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Old 28-Nov-2020, 1:26 AM   #90
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,747
Quote:
Originally Posted by tripelo View Post
Can the Airspy not scan & display a narrow 8-10 MHz region like the RSP1?
The Airspy R2 can scan 8 MHz with the SDR# software, similar to what the RSP1A does with the SDRuno software. It is important to set the gain at the correct level to obtain the proper presentation of the SNR; too much or too little will show the wrong SNR. Increase gain until the adjacent noise floor just starts to rise and the signal no longer increases in strength. That point should show MAX SNR.



R2 and Spectrum Spy at 10 MHz width:



Quote:
When the RSP1 scans from say 45 MHz to 80 MHz,
does the spectrum look like the Airspy R2 spectrum at the lower part of Channe 3?
As I said earlier, the RSP1A can only scan 8-10 MHz with the SDRuno software. It can only do a wider scan using the RSP Spectrum Analyser software (the software that you said has too many spurs). Some of the "spurs" are actually pilot carriers of weak ATSC signals. Some are noise spikes. Some are clock spurs that can be removed before a scan.

50 MHz width with RSP1A and RSP Spectrum Analyser:



I don't actually have an RF channel 3 in this area, or any 2-6 channel. That is why I bought the Thor modulator to simulate an RF 3 ATSC channel. I have been studying the affect that a high noise level has on the reception of VHF-Low channels.

I first became interested in that project while trying to help a Canadian receive RF 2 and 4. I thought a CH3 folded dipole had a chance of receiving both. He was having no luck using an FM folded dipole of twinlead with 30 gauge conductors. I encouraged him to make a CH3 FD with larger diameter conductors, but he seemed unwilling to do it. I suspected that he had sufficient signal strength, but a high noise level. He was able to receive 9 OK.







I have two CH3 folded dipoles. I have one connected to the output of the Thor modulator. The other is connected to my SDR or a TV. It picks up the CH3 ATSC signal from the Thor modulator as if it were an OTA signal AND the ambient noise. This tells me how much stronger a VHF-Low signal needs to be for a sufficient SNR above the ambient noise.

If you want a specific test done, I could set it up over the weekend. I don't keep the CH3 folded dipoles set up in my room. I would need to know exactly what test you want me to do.

I could try to do 45 to 80 with all three SDRs, but it would require both CH3 folded dipoles to pick up the ambient noise.
Attached Images
File Type: jpg CH16withAirspyR2_1.jpg (89.2 KB, 3407 views)
File Type: jpg CH16 with Spectrum Spy at 10 MHz width_1.jpg (93.2 KB, 3403 views)
File Type: jpg 11-1-2020 RSP SpecAnal-17dBamp_2.jpg (136.4 KB, 3402 views)
File Type: jpg cyclist44DHCreportTVF3.jpg (61.6 KB, 3400 views)
File Type: jpg cyclist44DHCantenna_1.jpg (228.2 KB, 3396 views)
File Type: jpg PET10-8110twinlead2.jpg (74.0 KB, 3398 views)
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Last edited by rabbit73; 28-Nov-2020 at 2:04 PM.
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