Shortwave listening and everything radio including reviews, broadcasting, ham radio, field operation, DXing, maker kits, travel, emergency gear, events, and more
No matter where you live in the world, everyone should have a battery-powered or self-powered (hand-crank) portable radio in their home.
Recently, the pace of articles here on the SWLing Post has slowed down. That’s because I live in Swannanoa, North Carolina—a town that was particularly hard-hit by Hurricane/Tropical Storm Helene, which brought unprecedented rainfall and caused widespread destruction.
In short, our rural mountain community was completely cut off for several days. Our bridge washed out, and a critical section of road crumbled daily.
At one point, two families had to be helicopter-evacuated for medical reasons, and less than a week after the storm, the Sheriff’s department came door-to-door recommending evacuation.
Our amazing community pulled together: we cleared our road of hundreds of downed trees and made sure everyone had food, water, and supplies. We took care of each other.
Now, things have improved dramatically. After two and a half weeks without power, we’ve been reconnected to the grid. The Kentucky Department of Transportation repaired our road, making it accessible to regular vehicles again. On Tuesday, an arborist crew finally made it up the mountain to remove fallen trees from houses.
Although things are starting to feel more normal at home, the impact on Swannanoa, Asheville, and surrounding areas has been profound. Entire neighborhoods are gone, numerous businesses have closed, and several grocery stores were severely damaged.
The Communications Void
The National Guard helped us for a full day at our home. Thank you 5th Battalion 113 Field Artillery!
It’s often said that modern communications infrastructure fails us after a disaster.
I can confirm, first hand, that this is true.
The mobile phone network went offline during the storm, leaving us without service for days. Even now, three weeks after the storm, mobile phone service remains unreliable. Calls drop every few minutes.
Mobile data services at home are still down at time of posting (October 18, 2024). Internet services like cable, fiber, and DSL are mostly still out across the county. Only those with satellite internet have a connection—I’m fortunate to be one of them. Our cell tower still only supports basic voice calls and text messaging, without data or media attachments.
Radio to the Rescue
As many of you know, I’m not just a radio listener, but also a licensed amateur radio operator, and both of these hobbies became essential post-Helene.
As highlighted in an article by WIRED, amateur radio proved to be our lifeline for communication when everything else failed.
Using the local repeater (N2GE on Mount Mitchell), I was able to pass wellness checks, coordinate helicopter evacuations, and arrange supply drops for our community. I handed out a few handy talkies to unlicensed neighbors so we could stay in touch.
My wife and daughter, who are also hams, helped tremendously. While I was out with a chainsaw, clearing driveways, they acted as net control operators on our community’s simplex frequency (147.555 MHz), passing critical messages.
For that first week especially, amateur radio truly was our community’s connection to the outside world.
AM/FM Radio: A Lifesaver
Fortunately, our local TV station remained online after the storm, but few people could access it. Many people rely on cable or internet to watch TV, and in areas like ours, the digital transition over a decade ago left many without the ability to pick up over-the-air signals.
In contrast, FM and AM radio became the most reliable sources of information. Here in Buncombe County, public information and news were broadcast on 99.9 MHz (FM) and 570 kHz (AM). Both stations stayed online throughout the disaster, and the information they provided reached a vast audience. Check out this feature from CBS Evening News:
In Henderson County, the local AM station WTZQ stepped up as well. They did incredible work serving their communities post-Helene, as highlighted in a report by Queen City News:
Information Lifeline
As a presenter in the above story pointed out, everyone should have a battery-powered (or self-powered) AM/FM/Weather radio in their home.
After a disaster, you’ll rely on that radio for essential updates like where to find clean water, how to apply for FEMA assistance, what businesses are open, and when services will be restored.
Even three weeks after the storm, much of the Asheville area is still without water, so radios remain vital for getting updates.
Here at SWLing Post HQ, I shared my extra portable radios with neighbors who needed them. I used my CC Skywave SSB 2 in the kitchen window to tune into local news on 99.9 MHz and 570 kHz. I also relied on my XHDATA D-109 and CC Radio 3—they became our constant companions for information.
Many of you here on the SWLing Post are already radio enthusiasts, so no doubt I’m preaching to the choir. But let this serve as a reminder to stock up on alkaline batteries and check your radios regularily to make sure they’re fully functional. Keep spares on hand so you can lend them to neighbors if needed—they’ll never forget your generosity.
And don’t assume your area is safe from natural disasters. Western North Carolina was considered one of the safest regions in the country for weather, yet we were hit by one of the most devastating storms in state history.
Stay prepared. Don’t become complacent.
Thank You!
Over the past few weeks, many of you have reached out with kind words and support, and I can’t thank you enough!
As of this morning, I have 310 messages in my inbox.
I’ve been too busy to reply to emails and comments—though I’ve read each one—but I truly appreciate your patience as I try to catch up. My days have been consumed by helping neighbors and getting our own life back in order. It’s been exhausting but incredibly rewarding, and we still have months of work ahead of us.
Thank you also to the contributors who have kept the SWLing Post running during my absence, and a special shout-out to my friend Vince (VE6LK), who has taken on a huge role in keeping QRPer.com updated.
