Hello Roger,
Maybe you can send us a circuit with its values. I have built class E
PA for 2200/160/80/40/30/17/10m and have some experience. If you are
using a IRF510 and stay in the QRP range (< 10 W) at 137 in a class
E stage you wouldn't even need a heat sink at all if well dimensioned!
See the infos at http://www.classeradio.com/ This is most useful if
you are starting with that design. On 137 kHz problems are much smaller
than on HF :-)
Best 73, Stefan/DK7FC
Am 07.09.2010 20:17, schrieb Roger Lapthorn:
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 <[email protected]>
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
--
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
http://www.youtube.com/user/g3xbm
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
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