Hello John, LF,
Thanks to Steinar/LA5VNA who kindly gave me the hint to a free program
to draw schematics on the PC (http://www.expresspcb.com/index.htm),
which works very well and intuitive.
Now i have now created the circuit of the exciter of my LF PA, as
promised. Here it is:
http://dl.dropbox.com/u/19882028/LF/LF%20H%20bridge%20PA%20Exciter%2C%20DK7FC.jpg
This is what i'm running here during the last months.
I will also create the schematic for the rest of the PA including the
complete H bridge configuration and LPF and publish that here, in a few
days.
73, fun, Stefan/DK7FC
Am 05.03.2012 09:28, schrieb John Rabson:
Thank you Stefan.
These pictures are very helpful. I look forward to seeing the exciter
information.
73
John F5VLF
On 4 Mar 2012, at 14:22CET, Stefan Schäfer wrote:
Hi John,
Am 04.03.2012 13:35, schrieb John Rabson:
You recently mentioned that you were using an H-Bridge amplifier for 137, but I
seem to have lost the details. Could you post them again, please? I am finding
that I am rather good at blowing up class E PAs and think I should look for
something that is rather more robust (and more tolerant of variations in load
isimpedance).
Well i have done some drawings and pictures in the last time, concerning my PA
and LPF and matching system.
Here they are:
http://dl.dropbox.com/u/19882028/LF/DK7FC_137kHz_TX_antenna_and_PA_schematic.jpg
http://dl.dropbox.com/u/19882028/LF/PA%20output%20filter.jpg
Hm, sorry i'm missing the photo of the drawing of the exciter. I know i have it
on a sheet but maybe i forgot to scan it. Will so that next week. Pse ask me
agn if i forget it.
BTW the blue output transformer in the photo handles at least 1.5 kW CW at 137 kHz. Usually if
people ask what type of ferrite is used in a PA, the answer is like "it is taken from a SMPS
or old TV and unknown origin", "found it in the junkbox"... But here i know the
exact type and even a distributor and even the price! ;-) It is even avaialable in quantity = 1 :-)
It is a B64290L0699X830. Datasheet:
http://dl.dropbox.com/u/19882028/Datenbl%C3%A4tter/B64290L699X830.pdf (page 3)
Available e.g. @
https://www.buerklin.com/default.asp?event=ShowArtikel(84D258)&l=d&jump=ArtNr_84D258
for 10 Euro :-)
73, Stefan/DK7FC
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