine, but remove your hand and signal levels plummeted. Usually, a full hand grip was necessary to obtain full sensitivity and any variation in grip reduced sensitivity – this was noticed mostly in shortwave mode.
Previous 360/365 models were known for the included small rotatable ferrite
AM amplified antenna which performed miracles in nulling mediumwave stations – for those who still like to listen to the AM band. The 368 also comes with this additional ferrite antenna.
And the 365/360 (which were and still are sold by CountyComm as the GP-5) used AA batteries, making it very easy to find replacements anywhere the radio is being used in the field. Tecsun changed that on the 368.
After the photos appeared, I contacted Benny Zhao, who had posted them on one of the Facebook groups and asked if he could send me a sample of the PL-368. He obliged and a 368 was sent on its way.
The radio was sent without the BL-5C flat lithium battery which was prohibited in postal shipments. It took a long, long time (3 months, apparently the package was sent by snail mail) but it finally arrived here and I have been putting it through some tests.
The PL-368 that I received has the notation “2020.12 VER 1” so it’s clearly a first version from 2020 production.
Like the models before it is a great, handy, portable to grab if you’re going on a trip. It is lighter than the older 360/365s. The change from three AA batteries to the flat BL-5C explains some of that. There is a heft to the older models that the 368 doesn’t have. I am not sure about differences in thickness of the 368 cabinet. Perhaps we will find out more from Tecsun (see notes below regarding issue of tapping the front of the 368 cabinet).
The 368 retains the two multi function adjustment wheels on the right side, one for Volume, the other for Tuning. These are also used for time and bandwidth control.
Tecsun PL-368 (left) and PL-365 (right)
On the 360/365 radios, I never found the tuning wheel approach to be particularly efficient since it was limited to a certain number of kHz per turn, either 5 or 1 kHz depending how fast you turned.
On the 368 it appears you can obtain up to 40 kHz from a single turn of the wheel, while on the 360/365 that was limited to 15 to 20 kHz depending on the speed you were turning.
Tecsun PL-368 (left) and PL-365 (right)
The antenna on the 368 is thinner, but 8 inches longer than the 360/365 models, and in the box you will find the included and very effective rotatable ferrite antenna for mediumwave that inserts in a jack on the top.
On the 368 the volume wheel has detents, whereas on the 360/365 the wheel had smooth turning.
We have gone from 14 buttons on the old PL-360/365 models to 28 buttons on the PL-368, including addition of the keypad.
UPGRADES
Tecsun has upgraded the 368 in line with improvements seen in the PL-990x and H-501 receivers. There are now adjustable bandwidths – a particularly useful tool. These bandwidths also operate in SSB, something that the new Sangean ATS-909×2 doesn’t offer. Bandwidths are: LW/MW 2.5, 3.5, 9.0 SW: 2.5, 3.5, and 5.0 SSB: 0.5, 1.2, 2.2, 3.0 and 4.0 kHz
Also in the 368 is now synchronous detection, a feature left off Sangean’s 909×2. And you get the same intelligent tuning features seen in the 909x/501x models as well as the previous PL-880.
Tecsun added a control that enables activation of the light – this is located on the same button as the Step control which adjusts the tuning steps.
The 368 display now has the ability to tune in 10 Hz increments, an overdue upgrade from the 360/365 models.
Charging of the BL-5C battery can be carried out by connecting a DC 5V/0.5A adapter to the micro-USB port on the side of the radio. The English manual notes that when charging, the charging time is displayed at the top right corner of the display while the “Charge” indicator flashes.
Adjustments for 9/10 kHz mediumwave, Longwave, and FM frequency range can be found on the 1, 2 and 3 keys.
The manual notes that in addition to the internal ferrite bar antenna, the external supplied MW/LW ferrite antenna can be connected to the antenna socket on top and rotated to obtain optimum reception.
Addition of the keypad makes the PL-368 far more useful than its predecessors for instantaneous frequency access. This was the major drawback of the 360 and 365 receivers. This can’t be emphasized enough.
This is a day versus night difference and vastly improves the attractiveness of the 368 over previous models.
There are 850 memory presets, 100 for FM/LW, 150 for MW, 300 for SW, and 100 each for SSB and SYNC.
ATS tuning, like the 990x and 501 receivers enables ATS within all meter bands by holding the [<] or within a selected meter band by holding the [>]. The manual also notes the ability to auto scan all stored stations within a frequency band or mode (SYNC/SSB) staying on each station for about 5 seconds before resuming.
The 368 has what Tecsun now calls Enhanced Tuning Mode (ETM+) – as explained in the manual, this allows auto tune and storing of FM, LW, MW and SW stations into ETM memory. Unlike ATS, scanned stations will not be stored into regular memory (VM) – in this way, when in a different city or country, ETM+ can be used to auto search new stations without overwriting any previously stored stations.
FM De-emphasis Time Constant – as explained in the manual, while receiving FM broadcasts, long pressing [4] will adjust the de-emphasis setting for Europe, Australia, Japan (and most other locations), or for Americas and South Korea.
Add Seconds to the Clock – with the device powered off, press and hold [8] to add seconds to the clock.
Sleep Timer – as with its predecessors, the 368 has a Sleep Timer, with an indicator on the LCD display.
Alarm – and like earlier models, there is also an Alarm function, which allows the radio to turn on at a preset time. It’s possible to select a specific frequency to be used with the Alarm.
RE-CALIBRATION – I have not been able to determine yet if the 368 has a re-calibration function as can be found on the PL-330, 909x, and H-501.
