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Old 27-05-2024, 17:11   #1
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Icom M710 Transmit Carrier



I have a couple of Icom M710 radios. I am trying to interface through the rear ACC1 connector. Any time I transmit using the ACC's Send line, there is a carrier in the lower sideband. Keying with the mic is clean.

This is on two different radios. Anyone know what I am missing. Obviously, I do not want that carrier even though it is not heard on USB.

Again, there is no carrier when using the microphone to transmit. Only when grounding the SEND line of the ACC1. No other wires are attached.
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Old 15-06-2024, 15:05   #2
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Re: Icom M710 Transmit Carrier

Quote:
Originally Posted by rvideo View Post


I have a couple of Icom M710 radios. I am trying to interface through the rear ACC1 connector. Any time I transmit using the ACC's Send line, there is a carrier in the lower sideband. Keying with the mic is clean.

This is on two different radios. Anyone know what I am missing. Obviously, I do not want that carrier even though it is not heard on USB.

Again, there is no carrier when using the microphone to transmit. Only when grounding the SEND line of the ACC1. No other wires are attached.



Howdy,



It appears that you might be transmitting in the FSK mode which would always be transmitting a signal when you "key" the "SEND" line.

(note, it's technically NOT a carrier, but I digress!)



If you select an FSK frequency, it might automatically select that mode. So maybe try manually selecting LSB/USB before keying the SEND line.



I do not have an M710 so I can only theorize. But with my M802 If I select FSK and key the mic, it does transmit a "carrier" (shifted 1kHz above the displayed freq and heard by others if using USB, and not heard by LSB users on that same frequency)


The M710 might shift 1kHz below (displayed freq) when transmitting FSK, but I would expect it to be the same as the M802


With the M802, I use the FSK mode (and low [20w] power) when tuning my HF-Auto tuner. (Selecting CW and keying the mic does not cause it to transmit.)


On the M710, to transmit CW, you would have to ground the send line ACC(1) pin 3 then "key" pin 1 to transmit CW


If you wanted to transmit FSK, you would still ground PIN 3 and your RTTY modem/TNC etc would then ground pin-1 as required during RTTY transmit to shift the signal freq..


BUT, in the FSK mode, it would transmit a continuous wave signal every time you key the SEND line. (MARK/SPACE.... one or the other....I cannot remember which)





Regards,



Rick
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Old 15-06-2024, 17:13   #3
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Re: Icom M710 Transmit Carrier

Thanks Rick...

That was my opinion also concerning FSK. It is definitely in the USB mode when transmitting. I have done some listening using SDR receivers and the carrier is no heard.

I am running everything through a mixer output. I am going to. do some more communication with it and not let the other station know about my concern to see if it something that they note.

I have used the M710 for digital operation (AFSK) in the past. No one noted anything about the carrier. I appreciate everyone's input. I have eliminated the suggestions one by one with no change in the output audio. I will post an update should I find anything in the future.
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Old 16-06-2024, 11:16   #4
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Re: Icom M710 Transmit Carrier

There's another point I should make. While I did download the M710 manual, I didn't read all the way through it. My Motorola Micom-3T does have a "Pilot" mode in the menu that actually transmits a reduced power "pilot carrier" when operating either upper or lower sideband.



Don't know if the M710 will do that (I know for sure that the M802 does not) and I don't think it's a "marine-thing" anyway so this may be a moot point but it's worth investigating. (The MICOM-3 series is not a marine radio, although I think they have had a "Marine" [firmware] version)


Otherwise, your M710 may just need an alignment.... (if it does this in a regular voice, SSB mode)
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