Mixer/Converter for SDR Question

[KB3DKS]

Hello,

  I have several receivers that have non standard IF outputs that need to be converted to a single IF for inputting to SDR hardware/sound card whatever.
  These are older EM type receivers mrg. by Stoddart/Singer, Empire Devices,  etc and have IFs of approx 6mhz for the 1.5 - 10 mhz receiver, 60 mhz for the 10 - 100 mhz receiver and 455kc/1.6 Mhz for the 1-5 - 30 mhz Empire receiver and the Sylvania R-1414 has an additional 3 IF frequencies if I want to source from that receiver for a panoramic display.
  I can produce just about any LO frequency for setup and determining proper xtal frqs but what mixer/converter would be used? I have seen several on e-bay that appear to fit the need but they are too costly to make a wrong choice. Mini Circuits, MCL, WJ, ETC.
 With plenty of RF output level available only a passive device is needed and I would assume that since the bandwidth of a soundcards input is inherently limited to begin with, a bandpass filter would not be needed. Could be wrong here.
  Trying to do this on a 0$ budget with what I have, the receivers and a good 24 bit 96K external sound card.
  Any Ideas or recommendations?

Bill, KB3DKS in 1 Land

[KA0HCP]

So, sounds like high fidelity is not a concern, and simplicity and cost are primary.

Use a diode ring mixer.  That is passive and yet still reasonably reliable.

If you are willing to spend just a few dollars for better performance you could use an op amp mixer using just one opamp or several for added features.   Putting an opamp as the pickup from the IF would keep from loading down the IF and provide isolation and consistent level into the mixer.

Any of these can be made from inexpensive parts at Radio Shack.  There are tons of various designs available.

Good luck.

[w3jn]

Bill, you got the R-1414 working finally?

[WA1GFZ]

A DBM with 3 dB pads on R and I ports should do it. Then just feed it the rated LO.
a diplexer will eliminate image. An image reject mixer even better.

[KB3DKS]

Bill, you got the R-1414 working finally?

The R-1414 has been working about 80% right along. Had several of the tricky little P.S. feed thru bypass filters go bad. They look like the 1/2" bolt type C feed thrus but are actually L/C filters using a small Tant off the end of the L. I made a couple discrete clones that work fine. Otherwise the receiver still needs the readout divider board, (missing) and the upper bands roofing filter, (bypassed).
  It is my primary receiver and only has a slight bit of drift in the tuning. Using a counter on the IF and chart to find where it is.
  Still looking for someone who can convert the manuals large fold outs to PDF. Might just have to section scan the pages but most of the important stuff is triple fold double side.
  When you get back to working on yours PM me and I can scan the sections you need for now.

A DBM with 3 dB pads on R and I ports should do it. Then just feed it the rated LO.
a diplexer will eliminate image. An image reject mixer even better.

  Can you point out a couple model #'s so I can get more of an idea what to look for?

Thanks, Bill

[WA1GFZ]

I like the SRA1H myself but there are many different mixers that will do the job. All you need to do is know what level the LO needs to be. 3 db pads will reduce unwanted  mixer products by providing a good VSWR to the R and I ports.

[KF1Z]

Data sheet

http://www.minicircuits.com/pdfs/SRA-1H+.pdf


Buy it

http://www.minicircuits.com/cgi-bin/modelsearch?search_type=model&model=SRA-1H&tb_no=


Little pricey at Over $25 each !

[WA1GFZ]

There are plenty of cheap mixers around and you can easily homebrew one with 4 switching diodes and two BB transformers.