Seeing all the email traffic about amplifiers driven by a K2, I thought that
I would relate my experience. Several years ago, I built a homebrew HF CW
transceiver for 40, 20 and 15m bands, and I built an amplifier into a unit
with a Transmatch to complement it. I used the EB27A from Communications
Concepts, Inc., in Dayton, Ohio.
(
http://www.communication-concepts.com/eb27a.htm) It is a 300 watt amp that
runs on 28 VDC. I was fortunate to be able to buy a 28V, 30A supply on ebay
at a very reasonable price.
The amplifier is fairly straight forward to build, though the instructions
are not up to Elecraft standards (at least they were not those many years
ago.) I purchased the solid copper heat spreader that they offer, and I
mounted the assembled amplifier board and heat spreader to a heat sink that
forms the back of the amplifier/Transmatch unit. I built low pass filters
for the output from the filter design tables in the Handbook. With the
purchase of my K2 (SN 5251), I added filters for the lower and upper bands.
I can now drive the amp to more than 200 watts on all 8 bands with the K2 (I
do not have 160 or 60 meter band mods installed). The amp has a nominal 13
dB gain, more on some bands.
To make this work with the K2, I needed a T/R relay driver (a design is on
the Elecraft website), and a means to activate relays to pull in the
appropriate amplifier output filter. For this purpose, I kludged in a driver
for an additional set of latching relays that are driven by the same signals
that drive the latching relays for the output filters in the K2 itself.
These new latching relays are used to switch power to the appropriate filter
select relays in the amplifier. I also added a relay for a separate Receive
Antenna, fooling the K2 into thinking that the 160 meter board is installed.
In all, the experience with this amp has been good. I did have some problem
with oscillations if the amp is left connected to the output filter with no
load attached (like when the T/R relay opens!), so I have the filter
assembly on the opposite side of the relay from the amp. This problem only
occurred with my homebrew rig driving it, not the K2, so it may not be an
issue for anyone else.
If anyone is interested in more details or pictures, reply and I will be
glad to help if I can.
Bill Stewart
WU0R
_______________________________________________
Elecraft mailing list
Post to:
[hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help:
http://mailman.qth.net/subscribers.htmElecraft web page:
http://www.elecraft.com
Locked