Thank you so much for your support and understanding—and, again, keep those radios ready. You never know when they’ll become your primary source of information!
Many thanks to SWLing Post contributor, Alexander (DL4NO), who writes:
A Message from Germany: Growing Disaster Preparedness favours Ham Radio
For a long time most radio amateurs in Germany found themselves in the defensive: Building regulations, combined with EMC standards, heavily restrict antenna possibilities. Neighbors fear “dangerous” radiation, often going to court without any legal reasons. Emergency services got a much improved digital communication systems (TETRA), removing many of the artificial borders where they sometimes used ham radio to build bridges.
This could be quite different, as you can see in Austria. If radio amateurs organize a congress about emergency traffic, even the federal government and the Austrian army send competent representatives.
But the political turmoil and the connected energy crisis change attitudes in quite some branches of administrations:
The county of Ebersberg, east of Munich, is well known for its initiatives. Recently they invited the regional chapter of DARC, our German ham radio society, to discuss the build-up of a resilient data net for the county. In normal times, this data net could be used as part of HAMNET, our part of 44net. The county and towns would help to get access to suitable positions, including power supply. Some of the stations, for example on town halls, might be dormant most of the time. But as soon as power goes out, local radio amateurs are to activate the emergency net. The first application is to be VoIP, i.e. a independent phone service.
The county of Freising, a few km to the north, is also interested in working together with radio amateurs. We are just building a task force for this.
These activities are quite different from traditional emergency traffic. The most important difference: We work as enablers, not as radio officers. Our task will be to maintain the system, make it operational in case of an emergency, and introduce the officials to its use.
This is critical as we do not have enough radio amateurs to get the messages, send them over our system, and hand them down to the respective officer: Multply 2 radio amateurs by 3 shifts per day by a new crew every second day by the number of sites.
And in normal times, we can enjoy a much improved HAMNET coverage. Until now, most radio amateurs only had to access 44net through VPNs over the Internet.
As I’ve mentioned in past articles, I believe taking some precautions against EMPs is important. While I feel that an intentional nuclear EMP is unlikely, our local star can cause even more damage to an even larger portion of our planet if it decides to cause a solar storm like the Carrington Event.
Many thanks to SWLing Post contributor, Jock Elliott, who shares the following guest post:
The Crisis Radio
By Jock Elliott, KB2GOM
Sooner or later, it will happen to you. What’s ‘it’? Short answer: a crisis.
It could be as simple as you wake in the morning to find the power is out; you don’t know how long it has been out, and you don’t know when it is coming back. It might be a weather event: a blizzard, a sandstorm, a tornado, a derecho, a hurricane. It might be a geologic event like a tsunami, earthquake, or even volcanic activity. As recent events have shown, it could even be a war or a revolution.
When normal life is disrupted, and uncertainty is perched on your shoulder like a vulture, you will want to know what’s going on, and your usual means of getting information – telephone, smart phone, internet device – may also be disrupted.
When that happens, radio can come to your rescue. Your local FM or AM (medium wave) station may be on the air, providing vital information to your community, or NOAA Weather Radio may be providing hazard information. In extreme cases, shortwave radio may be beaming information to your area when all else fails.
So I have a couple of very specific recommendations.
First, make sure that your household has a “crisis radio.” By that I mean one that will receive your local AM and FM broadcasters as well as shortwave radio, and, if you live in the US or Canada, NOAA Weather Radio. If you can afford it, I recommend getting a crisis radio that has single sideband capability (SSB) so that you have the ability to intercept ham radio communications, which might be another source of information.
Toward that end, I can heartily recommend the CCrane Skywave SSB radio. (Let’s be clear: I have no commercial connection with CCrane; I get nothing from them for making this recommendation, I purchased my Skywave SSB with my own money.) It has AM, FM, Shortwave, Weather, VHF, Aviation and SSB Bands. It is very small, measuring just 4.8″ W x 3″ H x 1″ D and weighing just 6 ounces without batteries. It will run for over 50 hours on a couple of AA batteries and comes with CC Earbuds, SkyWave SSB Carry Case, and CC SW Reel Antenna which boost sensitivity for shortwave and ham radio listening.
It is a crisis radio that you can stick in your pocket, backpack, purse or briefcase for deployment when the need arises or you simply want to listen to some radio programming. Further, you don’t have to be an expert to operate the CCrane Skywave SSB. Thanks to the Automatic Tuning System, just select the band you want to listen to, press and hold the ATS button for two seconds, and the Skywave SSB will automatically search for stations in that band (AM, FM, Shortwave, etc.) and store those stations in the memory banks for that band. You can later check those memories to hear what programming those stations are broadcasting.
Second, and this is important, if you listen to shortwave radio at all, take the time to let the stations know. Drop them a postcard; shoot them an email, do whatever you can to inform them you are listening, and you value their transmissions.
Why? Because we all want those stations to be there if and when the next crisis happens. And if your local AM or FM station provides special programming to the community a weather event or geologic emergency, for the same reason, be sure to let them know how much you appreciate their efforts.
As a fire captain observed a couple of years after the North Ridge earthquake in California: “You cannot be over-prepared for communications in an emergency.”
