SDR Starter problem

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m3ghe
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Joined: Sat Aug 08, 2020 2:58 pm
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Re: SDR Starter problem

#41

Unread post by m3ghe »

mbzadegan wrote: Mon Oct 12, 2020 6:36 am
m3ghe wrote: Mon Oct 12, 2020 6:02 am What is this other antenna that you have connected? Description please. You will need at least 10 metres of wire with an earth connection to receive anything.
woww, really!!
I have connected only 2m of single wire direct to the connector hole but still no vocal sound on any frequency.
Do you suggest 10m for AM frequencies?
Absolutely and that is still very very short. Ideally the shortest passive antenna for the 700kHz frequency for instance would be 428 metres. Your 2 metre wire is the shortest length you should use at 70 MHz!
The longer the wire the better, get it outside and stretched out. You will also need a good earth.

Remember the lower the frequency the longer the wavelength and the longer/larger the antenna. The higher the frequency the shorter the wavelength and the smaller/shorter the antenna.
Martin
m3ghe
IO92sc
G-QRP club 6129
Use my online radios http://remoteradio.myddns.me/ or http://remoteradio.changeip.org/

jdow
Posts: 800
Joined: Mon Aug 10, 2020 8:17 pm

Re: SDR Starter problem

#42

Unread post by jdow »

Martin, that's a little excessive. 2 meters should provide enough signal to hear something. I don't have one of those ripoff boxes myself so helping him further is not possible. I have a dongle I could open up and attach an antenna to it. But, "it just ain't gonna happen." What a user feels it SHOULD do and what one can reasonably expect it to do and what I suspect is all it can do are three different things. And it MAY be that the Q input is damaged. The proof for that would be somehow making it work on SDRSharp or some other SDR program. Then we can fuss about control settings. One thing I will repeat, though, is that he should not set the center of the spectrum display below 1.2 MHz with the 2.4 msps sample rate option, the only one I contemplate using because it gives me decimation gain after the artificially constrained 8 bit samples over the USB wire limitation. At least setting it there gets rid of some artifacts that may obscure getting other parts of the problem solved.

{^_^}

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m3ghe
Posts: 140
Joined: Sat Aug 08, 2020 2:58 pm
Location: Bedford
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Re: SDR Starter problem

#43

Unread post by m3ghe »

jdow wrote: Mon Oct 12, 2020 1:10 pm Martin, that's a little excessive. 2 meters should provide enough signal to hear something. I don't have one of those ripoff boxes myself so helping him further is not possible. I have a dongle I could open up and attach an antenna to it. But, "it just ain't gonna happen." What a user feels it SHOULD do and what one can reasonably expect it to do and what I suspect is all it can do are three different things. And it MAY be that the Q input is damaged. The proof for that would be somehow making it work on SDRSharp or some other SDR program. Then we can fuss about control settings. One thing I will repeat, though, is that he should not set the center of the spectrum display below 1.2 MHz with the 2.4 msps sample rate option, the only one I contemplate using because it gives me decimation gain after the artificially constrained 8 bit samples over the USB wire limitation. At least setting it there gets rid of some artifacts that may obscure getting other parts of the problem solved.

{^_^}
For a dongle in DS mode with no amplification 2 metres is no good for MF. He will need at least 10 metres to get any sort of signal on those frequencies. I have a RTl-SDR dongle here and just 2 miles away is a commercial station using 250 watts into a full size 1/4 wave vertical on 792 kHz. With a 2 metre length of wire I get little or no signal from that transmitter. Use an upconverter and of course the situation changes. Video attached.

Martin
m3ghe
IO92sc
G-QRP club 6129
Use my online radios http://remoteradio.myddns.me/ or http://remoteradio.changeip.org/

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