Other SOTA sites: SOTAwatch | SOTA Home | Database | Summits | Video | Photos | Shop | Mapping | Sotlas | FAQs | Facebook | Contact SOTA

Vacuum tubes on the summit

Test for use on SOTA activation:

Just did a first test hike with Hejkalset in my old comfortable metal frame backpack with a large load capacity (since a vacuum in electron tubes weighs almost nothing). I spent two hours on the trails with no real difficulties and ended up with four nice casual QSO’s.

Finally, I spent more than three beautiful hours on a trip that was supposed to take a few tens of minutes.


Vacuum tube rig on a summit, wonderful!


Ja! I always wanted to bring a WW2 stn to the summit on the back of a Haflinger.
And we need a second one for the power supply, hi
73 Martin OE3VBU

That is wonderful. What batteries/boost converters did you use to get the heater and HT?

Superb !! Congrats.

There are four double triodes ECC88 with a heater voltage of 6.3 V and one double beam power tetrode QQE03/12 with a heater voltage of 12.6 V in my homebrew QRP tube transceiver Hejkalset. Double triodes are paired up based on their heater current at 6.3 V and heater filaments of each pair are connected in series. The heater voltage should be kept within +/-10% of its nominal value for optimum valve performance. I started out using a sealed lead acid battery 12 V, 12 Ah. The anodes and grids are supplied by a high-voltage, non regulated push-pull converter with EMI suppression.



What fun, maybe a new trend ? How much did the vacuum containment structure weigh ?

This is where the “goat” comes in… Steve, WG0AT could bring
the whole HF station up the hill!
We brought a lot of old tube rigs up the hills for Field Day in the
old days (In a truck !)
John, K6YK

1 Like

I wonder how many shortwave activations with vacuum tubes took place so far.
Is there anyone who is using them in this manner?

73 Karel, OK2BWB

1 Like

Hi, I have one RA-200, would be fun to try it portable. It is a 3 men load to carry, and you need someone to pedal the generator.



By chance, a friend just sent me newsletter about using radios to support the 1933 Everest climbing expedition. Many technical details, and some pictures.
The article is in the K9YA Telegraph and can be found at at http://www.k9ya.org/index.php.

I have attached a clip of the front page of the newsletter;


From ancient times:

1 Like

Dynamotor :+1: :grinning:

I remember back in the 70’s I sketched out a design for a portable 2 metre rig using the 1.5volt filament valves (1T4, 1S4 etc) multiplying up from an 8 MHz crystal. I got as far as assembling the components but lost interest when I bought a Liner 2 and migrated to SSB. I’ve still got the valves somewhere.

1 Like

This 40m CW TX started out as a quick retro junk box project during the latest lockdown, but it has drawn me into revising my knowledge of class C operation through lots of tinkering! Currently producing 0.5W from 1.0W dc input. It uses two DL94 1.4v battery valves…


I know that are Paraset spy radio fans who activate /p.

https://youtu.be/kGBy0euU1JU :+1::+1::+1:

1 Like

Hi Karel @OK2BWB,
Fantastic :+1:
Nice to work you today from OK/VY-001 :wink:
Many thanks
73 Éric

Thank you, Éric.

The Armstrong triode regenerative detector (invented ín 1912), Hartley modification, my circuit to synchronize it with the transmitting Colpitts triode superVXO and some brain digital signal processing to suppress the unwanted sideband make Hejkalset a nest of clearly singing chasers. The shorter and the more linear the receive path is, the clearer the sound becomes. It was a great pleasure, even though I had to concentrate hard at first, to keep up with the wild communication arena. And straight keying is icing on the cake!

Karel, OK2BWB


Tnx Karel for FB contact today

SA4BLM / Lars

MM0FMF, I wonder how many folks have seen or used a dynamotor?
Or even know what it is? My first 2-meter FM radio had a dynamotor
in it! 500 volts at 200 MA as I recall. And the receiver ran from a
vibrator supply. Just the dynamotor weighed more than any modern VHF radio!
John, K6YK