PROBLEMS
Let’s get one headline out to start: The 368, as with the 909x and H-501 all have the useful Synchronous Detection mode. However, SYNC continues to be hobbled, showing distortion and loss of lock.
As I have mentioned in reviews of the 330, 990x, and 501x any successful use of SYNC requires a delicate dance involving careful selection of various bandwidths while in SYNC mode and fine tuning.
The 368 manual contains 3 pages of explanation of SYNC noting that it can “eliminate distortion generated in the IF filter due to local fading, slight offset, modulation overshoot, as well as inter-channel interference and cross-talk modulation, and can also reduce noise interference.”
The problem with all of the Tecsun DSP chip receivers after the PL-880, which had a hidden SYNC feature that was the worst of the bunch, is the extent to which SYNC still suffers from distortion and loss of lock that renders the feature far less useful than it could be.
Ideally, one would want SYNC to match the capability achieved in such older receivers as SONY’s ICF-2010, SW-100S, SW-07, 7600GR. You’re not going to get that with Tecsun receivers.
Like its predecessors, the 368 is still sensitive to touch. I noticed this immediately on the old 360/365 receivers, especially when using the radios
at the beach. If I was recording a station on shortwave, and left for a few minutes, I would return to find that sensitivity had dropped because the radio was not still being held in the hand, which rendered the recording useless.
I am continuing testing of the 368 to try to determine if this issue has been reduced to any extent and will update this review with any further findings. This sensitivity issue is not specific to the 368 – it can be seen on other older and newer receivers.
Many older portables (the SONY ICF-SW55 comes to mind) were constructed with robust cabinets that were less sensitive to touch. Touching the whip antennas on some older receivers improved reception, while on others touching the whip antenna actually reduced sensitivity.
URGENT ATTENTION FOR TECSUN: My initial testing of this particular China market unit of the PL-368 – again, it is marked as December 2020 Version 1 production – identified an additional issue.
When in SSB modes or SYNC, tapping on any area of the keypad and LCD display produces a warbling/distortion effect in the audio. One can only surmise that this is attributable to insufficiently robust construction of the PCB board underneath.
(Video shows problem created when physically tapping front of PL-368 cabinet.)
This is NOT a problem seen with my PL-365 when it is in SSB mode.
I hope that Tecsun gives this the attention it needs and corrects the problem in future production runs.
SUMMARY
Were it not for the major problems detailed above, the PL-368 would be an automatic must-buy receiver in my book.
Addition of the keypad is a night and day improvement and when combined with additional features such as multi-bandwidth options and the still-to-be-perfected synchronous detection, the 368 would be a killer portable.
But as with the PL-330, 909x and 501x the problem with SYNC mode is still a major drawback on a feature that is supposed to lift Tecsun receivers out of the pack of portables that are on the market in 2021.
One can live with the issue of cabinet sensitivity – but the additional issue I identified where there is instability introduced when tapping on the front panel/keypad/LCD is a QC problem that simply must be addressed by Tecsun.
But as I have said in reviews of other Tecsun receivers, let’s back up a bit. Imagine if we had had portable receivers with the capabilities that these have, back in the 1960’s or 1970’s.
It’s one of the great ironies of the radio listening hobby, that in 2021 any company is willing to continue producing receivers of this caliber as use of shortwave by major broadcasters continues to decline.
The obvious other killer feature to include in portables such as this would be to somehow integrate DRM into them. However, I have a feeling that will never happen
Many thanks to SWLing Post contributor, Dan Robinson, for the following guest post and review:
The H-501: Jewel in the Tecsun Crown, With Some Attractive Features
by Dan Robinson
Since 2020, there has been one Tecsun receiver I have been most looking forward to reviewing, and that is Tecsun’s H-501.
Videos showing the pre-production and mainland China versions of the 501 started appearing online at least a year ago. There are also numerous videos showing comparisons between the H-501 and PL-990x as well as the PL-330.
What I will do here is provide an assessment of the 501 informed by my use of a H-501 just received, the other two Tecsun receivers, and my decades of experience using a wide range of portable receivers. This review is based on initial tests of a H-501x, among the first production units.
Video: Unboxing
HOMAGE TO RECEIVERS OF THE PAST
The elephant in the room with the 501 is, of course, its two large left and right speakers. This reminds one of another Tecsun DSP portable, the PL-398BT with a similar left-right speaker arrangement.
On the left of the H-501, from the top, are the Volume, Treble, and Bass knobs which like the PL-880 and 990x has obvious lineage back to the famous Grundig portables of the 1990’s – the Satellit 500 and 700. Both of those were limited to two bandwidths. Only the 700 had anything approaching usable synchronous detection.
Each of the left hand control knobs on the 501 contains a dot to indicate where you are in the Maximum/Minimum range. At the bottom of the left side is a micro-USB port for when the receiver is used as a computer speaker – quite a nice feature!
On the right side of the 501 you find ports for AM and FM antennas, each with a rubber traction cap, similar to what is found on the PL-990x. There is also a three position sensitivity sliding switch for Local, Normal, and DX modes – that’s one more than usually found.
Knobs on the right side are the Main tuning and Fine tuning, again similar to the PL-990x. At the very bottom of the right side is the 5v 1.0 amp micro-USB charging port.
ERGONOMICS
NEGATIVE: Here I discuss one of two major negatives with the 501. The tuning knobs are embedded quite far into the radio body. Each has a round piece of rubber covering on the knob end surface designed obviously to provide traction, possibly also as a protective measure.
