Re: LF: Re: 137.7682kHz QRSS30 beaconing - reports appreciated

[Stefan Schäfer <Stefan.Schaefer@iup.uni-heidelberg.de>]

Roger,

If that small heat sink actually remains cold, efficiency must be quite 
good! Even switching the FET without a drain current causes losses... 
Since the IRF540 is a 100V device, you have plenty of space for QRO :-)
Nice circuit. It shows how easy one can build a LF PA! Not much 
difference for a 500W type, just the FET has to be changed to a IRFP260N 
or so...
73, Stefan/DK7FC


Am 08.09.2011 15:33, schrieb Roger Lapthorn:
> Photos of (a) the 137kHz QRSS30 beacon and (b) the 137kHz transverter 
> are on my blog page at 
> http://g3xbm-qrp.blogspot.com/2011/09/lf-kit-improvements.html .  
> Subject to test results, both may be tidied up and boxed later. 
> Otherwise it is back to the bench.
> The PAs run almost cold, whereas my 50 ohm dummy load is very hot, 
> suggesting very good efficiency from the IRF540 device in each case.
> 73s
> Roger G3XBM