In a message dated 96-12-16 19:51:00 EST, you write:
<< I have a Clipperton L amp and the output is down quite a bit on 160.
It looks like the tank coil doesn't have enough turns for 160 comparing
it to 80. Do you know anything about this and any suggestions on a fix?
>>
Hi Tom and all Cliperton L 160ers
Just finished playing with my Cliperton L, first I thought maybe tubes are
soft, got new tubes put them in and was getting only about 400 W output in
SSB position. I have noticed that both capacitors were fully in and plate
current quite high, which indicates that the whole PI netowrk is out of
range. (Antenna is full size baloon vertical resonating around 1830 perfect
1:1)
After playing around with different components around PI network I found that
by adding coil of about 5 turns of #12 wire to the end of the 160 m coil (end
close to the front panel) - you need to unsolder the wire going to the switch
contact from the end of the existing coil and insert the 5 turn coil. Wire
pitch - spacing and diameter about the same as existing coil. Then you need
to add 1000 pf ceramic transmitting capacitor (similar to existing one for
160) in parallel with that 1000 pf that goes to the 160 position on the
switch. (that is the one closest to the tubes.) I unscrewed the nut holding
the ground wire next to the front panel and screwed the capacitor onto the
existing screw and soldered the wire from the other end of cap to the 160 m
position on the switch.
My plate parasitic supressors smoked for some reason, so I replaced resistors
(original 100 ohm) with 47 ohm 2 W. 4x
Whoever designed the Clipperton L should have his nose put between the top
cover and coil. Way too little space. All the textbooks say at least half of
the diameter of the coil from metal parts. Clipperton has hardly .25 inch and
not much room to maneuver. With top cover on you lose about 80 W.
Yea, there is a bit of power drifting with plate capacitor ceramics warming
up, but on my amp its tolerable and you can tweak it for particular duty
cycle.
After this mod I am getting almost 1000 W out without cover, with cover about
900. Position of capacitors at the low end of 160 is just above max meshed in
and as you move up the band to 1900 the TUNE goes about to 10 oclock and load
within the range.
Input impedance of Clip-L is not 50 ohms. I can squeeze a bit more if I
engage TS870 tuner (which normally loses about 20 W) but improved match makes
ts870 and L hapier. That will be the next thing to check. Stay tuned. For
pure 160 operation the ferrite coil might be the best solution it would give
proper inductance and eliminate cover power suction effect, and maybe tuned
input.
Otherwise good amp for carry-on suitcase expeditioning and 115 V only hotel
service. With IC706 and bunch of wires you can put out decent signal.
Good luck and unplug it before you work on it, I am not responsible for
anybody except myself.
73 de Yuri, K3BU, VE3BMV
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