The reality is that on the 501, more seriously on the PL-330, embedding of the knobs so far into the cabinet makes it virtually impossible to undertake rapid tuning using those knobs if you are just placing your finger on the top barrel part of the knob itself!
As you will see in photos and video accompanying this review, holding a finger against the rubber on the end of each knob, or closer to the center, to achieve more rapid tuning. But it’s kind of annoying. On the PL-990x the knobs are somewhat different – extending a bit farther out of the cabinet, but also with the rubber coverings.
So, this is a design point for Tecsun to consider. Surely, it should be possible to come up with slightly different knobs for the 501 that make it more comfortable to achieve rapid tuning. As it is, the knobs on the 501 barely extend beyond the cabinet edge, including the end and rubber cap.
The same goes for the PL-330 – which has knobs that only one half inch in depth, and extending only about 1/16 of an inch beyond the cabinet edge. Part of the attractiveness of the 330 is its compact size and I doubt Tecsun will be moving to put slightly larger knobs on that radio anytime soon. But as it is, using the main and fine tuning controls on the 330 gets you maybe 10 kHz in tuning range.
[UPDATE] I realized after further use of the 501x that Tecsun clearly intended for the rubber knob cap covers to act as traction for tuning. The problems I see: after significant use over time, those rubber covers will lose their stickiness and thus their ability to help tuning will be reduced. Also, the fine tuning knob is smaller — and even using the rubber cover on the knob for more traction, it is somewhat difficult to achieve rapid tuning in 1 kHz mode. Tecsun could help 501x owners on the issue with the tuning knobs by including spare rubber knob caps. But it’s uncertain how the existing rubber knob covers are attached to the original knobs and how easy it would be to replace them when they lose their stickiness.
H-501 IMPRESSIVE FRONT PANEL
At the top of the H-501 radio above the LCD display can be found the Display/Snooze/Lock button. On an older Tecsun radio, the PL-880, this button doubled as the calibration adjust control. On the PL-990x this triple function button is located on the top of the radio.
LCD DISPLAY
POSITIVE: One of the big positives of the 501 is the large LCD display. The number digits are absolutely huge and make it easy to read frequencies.
Thanks Tecsun! The display contains numerous bits of information about receiver operation, the signal strength meter, etc.
Below the display is the keypad, with special dual keys for 9/10 kHz mediumwave, Longwave activation, and FM range adjustment. Backlight activation is on the 5 key. At the bottom you have the VF/VM key to select between frequency tuning and memories. To the right are the FM, MW/LW, and SW + and – buttons. These put the radio into shortwave mode and as is the case with the PL-990 and other receivers, activate ATS/ETM tuning.
At the very bottom of the front panel can be found PLAY/PAUSE, RR, and FF buttons for control of SD card audio when using the microSD card, which like on the 990x is located on the bottom of the receiver. According to the manual, by the way, the microSD slot accepts cards of up to 128 GB. Included in the box is a 16 GB SanDisk Ultra card. A reset hole is also on the bottom of the radio.
Finally, at the bottom of the 501 face are rubber covered input ports for Earphones, Line In, and Line Out.
METAL TILT BAIL
POSITIVE AND NEGATIVE: On the back of the receiver, you find the metal tilt bail which folds down and locks into two plastic tabs and can be lifted easily with a finger from an indentation in the cabinet.
This was a good design move by Tecsun, with the following observations: there are no incremental positions on the metal bail as you find on, say, a Microsoft Surface or similar tablet type PC. The only fully stable position is to have the metal bail fully extended back. That places the 501 in a great position if you’re standing or even sitting to a degree. But if you try to place the bail in any middle position you’re in danger of having the radio become unstable. Tecsun should definitely give some thought to a re-design, though the bail is better than the flimsy plastic stands found on the PL-990 and PL-880 and some older portables.
Still on the back of the radio, intelligently, Tecsun marks a screw hole which can be used to remove the telescopic antenna (marked as ANT SCREW). The other screw holes for removal of the back of the radio are also clearly marked. Thanks Tecsun!
However, one additional partial negative – there are no rubber pads on the bottom back edge of the 501x which will be contacting whatever surface the radio is sitting on while the metal bail is in use. So, if you don’t want that bottom back edge to be scratched, place the radio on something to cushion it.
BATTERY CHARGING
POSITIVE: Another interesting feature not found on other radios: Tecsun has created a dual charging system for the 501 which uses two 18650 batteries.
In viewing numerous videos, I have not seen this discussed much. Basically, this enables you to use the receiver’s internal charging capability to choose which battery you are charging. The manual states that the battery contains space for a “spare” battery. The charging indicator on the LCD display will flash while charging is underway – there does not appear to be a separate display for battery A or B. However, and this is quite a unique capability – while you are using the 501x, the switch changes which battery the radio is using.
It’s not clear to me whether the receiver while powered on is taking energy from one or both batteries simultaneously. As I note in my reviews, and this is amplified in the manual, do not expect to be able to charge a battery internally and listen to the radio at the same time because there WILL be noise.
HUGE WORLD MAP AND RADIO DIAGRAM INCLUDED
Tecsun includes a huge – and I mean HUGE – World Amateur Radio map in a plastic pouch with the manual. On the back of this is a large photo of the 501 with clear English guide points to each and every feature of the radio. In this, Tecsun is really going out of its way to make owning the 501 a special experience.
