In article , "S C" writes:

I am in the process of designing an ATU yet am having difficulty in locating
a company who can supply a suitable Variable Capacitor.

At the moment the only ones I seem to find are trimming capacitors and I
require an item which is somwhat larger than that - E.g in the region of
about 680pF.

Any suggestions as to a suitable supplier would be grately appreciated.

Access the Ocean State Electronics website at www.oselectronics.com
and you will find a number of variable capacitors (two pages worth in
their printed catalog). Their VC-250 and VC-2502 models are good
for just over 3 KV voltage breakdown. Quarter-inch shafts, almost
10 1/2 inches long. Inexpensive, no. Price is $70 and $80,
respectively.

Smaller (lower voltage breakdown) single to multi-gang units are
available including a 4-gang which can be paralleled to get
800 pFd maximum.

Ocean State also has a number of hardware components for
rotary components from shaft couplers through panel bearings
through flexible shafts and on into vernier reduction drives.

I have bought many many items from Ocean State and I have never been let
down.

I have several of their dual gang 365pf air variables here for monkeying
with crystal receivers and the like. Put them in parallel and add a series
gimic cap and you could be at 680pf pretty quickly.

(730 * X) / (730+X) = 680
(730 * X) = 680 * (730 + X)
(730 * X) = (680 * 730) + (680 * X)
(730 * X) = 496400 + (680 * X)
(730 * X) - (680 * X) = 496400
50 * X = 496400
X = 496400/50
X = 9928pf

So go with a .010 uF cap in series and you'll be cooking with gas.....if I
did my math right.


73 de KB9BVN


"Avery Fineman" wrote in message
...
In article , "S C" writes:

I am in the process of designing an ATU yet am having difficulty in
locating
a company who can supply a suitable Variable Capacitor.

At the moment the only ones I seem to find are trimming capacitors and I
require an item which is somwhat larger than that - E.g in the region of
about 680pF.

Any suggestions as to a suitable supplier would be grately appreciated.

Access the Ocean State Electronics website at www.oselectronics.com
and you will find a number of variable capacitors (two pages worth in
their printed catalog). Their VC-250 and VC-2502 models are good
for just over 3 KV voltage breakdown. Quarter-inch shafts, almost
10 1/2 inches long. Inexpensive, no. Price is $70 and $80,
respectively.

Smaller (lower voltage breakdown) single to multi-gang units are
available including a 4-gang which can be paralleled to get
800 pFd maximum.

Ocean State also has a number of hardware components for
rotary components from shaft couplers through panel bearings
through flexible shafts and on into vernier reduction drives.