I entitled this review an “Everyman” review because, while I am far from “normal” (just ask any of my friends!), I am not a hard-core SWL. I am a hard-core amateur radio operator perhaps, but only for the last decade(+). I have been casually listening to shortwave radio for about 50 yrs. So, my perspective on this radio comes from someone who cut his teeth on a Realistic DX-160 (still love those radios!), progressing through various desktop and portable radios, to three of my current favorites, the FRG-7, the Sangean 909X2, and the Sony 7600GR. Of course, this doesn’t count some vintage WWII-era radios and earlier, but they are favorites for other reasons.
Now, the purpose of this little reflection on equipment is to say all radios have their place in the pantheon of shortwave radios, and no one radio “does it all.” The Tecsun radio, I believe, fills a very specific niche in the radio world, and it is excellent for those purposes. It does not, however, rival other radios whose goals are different, such as ones designed around sound fidelity, digital signal processing, SDR capability etc.
What this radio does do is present a very capable radio in an ultra-small package, designed to fit easily for travel and for survival/emergency situations, or for armchair operation. That middle one may surprise you, so allow me to explain.
I have a previous model of this radio (GP-5/SSB still available) sold by CountyComm, which was modified from Tecsun’s stock production PL-365, to have features suitable for government use. This has become a rather popular radio for preppers because of those modifications. The idea behind this radio as a compact piece of kit for government embassy people was to have something which could be easily concealable, operated with one hand, and have a wide range of reception capabilities. Of course, good reception of shortwave, AM, and FM bands was considered a must. You can look at the CountryComm website to find out specific features of the modified units if interested, as that radio, or the PL-365, are not the subject of this review.
While not a real “prepper” myself, I was intrigued by the AM broadcast reception capabilities due to the plug-in ferrite antenna, and also liked the idea of the small footprint. In actual use I found the radio to be quite versatile, a good performer, but rather awkward to use as there was no quick way to get to specific frequencies, unless already programmed into a memory location. With no direct keyboard entry on the GP-5, going to random locations to channel surf was, for me, frankly a bit annoying.
Enter the PL-368 which boasts a direct keyboard entry! Yes!! This one feature has taken the radio to a new level of performance which makes it a joy to use in this reviewer’s humble opinion. (Full disclosure, the unit I received for this review was provided by ANON-CO, and is the latest model after the recent firmware update incorporated by Tecsun. However, I have no other connection to ANON-CO or Tecsun, and my willingness to do the review is purely based on my previous purchase and experience with the CountyComm model.)
Despite having an unusual number of stormy days and nights here in the Midwestern U.S. recently, I have managed to enjoy some very productive listening opportunities with this little radio. For example, being an amateur radio operator, I appreciate the ability to listen in on the amateur frequencies now an again, and the recent ARRL Field Day afforded me the opportunity to really test out the radio’s USB/LSB reception capabilities, and its ability to dig out signals on a really crowded band. I was quite impressed both with its DSP and bandwidth capabilities and the reasonable clarity of the audio when tuning in various signals. Does it have the richness of audio that my Sangean 909X2 has? No, of course not. The speaker is much smaller in the PL-368, but it was quite listenable. Likewise, listening to various nets on 80 meters was quite acceptable with the built-in antenna, where noise and local interference are common gremlins on any radio.
For shortwave stations I found the radio to be quite sensitive just using the built-in antenna, which is key to portable listening. If I have to attach an external antenna, my mobility becomes limited, and I might as well just listen to one of my desktop radios. Some reception examples include: NHK World Radio 9560, Helliniki Radiophonia Voice of Greece 9420, WRMI relay of KSKO 89.5’s Paul Walker from McGrath Alaska on 7780 (beamed to east coast U.S., as well as on 7730 beamed to west coast, Hawaii, and South Pacific).
Of course, reception of CRI, Radio Havana Cuba, and numerous religious broadcasts were heard on all the usual places. I also listened to WWV signals at various locations, my go-to initial band reception check, as well as listening to HF aircraft broadcasts, military planes training on 11175 (USB), and maritime weather broadcasts. While I did not try digital mode reception such as FT8 with WSJT-X from the headphone jack, I have no doubt I would have been able to monitor these stations on various bands easily as the signals were immediately recognizable. The same holds true for CW reception.
Operational Notes
For a thoughtful, in-depth review of many technical aspects of this radio Dan Robinson has written an excellent piece on the PL-368, along with an updated review of the latest firmware’s effect on the radio. One aspect worth mentioning in my experience with this radio is that, unlike Dan, I did not find an issue with changing sensitivity when touching/holding the radio versus the radio standing on its own. Your mileage may vary, of course, so this goes in the “for what it’s worth” category. Maybe this issue has been resolved in later production runs? Or maybe my capacitance is running low and I need more electrolytes<grin>!
Like Dan, I found the SYNC detection of USB/LSB to be marginal at best, mostly making the signals harder to hear. On the upside, standard reception was quite good, and I did not experience significant fading most of the time.
