[Amps] Ceramic capacitor ratings

[Gary Schafer]

Hi Peter,

I think my working Q has gone up also with the addition of the large copper
coil as tuning is sharper than before. I measured the total capacitance of
the plate tune circuit with the coil removed and it measured around 95 pf. 
Calculations show for a Q of 12 that plate tune should be around 55 pf on 20
meters. I also measured the inductance of my added coil by itself and it
measures around 1.4 micro henries or so. These measurements were done with
an mfj 259B. I used the minimum frequency of the unit that would be in range
to give a reading on the capacitance and inductance.
I think those values work out to be a Q of around 20. 

There are a lot of leads running around to various switch assemblies for
capacitor switching and a pretty long lead to the plates of the tubes so I
don't know how much stray inductance and capacitance is present.

As to your note about working Q staying the same, why would it? By changing
nothing but the coil and unloaded Q increases wouldn't that also increase
loaded Q?

Thanks
Gary  K4FMX

> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of Peter Chadwick
> Sent: Friday, April 13, 2007 5:12 AM
> To: amps at contesting.com
> Subject: Re: [Amps] Ceramic capacitor ratings
> 
> Why should the current have gone up? Yes, the unloaded coil Q is higher,
> but the working Q should, all things being otherwise equal, the same. Thus
> the circulating current is the same. There's less loss resistance in the
> coil, and as efficiency is proportional to the ratio of unloaded Q to
> loaded Q, the output is higher.
> The loss in the capacitors may or may not be negligible, but I don't see
> that it should have changed very much.
> 73
> Peter G3RZP
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