In the box (see photos) Tecsun includes 2 18650 lithium batteries, a 5 volt double USB A charging cube, a mini to mini cord, a USB charging cable, and to boot, a pair of fairly high quality wired earphones complete with spare ear tips.
PERFORMANCE
Anon-co advises that the H-501x uses a different IC than the PL-990x. No further details were available as of the time of this writing.
This is clearly a sensitive radio, as is the PL-990X. In these days of declining use of shortwave, almost any receiver is going to be able to hear “stuff” all over the bands and the 501x and 990x as well as the 330 are all quite capable in this regard.
In the video, I tune some familiar stations, including Voice of Greece and BBC
and move through the excellent bandwidth options. This is where the 501, with its large dual speakers, excels because if you’re on a strong station – Greece is a great example because of its great music programs – and you have that wider option, it’s really pleasant to listen to.
NEGATIVE: However, one has to puzzle over the decision to limit bandwidth to 6 kHz when in shortwave mode. On mediumwave (AM) you have a 9 kHz option which provides some fine listening. Perhaps Tecsun felt that there are few stations using shortwave these days that would benefit from having a significantly wider option? I would urge Tecsun to make 9 kHz available in shortwave.
SYNCHRONOUS DETECTION
NEGATIVE: I really had some hope that Tecsun would go farther toward
solving the problem of unstable/distorted SYNC mode with all of these recent radios. Unfortunately, it was not to be.
Using SYNC on these radios – though this was not the case with the PL-660 and 680 – involves a delicate dance, requiring using a combination of bandwidth filters and LSB/USB. SYNC works fairly well with some stations, but it really depends on signal level, and to an extent signal level of any station close to the frequency you are on.
There is a 1 kHz fine tune spread when using SYNC after which lock is lost. And still, lock is often lost even when you’re on center frequency and not using
fine tune in SYNC – the signal just becomes distorted. Not fun. The PL-990x has the same issues.
Now, Tecsun has definitely made progress since the horrendous implementation of SYNC on the PL-880, which wasn’t even an official feature. But it’s disappointing that given the design features in the 501, especially the wonderful dual speakers, a way has not been found to resolve this issue which obviously involves the DSP chip that is the brain of the receiver.
Video: Detailed testing of Tecsun H-501x
ANTENNA
NEGATIVE: One of the things the folks at SONY, Panasonic and some other manufacturers did so well was design radios with antennas that nested inside the radio and could be pulled up and out of the cabinet, and because of this, there was clearance from the top of the radio so the antenna can achieve vertical position. Tecsun has not done the same. Antennas on the H-501x, PL-990x, PL-330 swivel but cannot take up vertical position, and of course they are nested on the top of the radio. One would have thought that after years of producing portables, and coming to dominate the portable market, someone at Tecsun would have recognized the importance of antenna re-design. NOTE: the antenna on the 501x is sufficiently long, but on the PL-330 for example, seems to be not long enough.
BLUETOOTH
POSITIVE: Hooray for Tecsun in integrating BT capability into the 501x and 990x. This was such an obvious move and thanks to Tecsun for really hitting it out of the park. Unfortunately, we don’t get the ability to record audio from the radio on to microSD cards – that would truly have been a major step forward
CALIBRATION
The H-501 has the same re-calibration adjustment feature as is seen in the PL-909x and the PL-330. This involves going into LSB or USB mode, holding down the USB or LSB keys until a flash appears, then using the Fine Tuning knob to achieve zero beat on WWV or strong station that is known to be on frequency, then holding down USB or LSB again to have the radio re-zero itself. This is a fine feature that we have seen since the PL-880.
When I first received the H-501 it appeared that the receiver was fairly on zero beat from mediumwave up through 25 meters shortwave. Further testing revealed that re-calibration was necessary, but the degree of error from mediumwave up through 19 meters was not as significant as I have seen on the PL-990x. Re-calibrating at a mid-point of 25 meters appears to be a good mid-point choice, but inevitably, doing re-calibration on shortwave will throw the receiver off by a bit down on mediumwave.
A cautionary note: when undertaking this calibration function be sure to give the radio time to confirm it’s in calibration mode with the FLASHing LCD. Sometimes, the readout will jump a full 1 kHz above or below the frequency you’re zeroing on – if that happens use the MAIN TUNING knob to get yourself back (i.e. 9,704 to 9,705.00) and complete the zero beat operation with the FINE TUNING knob, then hold down LSB or USB to complete.
All of this may be overkill for most people – I am just among those who obsess over having receivers as exactly on zero beat as possible. That’s more difficult or impossible to achieve with older receivers that have no calibration function, such as the ICF-2010 or SW-55 without literally taking those radios apart to access internal points of adjustment. The fact that Tecsun provides this capability in these portables is something we should all be very grateful for.
CIRCUIT LOCKUP
All of the Tecsun radios have a “reset” hole to be used if the receiver is not functioning properly. I had one occasion of lockup with this sample of the H-501x. Rather than using the reset hole, I decided to remove one of the two 18650 batteries, which of course reset the receiver. I have alerted Anon-co to this issue, but it’s hard to tell whether it’s a major problem without having other H-501 units to compare to.
CARRYING CASE
POSITIVE: The H-501 that I received for review from Anon-co came with a beautiful faux leather case complete with a convenient carrying handle. My understanding is that this matches mainland China versions that have been widely seen in videos online.
Anon-co advises that the first batch of 501x to be carried by them will come in a gift box with this PU leather case, possibly to be followed at some later point by a hardcover carrying case. Indeed, a photo can be found online showing the H-501 in a hardcover carrying case similar to the cases for the PL-880 and PL-990x kits.
