[TowerTalk] Kilovac S05FJA238, DPST-NO in MFJ catalog

Jim Thomson jim.thom at telus.net
Thu Apr 13 13:05:11 EDT 2017

##  This item is on page 88  of the latest on line MFJ / Ameritron catalog.    http://www.mfjenterprises.com/catalog.php     Anybody know anything about these Kilovac relays ??   Ok,   I cant find em in the KILOVAC master listing, nor on the gigavac site, nor the Jennings site.   In fact none of those 3 x vac relay makers even list such a thing as a DPST-NO  vac relay.     I have an application  where a SPST-NO  vac relay would be ideal... on the REF + DIR of my 40m yagi, to shunt out a coil, to switch from CW to SSB.  

This  DPST-NO kilovac relay listed by MFJ, would work.  I would just parallel the NO contacts..and also the COM contacts.  Then I end up with redundant contacts and also double the RF current ratings.  I need something 100% bombproof for this application, as I cant get to the REF + DIR without a man lift..and tower cranked down.  Plan was to install one of these in a nema box, along with the pair of flat strap coils.  Top of each coil goes to each side of the insulator.   Bottom of each coil is bonded together.     Relay contacts would be wired to the top of each coil. With no coil V applied, coils are in the circuit and on CW. Energized, both coils are shunted..and on SSB.  So even if the vac relay coil crapped out, the default would be the lower, cw portion of the 40m band. 

$20.00  for a brand new Kilovac  DPST-NC is a bargain..provided they are built right.   I dont see any Ameritron amp, nor qsk box that even used this relay.   Normal deal would be to use a SPDT vac relay on the output of an amp. 

Jim   VE7RF    

These vacuum relays are
ideal for amplifier QSK
switches. Contacts are capa-
ble of carrying 10 Amps and
break down voltage is 5 kV.

08-8100, $19.95.

Kilovac S05FJA238, DPST-NO, contact form, 2A,
5kV rating between contacts, current is 10A DC or 5A RF, 12 VDC coil
voltage and 500 Ohm coil resistance.

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