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R: 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.

For the above reason i suggest to change the uplink1 (L1) in to 1269.600 to
1269.750 MHz because it fall in to a transmit IF from 145.600 to 145.750 MHz
wich is additionally 1 MHz far away from the actual received IF

In addition the uplink 1269.600 to 1269.750 MHz for P3-E do not fall in to
the actual 23 cm (1) uplink for AO40 so that there should be no problems to
change accordingly the uplink passband 1 MHz up as a safety precaution for
the benefit of those who are using 23 cm transmit converters or 23 cm
transverters.

Waiting for your comments

73" de

i8CVS Domenico

----- Original Message -----
From: Reinhard Richter <r.richter@dj1km.de>
To: <AMSAT-bb@AMSAT.Org>
Sent: Wednesday, February 04, 2004 9:45 PM
Subject: [amsat-bb] P3E Info


> Hello all,
> since AO-40 has become silent many people look forward for the next HEO
> project, which will be most probably be P3E of AMSAT-DL. There was a
> certain
> lack of information, although we had some on our webpage.
>
> During the last year there have 3 articles about P3E been published in our
> AMSAT-DL journal. These have been put on the site, and just recently we
> could add English translations, two by John J. Bubbers W1GYD and one by
> Georges Mathgen, LX1BB.
>
> Please visit the page under www.amsat-dl.org/p3e and surf through the
> various infos. In case you feel a strong desire to donate some for the P3E
> project there is also a link: www.amsat-dl.org/p3e/donation-e.htm
>
> 73
>  Reinhard, DJ1KM
> Webmaster AMSAT-DL
>
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
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