[NLRS] 400 W 220 MHz Solid State Amplifiers

[Rex Greenwell]

Re:  400 W Broadband Linear Amplifers from VHF TV Transmitter

The first two NLRS hams that responded which interested in testing the RCA
400 W PEP CCS rated 220 MHz linear amplifiers are K9LB and KB0CIM.  I have
done further research and have found that the 150 W modules used in the
amplifier arrays (there are three 150 W amplifier boards combined to rated
400 W PEP) are actually spec'd to 240 MHz.  At 220 MHz the boards are spec'd
at 15 dB power gain.  Of course there are losses in the combiner when they
are combined to 400 W.  These amplifiers are highly linear and rated CCS -
Continuous Commercial Service at that power level.  The amplifiers operate
with a power supply of 28 VDC on the collector of the "finals", 12 VDC for
the control and metering, and 8 VDC bias reference.  The amplifiers are
fully metered.  The amplifiers are spec'd down to 165 MHz so it may be
possible to adapt them to 144 MHz as well as 220 MHz.  It appears that it is
going to take in the area of 35 W + or - to obtain 400 W output at 220 MHz.
There may be some "tweaking" necessary on the input and output combiner
circuits to achieve maximum efficiency, probably more so at 144 MHz than 220
MHz.

Now we can wait on the results found by K9LB and KB0CIM.

If there is a "spare" 220 MHz exciter out there that could be loaned to me I
could experiment in this project myself as well.  Anyone interested in
making a loan for this worthy venture?

There are 12 ea of these amplifiers surplus at my TV stations WDSE 8 - WRPT
31 located in Northern Minnesota.  These RCA "G Line" high band VHF
transmitters were by far the most ppopular transmitters of the analog era
for TV stations operating on channels 7 to 13.  There is a good possiblity
that many of these are in storage waiting to be scrapped now that the
digital transition has completed.

I have assembled documentation on the amplifiers in PDF format, circuit
descriptions, schematics, and so forth if anyone is interested in reviewing
it.  I can send it by email.

Thanks again to NLRS for your encouragement and support in this project.  I
would be super if these at one time VERY expensive amplifiers can
be recycled and reused among hams rather than suffer the tears of scrapping
them.

73 for now ...

Rex K0KP EN36vw
Fish Lake - 20 kM NW of Duluth, MN