[Amps] GS35B Amp 15 m Situation

[Tony King - W4ZT]

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.
> 
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>