As of early April, Anon-co advises that while the price for 501x is not set yet, it’s expected to be somewhere in the $310 – 330 range including shipping to the U.S.
AM/MEDIUMWAVE AND FM PERFORMANCE
Not much to say here – I find FM performance on the 501x to be superb, and mediumwave reception is more than satisfactory.
CONCLUDING THOUGHTS
As I noted earlier, these days amid declining use of shortwave by remaining broadcasters, almost any DSP or older portable receivers are capable of producing excellent results for shortwave listening.
Facebook groups devoted to shortwave (they have become the new gathering place and information exchanges for those of us who still love the hobby) are
full of newcomers inquiring about which Tecsun, Degen, or other portables are best.
Often, my advice is to consider older portables that are still quite competitive, especially considering the reduction in the number of stations still on shortwave. These would include such classics as the Grundig Satellit 700/500, the SONY
ICF-2010(2001D), SONY ICF-SW77, and ICF-SW55, along with the venerable Panasonic RF-B65 and SONY ICF-SW100S in the smaller category.
What Tecsun has done with what we have to assume may be the final group of DSP receivers it produces is come up with small (PL-330), medium (PL-990x), and large (H-501) radios that combine extremely attractive features and excellent audio. The H-501x, in effect, is a Grundig Satellit 700 re-born for the 21st century and the path to it was paved by the PL-880.
Though implementation of SYNC in each of these receivers still leaves much to be desired, having this feature is enough to push prospective buyers to choose one or more of these Tecsun units over older portables.
Note that Sangean, which is now producing its ATS-909×2 (though the radio has growing pains and is having its firmware updated by Sangean) seems to have taken note of Tecsun’s dominance of the market and provided multi-bandwith capability, and an improved and enlarged LCD display on the 909×2 along with finer frequency resolution.
In a strange but perhaps understandable decision, Sangean left SYNC mode off of its new flagship receiver. Whether this had more to do with production costs or a decision that synchronous detection really brings little to the game these days, or both, along with other factors, remains a puzzle. It does appear, from early reviews, that Sangean may have improved sensitivity on the 909×2, though this too remains unconfirmed.
But again, even with the negatives I noted here about the H-501x, what Tecsun has accomplished is significant. It has given remaining potential buyers of multi-band portables three superb receiver choices. There are others in the Tecsun line such as the S-8800 and S2000, but of these only the S8800 is something I would recommend.
As I noted in a recent review of the PL-330, had we enjoyed a situation back in the golden days of shortwave in the 1960’s/1970’s/1980’s where a portable provided multiple bandwidths, advanced memory operations, and synchronous detection, DXing would have been even more of an enjoyment than it was. Certainly those Country Heard/Country Verified totals would have been higher!
The H-501x could easily be considered the crown jewel in the Tecsun group with its killer looks, large speakers, and performance equaling the PL-990x. Each of these receivers is arguably an easy choice as a “daily driver” for traveling, though where air travel and TSA issues are concerned, the PL-330 would be a better choice.
RECOMMENDATION: Of the negatives I discuss in this article, only one I would consider fairly huge, and that is the ongoing issue with synchronous detection. If the 501x, like the 990x and 330, were to have this issue resolved that would make it easy to recommend any of the three radios. As it is, the attractiveness of the 501x lies with its beautiful two speaker design. Even with the annoying SYNC issue, I would recommend the radio to anyone who understands the SYNC issue and doesn’t mind and who wants a nice, larger version of the 909x.
Many thanks to SWLing Post contributor, Dan Robinson, who shares the following guest post:
Tecsun PL-330: The Powerful Mini With One Serious Design Issue
by Dan Robinson
As SWLing Post readers know, I have a huge radio collection – including premium receivers and portables, now nearly 100 in all.
So, these days I am hesitant to add too many, but I continue to take interest in what companies such as Tecsun and Sangean are doing in the way of stuffing the latest chip technology and capabilities into portables radios.
The last receivers I reviewed included the Tecsun PL-990x, which has developed quite an enthusiastic following since its consumer version was released in 2020, and the Tecsun S-8800.
Out for some time now is the Tecsun PL-330. By now there are many reviews of it on You Tube and elsewhere.
It’s become a familiar observation for many of us – if this were still the 1960’s and 1970’s – even into the 1980’s, which could be considered the golden days of shortwave and we had receiver technology like this, well what a joy that would have been.
When I traveled around the world both before and after college, and professionally for Voice of America in the 1980s and 1990s, wow what a good time I could have had with today’s portables!
Some world band portables radios back then were superb performers. The Grundig Satellit series 500/700/600/650 come to mind – but these were not exactly what I would call small portables.
Paging through Passport to Worldband Radio from 1990 (wow, that’s 30 years ago!) you see others such as the SONY SW-1, Panasonic RF-B65, and of course, the SONY ICF-2001D/2010 which introduced killer synchronous tuning technology in the 1980s and remains popular today decades after it first appeared.
Also available were the SONY ICF-SW55 and later in competition with the 2010, the SONY ICF-SW77. Today, I have four SW-55s and two SW-77s and still use them regularly.
Tabletop receivers back in the good ol’ days offered multiple selectivity positions. One of those was the Lowe HF-225 (and later Europa version) along with the HF-250, Kenwood R-5000 and R-2000, ICOM IC-R71A, and Yaesu FRG-8800 among many others.
