Low power HF AM and FM: How far and how good?
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- Опубликовано: 29 сен 2024
- How far can you go with low power AM around 7 and 3.5 MHz? Does Narrow Band FM work better? What about slope detecting FM on an AM receiver? Discussion and on-air demonstrations with web SDRs here.
Contents:
0:01 Introduction
2:40 Evening tests on 7 and 3.5 MHz
13:08 Morning and daylight tests on 7 MHz
23:05 Slope detection test
22:55 Summary
28:41 Books
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You should also have used CW in comparison, just as a comparison. CW into SSB, CW into AM. A1A vs A2A vs F2A. It is a mind bending experience. Well done experiments. I did similar but not so extensive. Really well done. Thank you.
Have already done CW vs SSB. It's here: ruclips.net/video/t40UO1Trkjk/видео.html
@@vk3ye Wow! Thank you very much! I watch that and of course you deserve a fine upvote for your work OM + de DL7HH dDdDd
Just before watching this vid (I can't now), I'd like to say that while there's a lot of things that have an impact on how far a transmitter can be heard on a certain frequency, some outstanding results can occur :) A low-power MW station has appeared recently from near Milano, Italy on 1575 kHz, and while the operator said he currently runs it at just 10 watts into a 50m folded dipole, it was heard pretty well in The Netherlands. In fact, if that's the same station I've noticed already back in October 2022, then I've managed to hear them here in Poland, and even on a KiwiSDR as far away as North Sweden ✈️ although both receptions were made using some dedicated RX antennas (a terminated Delta here, and a 4-square there). The thing is 1575 kHz is now a totally empty channel across most of Europe, vacated by Italian public broadcaster RAI in September 2022.
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NBFM is doing surprisingly well 🙂
Hi, I was working on a low power AM transmitter at 4 watts running in to a random length wire laid on the plastic roof of of a garage with the rig set on 29.600 Mhz FM. This was in the south east UK. Whilst testing the microphone I received a call from a station in Norway who gave me a 59 from his set.
Admittedly his antenna was a beam fitted on a 100' tower and his QTH was on a mountain side in Norway. But for me with 4watts into a short wire laid on the roof of my garage I was very impressed! Just goes to show you never know what can be done until you try it :) 73 de G6PBS
Very nice! Is there a schematic available for your build? Im looking to build something like that for 10M. Most of the projects i see are for other bands and i don't know enough yet to say scale the Beach40 or NorCal to 10M
@@youtubeaccount931 Sorry this was many years ago. All I remember was it was an old CB radio and I had some paperwork I found online and was using this. The rig has gone many years ago. I suggest getting an old AM/FM CB and search online. It used to be a common tweak in order to get on 10 Meters cheaply.
I forget I can do this. There is a very good SDR receiver (KPH) about 300 miles from me.
I appreciate you doing these videos, good knowledge.
Any more DSB projects? G7VFY
Well, it seems that the best overall results were on ssb.
very curious
Peter, what is the lowest frequency you have ever worked or listened in on ?
472 kHz transmitted. 135 kHz received.
Aren't differences too big? Am thinking maybe all AM receivers are lower quality than SSB. Not considering the hardware problems, the difference is in theory a precise number of dB.
"In theory". Yeah.
@@MirlitronOne and the explanation is?
@@MirlitronOne AM should have at most 3 dB noise more than SSB, considering all effects i can think of, and lower distortion than SSB. However, the AM receiver must be equiped with crystal filter and diplexer, or else some 3 dB more would be added. Is there something i am missing? Am convinced the amateur AM receiver lines are all of poor quality, cause nobody wants AM anyway. Do you know something that explains?
Not sure what the mic element is in your mic, Peter. My MH-31 has been modified with an after market element and the toggle switch on the back is used to select SSB or FM, to provide a different equalization (reduce bass for SSB iirc). I have an inline audio compressor, but I don't use it on FM fearing it might sound too boomy.