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Author Topic: Adding PL tone encoder  (Read 4371 times)

Posts: 24

« on: March 15, 2009, 01:16:45 PM »

Hello all:
I have an ICOM IC-211 I inherited from a friend of mine's dad. I wanted to access the some if the local repeaters but almost all require a pl tone.I could have purchased one, but I dedided to get some building experince and built a PL tone encoder I found on the web by N1HFX..
   It is done, but I don't know where the deviation potentiometer in the transmitter circuit is exactly. I have a copy of a schematic for an IC 211E.  I believe the deviaton pot is r59. Can anyone point me in the right direction please?

Posts: 379

« Reply #1 on: March 16, 2009, 08:08:20 PM »

I think you want to be able to adjust the tone level seperately from the regular mic dev. Things could get tricky I should warn you.  If the output from the tone gen is low impedance and you hook it across say a 50k deviation pot, it might slightly load down the overall deviation.  If you inject the tone gen across the mic input, you might overload it unless the adjustment range can be set to a few millivolts reliably. I tried using a commercial board in an old Yaesu that didn't have the factory board installed. Plenty of room but my commercial board did not quite drive the dev. enough when hooked to the input conn. for the factory board.  I think you want maybe like 700hz. of deviation from a subaudible tone, for opening a repeater. YOu will need a deviation meter to set that, otherwise all I can suggest is to adjust it slowly from min. output till it opens the repeater reliably, then maybe just a tiny scootch more output. Better to use a meter.    

Posts: 24

« Reply #2 on: March 28, 2009, 10:11:11 AM »

I was thinking of first setting the tone encoder to the correct freq. that I need so I only deal with one issue at a time. I do have a frequency counter available. Can I connect the counter directly to encoder to set the frequency?

The one I built is this one:


Posts: 144

« Reply #3 on: March 28, 2009, 01:07:39 PM »

Here's how I interfaced my Communications Specialists TE-32 tone encoder to my IC-211 a long time ago.

I injected t the tone into pin #5 of the 24-pin Molex connector on the back of the rig (pin #8 is ground and you can pick off 13.8 VDC at pin #2)....that will put the PL tone just downstream of the mic input.

I then adjusted the input temporarily with a pot for a deviation of 3 kHz as I recall (I think that was the standard).  Did this on my service monitor which made it simple....then simply measured the resistance of the pot and installed a fixed resistor at that value in the line from the encoder to the injection point.

If you don't have a way to directly measure deviation another way to do it is increase the deviation from minimum while listening on another receiver....when you hear an increase in the background "white noise" level that is probably close enough.  Then test with a repeater and see if it works....if not bring it up a little more until it does.

Hope this helps.

Dino KL0S
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