Tagged: RF spikes
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January 11, 2020 at 10:07 pm #537btuv25Participant
Tuning across FM broadcast, VHF and UHF there are many spikes across the spectrum. They go away when I detach the antenna, but don’t seem to be something I am actually receiving. They do not respond much to various RF and IF gain settings. Any ideas what may be causing them? I have attached screenshots of SDRuno and SDRconsole. Thanks.
Attachments:January 12, 2020 at 11:47 am #540Andy2Participant
Hi. Could be lots of things, including radiation/conduction from your PC or anything that uses digital technology. First checks would be:
Try a different USB lead.
Is the braid of the antenna coax properly connected?
Where is the antenna located?January 12, 2020 at 3:34 pm #541diysdrParticipant
I see all kinds of things like that too and for whatever reason they just don’t get in the way of my receiving. Sometimes I’ll dial into them to see if I can hear anything intelligent and so far it just sounds like a constant carrier moving around. I think with conventional radios we dial around and just don’t notice them unless they are interferring with something that we are interested in.
I did what Andy suggested, put a dipole antenna as far away from the house as possible and brought the signal in with coax. that makes the noise floor drop down to the good old fashioned atmospheric noise that’s always there so then these noise spikes are not so noticeable. I understand its not an easy thing for someone living in a condo or apt or a neighborhood with self appointed HOA sheriffs.January 14, 2020 at 2:36 pm #550btuv25Participant
I tried a different USB cable (with noise suppressor) but that did not help. Then I found a bad ground on an antenna patch cable, that got rid of most of the spikes. Thanks for the replies, it motivated me to dig deeper.
BTW this highlights a feature of the RSP1A – it is very sensitive. When I used the same patch cable on my GRE PSR-600 there was no apparent problem. Turns out the RSP1A is much more sensitive than the PSR-600.January 14, 2020 at 8:27 pm #553merlinmaxwellParticipant
This is one “problem” with SDRs and waterfall displays, you can see much more than you can hear. Modern ones (like the RSPs) make it worse subjectively. I take a pragmatic view, if the “spike/sprog/thing” isn’t in the way of me listening then it is OK. I have a few SDRs (some quite expensive) and they all see a few spikes.January 15, 2020 at 6:06 pm #555diysdrParticipant
OTOH, I just connected a usb/rs232 cable for CAT on my TS50 and wow. solid s6 noise everywhere so something is going to have to give. I shudder to think what a panadapter view would look like. Let your ear decide if its a problem or not.January 17, 2020 at 3:23 pm #562Andy2Participant
Merlin makes a good point, and it’s one I’ve also made in the past. A spectrum/waterfall display will show all the horrors of images, IMD and other unwanted rubbish all at once and straight away the user wonders what is going on – surely these SDR’s cannot be *so* bad?
That’s because we’ve all been brought up without such luxury and simply haven’t been able to see all that junk, only being troubled by it as we briefly tune through it when twirling the tuning knob.
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