Motorola M100 Programmed to Transmit Only?

[mockinbird]

I have aquired two very nice VHF M100's. Plug them in to the RSS program them up and everything seems to work fine except neither one of them will receive. Even with the squelch off they do not pickup anything. Is there some function I am missing that would make these radios transmit only?

[Will]

Speaker jumper?

[mockinbird]

Thought that as well, however when you hold the monitor button down you can hear the static.

[HLA]

did it come out of a repeater? turn on the radio and turn the vol all the way up and put your ear close to the speaker and do you hear any hiss or static if the speaker is actually working?

[mockinbird]

Yes you can hear the static, when you press and hold the monitor button it opens the squelch and you can hear the loud static... The volume knob works also adjusting the sound of the static.

[Will]

HLA, the OP said he IS hearing "static on the speaker", so the speaker IS working.

That is also a good indicator that the second IF stage. discriminator and audio stages are working.

Next step is to check the programming.

Then check the RX second LO, the crystal may be bad.

No telling what happened before he got the radios.

[mockinbird]

What in the programming would make it transmit only?

[kcbooboo]

If the receive VCO is not locked, the receiver will hear nothing but the squelch will sound fine and the MON button will work normally. It may be a matter of simply adjusting it, or it might really be dead. A previous owner may have used the radio out of band and adjusted the VCO accordingly.

Bob M.

[motorola_otaku]

The M100 is the blank-face 1-channel variant of a Radius M120, right? There is no way to make those transmit-only in programming, and in practice the TX radio in a GR-series repeater will typically get the RX and TX freqs programmed the same.

That said, a bad LO crystal will cause the behavior OP is describing. It seems to be a more and more frequently-occurring issue in Radius GM-series radios from my observation.

[summitrt]

Sell or use them as TX only radios for APRS. I had a M216 that was deaf. It was a great radio for APRS when used with the TinyTrac device.