G8JNJ
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Yes I can see the problem you have. The top side of the antenna needs to be facing upwards with a clear view of the sky. In your case I think it would be worthwhile trying to extend the GPS cable. Either with a purpose bought male to male SMA cable…
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Hi Richard, At the time I was trying to avoid distortion and additional aliasing signals in the passband whilst I was investigating the sweeps, so used the same setting when making the frequency response measurements. But I understand the valid poin…
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Hi Richard, That's slightly different to what I measured, but it shows a similar trend apart from between 3 and 5.5kHz. At 6kHz I measured -10dB, which is close to your value. I used 0.5kHz deviation to try and keep the high level modulation sideban…
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Yes that worked, one of the few combinations I didn't try. The problem is that in order to work with all of the waterfall options they have to be fairly neutral non rainbow colours. Cyan and Magenta stand out really well and work with most of the o…
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WRT the colours Shades of Light Grey look quite good for the spectrum. #b3b3b3 or maybe #999999 However I can't get spec.peak_color1 or spec.peak_color2 to work for me. I tried a few variations of syntax, and had a very quick look through the code t…
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Update On a hunch I decided to try demodulating a plain carrier signal using NBFM, AM, SAM, I/Q and SSB. Just to check tha twhat I was seeing wasn't due to a problem with the signal generator. The same issue is occurring with all the modes. As soon…
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Hi John, Some sweeps made today at a low modulation index using 12kHz RX bandwidth. Frequency De-emph off De-emph on Predicted 400Hz 0dB 0dB 0dB 600Hz 0dB -2dB -3.5dB 120…
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For the best results the supplied GPS antenna should be sitting on a metal surface, as it needs some sort of 'ground plane' to function to it's full ability. I have one on a metal plate, inside a waterproof box, mounted outside, feeding two KiWi's,…
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Hi John, To the ear that sounds better when listening to noise (not many nbfm signals around at the moment). I'll do some more tests tomorrow and report back. Thanks again, Martin
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Hi John, Sorry I just realised that should have tried to measure the de-emphasis at the frequencies you used in your simulation. I'll try and do that in future, if it is required. However my figures and your predicted curve are a pretty good fit up …
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I later realised that there was a flaw in my thinking, as the FM noise floor will produce the maximum demodulated output and the AM noise floor will be at a minimum. Instead I decided to compare the recovered audio from a signal modulated with a 40…
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Hi John, I just made some further comparisons of the broadband background noise level for each of the modes, using the same arbitrary volume settings. The levels will be different again when demodulating actual signals, but I thought this may be a g…
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Hi John, I can't guarantee that these first sweeps are 100% correct. I generated them by feeding an audio sweep into an Icom IC3000 transceiver set to wide filter width. First the KiWi without any de-emphasis. https://forum.kiwisdr.com/uploads/012/…
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Hi John, Excellent additions :-) The new de-emphasis values make listening much less fatiguing, the narrow nfm setting sounds slightly muffled to my ears at first listening, but there is not much to lisren to at the moment, so I'll reserve my judgem…
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Hi All, A bit of an old thread, but I've just go around to putting my home KiWi inside a screened metal box in order to try and cut down on the overall amount of RF noise in the workshop. As part of this I thought I would try one of the MP1584 DC-DC…
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Hi John, Thnaks again fo doing this, you wouldn't believe how much of a pleasure it now is monitoring NBFM stations with the KiWi. In fact I'm considering permanently adding the 2m convertor (and possibly others) to my home KiWi. I don't think you n…
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Hi John, Thanks for looking at the NBFM problem. The new version is a VAST improvement, and as well as making the audio much more pleasant to listen to, it also seems to have improved the squelch action too. If you have the time, or the inclination,…
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OK I've forwarded the original emails.. If your generator will accept an external AF modulation input, you can use the audio generator in Soundcard Oscilloscope. This can also generate audio sweeps, which may be useful in conjunction with the scope …
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Hi John, Thanks again for taking a look at this, as it's been bothering me for a long time. I think that all that was originally asked for was the ability to quickly toggle between an RF bandwidth or 12kHz and 6kHz, so that it is easy to swap betwee…
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I think the high amplitude short duration noise spikes could also be the reason that the KiWi's NBFM squelch is so 'choppy'. It seems to require a much larger value to be set beyond the initial point of muting, before it stops opening up every few s…
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https://forum.kiwisdr.com/index.php?p=/discussion/comment/15456#Comment_15456 The use of the terms WBFM and NBFM are purely a "short hand" method of distinguishing between two general groups of modulation deviations and the pre/de-emphasis…
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Just found this evening in the UK, GYA Northwood on 2169.5kHz but not on the published frequency of 2618.,although it is present on the other published frequencies. Transmitting Surface prognosis at 20:24 which is in agreement with the published sch…
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Hi Richard, Good point about the spectrum without de-emphasis. I'd forgotten that bit of theory. It does suggest that there may be something wrong. Incidentally, I've also been looking at radars using the KiWi on the lower VHF bands. These links may…
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Whilst on the subject, I thought I'd investigate the 'rough' sounding NBFM demodulation that the KiWi produces. I made some comparisons between the NBFM audio output from an Icon IC7000 amateur transceiver just tuned to a quiet part of the 10m band …
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https://forum.kiwisdr.com/index.php?p=/discussion/comment/15446#Comment_15446 Ah no, please don't add that without being able to tuRn it off. It's often the only way to identify some signal from their tone frequency. It would be nice if there was to…
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Yes I was thinking about this too, and it's a good suggestion, especially now that conditions on the upper HF bands are improving, where NBFM tends to be used a lot. The incorrect De-emphasis value for NBFM is still a bit annoying though. Regards, M…
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https://forum.kiwisdr.com/index.php?p=/discussion/comment/15396#Comment_15396 Hi Glenn, I have used WSPR Daemon with good results, but unless you have set aside some KiWi channels to allow it to run, it's not really applicable to the average KiWi in…
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Yes that's the problem. If you take a look at the SNR graphs in the link I previously posted, you can clearly see the day / night variation on 'good' KiWis but this is not evident on a 'bad' one with spurs and noise. By measuring a KiWi's SNR variat…
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Asa follow up, I posted some suggestions regarding SNR ratings on linkfanel Github page. Including some example graphs and observations that folks my find interesting, or wish to comment on. https://github.com/priyom/dyatlov/issues/5 Regards, Martin
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Just some thoughts on the subject. I wish the map and listings could provide a bit more information about the performance of the web sdr's, and also the KiWi selection map markers in the TDoA extension. I admit I'm a bit biased about this, as one of…