Signals disappear

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Joined: Tue Jul 21, 2020 5:49 pm

Signals disappear

Post by chris_yorks » Tue Jul 21, 2020 6:06 pm

Hi from Yorkshire,
Fairly new to SDR and using the Nooelec NESDRsmart dongle with a home made discone antenna I have received some very good voice signals across a variety of bands.
Today was dismal though. I appreciate bands open up depending on weather conditions but very little activity with the same settings and setup.
I did notice a lot of unusual peaks on the spectrum and trying to tune to these, they moved away almost as if I was generating the signals myself with the laptop. As I said, same setup each day.
Would I need to add some sort of filter to the antenna line possibly? I know its difficult to diagnose for me, but do you think I could be generating signals and when trying to tune to the peaks, they drift off?

Anyway, it is fascinating what can be found and living by the sea, the coastguard / lifeboats come through well as does a lot of air traffic, and plenty of amateur stuff around 27mhz. We get quite a bit of military aircraft off this coast and have picked them up too so not bad for the home made antenna. Even had some gliders chatting and they were a good 90 miles away - I was watching them on Freedar at the same time.
Shame about tonights reception - any pointers would be helpful.
Thank you

Posts: 14
Joined: Tue May 26, 2020 5:27 pm

Re: Signals disappear

Post by LAH » Mon Aug 03, 2020 11:11 am

I have experienced this a couple of times, just like you described. I find a signal browsing around (usually happens in UHF), try to tune in but it seems to move away changing frequency as i try to tune in. I thought it could be internal to the dongle rather than an actual signal, maybe a byproduct of an overloaded dongle? Mine looks a lot like USB noise. It could have helped to listen, could have given a clue of the source but this is not possible since you can never tune in. I also lack the knowledge how these dongles actually work when tuning in so this is no more than speculation but I would also like to know what's going on.

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