R7100 IC-R7100 strange mod

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borjam

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Hi,

Bringing it up again in case someone knows about it.


Turns out this is the receiver I have purchased today. It works perfectly (except for a very minor misalignment between USB and LSB listening to an AM station such as the local airport ATIS) and it's so clean it looks like brand new. But of course there is a mystery switch (which is the most common switch you can buy), a 5 pin DIN connector and two number selectors which can go from 00 to 39 (decimal).

I dare to say it's a CTCSS squelch mode. This table of Icom CTCSS option codes linked from somewhere else shows the possible meaning of the codes.




The price was really good, I guess the owner was tired of listing it.
 

spongella

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I've got an Icom R7100 but not with that mod. This may be a stretch but I also have an Icom 25A 2 meter radio that can be programmed to CTCSS tones. Since it is an older rig, you have to use Icom's CTCSS code for each tone you want. From the picture is it possible that the radio was modified to receive based on what tone code was displayed on that digital counter to the left?
 

kruser

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Hi,

But of course there is a mystery switch (which is the most common switch you can buy), a 5 pin DIN connector and two number selectors which can go from 00 to 39 (decimal).
I do remember a PL tone board that used a pair of BCD rotary switches like in your picture.

Look inside if you open it and see if you can get some good pictures of the board the little toggle switch and the rotary switches are connected to.
Maybe write down any chip numbers if you can read them on any integrated circuit chips. That should be enough to confirm what the mod does.

I was going to add something similar to an R9000 but never did it as you could only use tones when monitoring single frequencies. The little toggle switch should bypass the tone board so the radio will work normally and pass all audio.

I also recall some people bringing the BCD rotary switches out to an external box that they placed in front of their radio so they could easily change the PL tone or flip the bypass switch on/off. The entire tone board may have been mounted in the external box for all I know. I don't remember ever seeing inside of one.

I think it was Piexx Piexx Company, Computers & Electronics that made the old PL tone boards that used the BCD switch wheel for setting the tone. They still sell tone boards today but I did not see any that use the old BCD rotary switches.
 
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kruser

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I think it's a number code, 00 to 39 (decimal), which matches the description in the ICOM CTCSS link above.
Yep, I'd think that is correct as it makes it easy to remember if you use certain tones often.
I know there were many times I wished I'd had a tone board when monitoring something with an old R7000 that had multiple users on a given frequency. Even with the limitation that only one tone could be used radio wide when the tone board was enabled, it would have still came in very handy at times.
 
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