But as far as smaller portables go, features such as synchronous detection and multiple selectivity were still pretty limited, and a number of receivers didn’t offer selectable synchronous as was eventually offered on the Drake R8B and later production of the SW-8.
The RF-B65 by Panasonic – which today remains sought after for its amazing sensitivity – was hobbled by having a single selectivity position. Same with SONY’s SW-1 and SW-100, and 7600GR, though SONY’s PRO-80 had two bandwidths.
Indeed, it wasn’t until Eton brought out the E-1, with its three bandwidths combined with Passband Tuning (though no notch filter) that a portable finally reflected capabilities of some of the better tabletop radios (though lacking a notch filter).
The Grundig Satellit 800 was close in competition with the E-1 (though the earlier Sat 600/650 series also had multiple bandwidths) but was bulky.
Fast forward to 2021 – credit due to Tecsun and more recently to Sangean with its 909X2, for some years now we have enjoyed Asia-originated portables with multiple selectivity and synchronous mode, though sync implementation on some has left much to be desired.
Which is where the PL-330 comes in. When I look at the 330, I am reminded of one of the now ancient SONY portables, the ICF-4920 which was a super small slide-rule receiver that nevertheless was quite sensitive.
Like the 4920, which you could easily slip in a pocket, the PL-330 is a perfect travel portable. Only the Belka-DX SDR and still wonderful SONY SW-100 compete in terms of performance and size.
The 330 is basically a PL-990x in miniature: smaller speaker obviously, shorter antenna, no bluetooth capability or card slot. But as many people who frequent the Facebook groups have observed, pretty much anything the 990x can do, so can the 330.
This radio has ETM/ATS tuning, synchronous detection, multiple bandwidths in AM, SSB and MW, FM mono-stereo speaker control, alarm/timer functions, external antenna jack, display light, and other features.
Tecsun decided to go with a BL-5C battery here – the same with the new PL-368. I think this is unfortunate, since it requires one to obtain a number of those flat batteries if you want to travel and not have to re-charge. On the other hand, this is not a crippling design decision.
What is an unfortunate design problem, in my view, involves the simple question of tuning the receiver.
The main and fine tuning knobs on the right side of the PL-330 are embedded into the cabinet just far enough as to make easy rapid finger tuning of the radio nearly impossible.
In fact, in my testing it’s impossible to thumb tune the radio more than 10 kHz at a time. The same applies to using the lower knob which controls volume. When in FM mode, this issue make tuning just as frustrating almost forcing one to use rapid scan mode.
Another puzzler: Tecsun limited bandwidths in AM SW to three, while in SSB you have 5 bandwidth options. In AM mode, you have a 9 kHz bandwidth, another puzzling choice. Longwave too is limited to 3 bandwidths.
But overall, none of these problems really knock the PL-330 down very far. This is one mini powerhouse of a radio, one that makes you think “wow, if I had just had this back in 1967 or 1973 or 1982.
Some additional thoughts. My particular PL-330 was supplied by Anon-co but is a pre-production version and so does not have the latest firmware. Thankfully, I have not experienced the issue of SSB tuning running in reverse as others have.
NOTE: As most users know by now, but some newer users may not, you cannot charge one of these radios – whether Tecsun or Sangean – using the mini-USB port and use them at the same time. . . there is just too much noise introduced from the charging process.
This little mentioned feature: just as the Tecsun 909x has a re-calibration function, so does the PL-330. Tecsun itself initially declined to acknowledge this, but finally confirmed through Anon-co.
The procedure: Switch to LSB/USB. If the station is not zero beat, hit STEP button once and then quickly again to move the flashing display down arrow so it’s above the far right digit. Then fine tune the station for zero beat. Hold LSB or USB in for a couple of seconds. The LCD blinks. You then have zero beat – but be sure to repeat the process for LSB and USB.
I should mention that just like on the 990x, the re-calibration process doesn’t mean the receiver is then zeroed up and down the shortwave bands. You will likely have to repeat the process from, say 25 meters, to 19 meters, to 49 meters, etc.
I have come to enjoy using the PL-330 here in my house, though like other portables in my collection I need to position it in one particular corner of my home away from incoming cable TV lines.
The PL-330 and the Belka DX are currently king of the pile when it comes to my smaller travel portables.
I fully expect there will be no further receiver development by Tecsun after the PL-330/990x/H-510 radios – but that company will certainly have left us with some great receivers as the days of shortwave approach an end.
Many thanks to SWLing Post contributor, TomL, who shares the following guest post:
Indoor Noise and Ferrites, Part 1
by TomL
My magnet wire loop antenna on the porch reminded me to revisit aspects about my noisy Condo that I still needed to understand. Some RF noise I could control if I could find the right kind of information that is understandable to a non-engineer like me. There is a lot written about the general problem of noise and radio listening, for instance this ARRL article with web links to research – www.arrl.org/radio-frequency-interference-rfi, but I needed to get more specific about my particular environment.
I had tried some common clamp-on TDK ferrites I had obtained from eBay a long time ago but they only seemed to work a little bit. I have since found out these are probably the ones which are widely used on home stereo system connections used to reduce noise on those systems. There must be a better way.
The more I researched topics, like a portable “Loop on Ground” antenna, or, using RF chokes on the magnet wire loop, it dawned on my feeble, misguided brain that I was wrongly thinking about how to use ferrite material. For one thing, the material used to suppress RF noise is made with a certain “mix” of elements, like Manganese-Zinc, that electrically “resists” a specified frequency range. Fair-Rite has a useful Material Data Sheets web page which lists the Types of ferrite material. For dealing with noise (at the Source causing the problem), I needed to use the right kind of “Suppression” materials and proper placement. So, it (partly) made sense why the TDK snap-on ferrites might not fully work to reduce certain noise coming from my computer screens, LED lights, USB devices, and cheap Chinese-made power adapters.
