Mike,
Have you monitored the drive signal at the same time? Does the drive
signal come up immediately? Are you using a dynamic bias circuit? How do
you switch your bias? Are you using a tuned input circuit? Are you using
ALC?
There may be a problem with RF getting back into your driver. Do you
have everything bypassed well? Since it is frequency dependent, I would
suspect that cable lengths may be causing an RF feedback problem either
due to no tuned input or needing more bypassing.
73, Tony W4ZT
Mike wrote:
> Hello,
>
> Having an issue with a homemade GS35B operationon 15 and 17 m. When
> keyed, the power seems to hesitate before going up to 1.5 KW
> output. CW is a mess on these bands due to this situation. On RTTY
> the power hesitation is so short that it doesn't present a
> problem. Amp. seems to be okay to about 1200 W, but the hesitation
> returns above this level. Other bands, 10, 20, 40, 80, 160 work okay.
>
> Using a TIP147 transistor in a bias circuit similar to Ian's Triode
> Board bias circuit. Cut-off bias is provided by a 10 KOhm resistor.
>
> The filament choke is ~25 bifilar turns of #16 on a 10"X1"X1/4"
> oblong ferrite rod. An additional choke of 20 turns #20 on a ferrite
> rod, 3.5" long and 3/8" dia., is in the line from the filament
> secondary center tap to the bias circuit.
>
> This a strange situation as seen on 17 and 15 meters using either an
> antenna or a dummy load. On the other bands, the power smoothly
> rises to full output.
>
> Any ideas on how to fix this situation are appreciated.
>
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>
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