[Amps] Ceramic capacitor ratings

[Gary Schafer]

Hi Dan,

Thanks for the reply. I did run across your old post on the subject however
I am not sure you were talking about the same capacitors that I have.
I found on the rf parts web site the 850s caps where they show the 100 pf
rated at 3.6 amps @1 MHz, 6.8 amps @ 10 MHz and 9.7 amps at 30 MHz.
With two in parallel that should give around 20 amps or so current carrying
ability just above 10 MHz if what they show is correct.

73
Gary  K4FMX

> -----Original Message-----
> From: Dan Hearn [mailto:dhearn at air-pipe.com]
> Sent: Friday, April 13, 2007 1:22 AM
> To: garyschafer at comcast.net; amps at contesting.com
> Subject: RE: [Amps] Ceramic capacitor ratings
> 
> Gary, a similar question was asked several years ago on amps and I replied
> to it with values from some info I have on CRL doorknob ratings. I can't
> seem to locate my data but here is my post. My understanding is that the
> circulating current in the tuned circuit is about Q times the plate
> current
> and your mod obviously increased the Q a bunch. I think the caps are
> overstressed. Here is the link
> http://lists.contesting.com/_amps/1999-08/msg00161.html
> 73, Dan, N5AR
> 
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]On
> Behalf Of Gary Schafer
> Sent: Thursday, April 12, 2007 9:58 AM
> To: amps at contesting.com
> Subject: [Amps] Ceramic capacitor ratings
> 
> 
> Working on my TMC amp with the pair of 3-500Z finals and the toroid tank
> coil. 1.6-18 MHz.
> 
> I tried  a tank coil for 20 meters that I made out of ¼ inch copper
> tubing,
> 2” diameter and 8 turns. I got another 300 watts out of the amp!
> Efficiency
> with that coil is 52% compared to around 38% with the toroid coil.
> 
> 
> 
> The amp runs 3000 volts at 700 ma.
> 
> 
> 
> Now the question is about ceramic padder capacitors used in the plate tune
> circuit. There is a variable plate tune cap that is 23-347 pf that is in
> series with two (parallel) ceramic small door knob type caps. The ceramic
> caps are 100 pf each for a total of 200 pf in series with the 23-347
> variable cap.
> 
> The ceramic caps are CRL 850S N750.
> 
> 
> 
> I am wondering about the current carrying capacity of these capacitors in
> the tank circuit being in series with the variable cap as all the tank
> current is going thru those caps. Now with a better tank coil that is more
> efficient I would guess that the circulating current is higher than it was
> before.
> 
> 
> 
> Also will they handle the current in this configuration at higher
> frequencies if I try to put the amp on 15 and 10 meters?
> 
> 
> 
> Any help appreciated.
> 
> 
> 
> Gary  K4FMX
> 
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>