[Amps] snubbing diodes for vac relays / notes.

[Jim Thomson]

Most DC relays without indication of "+/-" polarity are non-polarized.  For 
QSK operation, it may be best to add your own snubbing diodes to all relays, 
including the vacuum relays.  It may also be helpful to review the following 
discussion concerning the use of relay snubbing diodes:

http://www.cliftonlaboratories.com/diode_turn-on_time.htm

Paul, W9AC

##  I use a 1N5408  across the coil of my vac relays.  Some of the vac 
relays I use have 26.5 vdc coils, some have 12 vdc coils.  All get a 1N5408

##  To  INCREASE the RLS time of a vac relay...[faster rls]... that uses a diode 
 for back emf suppression... insert  a 2-3 W MOF resistor in series with the snubber
diode. 
Use  a value of 200-300 ohms.   Resistor can go on ether side of the diode of 
course, as both the diode and resistor are in series.   This technique is not described
in the above  url that Paul posted. 

## The diode + resistor combo is used on the INPUT  vac relay...[ + bias relay].
The OUTPUT vac relay gets JUST the diode only !   

## End result is [ with ALL  3 x relays sped up] all 3 x will  operate <1.8 msec.
The OUTPUT relay  will  RLS  dead last. 

The bias relay the fellow wants to use does not look like a reed relay to me.. dunno. 
In any event, the AUX  contacts on it are only rated for 28 vdc !!    You will destroy
them, if  using + 120vdc  for  switching cut off bias.  +120 vdcv  for cut off bias is
dinosaur technology.  Better  to simply use a 100 K  3 watt  MOF  in the CT of the
fil xfmr.. and short  the same 100 k R  out  with the  contacts   of the  bias relay. 
Only a spst relay is required for this. 

On another note.  He is using  2 x vac relays  +  3rd relay... with all their coils in series, plus
a  shunting resistor across the bias relay coil.  This will work  with +120 vdc.. and 
speed all 3 x of em up. 

On the 2 x GS35B  6m amp,  I  helped a friend with... we used  3 x  Gigavac GH-1's 
[like a rj1a]   one  for input, one for output, 3rd one for the bias [ shorts out the 100k R] 
All of  em have 12 vdc coils. All are very easy to speed up  with an overvoltage.. and just one
series  dropping resistor.  If u want to speed  em up even faster, install a 50 uf lytic  across
the  dropping resistor. Then u end up with a 'RC  hotshot speed up circuit' .  

On the 6m amp.. both GH-1's  mounted side by side, with 2 x SO-239's above them.
Bypass  swr on 6m is dead flat.  

For his proposal,  I would deep 6 the idea of using +120 vdc  for cut off bias.. and 
use the 100k  R  in the CT  of fil xfmr.   We always use 2 x 100 K  in parallel,,, for
redundancy. 

later... Jim   VE7RF