Hello Everyone!
I received my LimeSDR last week and am enjoying it.
I’m getting inconsistent results with different SDR tools and need some advice on the settings I should be using.
My applications include the HF/VHF/UHF ham radio spectrum as well as higher frequency applications. In all, my use cases cover about 3 MHz up to 3 GHz.
I began by removing the MN26 inductor to unlock HF frequencies on RX1_W.
Using SDR-Console, I verified that my LimeSDR can receive HF. I was able to clearly see and hear the 14.1 MHz beacon as well as JT65 signals as far down as 3.576 MHz (80m band).
However, I haven’t been able to tune in HF frequencies using either Pothos or Gqrx. When I tune to 88.5 MHz, I clearly see and hear our local FM station at that frequency in both programs. However, when I tune to the HF frequencies that work fine in SDR-Console (such as 14.1 MHz mentioned above), all I see is low-level noise across the band.
It seems likely that I have some of the settings wrong in Pothos and Gqrx. As far as I can tell, neither program is able to set the LimeSDR carrier below 50 MHz. To tune in HF frequencies as low as 3.5 MHz, the bandwidth has to be set to 100 MHz, so that the lower half of the band covers the HF frequencies of interest. Is that correct?
That allows me to tune to HF frequencies, but as I said, they look dead except for low-level noise.
I have my sample rate set to 10,000,000 samples / second as recommended in other threads in this forum. I can’t go higher on this particular PC because it only supports USB 2.0. Could that be the problem? Do I need a higher sample rate to capture 100 MHz of bandwidth? When I zoom in on the low-level noise, it looks heavily quantized, both in frequency and amplitude. Is that a symptom of a low sample rate?
I’ve played with the gain settings (LNA, TIA and PGA), but all they do is shift the noise up and down. I have also verified that disconnecting the antenna or switching antenna inputs drops the noise level as expected, so I don’t think the antenna setting is the problem.
Can anyone who has HF working in Gqrx or Pothos share your settings and/or a working project file with me?
Any and all help would be appreciated.
Thanks!
—Gary, W6ARY