[TowerTalk] Fwd: Topband: Fixed capacitor source needed (150pf 5KV)

[Hans Hammarquist]

I used short pieces of coax cables at capacitors years ago. RG8 (tells you how many years ago) will give you a capacitance of about 30 pF/foot. I don't know how much space you have but five 1' long in parallel will give you about the right value. You "just" have to terminate them well so you don't get flash-over there. If I remember right we used that cable for 5kV feeders to photomultiplier tubes.


Hans - N2JFS



-----Original Message-----
From: Charlie Cunningham <charlie-cunningham at nc.rr.com>
To: herbs <herbs at vitelcom.net>; 'TopBand List' <topband at contesting.com>; towertalk <towertalk at contesting.com>
Sent: Thu, Oct 3, 2013 1:04 pm
Subject: Re: [TowerTalk] Topband: Fixed capacitor source needed (150pf 5KV)


Hi, Herb

I would think that 2-3 of those 500 pF caps in series would be just fine!
Have you tried just one?

Also, are those capacitors on the load side of the tuner as an aid in
matching really low impedances?  If so, you can almost certainly use
something with less than 5KV working voltage, even at full power!

Check Digi-Key also

73,
Charlie, K4OTV

P.S.  I think you could avoid adding 5' of RG-8 or RG58 - but you could add
it in parallel with your 16o feed line via a Tee connector.


-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Herb
Schoenbohm
Sent: Thursday, October 03, 2013 10:46 AM
To: TopBand List; towertalk at contesting.com
Subject: Topband: Fixed capacitor source needed (150pf 5KV)

I have a Drake MN2700 so I can at least get the amp to work above 
1870Khz during contests.  The tuner used some fixed flat 150pf 5KV 
capacitors to switch in from the front selector as increased capacity is 
need to make the tuner work.  I can't find any door knob substitutes at 
that value in my junk box. I am thus looking for a source for these 
values but so far have not found anything that I can use as a 
substitute. I presume I could make some out of sections of RG-8 mini 
roller up in a coIl but before I try this I am searching for a door knob 
source.  I have some 500pf at 5KV and three of them in series might be 
close enough but i still need the correct values.  If any reader to this 
knows of other ATU manufactures that use the copper teflon flat 
capacitor in their units maybe   could order 150 pf 5KV from them.


Your help on this would be appreciated.


Herb, KV4FZ
_________________
Topband Reflector

_______________________________________________



_______________________________________________
TowerTalk mailing list
TowerTalk at contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk