Hi Carey, flapper tuning is the best (maybe only) method for resonating a
strip line plate circuit.
There are always losses in these circuits due to unavoidable resistance in
the metal parts and rf currents flowing through them.
For the lowest loss, highly conductive metal, such as copper, is used.
Brass is often used but the inherent resistive losses are much higher than
copper unless the brass is silver plated.
Losses are related to rf current squared. Using the minimum possible tuning
C will correspond to minimum rf current. The flapper should have a wide
spacing at the strip line and be well grounded at the cold end. The wider the
spacing, the lower the C and resulting rf current. If the flapper is too
closely spaced, the strip line length is too short.
The rf field around the strip line is very intense at the power levels
involved here. It is important for all metal joints in the strip line and the
enclosure be rf tight. Lots of screws are needed and everything has to be
clean and tight. Screw spacing of 2 inches is not excessive.
Your figures of 3400 volts and 1.2 Amps yield a dc input power of 4080
watts. If the output power is 1900 watts, that is 45% plate efficiency ignoring
feed through power. The actual power output may well be higher and a
better calibrated wattmeter will tell. Maybe a friend can loan you one for a
test.
73,
Gerald K5GW
In a message dated 5/22/2011 10:19:26 P.M. Central Daylight Time,
kc5gtt@gmail.com writes:
ok guys i have the amp back together in the yu1aw lazy builder. now i am
getting much lower efficent
plate 3400 full load
current 1.2a
drive 100w
output according to my cheap meter 1600 and my other cheap meter 1900
eff. around 35%
now i am wondering how to determin actual output from these values. is
there a way? also is the flapper capacitor a bad way to go?
Carey
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