I had a chance to look at the web sites. The PA3CSG design consists of
a "1/2" wave line load at both ends, tube output C at one end and the
tune and coupling C at the other end. The low impedance mid point is
where the DC feed choke attaches...note that it appears a bit off center
because the two 1/4 wave lines have different loading...apparently the
tube has less.
The way to find the low impedance point is to use a dip meter and touch
the line at various points along its length, the point with least change
in dip is the low Z point.
jeff, wa1hco
JMLTINC@aol.com wrote:
Hi QRO gurus -
Let's talk 1/2wl plate lines.
If you check out PA3CSG's website @ www.qsl.net/pa3csg , or PA7TA's site @ http://www.pa7ta.com/144MHz_RF-Deck.htm , the plate lines on their 2 meter, GS35B amps are about 20.8" (53cm) long.
Everything I have read regarding 1/2wl plate lines says to figure the length for a shortened 1/4wl line (the inductor), and then add a full 1/4wl to that. At 144Mhz that makes a total length of about 28" or so.
I cannot believe their shortened 1/4wl line (inductor) is only 3 tenths of an inch long. Obviously, I am missing something here. Please help!
Thanks in advance-
John, N9RF
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