Re: LF: 137.5kHz WSPR beacon ON Tuesday 5.30pm -11.00pm UK time

[Andy Talbot <andy.g4jnt@googlemail.com>]

Its not possible to run from a lower voltage - unless I use a Variac on the input.  

A half bridge arrangement, running direct from rectified mains - so Vcc = 320V  See http://www.g4jnt.com/137tx.pdf  for teh original QST article.

Its extremally robust  - I use the soft protection system originally employed on the Decca transmitters and detailed in the write up.   It can deliver 800 Watts - thats the limit I ran it to originally, so wound back to 600 Watts it will go on forever - which is more than the ATU housing could manage!

 

Increasing the output turns ratio would do the job, but I do need an intermediate power PA, so might as well build a quickie breadboard one.   All the components needed for just about any type of circuit configuration are all in the junk box.

Andy
www.g4jnt.com

On 21 September 2010 18:47, Rik Strobbe <Rik.Strobbe@fys.kuleuven.be> wrote:

> Just contemplating design option for a PA for the intermediate power range of 50 - 100 Watt

 

Andy,

 

running the 600W PA at 40% of the voltage should give about 100W

And the PA should be really fool proof at 1/6 th of the max. power.

 

73, Rik  ON7YD - OR7T