Re: LF: 137.5kHz WSPR Tuesday evening - reports appreciated

[Roger Lapthorn <rogerlapthorn@gmail.com>]

Just hit a bit of a snag and blew up my (last) IRF510 PA because of totally inadequate heatsink. So, I'm on 137.5kHz WSPR but only with about 1W from the simpler PA at present, so ERP low uWs.  I need to get some heatsink and more FETs!

Any reports (now less likely) still appreciated.

[Mal - it started out as a Class E design attempt but hadn't been optimised, so I guess this counts as class D. ]

73s
Roger G3XBM

On 7 September 2010 17:34, Roger Lapthorn <rogerlapthorn@gmail.com> wrote:

My 137.5kHz WSPR TX transverter is now working fine, so I'll be on-air with WSPR tonight (Sept 7th) from 5.30pm - 11pm UK time.

After my success on QRSS3 with G3XIZ I'm hopeful he'll now decode my WSPR signal tonight, assuming Chris can take a listen. If anyone else within, say, 100km of Burwell, Cambs JO02dg cares to take a look for the WSPR beacon (running around 35% TX time) I'd be most grateful.

Not sure if anyone else has had this problem, but I was using the small 16mm 3C90 cores (cream colour) as the PA bifilar output transformer and I had all sorts of issues with the darn thing overheating and even one cracking. I replaced this with a choke wound on a T106-2 core and made the output network work in class D/E and now everything is working very predictably. The larger diameter 3C90 cores seem fine in the step-down transformer matching the "in the air" loop.

The WSPR beacon is now going ON.....

73s
Roger G3XBM


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G3XBM   GQRP 1678    ISWL G11088

-- 
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
G3XBM   GQRP 1678    ISWL G11088