Hi All, LF
More comments in behalf of Oscar, LU1DOW and his thanks for the interest in his
work
Rik: Oscar included class B in the PA just for testing some linear modes if
there is any future need. It is true that DFCW do not need linear PA
Marco: It is not a modified PA. The output was designed as a simple PL circuit,
so to resonate it in LF with the coil shown in the pictures it was necessary to
add
a high capacity in parallel with the plate tunning capacitor. High voltage mica
capacitors are used there
Stefan: Oscar will be happy to make tests in EbNaut as soon as possible and he
is very grateful for your help and good advices
73 de Luis
EA5DOM
-----Mensaje original-----
De: [email protected]
[mailto:[email protected]] En nombre de [email protected]
Enviado el: martes, 13 de marzo de 2018 13:37
Para: [email protected]
Asunto: R: RE: LF: LU1DOW soon in MF/LF
Hi Luis, Chris and LF,
enjoyed the pictures from Oscar.. when I see tubes my heart..
I don't wonder for the filament current (at 5V it means 150W) but how Oscar
arranged the PI or PL output matching circuit: I guess he modified an HF PA and
it means a lot of L and C to retune from 160m..
Hope to hear soon Oscar on LF/MF.
Now I'm testing the new TX for MF it is on since last saturday 24h/24h
trasmitting WSPR2 every 10 minutes.
I need some fine (at least dry..) weather to tune and match better the antenna
because now the return loss is not really wonderful (almost 10
dB..) so I haven't any idea of the ERP but it should be in the range of 200mW.
Enjoy MF/LF and lower ;-)
73, Marco IK1HSS
----Messaggio originale----
Da: [email protected]
Data: 13-mar-2018 11.28
A: "[email protected]"<[email protected]>
Ogg: RE: LF: LU1DOW soon in MF/LF
Hi Chris, LF
Oscar answered the question. I'll try to translate, but can't promise not to
make a mistake in tube terminology :-)
He is not using filament choke as this is a direct heating tethrode. So the
midpoint of the filament transformer secondary is connected to ground The
driving is to the grid with a tuned circuit. It works in C class for QRSS and B
Class for DFCW. And YES, this a dangerous high voltage bricolage and a waste of
energy. Just the filament is sucking 35.5 Amps :-O
Oscar plans to test first single carrier in LF with LU8YD at 1000Km first to
check if all is going as in previous tests some time ago.
After that he will switch
to MF and test again
73 de Luis
EA5DOM
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