OK. My reason for mentioning these amps was to answer some of the
negative points being made in regard to a fictitious KPA1500. These
days one does not have to combine a lot of lower power FETs to reach
QRO. I gave you a link to the device which is made by
Freescale. There are comparable devices made by NXP.
I replied to the argument that one can not run them linear at
1200w. To quote myself: "So combining two running 750w each gets you
1500w in linear operation with 2400w dissipation." Most RF
transistors will not be linear if driven into saturation so one backs
off on the drive and resultant output to improve linearity.
Heat dissipation is taken care of by using copper heat spreaders
under the transistors coming from all these suppliers unless you buy
the LDMOS directly (W6PQL uses a 3x5x1/2 inch copper spreader). I
would suggest either the amp kits or buying assembled amp pallets to
build with.
Price: two LDMOS would run roughly $500. I new 8877 from RFParts is
$1450 (Eimac) or $665 (Taylor). Of course you can purchase a used
8877 in the $350-450 range. The HVPS will run about $500 and you
probably would have another $400 in materials to complete a basic HF
amp with manual tuning (total= $2350 (Eimac) to $1250 (used 8877)).
W6PQL is offering an assembled single LDMOS amp for $825 so two would
run $1650 and probably another $400 to make a complete 1500w SSB HF
amp. Surplus HP Blade 50v -50A PS run $30-50 on e-bay. To run two
LDMOS you just have two 50vv PS supplying each separately. Total= $2150.
If you build your own you can save a little off this total - W6PQL
kit is $563 which includes the NXP BLF-188XR.
http://www.w6pql.com/parts_i_can_provide.htm est. total
2x$563+$400+$100 = $1625
No point belaboring this as there are going to be some amps showing
up this coming year using these LDMOS devices.
-----------------
From: Kevin Stover <[email protected]>
To: [email protected]
Subject: Re: [Elecraft] LDMOS for QRO
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
W6PQL has designed and built a 1KW SSPA for 1.8-54MHz using an LDMOS
device. Freescale I think.
he has also designed a pretty stout Low Pass filter designed for 1.5KW
1.8-54 MHz.
He can get 1.2KW out of it at saturation with 2-3 W drive.
A pair of these devices @ 750W could do 1500W all day any mode. but then
the power supply becomes the limiting factor.. 50V at 70amps?
http://www.w6pql.com/1_kw_sspa_for_1_8-54_mhz.htm
73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[email protected]
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