Hi, all, I have a Cobra 139XLR (with the 858 chip) and when testing AM transmit I find the radio is a little off frequency. For example on Channel 20 which is 27.205mhz my radio read 27.2046mhz. I know it;s not a huge difference but I would like to adjust it and I tried adjusting CT6 which should work for AM but moving CT6 does Nothing. Any help please? Thanks, Adam
-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
Help with frequency adjustment on Cobra 139XLR
- Thread starter Adamf
- Start date
CT6, and the 11.285 crystal it's connected to are only active in receive mode for AM. That trimmer does nothing in AM transmit.
As you discovered.
If the radio is stock, and the clarifier is still active ONLY while receiving, you would use VR9 to set transmit frequency to agree with the clarifier's 12-o'clock frequency.
If the radio has been modified to "lock" the transmit and receive frequencies to each other on the clarifier knob, you'll need to set it to 12 o'clock first.
The AM frequency trimmer for transmit is the same as the trimmer cap CT4. This one controls transmit and receive for USB. Also sets AM transmit frequency. If it's set right on USB, there will be no need to adjust it for AM.
73
As you discovered.
If the radio is stock, and the clarifier is still active ONLY while receiving, you would use VR9 to set transmit frequency to agree with the clarifier's 12-o'clock frequency.
If the radio has been modified to "lock" the transmit and receive frequencies to each other on the clarifier knob, you'll need to set it to 12 o'clock first.
The AM frequency trimmer for transmit is the same as the trimmer cap CT4. This one controls transmit and receive for USB. Also sets AM transmit frequency. If it's set right on USB, there will be no need to adjust it for AM.
73