Below are some of the hidden keyboard functions as listed, provided by Anna of ANON-CO, but I wanted to mention a feature I have either forgotten when using my GP5 CountyComm model, or which has been added (sorry, I don’t have access to the GP5 right now as it is packed away due to a recent move in progress). When “speed tuning” as I call it (turning the tuning dial quickly) with the “step” selected to the smallest increment on SW, what starts as increments of 10Hz will jump to 50Hz at a time after a few moments. This helps in trying to quickly latch on to a signal when increments of 10 are not necessary. The tuning will revert to 10Hz units when stopped for a few seconds.
Now for some undocumented features:
Switch between internal ferrite rod and whip on AM (MW & LW)
Select the MW or LW band.
Press and hold key ‘3’ for about 2 seconds.
When the display briefly shows “CH-5” this means that the device is set to MW/LW reception using the telescopic antenna. The display shows MW (or LW) and SW on the left side of the screen.
When the display briefly shows “CH-A” this means that the device is set to MW/LW reception using the internal ferrite antenna. The display shows only MW (or LW) on the left side of the screen.
Adjusting the maximum volume level
Select the frequency band, then press and hold key ‘7’ for 2 seconds until a number is displayed. At this moment, rotate the [ TUNING ] knob to adjust and press the key ‘7’ again to save and exit.
Firmware Version
In power-off mode, press and hold [ VF/VM ] for 0.5 seconds until all characters on the display are shown, then wait a few seconds until the firmware version is briefly displayed in the middle of the display.
Extend SW-range for European setting (1621-29999 kHz)
In power-off mode, press and hold the [ 3 ] key to set the MW tuning steps to 9kHz.
Select the SW band, and then press and hold the [ 5 ] key for 10 seconds to enable/disable the SW frequency extension. The starting point of the SW frequency range will become 1621 or 1711 kHz.
Some Nitpicks (There had to be some, right?!)
I wish the batteries were still standard AA units instead of the flat rechargeable unit. This is merely a personal preference, but as a radio designed for carry-anywhere usage, I like a radio to use batteries I can pick up anywhere if needed. I tend to use rechargeable AA and AAA batteries anyway, but I like knowing I can use ubiquitous alkaline batteries available at almost any store in a pinch.
I suspect the change was made to allow for more space for the direct keypad entry, and that is definitely a tradeoff I am willing to make!
On a related note, the recharging port uses the USB micro-b connector which I have found in cell phones, tablets, etc. to be a weak point as cables often seem to go bad, or the connector itself gets damaged. The larger mini-b would be my preference, but hey, again, that’s a nitpick.
Finally, the case does appear to be a little thin which makes me wonder how it might survive if dropped or knocked off a table. This is not a deal-breaker by any means, but something to consider when carrying it around or when packing it for a trip. It may survive quite well, but that’s a test I don’t want to try out just to see what happens.
Final Thoughts
For me, as a casual shortwave listener, I look for several things in a portable radio. I want true portability – if a so-called portable radio must be tethered to an external antenna to work decently, chances are I am not going to use it often – my various desktop models attached to outdoor antennas will always out-perform a portable. I also want a simplified layout of controls. I do not want to dig through menus, have be a contortionist to work the buttons/controls, or carry a manual with me to find out how to use the radio each time because the controls are confusing. I also want reasonable audio and clarity, or the ability to fine-tune a signal to minimize adjacent signals.
I find the PL-368 does for me what I want a portable to do and does it reasonably well. Is it the best portable out there? No. Is it a benchmark radio? No. But it is extremely portable, easily handled with just one hand, and its reception capabilities put it far above some other portables I have used. If you are looking for something which can easily fit into a pocket, bag, or purse, this radio is great. If you want a radio which performs well over a wide range of signals using the built-in antenna, this radio fills the bill. And if you want true USB/LSB, along with good bandwidth options in your portable, this is a great choice. Cheers!
(edit, July 23, 2021: an additional “hidden” feature to be included in the shipping version not included in this reviewed unit is an SSB calibration capability – definitely a plus! — Robert)
Many thanks to SWLing Post contributor, Kostas (SV3ORA), for sharing the following guest post which originally appeared on his radio website:
Emergency transmitter: An 8-component, high-power 40m/30m transmitter to get you quickly on the air
by Kostas (SV3ORA)
Introduction
QRP is all about doing more with less. This is more than true, with the construction of this cheap, simplistic transmitter presented here. It is designed primarily as an emergency transmitter (EMTX) that can be built or serviced in the field or at any home. However, it can be used as a HAM radio transmitter as well. Do not judge by its low components count though. This transmitter is powerful, more powerful than anything the QRPers would dream of. It is just remarkable how 8 components can lead in so much output power, that lets you communicate with a big part of the world, when propagation conditions are right. It is very difficult for a circuit to match that kind of simplicity in balance with such performance.
Following my detailed instructions, the EMTX can be reproduced easily, within hours. The result is always success, this is one of the circuits that are not critical at all and a successfully working transmitter can be reproduced every time. I have built this transmitter several times, using similar components (even toroids) and it always worked. The transmitter meets the next expectations:
1. Output power (including harmonics): A few mW up to 15W (depended on transistor, crystals and voltage/current used) at 50 ohm.
