Many thanks to SWLing Post contributor, Pedro Andrade, who writes:
Hi Thomas!
I’m a noob when it comes to DXing, I only got into the hobby late 2020, and I got to say: I’m hooked. So, sooner or later, I would hit your website/blog. For that, and the continued work in every aspect of the hobby (technical issues, tips, tricks, schedules, etc), I thank you from a noob perspective and from someone that believes the internet is beautiful when it comes to sharing and getting communities together.
That said […]the reason for writing this email, is that I found out that the ETM scan could be very much improved on the Tecsun PL-310et (and I think others).
You simply change the filter sensitivity prior to the scan: the higher the filter the lower the sensitivity. The lower the filter (1 kHz) the higher the sensitivity and thus more stations caught by the scan.
Here’s a video showing it in action:
I hope you find this useful and worth sharing for your readers.
Thanks again for the continued work on the radio side of things.
Regards, Pedro.
What a brilliant tip, Pedro! Thank you for sharing and also for demonstrating in your video! Also, thank you for the kind words about the SWLing Post–an amazing community of folks like you and a pure labor of love!
Hello. My radio came to me with the frequency in MW of 522 – 1620 KHz. I don’t know how to change it to 520 – 1710 KHz. Some help?
Hello Valdy,
I do not have the Tecsun PL-310ET, but I do have the similar PL-380. And I would try this for the MW/AM Step Setting:
“Turn off the radio, long press [9/10 kHz] button until ‘9 kHz’ or ’10kHz’ appears in the display. By long pressing again, the alternative band step would be shown. The temperature is also shown on screen at the same time.
In general practice, the frequency step of 10 kHz is to be used for broadcasting MW(AM)
as well as the temperature in the degree of Fahrenheit (?) for use in North America.
In order to provide convenience to the end users, the ’10kHz’ of frequency step is default to be displayed with temperature in the degree of Fahrenheit (?) together as well as ‘9kHz’ to be displayed with temperature in the degree of Centigrade (?) together.
If the display shows ’10 kHz’ with degree of Fahrenheit (?), the radio is set to 10 kHz step for MW(AM) and temperature display is in Fahrenheit (?) for the North America region.”
I hope this helps.
Dear Roger Fitzharris
Thanks a lot for the help. What was strange for me was the connection between temperature and kHz bandwidth. Go figure…
73 of Porto Alegre (BR)
Dear Valdy,
You are welcome — glad to be able to help. I also find it interesting that our Canadian neighbors, in North America, are stuck with the same problem. A 10 kHz AM bandwidth, but would prefer the metric temperature display — in degrees Celsius. 73 from SW Ohio (US)
Receiver bandwith and sensiivity.
Pedro Andrade came up with a very good idea yesterday, showing how to increase the sensivity of a receiver by decreasing the receiver bandwith. This fact was discovered by the pioners already during the very first years of radio communications.
Therefore, it makes me sad to read comments like: “..the filter is for selectivity and not sensitivity”. This only demonstrates the writers lack of knowledge. So maybe Pedro’s article can be an eye-opener for people that want to learn how radio communications really work? Many of the new digital modes work solely because the selectivity is decreased to a minimum.
I enclose a screen dump of the start of a paper discussing receiver sensivity in a scientific way.
The full paper can be downloaded as a PDF file from:
https://www.phys.hawaii.edu/~anita/new/papers/militaryHandbook/rcvr_sen.pdf
So thanks to Pedro for reminding us of this obviously forgotten knowledge.
Happy listening!
LA2PJ – Egil
Thanks for the kind words. I actually read about this somewhere in the we the next week after i got the radio (early january 2021), so i decided to give it a go. guess it did worked.
thanks again 🙂
The usual standard for FM signals is a 75 kHz deviation for the highest volume and for the highest frequency at the same time produces a bandwidth of 200 kHz. This is true for mono and stereo signal.
For those of you in North America, hybrid HD radio uses a total bandwidth of 400 kHz.
If the receiver bandwidth is less than the transmitter bandwidth distortion will rise and the sound becomes mono.
By comparison DRM on frequencies above 47 MHz is 96 kHz and channelisation is 100 kHz. Thus it is possible to transmit up to 4 DRM channels inbetween existing FM transmissions. Each of those DRM channels commonly will carry 3 audio programs.
So that those with mechanical tuning it is usual to allocate FM transmitters on the same site to be 800 kHz apart. This makes it easier for listeners to select stations. Those transmitters in adjacent areas use the same 800 kHz spacing but are offset by 400 kHz to the adjacent site.
