xb-200 and the MF band

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xb-200 and the MF band

Postby belza » Fri Feb 24, 2017 7:25 am

Hello,
Some time ago I purchased a xb-200, which I finally got the time to install and test. The idea was to tune some AM broadcasts in the MF band to show our students. However, although I can see/listen to FM radios, at the MF band I see mostly nothing.
As an antenna, I first tried using a simple telescopic (the same I use for FM), but I've tried several other more "homebrew" solutions (such as making a long cable), to no avail.
Any ideas/suggestions? Maybe someone's used the xb-200 to successfully tune an AM radio?
best
Pablo
belza
 
Posts: 12
Joined: Thu Nov 20, 2014 12:32 pm

Re: xb-200 and the MF band

Postby bglod » Mon Mar 20, 2017 1:50 pm

AM in general might be difficult because of how low the frequencies are, but I am able to receive some AM stations in Gqrx. I found I had to play around with the bandwidth, sample rates, and offset tuning. I also had to touch my telescopic antenna to receive the stations. I also noticed saw one or two strong FM stations down in the AM bands (harmonics?). My Gqrx settings are listed below. I hope it helps get you closer to a working setup.

My XB-200 filter path is "custom" but am just using straight SMA cables, no filtering.

Device string: bladerf=0,buffers=128,buflen=8192,transfers=32,xb200=custom
Input (sample) rate: 1000000
Decimation: none
Bandwidth: 1.5 MHz
LNB LO: 0.0

In Gqrx, I set the demod to AM, squelch at -90 dB, frequency to 1 MHz, and offset tuned to each signal spike I saw. In Rochester, NY, I was only able to see 1040 KHz (very weak), 1180 KHz, 1280 KHz, and 1370 KHz.
bglod
 
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Joined: Thu Jun 18, 2015 6:10 pm

Re: xb-200 and the MF band

Postby belza » Thu Apr 06, 2017 9:16 am

Thanks for the pointers, but I still don't get an AM station. As you mentioned, I get a couple of FM stations (may be harmonics, probably from the absence of an RF band-pass filter, but that's just my guess), and some veeeery weak signals, which may (probably not) be AM stations, but I only get noise. Guess it cannot be done with my current setup.
best
belza
 
Posts: 12
Joined: Thu Nov 20, 2014 12:32 pm


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