2. It can drive any antenna directly, 50 ohm or higher impedance, without external tuners.
3. Bands of operation: Currently 40m, 30m
4. Mode: CW, Feld-Hell (with external switching circuit), TAP code and any other ON/OFF keying mode. AM modulation has been easily applied too.
5. Options like reverse polarity protection diode (useful in the field when testing different unknown polarities PSUs) and current meter (for easier tuning) are available.
The challenge
The purpose of this transmitter is to be used primarily as an emergency transmitter. This poses several challenges that influence the design of the transmitter:
1. It must be able to be built or serviced easily in the field or at any home, with components that could be salvaged from near by electronics sources or a small electronics junk box. This means that components count should be kept very low and they must not be rare to find but commonly available parts. As a side effect cost would also be kept small, if one is to buy any component. Also, the active components must be interchangable with many other devices without the need for the design or the rest of the circuit components to be changed.
2. It must be able to operate from a very wide range of DC voltage sources and at relatively low current, so that common house power supplies could be used to supply power to it. Such devices include linear or switched mode power supplies from laptop computers, routers, printers, cell phone chargers, Christmas lights or any other device one might have available.
3. It must be capable of transmitting a powerful signal, so that communication is ensured. An emergency transmitter that is capable of a few mW of output power, might be heard locally (still useful, but there are handheld devices for that already) but isn’t going to be of much usage if it can’t be heard really far away.
4. It must be capable of loading any antenna without external equipment required. In an emergency situation, you just don’t have the luxury of building nice antennas or carrying coaxial cables and tuners. There may be even extreme cases where you can’t even carry a wire antenna and you depend on salvaging wire from sources in the field to put out a quick and dirty random wire antenna.
5. Adjustments of the transmitter should be kept minimum without the help of any external equipment and there must be indication of the correct operation of the transmitter or the antenna in the field.
Components selection
The transistor:
This transmitter has been designed so that it can operate with any NPN BJT in place. This includes small signal RF and audio transistors and high power RF transistors like the ones used on HF amplifiers and CB radios. Despite 2sc2078 is shown in the schematic, just try any NPN BJT in place and adjust the variable capacitor accordingly. When you are in the field, you do not have the luxury of finding special types of transistors. The transmitter must operate with any transistor in hand, or salvaged from near-by equipment. Of course the power capability of the transistor (as well as the crystal current handling) will determine the maximum VCC and current that can be applied to it and hence the maximum output power of the transmitter. Some of the most powerful transistors I have used, come out of old CB radios, such as the 2sc2078, 2sc2166, 2sc1971, 2sc3133, 2sc1969 and 2sc2312. There are many others. As an example, the 2sc2078 with a 20v laptop PSU, gave 10-12W of maximum output power into a 50 ohms load.
Schematic of the 8 components EMTX for the 40m/30m bands. Components with gray color are optional.
The crystal:
This is the most uncommon part of the transmitter. You have to find the crystal for the frequency that you want to operate on. Crystals within the 40m or 30m CW segments are not that common. Further more if you operate the transmitter at high powers and currents, you will notice crystal heating and chirp on the frequency of the transmitter. The current handling capability of your crystal die inside the crystal case, will determine the chirp and the amount of crystal heating. You can still work stations with a chirpy transmitter provided that the chirp is not that high, so that it can pass through the CW filters of the receivers. However, if a small chirp annoys you or if this chirp is too much, then you have to use these vintage bigger size crystals (e.g. FT-243), that can handle more current through them. But these are even more uncommon today.
The approach I have used in my prototype, was to connect more than one HC-49U crystals of the same frequency in parallel, so that the current is shared among them. This reduced the chirp at almost unnoticeable levels, even at high output power, just if I was using a single FT-243 crystal, or even better in some cases. Again, this is optional, but if you want to minimize chirp (and crystal heating) without searching for rare vintage crystals, this is the way to go.
A bit of warning. If you notice a very high chirp when plugging in a crystal to the EMTX, you should consider this crystal as inappropriate for this transmitter, as it cannot handle the current required. If you continue to use this inappropriate crystal, you could easily crack it inside and set it useless. Don’t use these tiny HC-49S crystals, they won’t work.
The current meter:
A 1Amp (or even larger) current meter can be used to monitor the current drawn by the transmitter during key down. The recommended current operating point is anywhere between 450mA to 1A, depended on the output power (and harmonics) level you want to achieve. The current point is set by the variable capacitor. I would avoid setting the current to more than 1Amp, although it can be done. The use of the current meter is optional, but along with the incandescent bulb, will give you a nice indication of the correct tuning of the transmitter, so that you do not need to have an external RF power meter connected to the transmitter output. If you do have, then you can remove the current meter. If you don’t have a 1Amp analogue meter available, but a smaller one, you can parallel a low value power resistor across the meter. In my case, I only had a 100uA meter and I paralleled a 0.15 ohms 5W resistor across it to scale down 1Amp to 100uA, The resistor value depends on the internal meter resistance so you have to calculate this for your specific meter. When the 2sc2078 is used at 20V, 500mA in the current meter indicates around 5W of output power, 600mA indicates around 6W, 700mA 7W, 800mA 8W, 900mA 9W and 1A around 10W. So the current meter can be used as sort of power meter without the need to do any scaling on it.
