>
>
>> 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.
Amen to that, Phil.
>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.
>
So is every other g-g amp that is driven by a radio with a Chenbyshev
filter.
cheers, Phil
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|