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Here you can see the last prototype of the satellite transponder that I designed and made.

The idea of me is to make an lineair satellite transponder, because todays new amateur sats can only do

the easy to ake FM modes, or PACSATs where the mode is only packet.

With an lineair transponder you can do lot of more experiments, and it is much more funny to have an

analog contact in voice or send SSTV pictures, or do RTTY, or what ever you want to do.

I am an student and I like my hobby because of the elektronical part.

My interrests are space communications in the VHF and up area.

I did already made 3 lokal FM repeaters, and now I wanted to make something more.

I tried to find some interrested people. At my school I find none, and in the lokal amateur world I found

nobody interrested in sat. and not with such elektronical level of knowledge.

So, I started to do it by my own, I already designed 3 lokal FM repeaters. <REPEATER SITE>

So why not an sat-transponder ?

To get the best chance of an lift into space and operate for long time it has to get some conditions.

  1. It must be small in size, and leight in weight to get easier an "second payload" place into an rocket.
  2. It must be sensitive and enough output power that it can be used easy.
  3. Good effeciency to get low current (smaller solar+batteries = smaller size) , and low heat production.
  4. It must be temperature stable for good radio contacts.
  5. Radiation proof to get longer life time.
  6. All must be vibiration proof to get no suprises after lauche,
  7. So, no wires , no internal connectors, all no SMD components made vibiration stable.


This prototype is an lineair mode-B transponder. (ALL MODE 150 kHz bandwith.)

RX: 435.175 MHz - 435.325 MHz. LSB

TX: 145.975 MHz - 145.825 MHz. USB

This prototype has 15W output at 2 meter, and GaAs Fet amplifier on 70cm RX



The whole transponder is made into an metal box of 16cm x 10cm x 3cm.

I use SMA because the connector can not disconnect due to launch vibirations, and the size is small.



To make it as light, small and shock proof as possible, 95% is made of SMD components.

Some closer view.


The component side.


Upper right you can see the power module.

The two (black) coax cables are quarter wave second and third overtone filters.

Upper middle the crystals (temperature stable) with adjusting coil.

Left you can see the 2m helical filter to get only the 2m signal before going to the power module.

Below middle, Completely left you see one of the two mixers, and in the middle you can see two

transformer coils for the IF filter impedance matching.

Below righ you see the 70cm RX helical.

I used 3 SMA connectors visible at the right, upper is 2m TX, middle 12V DC, lower 70cm RX.

Everything is 100% shielded from each other, because interference at such small space is an very big

problem and 100% shielding is the best sollution.


The final design.

I have no pictures of the final design because I am still busy with assambling it.

I made some changings it the design.

I removed the 15W power module, because it produces much heat and takes high currents.

To use such amoung of power into an satellite you need lot of solar cells ($$$) and large size of satellite

body to get enough cooling and no over heating.

Now I use the MRF237, it gives about 3W and cooling goes via the metal body of the transponder.

I only needed 1/2 of the space now , the other 1/2 of space I put in an CW beacon.

It will work with an 83751 uController that has an PROM and will not be erased due to radiation.

(Ofcourse I will take the large temperature device)

I could also include an watchdog circuit, that will reset the uController when it fails to work for some

reason. I have no shuttle to go up and reset it hihi.


Some word from me.

I made this all because of HAM spirit.

I like HF elektronics in relation with space, and to design circuits with extreem conditions.

I designed circuits, designed PCB's, made PCB's, assembled everything, measured everything

and also payed everything by my own !!! I got some help with testing from ON1DLL, and DL4EEC

he helped me with making the pictures at his "QRL".

I liked this project very much, and I will call my satellite: PE1RAH-SAT

After my school I will look for such an job (designing sats), maybe someone knows something !


Unfortunatly I can not effort high effecient solars and batteries that I need.

I must also find some way to make an outer body for it, that gives also some extra radiation protection.

I think stabilisation is not needed, maybe with magnets but I have no final idea.

Maybe someone knows some more about how to get space solars, or space batteries.

Maybe someone can help with making an one peace light metal box as satellite body.


An idea of the final satellite.


Let's hope I will find some lift into space at the end, I will go for it !!!

When you know something, please tell me [email protected]


This page is very new, and the main goal for me is to give technical information, so don't look at my English.


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