The incandescent bulb:
A current meter alone, without the use of the incandescent bulb, will not give you the right indication of the operation of the transmitter. In some cases, the transmitter might be drawing current without actually generating much, or even any RF. When you are in the field you do not want to carry extra monitoring equipment with you. The incandescent bulb will light on when the transmitter oscillates. It monitors the actual RF signal, so it’s brightness changes according to the amount of RF power the transmitter produces. Along with the current meter reading, this is just what you need to know in order to set the variable capacitor properly. Note that the bulb will not lit at very low signal levels. The one used in the prototype starts to glow up from a bit less than 1W. Miniature incandescent bulbs may not be that easy to find nowadays. However, there is a good source of these, that almost anyone has in their houses. This source is the old Christmas lights. You do save old Christmas lights, don’t you? The incandescent bulb indicator as well as it’s single turn winding on the transformer, are optional components. If you have an RF power meter connected to the transmitter, you can remove these.
The diode:
The protection diode is an optional component to the circuit. If you are in the field, correct polarity of a power supply may not be obvious. Without a multimeter it might me difficult to determine the correct polarity of the PSU. A power diode (I used a 6A one) will protect the transistor from blowing up in the event that reverse polarity is connected to the circuit.
The Cx and Cy:
The Cx and especially the Cy capacitors need to be of good quality. The Cy will get hot on high output power if it isn’t. In the tests, I have used homemade gimmick capacitor and even double-sided PCB as a capacitor for Cy and they all got hot at high power. Silver mica capacitors run much cooler and they do make a small difference in the output power, so I suggest to this type. Cy must be able to handle quite a lot of voltage, so silver mica type is ideal.
The variable capacitor:
The variable capacitor can be air variable or ceramic, although I prefer air variables in tis application. In any case it must be able to handle a high voltage just as the Cy.
The key:
The key directly shorts the transistor emitter to the ground, therefore it is a part of the active circuit. For this reason, I suggest the key leads to be kept as short as possible. The key must be able to handle the voltage (20v) and current (up to 1A) on its contacts, which is usually not a big deal.
Transformer construction
The construction of the transformer is shown below step by step. Note that if you decide that you don’t need to drive higher impedance loads but just 50 ohm ones (eg. antenna tuners or 50 ohm matched antennas), you just need to wind 2t in the secondary and not 14t. You also don’t need any taps of course.
Step 1:
Take a piece of 32mm external diameter PVC pipe from a plumber’s shop. Alternatively, a suitable diameter pills box can be used, or any other suitable diameter plastic tube.
Step 2:
Cut a 4cm piece out of this tube. 4cm is the minimum length required.
Below a 4cm PVC tube has been cut in size.
Step 3:
Wind 16 turns of 1mm diameter enameled wire onto the PVC pipe and secure the winding in place as shown in the picture below. Notice the winding direction of the wire. This is the primary of the transformer, the one that is connected to the two capacitors. Notice that this winding is wound a bit offset to the right of the pipe.
Step 4:
Wrap the winding with 3 turns of PTFE tape. It can be bought at any plumber’s shop, just like the PVC pipe. The PTFE tape will help in keeping the second layer turns in place and it will provide extra insulation.
Step 5:
Wind 2 turns of 1mm diameter enameled wire on top of the primary winding and secure the winding in place as shown in the picture below. Notice the winding direction of the wire, as well as it’s position relative to the primary winding. This is the feedback of the transformer, the one that is connected to the collector of the transistor.
Step 6:
Wind 14 turns of 1mm diameter enameled wire on top of the primary winding, starting from just next to the 2 turns one and secure this winding in place as shown in the picture below. Notice the winding direction of the wire, as well as its position relative to the primary and the 2 turns windings. This is the secondary (output) of the transformer, the one that is connected to the antenna. At this point do not worry about the taps yet.
Notice in the picture below, the way the windings are secured in place onto the pipe. The wire ends are passed through the pipe using small holes and then bent towards the ends of the pipe and once more to the surface of the pipe, where the connections will be made.
Step 7:
Wind 1 turn of 1mm diameter enameled wire onto the pipe and secure the winding in place as shown in the picture below. Notice the winding position relative to the other windings. This 1 turn winding is placed about 1cm away from the other windings. This is the RF pick up winding, the one that is connected to the incandescent bulb.
Step 8:
Use a sharp cutter (knife) and carefully scrap the enamel of all the windings ends. Do not worry if you cannot scrap the enamel at the bottom side of the wire ends (that touches to the pipe). We just want enough copper exposed to make the connection.
Step 9:
Tin the scrapped wire ends, taking care not to overheat them much.
Step 10:
Now it’s time to make the taps on the secondary winding. Use a sharp cutter (knife) and very carefully scrap the enamel of the wire at the tap points (number of turns). Take much care not to scrap the enamel of the previous and the next turn from each tap point. Do not worry if you just scrap the enamel at the top of the wire (external area). We just want enough copper exposed to make the connection.
Make each tap, a bit offset from the near by taps, like shown in the pictures. This will avoid any short circuits (especially at the 4, 5 and 6 taps) and it will allow for easier connections, especially if alligator clips are used to connect to the taps.