A very good paper is by Jim Brown (K9YC) of Audio Systems Group entitled, “Understanding How Ferrites Can Prevent and Eliminate RF Interference to Audio Systems [PDF]”. There is a longer paper speaking directly to Amateur Radio folks, but the Audio version is simpler and it uses some of the same graphs and ideas. I was drawn to the very detailed Impedance measurements of many different “Types” of ferrite material used for different noise mitigation. I remember the traumatic pain of my college experience trying mightily to understand the Van Vlack Materials Science text book to no avail. But Jim’s paper reminded me of the importance of using the correct type of ferrite material and in an optimal way that reacts favorably in the target frequency range to solve a particular noise problem. So, what are my problem areas?
Shortwave Noise
Loop antennas have been what I have experimented with the most. They do not pick up as much man-made noise (QRM) and they have a space saving footprint. Fortunately, there is a wooden porch where these things have been tried. I had successfully built a broadband amplified “ferrite sleeve loop” (FSL) in the past. It was useful for a while but it fell into disrepair and also the Condo building has steadily increased in noise output. The amplifier was just amplifying the noise after a while. I also tried phasing two antennas but found the ever increasing noise cloud was coming from all directions and I could not null it out. I even tried a “mini-whip” from eBay but that just produced a wall of noise.
I recently tested AirSpy’s YouLoop written about before, and the results were good. However, it seemed obvious to me that it was too small as a passive loop to capture shortwave signals strongly enough without resorting to another amplifier attached at the antenna and would not improve the signal/noise ratio. My current solution is a unamplified stealth magnet wire loop about 32 feet in circumference. In that article, I mention things like common mode RF chokes at both ends of the antenna connection, horizontal polarization, and basically accepting that only the stronger shortwave signals will be received in a predictable manner. I think for now, this is about all I can do for shortwave and mediumwave noise, as far as my own Condo-generated noise. Neighborhood noise is a different topic.
VHF Noise
I then started to isolate which devices caused which kind of noise when listening to my outside amplified antennas for FM/VHF and UHF-TV transmissions. Many consumer Power adapters make a lot of noise from VLF up into UHF ranges. One thing I did right was to try a 10 pack of these little miracle “Wall Wart” toroids from Palomar Engineers. One by one, I put one of these small toroids (19mm inside diameter) on my home AC adapters as shown in the pictures, and the noises started disappearing. It does not explicitly say, but I believe it is Type 75 material which suppresses the noise generating AC adapter (at very low frequencies) when wrapped 8 – 12 times.
Most egregious of these was my CCrane FM2 transmitter. A strangled warbling sound kept emanating from the monitor closest to my laptop. Installing ferrites on the laptop and back of the monitor were not working. I moved the FM Transmitter and noticed a reduction in noise. So, I put one of these little toroids on the power input of the device and the noise disappeared. Apparently, it was picking up noise from the monitor (as well as its own power adapter) and rebroadcasting it to all my other radios! The strangled warbler is no more, I choked it (HaHa, sick bird joke).
While looking for the monitor noise, I put the eBay TDK ferrites on all the USB ports and HDMI ports. This has helped greatly on VHF and confirms my suspicion that these cheap TDK ferrites are indeed a common type of ferrite material. Some informative graphs can be seen in Jim Brown’s Audio paper mentioned before. One example might be Figure 22, which shows the #61 Series Resistance which peaks around 100 MHz when using a toroid with three “Turns”. More confused, I could not find a definition of a “Turn”. Eventually, in his longer paper to Amateur Radio operators, he defines it, “…is one more than the number of turns external to the cores”. Somewhere else he describes using many single snap-on ferrites being electrically equal to just one toroidal ferrite with multiple Turns. And interestingly, more Turns shifts the peak impedance substantially lower in frequency. So, using the graphs he supplies, one can target a noisy frequency range to try to suppress.
I then put 6 of the TDK ferrites on the VHF input to the AirSpy HF+. Some FM grunge was reduced and was thankful for that. The rest of the background noise truly seems to be coming from the outside picked up by the amplified antenna.
Also, I juggled a couple of the amplifiers around and now have separate VHF/FM and UHF/TV amplifiers which cleaned up the FM reception a little bit more – https://www.youtube.com/watch?v=zkDsy95et2w .
UHF TV Quality
On a whim, I put the balance of the TDK ferrites on the FM/TV splitter input cable, 10 in all. The FM reception did not improve but the Over The Air UHF TV reception Quality improved noticeably. My weakest TV station now has a stable Signal level and the Quality is pegged at 100%. This is a nice surprise since it means that now all local TV stations on UHF will come in cleanly without dropouts and I can view all digital subchannels. I was even able to rescan and added two more low-power stations never seen before. ?
LED lights
I have common LED lights hanging over a number of fish tanks and some grow lights over an indoor plant box and can hear this noise on upper shortwave and higher radio bands. In a future article, I will explore RF noise from lights as its own special topic. For instance, why do some LED lights generate RFI and how to know before buying (I am using BR30 spot bulbs from name brands)? Also, there is a new kind of LED “filament” light out now that uses much smaller LED’s on both sides of an aluminum strip, greatly reducing electromagnetic noise output (or do they??). More questions than answers.