As you can easily see from my ham radio callsign, I talked about European conditions. I also made clear that such a reduced bandwidth reduces audio fideiity. But if you reduce the bandwidth for an AM signal to 3 kHz or even less, you will hardly understand anything. But that was not what this blog post was all about.
Sensitivity vs. bandwidth is a very basic concept that is used in many fields.
If the band is free, a smaller bandwidth cuts away on noise – from the antenna, but also from the receiver.
In congested conditions, you might be able to find a weak signal between much stronger ones.
This is especially true for SDRs (software-defined radios) where you can see the spectrum and narrow the receiver bandwidth continuously. You can even select a single side band of an AM signal to avoid a strong signal on the other side.
An especially interesting usage is in the FM broadcast band: Nominally, each program needs 300 kHz of bandwidth. Most of the energy of an FM signal is near the carrier frequency. This is used to pack more transmitters into the band by spacing them in a 100 kHz grid. It is not unheard that two transmitters in an area are spaced by 400 kHz or so.
If you can reduce the bandwidth of your receiver to 100 kHz or even a bit less, you might be surprised about how many new programs suddenly appear. True: The narrow bandwidth reduces the sound fidelity. But this is not the problem for a DX hobbyist.
Will this same tip apply to my Pl-880?
Larry, I can’t honestly say for sure. I don’t own one. My next upgrade will be a pl-680. But give it a go and tell us. I think it should work if it has ETM.
thanks.
So, the question is, is this actually a feature? As someone else notes, narrowing filters is a selectivity action not a sensitivity action.
Dan,
Yes, that’s right.
But in this case, I can see the OPs point. Selectivity … changing the BW … is what one does to separate adjacent signals (rejecting unwanted signals) and/or finding the best BW to “lock-in” to a particular signal. But in the OPs example, he’s decreasing the BW because via ETM the radio is actually capturing (saving) more signals, more “potential” stations. Thus if one – hypothetically – uses ETM & captures (saves) 20 stations in ETM memory with a lower BW versus 12 in ETM memory with a higher BW, his radio is [appearing to be] more sensitive (because sensitivity is the ability to detect signals).
Of course, are all of those stations captured in ETM memory going to be strong enough to effectively listen to? Probably not, but the OP can whittle down the 20 “potentials” in his lower BW scan versus 12 at a higher BW. Since he *potentially* captures/saves/detects more signals, I guess technically you should also say it’s more sensitive because when comparing two different receivers, if one radio picks up 20 and the other 12 we say the first radio is more sensitive.
Thank you both for commenting. indeed, from my experience, i get more stations, however say 15 to 20% of the extra stations are inaudible or hard to listen to.
I use ETM to get me my SW fix at lunch time during work. easy quick and simple. 🙂
have a great week.
One correction, the filter is for selectivity and not sensitivity.
*Personally I see no practical use for scanning the full HF to fill up the memories here but your end might be different.
I use the ETM scanning feature of the Tecsun radios a lot. A quick scan of all the bands give me a fast way of determining how the bands are doing. If the scan shows only a few stations, then I know the propagation is not very good. If I see a lot of stations then propagation is better. A quick look at the first few stations found will tell me the the lowest range of frequencies that were received while the last few station will tell me the upper range.
I find it very useful for getting a quick idea of band conditions. After doing the ETM, I then have an idea whether I should be concentrating on the upper, lower or middle SW bands for further tuning.
73
Bill WD9EQD
Smithville, NJ
Bill,
An absolute great comment, Sir … I’ve done that to essentially gauge the current propagation, but I never fully engaged my own thought process to break it down to “upper, lower or middle SW bands”. Thanks mate!
Great info, Pedro – we all learn from each other! Cheers!
Indeed we can. Sharing is caring 🙂
thanks for your kind comment. have a geat week.
What a great tip. I expect this should work on my PL-380 as well, as it also has ETM tuning and a bandwidth selector. I’ll give it a try. Thanks!
Hello Paul,
Don’t know whether you got to try Pedro’s technique or not?
But I was curious enough that thought I would give it a try on my PL-380. Using only the whip, and the narrow (1 kHz) and wide (6 kHz) bandwidth settings. I ran two sequential ETM scans, starting at 1800 UTC. With the bandwidth filter set at 1 kHz, I was able to copy 10 stations. On my second ETM scan, with the bandwidth filter set at 6 kHz, I was only able to copy 2 stations.
Thanks Pedro for sharing your observation.
Cheers and 73
Glad it could help and you can enjoy your radio a bit better.
73s 🙂