Step 11:
Tin all the tap points, taking care not to overheat them.
Step 12:
This step is optional and it depends on how you decide to do the connections to the taps. You may solder wires directly to the tap points, but in my case I wanted to use alligator clips, so I did the next: I took a piece of a component lead and soldered it’s one end to each tap point. Then I bent the component lead to U-shape and cut it accordingly. This created nice and rigid tap points for the alligator clip.
Step 13:
This step is optional and it depends on how you decide to mount the transformer to your enclosure. In my case, I wanted to create three small legs for the mounting. I cut three pieces of aluminum straps and made holes at both their ends. I made three small holes onto the transformer pipe end and mounted the aluminum straps using screws. After mounting them, I shaped the straps to L-shape. Then I used three more screws to mount the transformer to the enclosure.
The completed transformer is shown in the pictures above and below. The 6 connection points at the bottom of the pipe, are the low voltage points, whereas the 2 points at the top of the pipe, are the high voltage points.
If you have built the transformer as described, the bottom connections are as follows (from left to right):
Wire end 1, connected to the incandescent bulb
Wire end 2, connected to the incandescent bulb
Wire end 3, connected to the current meter
Wire end 4, connected to the current meter
Wire end 5, connected to the GND (ground)
Wire end 6, connected to the transistor collector
The top connections are as follows (from left to right):
Wire end 1, connected to the 25pF variable capacitor and the Cy fixed.
Wire end 2, is the 14th secondary tap and it is left unconnected, or tapped to the appropriate impedance antenna.
Videos of the EMTX in operation
I have made two small videos of the EMTX in operation.
The first 13.5MB video (right click to download), shows the operation when the transmitter is set for a bit less than 10W of output power.
The second 3.5MB video (right click to download), shows the operation when the transmitter is set for about 5W of output power.
EMTX chirp analysis
Every self-exited power oscillator (and even many multi-stage designs) exhibits some amount of chirp. Chirp is mainly considered as the sudden change in frequency when the power oscillator is keyed down. Apart from chirp, there is also the longer term frequency stability that may be considered. The chirp in the EMTX is surprisingly low, if it is built properly. Hans Summers, G0UPL has performed a chirp analysis on my EMTX (PDF) and the EMTX built by VK3YE and presented on YouTube. Hans, performed the analysis from the video/audio recordings of both transmitters. I sent him two videos, one with the EMTX set for an output power of 10W and one where it is set for 5W. The chirp at worst case (10W) was about 30Hz and at 5W in the order of 10Hz or so. Being so small, the chirp is almost undetectable by the ear and it surely poses no problems when passing the tone through narrow CW filters. This is an amazing accomplishment from a transmitter so simple and so powerful.
EMTX harmonics measurement
Every unfiltered transmitter will excibit harmonics at it’s output. This means that the output waveform has some distortion in comparison to a pure sinewave. Many of the transmitters I have seen, present a very distorted output waveform and absolutely need a LPF if they are to be connected to an antenna. I can’t say that this is true for the EMTX, because surprizingly, it has low distordion, despite the high output power it can achieve. Although a LPF is always a good idea, it is not that much needed on the EMTX. However you have to use one to comply with the regulations.
The image above, shows the measurements on the output of the EMTX, when it is set closely to 10W at 50 ohms. The main carrier is exactly at 9.9W and all the harmonics are less than 50mW! Also, the harmonics, do not extend into the VHF region.
The image below, shows the measurements on the output of the EMTX, when it is set closely to 5W at 50 ohms. The main carrier is exactly at 5.17W and all the harmonics are less than 9.6mW! Again, the harmonics, do not extend into the VHF region.
These small harmonics levels aren’t going to be heard very far at all, compared to the powerful carrier. This means only one thing. A LPF, although a good practice, is not mandatory in this transmitter. But you should better use one so that you comply with the regulations.
Many HAMs use just a watt meter to measure the output of their homebrew transmitters. This is not the proper way of doing it, because the watt meter is a non-selective meter. It will measure both the fundamental carrier and the harmonics, without being able to distinguish them. So in an unfiltered transmitter, or in a transmitter with a simple (often non measured) LPF, this way will give a totally false reading of the output power of the transmitter at the set frequency.
The proper way of accurately measuring the output power of a transmitter and the harmonics levels, is a spectrum analyzer. The FFT available in many modern oscilloscopes, having a dynamic range of approximately 50-55dB, is adequate for this purpose as well. A 50 ohms dummy load must be connected at the transmitter output and then the high impedance probe of the scope, is connected to the output of the transmitter as well. This was the way that the above measurements have been performed.
WebSDR tests
Here are some test transmissions, to determine how far one can get with such a transmitter. I have to say that there is an antenna tuner between the EMTX and my inefficient short dipole (not cut for 40m and not even matched to the coaxial). However I could still cover a distance of more than 2500Km even on the 5W setting.
A screenshot of the transmitter signal, as received on a WebSDR 2500Km away and when the EMTX is set for an output power of 10W.
Below, is a picture and an audio recording of the transmitter signal, as received on the same WebSDR and when the EMTX is set for an output power of 5W.
