Home |
Search |
Today's Posts |
|
#1
|
|||
|
|||
ICOM IC-260A CTCSS - using Pin 5 of accessory connector?
I need to add CTCSS to transmit of ICOM IC-260A. I have a manual (file)
but no schematic. The manual says that the accessory connector pin 5 is "output of transmit mic amplifier" or words to that effect. Can I put CTCSS tone signal into that pin on transmit? Other suggestion? Anyone care to look at their schematic of this rig to tell me where this pin of the accessory connector goes? Very tks, 73 Dave WB0GAZ |
#2
|
|||
|
|||
"wb0gaz" wrote in message oups.com... I need to add CTCSS to transmit of ICOM IC-260A. I have a manual (file) but no schematic. The manual says that the accessory connector pin 5 is "output of transmit mic amplifier" or words to that effect. Can I put CTCSS tone signal into that pin on transmit? Other suggestion? Anyone care to look at their schematic of this rig to tell me where this pin of the accessory connector goes? Very tks, 73 Dave WB0GAZ Hi I have posted the schematic for this radio in the manuals section at. www.mbars.co.uk |
#3
|
|||
|
|||
Dave,
the internal mic circuit has audio HF & LF filtering. This means that if you were to apply a signal below 300Hz or above 3,400Hz into the mic circuitry,then the level of this signal will be greatly reduced, or even removed. The CTCSS signals centre around 100Hz and therefore cannot be injected into the mic socket. In fact you have to travel all the way through the mic circuit until you get to the microphone op-amp (IC1) See circuit as per Paul. The amp IC, IC1 has a resistor/cap feedback circuit which provides the req'd filtering. The CTCSS encoded signal output should be injected around Pin 1 (output of IC). There maybe voltages at this point ,so a capacitor must be used to block this voltage. You will see two varicap diodes D1/D2 and it is the varying AF voltage feeding these diodes that produces the modulation of the carrier. I have carried out this mod on my IC-290E, by using an external CTCSS encoder chip (FX315) mounted in a small aluminium box with DIP switches for selection. I connected a small piece of screened wire from Pin1of IC1 and connected it to a spare pin on the nine way facility socket on the rear panel. At this point I also connected the aforementioned cap. A transmit switched voltage for feeding the external CTCSS unit supply line was found on this facility socket. Please check the circuit for your radio. Remember that the CTCSS encoded signal should only be activated when you transmit. Dave, you must have a good look at the schematic provided by Paul and come up with a plan of attack. You will of course understand that you attempt these modifications at your own risk. It worked for me on my IC290. Do a search for FX315 encoder/decoder chip circuitry on the net. I got my chip(not cheap) from Mode Components.(UK) Regards and good luck and thankyou Paul for schematic. Roger, G7JAQ http://www.btinternet.com/~g4kqu/Mod...nts/index2.htm I choose Polesoft Lockspam to fight spam, and you? http://www.polesoft.com/refer.html |
#4
|
|||
|
|||
Paul and Roger - thank you very much for the very helpful information.
I've retrieved the schematic and had already obtained the user's manual from the ICOM website. I'll study the schematic. As for the tone generator, I'm planning on using an old laptop computer and "nch tonegen", which is a software program that can generate an arbitrary sinewave signal. The main task at hand is to isolate and bring the appropriate connection point out to the back panel where I can supply the tone on transmit. Again, thank you both for your fine support! 73 Dave WB0GAZ |
#5
|
|||
|
|||
Got a close look at the schematic, and indeed the external "mic amp
output" connector pin 5 of accessory jack is basically the same as the audio output of the microphone itself, useful for DTMF insertion but not useful for CTCSS. It appears likely I can attach near/to the output of the deviation control R115 which feeds through a series resistor and capacitor to the FM modulation varactor D32. This looks like it's near the center of the lower PC board in an area that's not too cluttered. I'm not sure if I'll need to inhibit the tone on receive or not; the circuit appears dedicated to transmit mode only. Again, thank you very much for the insight - it would not have been possible to start this project without your kind help! 73 Dave WB0GAZ |
#6
|
|||
|
|||
Dave,
you're more than welcome. It's all about keeping the hobby alive I suppose. I wish you well with your laptop generated CTCSS tones. It certainly is an interesting and novel approach!. Post again when you have some more info. Be careful about "loading up" the varicap circuit and thereby reducing the deviation, when you connect your soundcard? You'll need to check that the deviation levels of voice signals mixed with CTCSS do not become excessive. regards, Roger, G7JAQ. Surrey, England I choose Polesoft Lockspam to fight spam, and you? http://www.polesoft.com/refer.html |
#7
|
|||
|
|||
"Roger Adam" wrote in message ... Dave, you're more than welcome. It's all about keeping the hobby alive I suppose. I wish you well with your laptop generated CTCSS tones. It certainly is an interesting and novel approach!. Post again when you have some more info. Be careful about "loading up" the varicap circuit and thereby reducing the deviation, when you connect your soundcard? You'll need to check that the deviation levels of voice signals mixed with CTCSS do not become excessive. regards, Roger, G7JAQ. Surrey, England I choose Polesoft Lockspam to fight spam, and you? http://www.polesoft.com/refer.html Glad i could help with the shematic. Keep your eye on the site as over the next few months i have over a thousand files to add to the manuals section. good luck with the project. Paul 2E0DXO |
#8
|
|||
|
|||
On 14 Mar 2005 09:05:34 -0800, "wb0gaz" wrote:
Paul and Roger - thank you very much for the very helpful information. I've retrieved the schematic and had already obtained the user's manual from the ICOM website. I'll study the schematic. As for the tone generator, I'm planning on using an old laptop computer and "nch tonegen", which is a software program that can generate an arbitrary sinewave signal. The main task at hand is to isolate and bring the appropriate connection point out to the back panel where I can supply the tone on transmit. Again, thank you both for your fine support! 73 Dave WB0GAZ When I worked for Icom America on the tech support line I used to advise attachment to the wiper of the deviation pot. Always seemed to work. Gary K8IZ |
#9
|
|||
|
|||
|
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Useful Icom IC-R75 [R-75] Links for Facts and Information about the Icom IC-R75 [R-75] | Shortwave | |||
FS New Icom OPC-599 Accessory Cable | Swap | |||
Icom R-75 question | Shortwave | |||
Help on Icom R70 Interfacing via Accessory socket | Equipment | |||
Help on Icom R70 Interfacing via Accessory socket | Equipment |