"Real" receiver to SDR

[DaveNF2G]

I recently acquired an Icom IC-R71a and IC-R7000.

I would like to connect the "scope" ports (70 MHz IF signal) to an SDR dongle. Do I need to put any additional hardware in that path?

 

[majoco]

Lucky you!. My first answer would be "no" - try it and see. The only problem I can think of is that the IF out signal may be far too much - if it's designed to be seen on a scope than it will need an attenuator. If you connect an 82ohm resistor across the output socket inside the radio (to nearly match the 75ohm input to the dongle) and the try a selection of resistors in the lead , say start at 1000ohms and see how it goes. You've just made a 12:1 divider, I would have thought that would be enough - but - try it and see!

One test is worth a thousand opinions!

 

[KA1RBI]

I recently acquired an Icom IC-R71a and IC-R7000.

I would like to connect the "scope" ports (70 MHz IF signal)

Dave

Referring to the IC-R7000, (haven't checked the R71a):
1) the R7000 has no "scope" output port
2) the R7000 has several IF's, but 70 MHz isn't one of them, according to my service manual.

Max

 

[prcguy]

The IC-R7000 and R7100 have a 10.7MHz IF out originally intended for the optional TV converter box. I once connected a spectrum analyzer to my 7100 and was very disappointed at what the receiver AGC did to the IF output.

When signals were far away from the where the receiver was tuned they were at expected levels on the spectrum analyzer but when you tuned to them in and the signals were finally within the receivers IF filter range the AGC would take over and run the receiver gain down and the feed to the spectrum analyzer would greatly diminish. It made the spectrum analyzer almost useless on that series of radios.

Most of the inexpensive dongles will not go down to 10.7MHz without an outboard HF converter anyway.
prcguy

 

[DaveNF2G]

I posted before consulting the R-7000 manual. The R-7000's IF output is at 10.7 MHz and the manual warns that it carries DC.

 

[jcardani]

Hi Dave,

You can easily block the DC by using a DC block "adapter". You can get them at Minicircuits or other electronics shops.

Also the AGC can be defeated on the R7000. You would need to simply cut a resistor on one side and wire a spst switch. Contact closed = AGC on/ Contact open = AGC off. See the mod here:

http://home.comcast.net/~shannip/icr7000mods.pdf