Gents
I just posted some new pix.[page-3 of my pix page]..... depicts how
we paralleled the 3 x wafers of the Model 85 switch. We
used 1" wide CU strap... x .022" thick... formed into a..."U".
Each strap was formed on some scrap square material..... forget
the precise width... believe it was aprx 3/8" wide. This
allows for maintaining the 13 KV air gap between adjacent
contacts. Using 1" wide strap... in a "U", also allows for
zip stray L through the 3 x wafer's... and also will handle
literally globs of RF current.
Wafer at back end... closest to tank coil, we call wafer #1....
this is where the various coil taps terminate. The wafer
closest to the front panel/knob, is wafer #3. The output of
this switch is on wafer #3..... which of course, feeds both the vac
load cap and the low freq end of the huge Multronics Jumbo tank
coil. This "in on wafer #1.. and out on wafer #3" allows for an
almost even RF current sharing, between the 3 x paralleled wafers.
This same scheme has also been done on a model #88 switch. Just
make sure you use "double commons" on all 3 x wafers.. on any of
these series of switch's. The double commons allows grabbing
the central rotor hub on BOTH sides.... handles WAY more RF that
way. Stock, they only come with one common per rotor... grabbing
the rotor on the top side only. Skip Coleman at Multi-tech
Industries supplied me with all the bits and pieces I needed
for my model 85 and 88 switch's. There is also a pix depicting
the "double commons" portion of the switch... [page 2 of pix page]
The next pix just shows a close up of the surplus [$20.00]
Multronics 14 uh tank coil model MI-14 [it actually measures
12.2 uh] It came with just one multronics 1/2" tubing
clamp. A friendly machinist made a bunch more for us... virtual
carbon copies too ! Good thing too... since Multronics wanted
$50.00 for EACH tubing clamp ! ....ouch. Taps from the triple
wafer bandswitch to the Multronics coils, etc... was done using
1" wide flat strap x .022" thick.... zip stray inductance....
even though most of the taps were very long. Else where on the pix
page... shows the HB 1/2" tubing coil.. smaller ID [3"] used
for 20-17-15m.... it was added to the HF end of the 12.2 uh
Multronics coil....which has a huge ID to it. Tapped for 160-80-
60-40-30-20-17-15m.... NO 10/12m.
The last new pix, shows the 1 in 9 out 15 kw remote ant
switch... from a different angle. The strap is all 3/4" wide
x .022" thick... spaced aprx 5/16"... which gives us 50 ohms.
Although the DPDT relays are rated for just 277 Vac... they
hi - pot tested to 3 kv..... and have had as much as 17 kw pumped
through em........ surplus $4.00 each. 12 vdc. I previously
posted the url for both these surplus 12 vdc DPDT relays... and
also the 3 x pole contactor's [with 220 v coil].
Later........ Jim VE7RF
