[AMPS] Re: [TowerTalk] Matching capacitors

[Pat Barthelow]

Hi Guys,

I have been wondering the same....Some time ago, I measured capacitance of
selected double sided PC Boards, that, as I remember, were abt 1/16"
thick, and blue in color, not the typical green/epoxy type...I measured
about 16pf/sq inch....Which would allow a 3"x 3" piece to be about 150
pf...  I wonder if you might have to etch back some of the copper from the
edges of the board, to get into the higher voltages ranges?  Also, We have
a hi-pot tester at work that simply has a neon panel lamp indicator that
fires if voltage breakdown occurs.  It can go up to 6KV AC or DC.  Putting
a high ohms load on it showed that it lugged down considerably even with a
1 ma
load.  Could this Hi Pot tester be used in
a valid voltage ratings test for the Caps?  If a breakdown using the HIPOT
occurs across the PC board, does the breakdown path permanently short, or
greatly reduce the future voltage withstanding capacity of the piece under
test?

BTW, I lost a lot of recent past  Email, (due to a system crash
here at tmx.com,) including several who were
interested in the 4uf, 15kv oil caps I have...for that big amp,
apparently....Please re-contact me....


Another brain storm/scare...If I put the HI Pot tester across that  big 4
uf 15kv, capacitor, could it charge the cap to dangerous levels?

73, DX, de 
Pat, AA6EG/N6IJ; 
aa6eg@hh.tmx.com;n6ij@hotmail.com
599 DX Drive, Marina CA 93933
See us on the web: www.polkinghorn.org/n6ij
"The Contest Station from the Government"

On Mon, 9 Aug 1999, Jim wrote:

> 
> Drake uses PC board caps in the L7. The L7 uses a pair of 3-500Z. They use
> one across the plate choke. The plate choke has a tap about 2/3 the way up
> from the bottom. The cap is to stop a series resonance.  They also use one
> for a padder cap for the tuning cap on 160 meters. It is about 1.5" by 2.5".
> The value of this cap is 300pf.
> 
> Thought is was intresting that Drake did that.....
> 
> 
> 73 and good luck!
> 
> Jim W7RY
> 
> 
> -----Original Message-----
> From: Scott Bullock <sales@radiosonline.com>
> To: towertalk@contesting.com <towertalk@contesting.com>
> Date: Monday, August 09, 1999 1:26 AM
> Subject: [TowerTalk] Matching capacitors
> 
> 
> >Hello TT'ers,
> >
> >Has anyone ever experimented with using Double sided G10 Copper clad board
> to make capacitors for matching antennas? I been experimenting with this,
> and just curious if anyone knows what the RF breakdown voltage of this type
> of board is. The thickness is approximately 1/16".
> >Seems to be easy to make different sized capacitors with it just by cutting
> the board larger or smaller. I'm going to mount them with porcelain
> standoffs inside an aluminum box to the side of the tower.
> >Thanks in advance,
> >Scott
> >KA1CLX
> >
> >Advantage Communications
> >Professional Wireless Communications
> >www.radiosonline.com
> >800-851-RADIO
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> 
> 
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