Activation via satellite AND websdr?

Yesterday there was an Oscar 100 activity in my home town Hannover. My friend Torsten DL1TOG is currently in Antarctica at the Neumayer Station. There they successfully put a Es’hailSat-2 TRX into operation in company with Felix DL5XL. Here is a 35min long recording in German of the contact. QSO in mp3

The activity motivated me to build a portable TX for 13cm myself and also to perform Sota activations this way. The downlink on 10GHz requires a 40cm or bigger dish. Therefore, I plan to use a 13cm Helix for the tx and the WEBSDR for reception.

Now my question. Would such a QSO count as a valid activation?

73 Chris

Hi Chris,

I don’t see why it wouldn’t.

Satellite communications are a special case under SOTA as terrestrial repeaters are not allowed but satellite based ones are.

The fact that you use the WebSDR at Goonhilly Downs in the UK to receive I don’t see as a problem as in the scale of things - that is relatively close to your location, when you consider how far out QO-100 is.

I’ll leave the MT to come back with a clear yes/no answer but I’d say just go do it - irrespective of SOTA, operating through QO-100 from a summit will be a great achievement.

By the way if the 2.3GHz helix doesn’t work for any reason, or you want a simpler solution than building the helix (although building is half the fun) there are 2.4GHz WiFi extender Yagi antennas that might also fit the need.
73 Ed.

As QO-100 has been worked where the activator had a dish and 3cms downlink gear on the summit with him there doesn’t seem to be any justification to only go half-way towards doing it all yourself.

As of now it would be within the rules. Or more accurately, it would not be outside the rules. Rules can change.

Whilst WebSDRs all not explicitly outlawed for chasers we can point at general rule 3.7.1 for at least two ways it would be hard to comply as an activator.

The activation team would have had to have carried said WebSDR to the site. Also the WebSDR could not be powered by mains or a generator.

So, if you want to duplicate the Goonhilly setup and carry it to site along with sufficient batteries that’s probably Ok then to use it as your RX. But I’d suggest it’s probably easier to eliminate the Web bit!


I am working on my system for QO-100. At present it has only been used on SOTA Carparks, but later this year it will go up the hill once we get some calmer weather. There are one or two bugs, the most tricky is the Rx stabilty without a GPS reference but this is being worked on. The dish is 50cm, this is adequate with a strong station on the sat and I Tx about 1.5W.

73 de
Andrew G4VFL


Thank you Edward for your support. Basically, I want to achieve a sattelite qso on a summit, whether it is valid or not.

The very cheap one you suggested doesn’t seem to be any good if you look at the reviews on Am.z.n.

73 Chris

Andrew, nice equipment. 1.5 Watt at 13cm and a gain of 20dbi is enough for the uplink? Good news for me.

73 Chris

This looks very misleading to me. To my mind it is outside the rules as the actual receiver of the WEBSDR is neither carried to the summit by the activator nor powered by a portable power source. @G4TJC has stated this correctly in his post.

I understand that it is harder to do QO-100 activations without the use of a websdr. But in times of remote stations rule changes in this direction seem to be very dangerous to me.
In the next step activators will only carry a HF receiver up to the summit while they transmit with their remote controlled station at home.

73 de Michael, DB7MM


Nice set up, what’s in the white box ?

A rats nest !

The UP link trasverter from sg-lab
The DOWN link converter and bias T for the LNB from Transverter store
2.7AH LiIon battery (14v) to power the transverters and the FT-817, with some luck I should get about 30-60 min operation on the summit.

There are some power pole connectors to recharge the battery and power the whole setup in the shack when I use it at my home QTH.

The FT-817 runs split mode with Rx 144MHz on the front connector and Tx 432MHz on the rear.

I have also made an arduino use the CAT interface on the FT-817 to set the two VFOs and setup split mode etc. With the buttons on the mic I can then set the Tx Freq based on the Rx Freq and the relative difference from the beacon freq, I bit like SDR-Console but it does not automatically track the drift in the LNB.

The setup does not require a computer on the summit.

73 de
Andrew G4VFL


On June 29, 2019 LZ1GJ and LZ1NG, we activated the LZ / RO-086 via QO-100 with the courtesy LZ1NY equipment. TX - FT-817 + SG LAB 430MHz to 2.3GHz transverter (SG Laboratory Ltd.), RX - RTL SDR and 10GHz LNB + 2.4GHz Patch Antenna (http / and a 60 cm dish.

1 Like

I’m sure you’re right, Michael. Every technical aid - in this case a WebSdr - reduces the challenge and thus the sense of achievement when activating.

I even include spoting by mobile phone, although I don’t want to do without it.

Wolfgang, DK1HW told me that during his many initial activations in our area he was without a cell phone.

He called on a qrp frequency in CW and was mostly heard by the chaser. Respect!

73 Chris

1 Like

I was always under the assumption that any RF TX/RX equipment had to be located in the proximity of the activator. Wouldn’t using a WebSDR, with the receiver being hundreds or thousands of miles away, be outside the spirit of SOTA? You’re not always going to have an internet connection and I thought SOTA was supposed to be sort of “off the grid”.

Agreed. I always thought RX/TX equipment had to be located with the activator.

I made the first successful attempt to receive the QO-100 today. Without dish, only with LNB, SDR and notebook.
Here is a short video of my primitive construction: DL1CR First attempt receive QO-100 - YouTube
73 Chris


Why stop there? Just take your phone up and work completely from your mobile device controlling your rig back at the QTH. No pesky antennas to deal with, no challenge of how to set up on the summit, and no issues with power! :roll_eyes:

Does your signal then come from a summit?

Yes, that’s the plan. Send at 13cm via an Adlam Pluto, a 1W Pa and a 1m long helix. Received via a 40cm Planar Sat dish with integrated LNB and the Pluto.

With a notebook brought to the summit by hand and on my own feet, hi.
73 Chris


Today I had my first QSO via the QO-100 satellite. The homebrew equipment is not yet suitable for a summit and not very stable in terms of frequency, but we are on the way.

73 Chris

The new step to summit qso via QO-100 has been made. I was able to replace the master oscillator from the Adlam Pluto. The TCXO is damn small, with two reading glasses on top of each other I made it. Now there is no frequency drift anymore. At the moment I have an output power of 1W and use a self-made helix as an antenna. The ERP is about 30 watts. It generate a decent CW signal on the satellite, but it’s not enough for SSB. I have therefore ordered a 20W Pa, so it should work safely.
Here is a short video of my attempt today, unfortunately in German. The websdr serves as the downlink.

73 Chris