The AM Forum

As some know, the R388 has an IF output connector on the back. Has anyone hooked this IF output to an SDR? I was considering doing this with my Flex 5K so I could see the IF passband on the panadapter.

Tnx

Philip

A different approach for the I.F. output would be the SoftRock boards that accept the I.F. freq, and then you can use the Flex radio software to demodulate the IQ signals from the ckt board.
I went online to look at the Flex 5k manual and there is no 455 I.F. input.
You could try to connect the I.F. out to the RF input and tune the 5K for 455. I do not know if it will tune that low. The input might be overloaded from the R388. Volts going into the 5K when it expects microvolts.

Try it, you might get something on the flex 5000.
There may be an input on the back of the 5000 that bypasses the front end, there are a lot of connections on the back of the flex, maybe a transverter IO or something...

The sdr-iq goes down to 100 Hz, that would work.

Which makes me think, I never hooked the sdr-iq I have up to the IF output of my homebrew receivers to look at the passband.
I have it hooked up to the O scope, but never looked at the IF with the sdr.

Not that it matters much, the homebrew rx has broad band IF transformers and uses a Kiwa filter to do the filtering right after the mixer.

But in normal ham type stuff, it would be very useful to adjust the IF cans per the sdr to get the best shape.

Hmmm!  Why didn't I think of that?  Before hooking the IF from my SP600 to the Flex input, I will probably temporarily hook up a switchable attenuator just so I don't put too much signal into the Flex

Al

The flex 5000 goes down to 100KHz, and has an attenuator built in...

http://kc.flex-radio.com/KnowledgebaseArticle50044.aspx

I just did this with the sdr-iq and my home brew receiver IF out.
Looked just like a typical mechanical filter passband.

This would be very useful for setting up IF cans in vintage receivers.

The sdr stuff (like the sdr-iq) is very useful as a piece of test gear, as well as a good receiver.

A program like spectraview even has markers you can set, the sdr-iq does 192 KHz of bandwidth, so you can look at frequency, amplitude, drift, range, signal purity of things like a local oscillator or a vfo, the IF passband of a receiver, and the frequency, modulation and signal purity of your transmitter (and others transmitters).

 

Bad news about the Flex, though.....the filtering on it is pathetic below the AM BCB and all one sees/hears are images. Without an external filter that kills everything above 500 KC, you really can't do much at all with LF.

P

I'll guess that an SDR IQ is like a softrock board. You input an I.F. and it becomes almost like a complete SDR receiver.
I didn't think the actual Flex 5000 would accept that 455 input from another receiver. If it's not attenuated down to microvolts the Flex will go bonkers. Plus Phil mentions that LF is useless on that radio.
Fred

Fred, FYI, the IF freq of the R388 & R388A (51J4) is 500KC !

No, its a direct digital sampling receiver that works from 100 Hz to 30 MHz.


http://rfspace.com/RFSPACE/SDR-IQ.html

No sound card, no power supply, it runs off a USB port.
Its its own standalone receiver, but the ability to go down to 100 Hz (NOT KHz) makes it useful for looking at IF frequencies.