AOR 5000 as front end to USRP


#1

Hello,

Does anyone use a AOR 5000 as a front end for the USRP? The docs for
the USRP say that it is not very sensitive but I thought the IF Output
from a AOR 5000 could drive it. It seems to work for strong signals but
I am getting the impression that a 10 dB or so amplifier would improve
the situation. Is there a difference between the Basic Rx and the LFRX
board? I have the LFRX board. Is it better to drive the LFRX single
ended into one input or differential with the A and B inputs?

73 Eric


#2

Eric A. Cottrell wrote:

Hello,

Does anyone use a AOR 5000 as a front end for the USRP? The docs for
the USRP say that it is not very sensitive but I thought the IF Output
from a AOR 5000 could drive it. It seems to work for strong signals but
I am getting the impression that a 10 dB or so amplifier would improve
the situation.

Did you turn up the RX PGA gain? You can get an additional 20dB there.
Also, the BasicRX and LFRX inputs are 50 Ohms. Can the AOR drive that?

Is there a difference between the Basic Rx and the LFRX
board?

The BasicRX sends the input through a transformer and into the ADC. The
LFRX sends it through a unity gain amplifier first. For 10.7 MHz there
should be no difference.

I have the LFRX board. Is it better to drive the LFRX single
ended into one input or differential with the A and B inputs?

The A and B and independent inputs. you can use them as separate
signals or as I and Q for the same signal. They are not differential
inputs. They are single ended.

Matt


#3

On Sat, Dec 30, 2006 at 07:23:19PM -0800, Matt E. wrote:

Also, the BasicRX and LFRX inputs are 50 Ohms. Can the AOR drive that?
On my AR8600, I need to use 10 to 20dB of gain between the output of
the 8600 and the USRP basic rx. It depends highly on which band
I’m tuned to. BTW, on the AR8600, there’s a slight mod you’ve got to
make to the board to enable the IF output on all the bands.

Eric


#4

Eric B. wrote:

Also, the BasicRX and LFRX inputs are 50 Ohms. Can the AOR drive that?

On my AR8600, I need to use 10 to 20dB of gain between the output of
the 8600 and the USRP basic rx. It depends highly on which band
I’m tuned to. BTW, on the AR8600, there’s a slight mod you’ve got to
make to the board to enable the IF output on all the bands.

Eric

Hello,

Thanks to both of you for the information. I got the RX PGA gain up all
the way. I rewound the isolation transformer to be 1:1 with 14 turns.
I still have to turn off AGC for good signal levels but I got 20 to 30
dB SNR on RCI at noon today.

Doing some simple tests with the PSD display in DReam I can not see the
noise floor increase when the receiver connected. The FFT from the
USRP data also shows no increase so an amplifier is needed. What
amplifier do you use on the AR8600?

Everything is jury-rigged so I need to sit down and design an real
circuit. It is getting better. It was frustrating to hear good signals
and get nothing.

I also have an AR8600 and an Icom R-2500. Someone modified a R-2500 for
IF Out and mentioned strong signals. I may try that as well.

73 Eric


#5

On Sun, Dec 31, 2006 at 01:42:31PM -0500, Eric A. Cottrell wrote:

amplifier do you use on the AR8600?
I used a Ramsey PR2 broadband preamp (it’s probably overkill, but it’s
what I had on hand)
http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=PR2

Eric


#6

Eric B. wrote:

USRP data also shows no increase so an amplifier is needed. What
amplifier do you use on the AR8600?

I used a Ramsey PR2 broadband preamp (it’s probably overkill, but it’s
what I had on hand)
http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=PR2

Eric

Hello,

Yeah, it looks like exactly what I need. Maybe I will also try hooking
an antenna up to it and fry my LFRX board from the local AM radio
station down the street. :slight_smile: There is a local store that sells Ramsey
Kits so I may look there Tuesday night.

I seem to remember AMSAT-NA was giving out MMICs one year at the
symposium. I should see if I have any. The problem is finding them as
my “for a rainy day” cache is huge.

Is the PR2 battery powered or does it have a DC In? I hope it is 12
volts.

73 Eric