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MODE-UV lineair transponder design for P3e.


Before I left on a world-travel in October 2003 I made an SMD MODE-UV transponder for P3e.

A prototype of this transponder has also been tested on a high altitude balloon in Germany, with good results. Unfortunatly, during my travel I got the information that this transponder was not good enough to fly on the P3e satellite.

As a designer it doesn’t mean for me that everything ends with this. During my 10 month travel I think out a way to make a better design, but it has to be in a short time, and with less technical risk.

When I finally arrived home again from my long travel in August 2004 I directly started working on my new idea. The idea was to make the transponder in good old (none-SMD) component style, and cut the whole system in separate modules. The small separate modules make it much easier to measure and when problems occur only a small module has to be changed instead of a whole design.

After my travel, in just 6 weeks, I made a prototype design ready and present it in Bochum (Germany) at the 30th aniversary of AMSAT-DL. On the following link of AMSAT-DL my experimental prototype can be seen:



This experimental design I finally improved into a flight version transponder, and now, about 3 months later I can show some more interresting pictures. The transponder is still not ready, and there has to be done a lot of work to finish it completely. The work is not only soldering, but also lot of testing to be sure that the transponder will work under all conditions. Unfortunatly my free time is very little (just few hours a day) but when I can contribute to have more linear transponders in space I am not complaining J

To all AMSATs around the world… Instead of only talking I just show you what I have for you J


Left on the paper you can see the drawings of the module placements. On the right you can see the modules I already made.

Another view…

Ofcourse there is something inside J

What is what?

The most right-top (long-small box) is 435MHz to 1st IF converter. The one on the left to it (also long-small) is the 1st IF to 2nd IF converter with AGC control.

In the middle, on the top is the UHF-receiver local crystal oscillator. In the middle-below is the VHF transmitter crystal oscillator.

The second from left box is the IF combiner unit. Here all separate IF’s from RUDAK, Telemetry, 10m RX and 70cm RX are combined to one IF with extra care of intermodulation.

The most left box is a transmitter upconverter, from 1st IF to the 2nd IF. This module has a phase and envelope output, to drive a high efficient HELAPs amplifier.

·        What is failing is the converter from 2nd IF to 145MHz, an IF RX splitter, and the crystal filter matchings.

·        All three things are under construction, but are not concidered to be problematic.

Some more close-ups:

Below: 70cm RX to 1st IF;

Top: 1st IF to 2nd IF, AGC control


Below: The VHF transmitter crystal oscillator

Top: The UHF receiver crystal oscillator


Right: 4x IF combiner (2 inputs are on/off switcheable)

Left: 1st IF to 2nd TX IF up-converter, with phase and envelope output to drive HELAPs high-efficient final amplifier.



73 de PE1RAH, William Leijenaar…


This page is designed and created by PE1RAH. (William Leijenaar).