--- Eric Lemmon <[EMAIL PROTECTED]> wrote:
> Stu,
>
> I think 250 watts is far too much power for that
> duplexer to properly
> isolate. Try running just your exciter, or try no
> more than 30 watts or so.
> My 220 repeater runs just 18 watts, and it is almost
> perfectly balanced. I
> am using the same Telewave duplexer, and I have zero
> desense.
>
> According to my CommShop program, you need more than
> 90 dB of isolation for
> 250 watts TX and 0.25 uV RX- and that's assuming a
> tube amplifier. The
> Telewave TPRD-2254 duplexer is spec'd at 85 dB, so
> it is borderline, even
> when perfectly tuned. You might try a sharply-tuned
> bandpass cavity to
> clean up the transmitter output, to see if sideband
> noise is causing the
> desense. Also, try a bandpass cavity on the RX
> input. As has been
> explained many times on this list, a BpBr duplexer
> has practically no
> bandpass effect, and what little effect there is, is
> very broad.
>
> 73, Eric Lemmon WB6FLY
>
>
That was my thoughts also. Seems too much power for
the ammount of isolation. Especially if a preamp is
used on the receiver.
I would like to know the modifications to the
amplifier to get it to run that much power in repeater
operation. I have one that will run around 500 watts
but use it for ssb. As this was origionaly a 50 watt
AM amp, I might see it running 100 to maybe 150 watts
out in FM repeater service.
Inside the amp are several pieces of coax. Is this
double shielded or has it been changed to double
shielding ?
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