> I need some help with the tuned input for 4 811A's. I am using the
> National 3/8" red core tunable cores for the L. Fixed values for the C.
> I tried to copy what Collins did in the 30L1, not much luck. Using an
> MFJ analyzer I tried to tune each band 10-80. Altho on some bands I get
> somewhat of a dip, on others it almost shows infinite SWR. I did find
> that tuning the 15 meter slug for 10 meters I had a real nice dip and
> the bandwith was about 800kc's. If I used the 40 meter slug on 20, I
> also had a nice dip with good bandwidth. Any suggestions as to where I
> go from here ??? I looked at Ameritrons values and found them somewhat
> confusing, as the higher C was on the tube side, not the input side.
> Always thought the higher C went to the input side ?? Golly, aint this
> fun !!!!
> 73...Ed W3NR
Almost impossible to do with the MFJ.
I start out with the values in the chart in the ARRL Handbook or Orr's Handbook
to get me in the ballpark. Then the amp must be fired up and the input tuned
for minimum SWR in the center of the band. If the Q is low enough it will
present
low SWR at the band edges. Remember that the values for the L and C are affected
by your layout , stray C and the input C to the 4 tubes. C2 and L in your tuned
input
must be adjusted to compensate. This is not an easy task, and is dangerous if
the
proper safety precautions are not taken. A good friend of mine was killed
adjusting
the tuned input on a 4-1000 amp.
The 30L1 is not a good circuit to copy as the length of coax from the exciter
to the
input of the amp is critical.
GL, and be very careful!
(((73)))
Phil, K5PC
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