I will explore creating my own customized AC power cord attached to the AC power strips of the LED lights. I will need to test this for safety and efficacy, so I will want to take some time to do this right. The hope is that, using Jim’s info, I will be able to create a broad spectrum RFI suppression AC power cord and cost less than $30 each cord. We’ll see.
Finally, I will look at “stacked” toroids using different mixes of ferrite Types, creating a custom RF suppression better than using just one Type of ferrite material, using AC cords as the main examples. For instance, the best set of graphs in Jim’s paper, in my opinion, are Figures 21 and 24 compared to each other. Something I did not know before is that one can not only use multiple turns on a single toroid to get a lower, peaked frequency response, but also stack multiple toroids of the same Type to get a smoother frequency response. Then on top of this, combine that set with other Types to create a customized frequency response curve.
Radios are quieter now. Those pesky grow lights are still a problem as well as the upstairs neighbor’s lights which seem to be on a timer, making FM reception noisy again after 5pm!
Many thanks to SWLing Post contributor, Michael Ye (BD4AAQ), for the following guest post:
In the Loop: PL-990 and LA400, a Perfect Match
by Michael Ye (BD4AAQ)
PL-990 and LA400
I have been a happy owner of Tecsun’s PL-880 world band receivers for years. In fact I have two PL-880 radios, one sitting at home and the other staying in my car. So, after Tecsun introduced the new model PL-990 in late 2020, it didn’t take me long to decide to purchase one. In this article I will discuss the Tecsun PL-990 receiver working with loop antennas, while referencing some relevant features of the PL-880.
Overall performance of the PL-990
Merely by its model number, it is easy to regard the PL-990 as an upgraded version of the already highly reputable PL-880. As expected, the PL-990 can very much be regarded as a combination of all the existing fine radio features of the PL-880 AND the music and bluetooth additions, with a number of improvements for instance in shortwave and medium wave performance. The ergonomic design of the PL-990 looks and feels different from that of the PL-880 in a number of ways. Although I may prefer the the more slim and elegant appearance of the PL-880, the PL-990 gives a more rugged and durable feeling, among other improvements over the older PL-880.
Working with loop antennas
The PL-990 and the PL-880 side by side
Living on the twelfth floor of a condominium in the crowded Shanghai, I have often been fascinated with loop antennas. As a licensed amateur operator, I have used the MFJ-1786X and have been impressed with its performance. On reception, I also find loop antennas appealing, as they are able to pull in weak signals while noticeably reducing electro-magnetic interference rampant in the urban environment. I have an unbranded shortwave loop antenna which I believe is based on and performs similarly with the AOR LA320. Despite its excellent performance, it is only good for the 5MHz – 15MHz shortwave range. So a few years ago when AOR launched the new LA400 wideband loop antenna, I bought one, which I often pair up with the PL-880 and other radios for shortwave listening, and get satisfactory results!
Antenna Switch on the PL-990
Now, back to the PL-990. When I first tried the PL-990 with the LA400, the results were generally good but not as good as as compared with using the same LA400 on my PL-880. This puzzled me for a day or so until I realised that the PL-990 actually has an antenna switch which the PL-880 does not have. The switch is used to toggle between an internal antenna (i.e. the built-in ferrite bar/telescopic antenna) and an external one (e.g. the AOR LA400). So a new PL-990 user who has often operated the PL-880 when first using the PL-990 could easily ignore the switch which should be pushed to “Ext” when plugging in an external antenna. This explains why the PL-990 may suddenly appear less sensitive than expected.
“Ext” antenna input for all bands
Contrary to the PL-880 whose external antenna socket is only good for shortwave signal input, the PL-990’s external antenna socket works with all bands, from long wave to FM. I found this to be an important and very useful change, and a pleasant surprise for my LA400, which covers a wide range of frequencies from long wave to medium wave to FM and up to 500MHz.
Once the LA400 is connected, the correct band selected, and last but not least the antenna switch turned to “Ext”, the PL-990 and the LA400 work like a charm in the indoor setting, remarkably better than the built-in telescopic antenna. With the loop connected, while there is not much to expect on the long wave band because of very few long wave stations remaining in the world, reception improves considerably on all other bands including on the medium wave and FM bands, as is also reflected on the upper right hand display of the signal strength and S/N ratio readings. Needless to say, performance on shortwave is as good as on the PL-880, if not better (again, remember to push the antenna switch to “Ext” when using it on the PL-990). Using the AOR loop on the PL-990 for FM reception is somewhat different as there does not seem to be a noticeable tuning point. Simply select the “Others” band, which appears to be broad enough for fair FM reception.
Tecsun AN-200 loop antenna
It is worth mentioning that I have a Tecsun AN-200 tunable medium wave antenna, which I have not used often. As its name suggests, it is for medium wave reception only. I tried it on the PL-990. Works great.
The AN-200 and the PL-990
It is hard to tell which one, the PL-LA400 or the AN-200, fares better, as the signal strength and S/M readings are quite close. They both perform better than the radio’s internal ferrite bar antenna to varying degrees, by improving the signal strength or the S/N ratio or both. The Tecsun loop is a passive antenna, meaning no power is required, making it easy to be used “wirelessly”, by simply placing the loop close to the radio, without having to be connected to the radio via a cable.
Chocolate, our house cat, tries to enhance reception with her tail
It should be noted that in the “wireless” mode of the AN-200 the antenna switch on the PL-990 should remain at “Int” so as for its built-in ferrite bar and the loop to couple with each other.
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