R2500 and 10.7 MHz IF Output

[blantonl]

Has anyone found a definitive source for a modification to allow 10.7 MHz IF Output on this radio?

Is there a tap point?

This would be a critical mod for me and I'm very interested if someone has found the 10.7 MHZ If output for both receivers in the 2500.

Any assistance would be greatly appreciated!

Warm regards,

Lindsay

 

[W1PC]

I have the service manual for the R2500 and have found the 10.7 MHz signal on the schematics and the circuit board layouts for both receivers. I have not tried to tap the signal from either receiver, though, so I can't confirm that the taps points I have found will work.

If you'd like, I'll be glad to try and scan the relevant parts of the schematics and circuit board layouts and email them to you. Just sent me a PM with your email address and I'll get these off to you.

 

[blantonl]

Hi There W1PC - email is:

webmaster at radioreference.com

Thanks for your help.. I am very interested in getting this information up on the wiki as well as a good reference for this receiver... all in all I am thrilled with it's performance, and for monitoring some special systems, the 10.7 IF output is critically important.

Thanks again!

Lindsay

 

[W1PC]

Lindsay -

Email and PDFs sent. Hope they help.

 

[KC1UA]

Hopefully Eric C. will chime in on this as well. As I recall he was using a probe attached to his Avcom SDM-42A and displaying spectrum off of one of the tap points. Eric, have you gone any further with this?

 

[EricCottrell]

Hello,

No, I have not gone further.

I would suggest the person with the Service Manual look up the 10.7 MHz mod for the PCR1000. The IF section is similar and I was able to figure out the tap point by comparing the PCR1000 board with the R2500. The service manual with give the right component designations for the R2500.
http://wiki.radioreference.com/index.php/PCR-1000/100#10.7_MHZ_IF_Output

73 Eric

 

[W1PC]

This is an excerpt from the Service Manual showing where I think the 10.7 MHz tap point would be. Since I haven't actually done it, those with more expertise will have to comment whether this is correct. Sorry for the fuzzy image but it should be readable.

http://www.radioreference.com/forums/attachment.php?attachmentid=5820&stc=1&d=1163298177
IF Tap Point.pdf

 

[RBMTS]

Hi Guys. Pardon me for asking, but what is the advantage for a 10.7 tap point? Would this be for a spectrum display, a scope, or a external display?

 

[blantonl]

all of the above... in addition to up-mixing the signal to a radio that demodulates certain types of digital communications - say provoice.

 

[blantonl]

PCR2500 - Confirmed IF Output 10.7 MHz Working

Good News Folks!

The above suggestions, diagrams, and modifications do indeed work. I tapped the point recommended by W1PC, and fed it to a BNC jack that I installed on the back case.

It works perfect, and provides a VERY clean, strong, 10.7 IF Output signal.

Hurray!

Next step is to tap the 2nd receiver's IF output, and then I'll really be pleased... this will replace my previous need to use two R8500's for IF Output radios just for trunktracking, and is a MUCH more cost effective approach. Both RF boards look very familiar so the process should be similiar.

Word of warning - the tap point is extremely small, and not for the faint of heart. I actually went out and purchased a professional Weller Soldering iron and special soldering tip just for this task. Using the least amount of heat possible, I glued a pre-tinned small piece of wire next to the tap point, and then dragged some solder from the VERY small surface mount point to the wire. I then ran this 1 1/2 inch short length of wire up through the hole next to the center screw, and soldered some shieled cable to that for the run to the BNC connector.

I'll get some pics and a wiki writeup on the procedure shortly.

Thanks agian W1PC for your assistance, and if you've got the trace/tap point for Receiver #2 that would be great!

Lindsay

 

[KC1UA]

That's great news, Lindsay. Are you able to tell with the application/equipment you're using how wide of an output KHz or MHz-wise this provides?

Edit: If I'm reading the schematic correctly, only 50 KHz in FM mode...won't provide much for a spectrum display, unfortunately, if that is correct.

 

[W1PC]

Lindsay - I'm glad the tap point I suggested worked.

I'll send you copies of the 2nd receiver schematic and circuit board layout tonight if I can (I may have a school function so it might be late) but I think the IF section of the 2nd receiver is exactly the same as the main receiver so the tap point should be in an area that looks the same.

 

[blantonl]

Wiki page at:

http://wiki.radioreference.com/index.php/10.7_MHz_IF_Output_for_the_2500

 

[W1PC]

Attached is a pdf which shows the 10.7 MHz tap point for the 2nd receiver. Note that the circuit board diagram is of the bottom of the board.

 

[W1PC]

If I'm reading the schematic correctly, only 50 KHz in FM mode...won't provide much for a spectrum display, unfortunately, if that is correct.

Since the tap point is before the BW filter, you may not have this limitation. I'd be interested to hear from anyone who uses this tap point as to their experience with the bandwidth on a spectrum analyzer.

 

[KC1UA]

Since the tap point is before the BW filter, you may not have this limitation. I'd be interested to hear from anyone who uses this tap point as to their experience with the bandwidth on a spectrum analyzer.

This is just another example of my technical expertise...or lack thereof! Hey Lindsay, can I borrow your soldering iron....oh, and can you come along with it? I can't use my jeweler's screwdriver for this mod. Rats.



Actually, John is closer...John, thanks for your efforts on this. Truly great stuff.

Eric, when you were using your probe at the tap point and viewing your SDM42A, do you recall what the bandwidth of the output was? Even a MHz or two would be very very useful for spectrum displays, IMHO. RFSpace has just introduced a new and less expensive SDR that would probably work dandy with this mod if the output was wide enough.

http://www.rfspace.com/sdriq.html

 

[hotdjdave]

Fyi

FYI only. Some guys have been discussing this on the PCR2500 Yahoo Group, as well. Not sure if this will help.

 

[EricCottrell]

Hello,

I did a search and found a June post I made:
"As a test I connected a scope probe up to my SDU-42 and connected it to the right rear lead of the transistor. I was able to see IF signals in any mode. If I turn to maximum span I could go 5 MHz up the band and see signal clusters move over to the edge. I did not notice any decrease in signal as it moved to the edge of the display. Of course the AGC caused the display amplitudes to decrease when I tuned in a signal."

So it would be at least +/- 5 MHz. I also found the built-in bandscope useful when I used it with the computer software.

73 Eric

 

[KC1UA]

Using 10.7 Output for Spectrum Analysis

Eventually it will be my intention to tap the 10.7 MHz output of my 2500 for simple panadapter use. Does anyone have any comments or thoughts on the use of this hardware/software combination for such use?

http://www.vellemanusa.com/us/enu/product/view/?id=351206&printable=1

These kits can be had for a song, and seem to provide FFT capabilities through PC based software and a hardware box that would apparently accept a 10.7 MHz input signal. The box is connected to the computer via parallel port.

Edit: The software can be downloaded and run in demo mode: http://www.vellemanusa.com/us/enu/download/files/

Thanks in advance.

 

[KC1UA]

The above will not work. I posted the question at qrz.com, here are the replies.

http://www.qrz.com/ib-bin/ikonboard.cgi?;act=ST;f=5;t=139104

Ah well. Worth a look anyway.