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Re: [TowerTalk] Gigavac Relays

To: "Richard \(Rick\) Karlquist" <>
Subject: Re: [TowerTalk] Gigavac Relays
From: "Jim Thomson" <>
Date: Fri, 31 Dec 2010 08:09:45 -0800
List-post: <">>

From: "Richard (Rick) Karlquist" <>
Sent: Thursday, December 30, 2010 8:15 AM
To: "Jim Thomson" <>
Cc: <>
Subject: Re: [TowerTalk] Gigavac Relays

> On 12/27/2010 12:40 AM, Jim Thomson wrote:
>> ##  Kilovac engs  told me years ago, If you are limited with vdc...and 
>> you want to speed up a 26.5 vdc relay.... then  simply
>> use the 12 vdc version instead. With 24-30 vdc applied  with a simple 
>> drop resistor..they operate blazing fast.  If you want em still
>> faster, then use a small 50 uf lytic across the drop resistor, then it 
>> becomes a 'RC hot shot circuit' .  If you have +48 vdc available,
>> you are laughing.
> The drop resistor with 2X voltage only gives half as much
> speed up as the K6XX circuit I cited.  However, you cannot
> speed it up by going to still higher voltages because
> it is limited by contact bounce at that point.
>> ##  I had no problems  with building a +120 vdc  supply, using a FWD..for 
>> use  with speeding up a 26.5 vdc  vac relay.  I use a
> Rich Measures assumed the user would have a 90V grid bias supply for free. 
> I don't have that but I already have 12V in the shack.
>> Later.... Jim   VE7RF
> Rick N6RK

&&&  The K6XX  circuit just doubles the OCV when T=0     The 12 vdc  across 
the 47 uf cap in his circuit is now in series with the
12 vdc OCV... so you end up with 24 vdc... for a split second...until the 
cap discharges..then u down to 12 vdc.

&&&  I don't see any difference between that method of temp obtaining 24 
vdc..... VS  using 24 vdc + drop resistor.   The 24 vdc
+ drop resistor  will  def  speed  up any 12 vdc relay.   If you then wire a 
47 uf cap  across the drop resistor, then it's even faster still.
The big advantage of the K6XX  circuit is.... you don't require a  24 vdc 
supply.  You can use the existing supply.  FWIW... in my L4B amp... it
used a 24 vdc relay...and the  24 vdc  came  from a simple  1/2 wave 
rectifier. [ one diode, one cap].  I was going to change it to a 
decided to change to a FWD. [ 2 x diodes and 2 x caps].   The stock 27 vdc 
from the  1/2 wave rectifier then became +63vdc  with the doubler.
A simple drop resistor used..and then the stock  24 vdc  relay  now operates 
very fast.  Not fast enough for qsk..for way better  vox  cw/ssb.
Adding the 47 uf cap  across the drop resistor speeds things up a bit more. 
I found you can  speed up any slow mech relay  with that scheme.

&&  With those big gigavac  G-2 relay's  I use, they are 15-18 msecs 
operate..and 9 msecs  rls.....stock.  With the speed up circuit, they are 
blazing fast
on operate... but still not quite fast enough for  QSK.    I don't  operate 
qsk, so that was not an issue.  For remote ant switch's, etc, speed is not 
an issue.
On vac relays used for  stuff like remote  ant switch box's.... I order then 
with a 12 vdc coil.    Then with 13.8 vdc  applied..and small ga 
wire...they operate just
fine.   I parallel 2 x  wire's to make one... then repeat  for other 1/2 of 4 x wires in total.   Then I have redundant relay coil control 
wiring to all  vac relays
up the tower.   That's the most reliable thing I have been able to cook up 
so far.   Then no contacts to ever get dirty..or wet !  100% reliability. 
IF mech open frame
relay's used... I use a DPDT  instead of a SPDT.... and then parallel all 
contacts.   Then it's more reliable  with  redundant contacts.   Then the 
chances of both going
open are slim to with parallel  contacts.. you can have now 
doubled the current rating  [and quadrupled the power rating].

&&  I did  notice that on any of these  26.5 vdc latching type relays..that 
the coil resistance on em is very low..and blows my 5A current limited lab 
into the red.  A quick pulse  of 12 vdc  is more than ample to operate a 
26.5 vdc  latching type  vac relay.

later....... VE7RF



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