If the PA microphonic AM'ming is severe enough, there could be enough power
supply modulation, due to the PA current varying by the AM occuring in the
PA, that FM at the same modulation rate can occur in preceding exciter
stages (such as in the crystal oscillator, modulator, active temperature
compensation circuits, etc.). Not knowing how a T301 is designed I don't
know how likely this is, but it's quite possible.
--- Jeff
> -----Original Message-----
> From: Repeater-Builder@yahoogroups.com
> [mailto:[EMAIL PROTECTED] On Behalf Of Bryan Fields
> Sent: Tuesday, December 20, 2005 2:11 AM
> To: Repeater-Builder@yahoogroups.com
> Subject: Re: [Repeater-Builder] Re: Hamtronics T301 220
> exciter Final and microphonics
>
>
> On Monday 19 December 2005 11:48 pm, Ken Arck wrote:
> > Don't forget that in both PM and FM schemes, the modulation
> is done early
> > on and multiplied. So for a typical multiplication scheme
> of x 9, the
> > modulation introduced only needs to be 550 Hz or so (for a
> 5 Khz spec). And
> > even a paultry 550 Hz requires a fair amount of audio voltage to
> > accomplish.
>
> In most PLL units I have worked with in the "ham" market the
> vco is modulated
> directly on the loop op amp. There in no multiplication the
> VCO runs at the
> output frequency.
>
> As to the origional question, anyone fixed the microphonics
> problems with the
> exciter?
>
> --
> Bryan Fields, KB9MCI
> ____________________
> 01:07:04 up 3 days, 14 min, 2 users, load average: 0.31, 0.23, 0.26
>
> Somewhere in DOWNTOWN BURBANK a prostitute is OVERCOOKING a
> LAMB CHOP!!
>
>
>
>
>
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