Paul
910 Kc is twice the 455 Kc IF. Possibly there is a clue here. Motorola had
problems with spurs in the Metrum VHF ham transceiver. It also used one
crystal for both transmit and receive. I guess that this is a good data
point as to why mobiles should not be used as repeaters. The repeater and
base station is a complete redesign and uses separate crystals for transmit
and receive. Probably they saw the problem and made the intelligent
decision to keep the spurs at ground level in the mobiles and use a clean
transmitter for base stations and repeaters.
This is an observation from someone that made a decision a long time ago
that mobiles were not designed for repeater service.
Hope you can solve the spur problem. Probably related to the
transmitter/receiver offset and will probably require a redesign to get rid
of the spur.
73
Glenn
WB4UIV
At 10:39 AM 07/02/05, you wrote:
>So, no one here has ever run into this before? Really??!
>
>I found and tested a third radio... same problem.
>
>To restate what the problem is: Micor mobile UHF T34...
>when running in the ham band transmit low / receive high
>they are spurring 910 kHz above the transmit freq. I don't
>know what would happen if the frequencies were reversed.
>
>443.750T 448.750R spur at 444.660
>444.000T 449.000R spur at 444.910
>
>It's not a power supply problem. The spur is generated low
>level, not in the PA (it's somewhere before or at the
>exciter mixer, Q305). It's not the offset oscillator. No
>amount of tuning or de-tuning various stages has any affect
>on the spur.
>
>Paul N1BUG
>
>
>
>
>
>
>Yahoo! Groups Links
>
>
>
>
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