--------------------------------------------------
From: "Richard (Rick) Karlquist" <richard@karlquist.com>
Sent: Thursday, December 30, 2010 8:15 AM
To: "Jim Thomson" <jim.thom@telus.net>
Cc: <towertalk@contesting.com>
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
FWB....then
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
coil...so 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 none.......plus 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
supply
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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