Photos
Pictures of the finished transmitter. You don’t have to build it that nice-looking if you don’t care.
EMTX prototype built on a breadboard. Yes it worked just fine onto a piece of wood.
This is a phenomenal project, Kostas. Thank you so much for sharing it with us. I love the simplicity of this design–truly form following function. With a little patience, anyone could build this transmitter.
My Red Oxx Micro Manager packed with a full radio field kit
Yesterday, my family packed a picnic lunch and took a drive through Madison County, North Carolina. It was an impromptu trip. Weather was forecast to be pretty miserable that afternoon, but we took the risk because we all wanted to get out of the house for a bit.
Although that morning I had no intention of performing a Parks On The Air (POTA) activation, my family was supportive of fitting in a little radio-activity, so I jumped on the opportunity!
A quick glance at the POTA map and I determined that the Sandy Mush State Game Land (K-6949) was on our travel route. Better yet, the timing worked out to be ideal for a lunch picnic and before most of the rain would move into the area.
Ready for radio adventure
I had no time to prepare, but that didn’t matter because I always have a radio kit packed, fully-charged, and ready for the field.
The Micro Manager pack easily accommodates the entire kit
This 20 year old blue stuff sack is dedicated to antenna-hanging. It holds a reel of fishing line and a weight that I use to hang my end-fed antenna in a tree or on my Jackite telescoping fiberglass pole. The sack also accommodates a 10′ coax cable.
The Elecraft KX2 transceiver, EFT Trail-Friendly Antenna, hand mic, CW paddles, C.Crane earphones, and wide variety of connectors and cables all fit in this padded Lowe Pro pack:
The advantage to having a simple, organized radio kit at the ready is that everything inside has its own dedicated space, so there’s no digging or hunting for items when I’m ready to set up and get on the air.
This level of organization also makes it easy to visually inspect the kit–missing items stand out.
Yesterday I parked our car at one of the Sandy Mush Game Land parking areas, deployed my field antenna, and was on the air in a matter of seven minutes at the most.
Technically, this should read “Activator” parking area! (A questionable inside joke for POTA folks!)
We planned for heavy rain showers, so I fed the antenna line through the back of my car so that I could operate from the passenger seat up front.
I also brought my Heil Proset – K2 Boom Headset which not only produces better transmitted audio than the KX2 hand mic, but it frees up my hands to log stations with ease. This is especially important when operating in the front seat of a car!
The great thing about the KX2 is that it’s so compact, it can sit on my clipboard as I operate the radio (although typically I have an elastic strap securing it better). Since all of the KX2 controls are top-mounted, it makes operation a breeze even in winter weather while wearing gloves.
Since I routinely use the KX2 for shortwave radio broadcast listening as well, I know I always have a radio “locked and loaded” and ready to hit the air. My 40/20/10 meter band end-fed antenna works well for the broadcast bands, as long as there is no strong local radio interference (RFI). When I’m faced with noisy conditions, I pack a mag loop antenna as well.
What’s in your radio go-kit?
Having a radio kit stocked and ready to go on a moment’s notice gives me a great sense of security, and not just for recreational ham and shortwave radio listening reasons.
Sometimes I travel in remote areas by car where I’m more than an hour away from the nearest town and where there is no mobile phone coverage.
If my car breaks down, I know I can always deploy my radio kit and get help from the ham radio community in a pinch. Herein lies the power of HF radio!
If you haven’t built a radio go-kit, I’d highly recommend doing so. Although I’m a bit of a pack geek, keep in mind that you don’t need to purchase special packs or bags for the job. Use what you already have first.
I’m plotting a detailed post about the anatomy of an HF radio field kit. In the meantime, I’m very curious how many of you in the SWLing Post community also have a radio kit at the ready–one based on a transceiver or receiver. Please comment!
Better yet, feel free to send me details and photos about your kit and I’ll share them here on the Post!
Recently, the pace of articles here on the SWLing Post has slowed down. That’s because I live in Swannanoa, North Carolina—a town that was particularly hard-hit by Hurricane/Tropical Storm Helene, which brought unprecedented rainfall and caused widespread destruction.
At one point, two families had to be helicopter-evacuated for medical reasons, and less than a week after the storm, the Sheriff’s department came door-to-door recommending evacuation.
Using the local repeater (N2GE on Mount Mitchell), I was able to pass wellness checks, coordinate helicopter evacuations, and arrange supply drops for our community. I handed out a few handy talkies to unlicensed neighbors so we could stay in touch.
For that first week especially, amateur radio truly was our community’s connection to the outside world.
Here at SWLing Post HQ, I shared my extra portable radios with neighbors who needed them. I used my CC Skywave SSB 2 in the kitchen window to tune into local news on 99.9 MHz and 570 kHz. I also relied on my XHDATA D-109 and CC Radio 3—they became our constant companions for information.
Over the past few weeks, many of you have reached out with kind words and support, and I can’t thank you enough!
Thank you also to the contributors who have kept the SWLing Post running during my absence, and a special shout-out to my friend Vince (VE6LK), who has taken on a huge role in keeping QRPer.com updated.
