Re: [Discuss-gnuradio] WBX Lo leakage to LFRX

[Ralph A. Schmid, dk5ras]

Hi,

 

The box is the first step; you also need to block the power supply line against any incoming RF, your 10.7 MHz IF out needs a low pass filter that cuts off all higher frequencies coming back in on this path, and your 433 MHz in needs to be shielded 100%, with some double shielded coax or semi rigid.

 

The LO strays quite a bit, it is not a very good idea to have a second RX on the same frequency in one box...the fun with direct conversion receivers :-)

 

Ralph.

 

 

 

From: address@hidden [mailto:address@hidden On Behalf Of Nemanja Savic
Sent: Tuesday, December 10, 2013 3:49 PM
To: GNURadio Discussion List
Subject: [Discuss-gnuradio] WBX Lo leakage to LFRX

 

Hi all,

As I described in one of my previousposts, I wanted to have several receiving paths for 434 MHz, and my USRP is equipped owith WBX and LFTX. So WBX is one, and for the other, I designed small RF frontend using TI's CC1000 that donwnconverts the signal to 10.7 MHz which can be used with LFRX. Now the problem is that i have like 30 - 40 dB spike in the spectrum of received signal at LFRX thata comes from the LO of the WBX. Is there any suggestion how to supress this signal, but first from phisycal point of few, and later if not possible trying to use some DSP manipulations. Namely, I packed new frontend in the alu box, so it's kind of shielded, but it didn't help that much.

Thanx,

--
Nemanja Savić