Ground control to major Tom ;)

While ago @andrewback mentioned project with LimeSDR on board of ISS
So here is my humble experiment in attempt to support their efforts… So far the result is no detection.
Please read about that here / chat bellow:

I am limited with resources regarding equipment, main RF tools antenas and PA
are not on hand. Therefore I decided to try with some QRP level of signal from FT817 5W on 70 cm,
but with some math =>

My optimistic math on 547 km @ 435 MHz
-Effective Isotropic Radiated Power Level of: 43.99 dBm

Free Space Path Loss: 140.0 dB
Expected sensitivity on ISS side -98 dBm (20 dB loss of cables + coupler, included)
My local measurements on the same LNAL modified LimeSDR RX are:
-60 dBm source signal & – 50 dB att & – 6 dB signal spliter
& still plenty of available/detectable signal)

Left CubicSDR & LimeSDR on Right SDRPlay RSP1 in SA mode

LimeSDR and ERASynth+ @ 435MHz -60dBm swap on

signal splited

In separate test on place of RSP1 was FT817 on RX which is able to hear the same level like
modified LNAL on LimeSDR.

This is the configuration on ISS

Still consider, that my 5W must be detectable on clear freq by major Tom aka LimeSDR on ISS :smiley:


Very cool, thanks for sharing and keep us posted!

Also moved to the new sat apps category, as seemed like a close enough fit and this is something where there will be more news and activity in due course. :smiley:


Thanks Djani for posting this here. I knew I forgot an important ToDo on my list, which is announcing MarconISSta here. If anybody has any questions on the sytem, let me know. We plan to do some experiments where other ground station operators will be included to measure their signal strength from space. I will announce it in the new satellite category!

Best regards


I was ready for today pass by:
Maximum altitude 12:50:00 77° 146° (SE) 422 km

But, Marfi rides again:
something wrong in the parameter list that I sent to the ISS last week. Although tuned to UHF, we accidentally use the L/S band patch antenna for this week’s run,
So swimming, instead of ISS :sunny:

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