Hi Geert
Missed that from your site - I have studied it quite closely when I
building the 70cm amp.
(now I need antennas and a transverter for 70cm! To do eme)
The 2m SSPA using BLF578XR is already built and somewhat smoke tested, I
will post some building history when I have time ;)
Guess I will just try it out ! - I was thinking of selling the gs35b’s but
the cost of shipping etc made them to expensive compared to ebay.. So
better use them
I also have a gm3sek board lying around doing nothing.
73, Benni TF3CY
On 04/04/14 16:55, "Geert PA3CSG" <pa3csg@hoeplakee.nl> wrote:
>Hi Benny & list,
>
>I use a 2 X GS31 amp on HF.
>
>With 100W of drive you will see around 2kW. I run them in parallel with
>the grid grounded. Well below tube spec!
>
>I did worry about input impedances in the beginning but forgot what is
>was... It is pretty close to 50 ohms for sure as on some bands I don't
>need the build in antenna tuner of my rig. Not much thinking plain
>building :-) And it saves alot of switching and stuff
>
>Some pics:
>
>http://pa3csg.hoeplakee.nl/joomla25/index.php/rf-construction/87-hf-amplif
>ier-2-x-gs31
>
>These are old pics. I replace the roller inductor because of too many
>parallel capacitances to ground and replaced it by a switched coil.
>
>Regards,
>
>Geert PA3CSG
>
>
>Benedikt Sveinsson schreef op 4-4-2014 18:02:
>> Hi amps specialists
>>
>> As a side project I have been building a HF amplifier.
>>
>> I have successfully built a GS35b 70cm amplifier, I have a big external
>> power supply (1,5A ICAS @4kv) that I previously built.
>> I was going to build a GS35b 2m RX1AS style, but decided on going for a
>> SSPA as my K3 that I use for EME can only output 10w, so driving the amp
>> would need a separate driver amp and I just went for the SSPA and that
>>is
>> near completion.
>>
>> I bought some GS35b¹s in Friedrichshafen last summer and I have sockets
>> etc...
>>
>> And for some more back story - the idea was to buy a GU84 or similar
>> tetrode for the HF amp, but I wanted to build the tank first and see if
>>I
>> could indeed build the damn thing. Now I think I have the tank fully
>>built
>> - and I started contemplating just putting a single GS35b in as I have
>> some around.
>>
>> What about 2x GS35B¹s ?
>>
>> Has anyone here done that ?
>> What is the input impedance of the two tubes ? (scarse info available)
>>(I
>> have a WD7S input board that he mailed to me by mistake, I will pay you
>>if
>> I decide to use it! ;)
>>
>> I imagine it being a helluwa high power amp - but good for 48 hrs
>> contesting doing 1.5Kw (not imagine driving it hard!)
>>
>> What would be the drawback on using two tubes - I read somewhere don¹t
>>use
>> two tubes, use a bigger one!
>>
>> There is a considerable investment in a GU84/GU78 with a proper socket -
>> and I¹m worried about stability of a high gain tubes - (do I have to?)
>>
>>
>> 73, Benni TF3CY
>>
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>
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