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RE: P3E Info




>
>
> Hello Reinhard DJ1KM and Peter DB2OS
>
> I was looking in to the table of P3-E frequency proposal and i found a
> possible source of problems.
>
> The uplink1 (L1) passband for linear is from 1268.600 to 1268.750 MHz
>
> The downlink (S) passband for linear is from 2400.275 to 2400.425 MHz
>
> Many of us are using transverters with 144/146 MHz input IF and
> 1268/1270 MHz 23 cm output
>
> The most part of us are using S band converters with input 2400/2402 MHz
> down to an IF of 144/146 MHz
>
> Accordingly to receive the passband 2400.275 to 2400.425 MHz we must
> tune an IF receiver from 144.275  to 144.425 MHz
>
> Since P3-E has inverting transponders to be translated in to the above
> passband neglecting doppler we must excite our 23 cm transverters with a
> transmit IF from 144.750 to 144.600 MHz
>
> In this condition the received IF passband 144.275/144.425 MHz is
> too close
> to the transmit IF passband wich fall in to 144.750/144.600 MHz band
>
> For example,neglecting doppler,a 144.425 MHz receiving IF is only 175 KHz
> away from the correspondent transmit IF of 144.600 MHz and consequently
> desensing or gain compression of the IF receiver is possible.

WHAT!?

Someone still using passive upconverter? Open line feed? Unscreened coaxial?
If You use separate rigs, it is no problem. If You use modern rig with
the second inband receiver, it has good dynamics. (Not excellent ;-)
Experiencing wideband noise blocking signals even without drive power,
it is then time to get a new rig.
It is not good practise to drive 100W to a power attenuator to get a couple
of
milliwatts for transmit converter.

However concerning the bandplan nothing is lost yet.

-Jari OH3UW

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