On Tue, 5 May 1998 14:30:58 -0600 "Richard W. Ehrhorn" <w4eto@rmii.com>
writes:
>Hi Mark & everyone...
>
>Got the same question from one or two guys at Visalia last week. In
>most
>practical amplifiers, including the ALPHAs 87A, 89, and 91B, the tank
>(pi)
>"Q" tends to be a bit higher on 10 & 12M than on lower bands,
>resulting in
>correspondingly greater circulating current. Also, the rf resistance
>of a
>given size connecting wire or strap increases with freq. The result is
>
>somewhat greater heating of the conductor from the pi coil to the
>bandswitch on 10/12M than on the lower bands.
>
>But wider strap is harder to connect neatly to the switch lug, so we
>attach
>a small copper heat sink to the 10/12M tap-strap. It's probably not
>necessary, especially since we use silver-bearing solder for high
>current
>rf connections, but it never hurts to have a little extra margin.
>
>73, Dick W0ID
Probably not an Alpha issue Dick, but I have noted in many other amps
that when the 10M tap lead shows signs of overheating the bandswitch and
tap solder is often crystalized. I use #12 stranded, silver plated with
Teflon insulation ( cause it is available) and silver bearing solder
also. In an amp such as the LK-800A I replace the wires for 10 thru 20M.
73 Carl KM1H
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