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10.7 MHz IF Output for PCR100/1000

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blantonl

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Folks,

Recently we discussed in this thread...

http://www.radioreference.com/forums/showthread.php?t=34212

... IF Outputs for computer controlled scanners.

Someone attached a PDF in that thread that showed how to do a 455 KHz IF Output mod for the PCR1000, but not the 10.7 MHz IF output. Does anyone have instructions or information on the tap point for a 10.7 MHz IF Output for the PCR1000? How about the PCR100?

I'm interested in picking up a few of these receivers for IF Output work, but need to do this mod for this project to be successful.

Any help you folks can provide would be great.

Thanks!

Lindsay
 

blantonl

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Ok, that attachment from that thread was actually invalid... and the next attachment in the thread was a PDF that showed how to do a 455 KHz IF Tap which is not what I'm looking for.

I'm looking for info on a 10.7 MHz IF Tap for the PCR-1000.

Lindsay
 

blantonl

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Nah, this doesn't help - this is a discriminator output... not 10.7 IF Output.

I've got the service manual for the 1500.. will be looking shortly.

As for the ARD-25's - I don't own one... however feeding the IF output thru a mixer to a ProVoice Digital Radio listening in conventional allows one to monitor and track EDACS ESK ProVoice systems. I currently use an 8500 to do this, and the ability to black box this function would be very much a nice thing.

See: http://wiki.radioreference.com/index.php/Digital_Voice_Conversion_Method for details
 

bagmouse7

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PCR-1000 IF output

Lindsay,
If you look closely at the .pdf halfway down the 2nd page you will see a note that says, "Note: A 10.7Mhz signal with an estimated bandwidth of several megahertz is available at the output of buffer amplifier Q85 above."

I have not taken a close look at the PCR's schematic to identify exactly where the output of Q85 is, but it looks like it feeds directly in the 50 kHz and the 230 kHz filters so it should not be that hard to find.
Thanks.
 

blantonl

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bagmouse,

I did see that section, however it wasn't intuitive from the PDF where exactly the output of Q85 actually is...
 

bagmouse7

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The schematic I have is very blurry, but I am going to look at the service manual to see if I can identify the correct point. I have been wanting to do this anyway to try to see my SDR-14 with the PCR-1000.
I will let you know what I find.
Thanks.
 

gr8amp

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blantonl said:
bagmouse,

I did see that section, however it wasn't intuitive from the PDF where exactly the output of Q85 actually is...

Lindsay,

Q85 is located close to the edge of the large board, near J1. If you place the radio with the antenna connection to the left, Q85 is the first transisor to the right of the smaller IF filter at the top lefhand corner of the RF board. This is directly above the metal can for one of the LO's.

The buffered 10.7MHz IF is available at the emitter of this transistor, which is the upper left terminal (if the radio is oriented as described above). There will be a DC level at this point, so will want a coupling cap.
 

blantonl

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Outstanding information.

Would a 0.1uf capacitor be put in parallel between ground and feed, or in series on the feed?

Looks like I'll be picking up a few of these now....

Thanks so much for your assistance on this one! I'm going to add this information to the Wiki.
 

EricCottrell

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Hello,

The 0.1 Cap would be in series with the output lead to keep the DC voltage out of the external circuit.

I should check to see if the R2500 is similar. Thanks for the information.

73 Eric
 

KC1UA

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EricCottrell said:
Hello,

The 0.1 Cap would be in series with the output lead to keep the DC voltage out of the external circuit.

I should check to see if the R2500 is similar. Thanks for the information.

73 Eric
Does tapping the 10.7 MHz IF where Jim suggests offer all modes? I thought I read somewhere that this just dumped out WFM, but perhaps this is another tap point.

Eric, as mentioned elsewhere it would be nifty to have a 10.7 off of the 2500...really nifty.
 

blantonl

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Yes, it would be very nifty... especially if someone could identify the outputs for BOTH receivers... that would be pretty cool.

I received my 2500 from Japan last week, and frankly I absolutely love the radio (minus the P25 issues)
 

EricCottrell

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Hello,

The R2500 is similar. I popped the covers of the receiver and subreceiver. The receiver and subreceiver have similar layouts. If you look from the front there is a surface mount transistor between the 6 in a circle and the two filters (FI5 and FI6). The transistor is the black rectangle with one lead coming out the center on the left side and two leads coming out the right side. I think the tap is the lead on the right side that is towards the back. It is connected to a resistor going to ground and a feedthru. I measure 58 ohms to ground at the lead.

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.

I will likely tap only the main receiver.

73 Eric
 

gr8amp

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The output of the Q85 buffer feeds two filters which are switched depending on the mode. The output of the filters feed another buffer whose output is switched to either the narrowband detector/final mixer, or the WFM detector. If you tap the 10.7MHz IF inpupt to the narrowband IC (IC10 pin 16, Toshiba TA31136), this signal will be switched depending on the mode. If you tap after the filters (Q39), you will end up with a 10.7MHz IF whose bandwidth will depend on the mode (50khz, 230khz). The Q85 tap is before all of the switching, and should be available independant of receiver mode settings.
 

bagmouse7

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This is a super thread by the way...

More good info.
Go here and grab the PCR-1000 service manual:

http://www.arpa.org/radio/software/pcr/manuals/

On the first page there is a picture of the inside of the PCR-1000 with a pointer to Q85. Also, on page 19 you can see Q85 marked on the circuit board layout.
Thanks guys for adding to this tread!
 

JimTailor

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Try this location

This is the web site for TrunkPcr which gives the PCR100 the ability to do trunk tracking once the mod is performed. I have no personal experience with this software or the mod. If this link doesn't get you there directly, do a Google search for TrunkPcr. That will get you to the web site which includes the mod information.

http://members.cox.net/fiftyone.50/TrunkPcr/TrunkPcr.html
 

EricCottrell

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bagmouse7 said:
This is a super thread by the way...

More good info.
Go here and grab the PCR-1000 service manual:

http://www.arpa.org/radio/software/pcr/manuals/

On the first page there is a picture of the inside of the PCR-1000 with a pointer to Q85. Also, on page 19 you can see Q85 marked on the circuit board layout.
Thanks guys for adding to this tread!
Hello,

Thanks for the link.

The only other thing I would consider is put a buffer in to minimize the effect of the IF Output on the filters and to stop ingress of 10.7 MHz region signals from outside the receiver.

73 Eric
 
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