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Terrible sensitivity?

Posted: Mon Jul 02, 2018 7:06 am
by txjacob
I recently built a QFH antenna for receiving NOAA weather satellites. I did some initial testing with my kenwood handheld and got a strong clear signal, however when I hooked the antenna up to my BladeRF it couldn't see anything. I even turned up all the amplifiers and nada. Do I need to add an LNA to my antenna to get it to pick up anything? It seems like the sensitivity should be better...

Re: Terrible sensitivity?

Posted: Tue Jul 10, 2018 9:39 am
by bglod
The NOAA satellites are at 137 MHz, so I assume you are using the XB-200. There are some additional losses that occur on that board in addition to the bladeRF itself, so you may need an LNA. What is your filterbank set to on the XB-200? The custom path is probably where you want to be, and either using a cable to jumper across the RXFILT SMAs (no filtering), or if you happen to have an external filter with 137 MHz in the pass band, that may be helpful.

Re: Terrible sensitivity?

Posted: Tue Jul 10, 2018 9:55 am
by txjacob
I've tried using custom as the filter with a FM bandstop, and a LNA behind it. At this point the BladeRF could just barely pick the signal out of the noise. It seems odd to me because my RTL-SDR can pick up an incredibly strong signal with the same configuration.

Re: Terrible sensitivity?

Posted: Thu Jul 12, 2018 12:34 pm
by rtucker

I'd like to make sure everything is hooked up correctly. Can you verify that:

- RXIF on the XB-200 is connected to RX on the bladeRF
- RXFILT and RXFILT-ANT are directly connected via SMA cable (if using the xb200=custom setting)
- RXANT is connected to the antenna

Also, it's very unlikely unless this is a very old board, but ensure that R62 and R63 are not populated (see ... 62_R63.png).

Could you also try receiving a signal above 300 MHz, with and without the XB-200 connected? This will use the internal bypass path on the XB-200, and should yield similar results (minus a bit for insertion losses) as having no XB-200 connected.