FWIW I am running the AN-762 at 140w using 12v with either the K3 or
KX3 with no complaints. It takes only 3.5w drive on 20m.
But no longer do you need to run a dozen "pills" (man I hate that
term). Here is all you need for 1250w 1.8-600 MHz:
The
MRFE6VP61K25HR6 1.25KW LDMOS from Freescale at $241.50 from:
http://www.communication-concepts.com/mrfe6vp61k25hr6-1-25kw-rf-mosfet/
Or several others. I haven't seen the article in QST but suspect
they are using this device. It runs on 50v at under 50A and only
requires 3-4w drive for 1200w output. KX3, FT-817, K3/10 all capable
of driving it directly.
73, Ed - KL7UW
$241.50 compared with the new price of a 8877 is pretty cheap!
73, Ed - KL7UW
They don't need to be dirty ... the problem is that it takes so many
"pills" to make the power that designers tend to use the 60, 80 or
100W rated transistors right up to their saturated output rather than
limit each pair of devices to 50 - 60% of PEP output. For example ...
the MRF-421 is rated as a 100W transistor but third order IMD is
minimized around 50-55W. An "eight pill" design could make 900W in
saturated mode but in order to keep it clean, the output would need to
kept to 500 W PEP. This, in spite of the fact than Communications
Concepts sells a 2 x MRF-421 board set as a "180 Watt HF amplifier"
(Motorola AN-762).
73,
... Joe, W4TV
73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
dubus...@gmail.com
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