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
> 
>