[amsat-bb] Re: V/U Linear Transponder

William Leijenaar leijenaarelectronics at yahoo.com
Thu Aug 1 05:26:52 PDT 2013

Dear Tanan,

I am sorry when I didn't noticed your email before.

The choice between FM transponder or linear transponder depends on the purpose of the satellite.

FM transponders can only adress one station at a time (the one with the biggest uplink power will win), and can only do FM, which is available to all hams, which makes it even more crowded on this one channel.
On the other hand it is easy to make (one chip solution).

Linear transponders use some more DC power, but can address multiple stations, in multiple modes (CW, SSB, FM, BPSK, etc), it also leaves room for new (experimental) modes (as long as it fits in the bandpass).
The disadvantage is the more difficult RF circuitry, which needs quiet some RF knowlegde and RF experience.
To overcome these disadvantages I put my experiences in the developed of the small linear transponder LE005-R2.
It can save development time and development cost on (satellite) projects a lot.

Kind regards,

William Leijenaar


 From: Tanan Rangseeprom HS1JAN <hs1jan at tamsat.org>
To: amsat-bb at amsat.org; leijenaarelectronics at yahoo.com; PE1RDW <sats at pe1rdw.demon.nl>; g0mrf at aol.com 
Cc: thidad1 at gmail.com; hs5igy at hotmail.com; chawalit at station.in.th; hs2jfw at gmail.com 
Sent: Tuesday, July 30, 2013 6:04 PM
Subject: Re: [amsat-bb] V/U Linear Transponder

Dear All

Thanks respond for help to me

1.Thailand has regular to forbid for transmitt UHF band but can receive the signal for amateur radio satellites only. we need to used VHF band same like transponder  of Japanes (FO-29) , AmSat AO-51 , Saudiarabia SO-50 and other satellites. for interference from China Thailand and other countries on VHF is normal.

2.Ok, I do not have knowledge 100 khz bandwidth is too much for the over power. please advice me for 30 khz uplink 145.90-145.92 MHz VHF / 435.10 - 435.12 MHz UHF of  liner transponder.

3.We have to design FM repeater use to modify HX1 / RX2A RADIOMETRIX VHF / UHF transmitter module we have change x-tal to 145.90 MHz / 13.59 MHz and used MC3361 with x-tal 10.245 MHz and CML IC FX465 CTCSS Encode/Decode build test it to be successful.

We and technical team of TAMSAT group would like to help and advice for circuit diagram of V/U transponder same like transponder
 of Japanes (FO-29) and other satellites. We had mail to Mr.William Leijenaar PE1RAH  but do not have respond feedback. Mrs Thida of 100watts ham radio magazine of thailand sugges me to know Mr.William.because she meet him on Tokyo ham fair 2009.

On this time we and technical team of TAMSAT group need help very urgent. we need advice of circuit diagram or datasheet  IC for build V/U Liner transponder  for payload 1U cubesat of JAISAT satellite project.

best regards

Tanan Rangseeprom HS1JAN
Project Manager of JAISAT-1
member of RAST
email : hs1jan at tamsat.org

----- Original Message ----- From: <g0mrf at aol.com>
To: <hs1jan at tamsat.org>
Sent: Monday, July 29, 2013 5:24
Subject: Re: [amsat-bb] V/U Linear Transponder

Dear Tanan.

Thanks for the mail via AMSAT.org

My name is David Bowman  G0MRF and I'm a member of the team building
FUNcube, due for launch this November.

I can help with transponder design, but there are some points which you
need to consider.

1) The use of V band for the uplink will be a poor choice for your
location.  The interference from China and other countries on 145MHz
will mean the transponder will not be usable.   Using U band for the
uplink is a much better choice.

2) The 100kHz bandwidth is too much for the typical power available
from a CubeSat. If you get your RF team to do a link budget analysis,
you will see the cubesat power budget will not support 100kHz of
bandwidth. Ususally 30kHz is as much as you can do with a 1U cube.

3) You may want to
 consider a FM 'repeater' as there is now only 1 in
orbit, while there are several linear transponder satellites ready to
be launched.
The FM design will allow you to run a very efficient power amplifier
(70%) and power can be saved over oceans and areas of low population by
using a 67Hz access tone (CML FX465)

I can assist with design but would need to know if you are planning a
1U 2U or 3U design.

William PE???? is good, but will probably just offer to sell you a


David  G0MRF

some old info is available at  www.g0mrf.com/transponder.htm

The attached powerpoint has some pictures of the UV transponder and
other boards in FUNcube from AMSAT-UK 

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