[Moon] [Moon-net] All I want for Christmas...

[w2drz]

A added note that should have included,
The receive relay used should have a voltage reduction to the relay
coil,
This is to reduce the heat of the coil and destruction because of the
heat.

Many antenna relays are not intended to be "ON" 24/7,

On my receive, 24 volt DC relay is what I do,

 so what I have is a 220 ohm with a 220 MFD across the resistor,
 the resistor then will be at the relay hold current,
 this is MUCH less than what is needed to properly switch the relay
"ON",
 in the RX relay it is 24 volts to switch on,
with 12 volts hold voltage.

The capacitor across the resistor will bleed to zero volts in a second
or so when "OFF",
 that the relay will be hit with 24 volts as the capacitor is a dead
short across the resistor,
 then as switched in the "ON" state will charge to the resistor drop
voltage with much reduced coil current on the RX relay.

Each relay will be different hold current and voltage so do a bench mock
up to test what the switching current is normal and a good hold current
as the voltage is reduced.

Be sure to also have a good ohm meter on the common and the switched
port as must have a good hold current so the contact pressure is
properly maintained by the hold current.

Too little will increase the contact resistance and be a resistor in
series to the preamp with of course a reduction of the noise figure by
this series resistance.

In the case of the RX relay it was a zero resistance to about 9 volts
and the contact pressure started to reduce, with the contact resistance
going up in resistance, to the point of ohm's before it relaxed to the
open condition, so I selected the current/voltage (my case 12 volts) 
above the minimum hold point to be a solid zero ohm hold value and if
hot or cold out side condition..

Happy Holidays and

 as I'm not a Politically Correct person,

 I am wishing " MERRY CHRISTMAS " to all......

tom


w2drz wrote:
> 
> Hugh,
> 
> Here is what I suggest the sequence to use, will fix blown up stuff,
> don't need a pile of relays and preamps.....
> 
> (1.)     Preamp protect relay in standby receive mode,
>  suggest that relay be powered on in receive mode,
>  off in tx mode..
>  reason is loss of power to relay,
> broken wire/shorted wire to relay,
>  always protected and if station is shut down,
>  receive relay is in the protect mode.
> (2.)    TX antenna relay "ON"
> (3.)    Power amp "ON"
> (4.)    Driver system "ON"
> 
> tom
> 
> Hugh VA3TO wrote:
> >
> > ...is a new RF relay.
> >
> > On Friday evening I rushed home from work to participate in the DUBUS 2m
> > CW event with hopes of working some new initials using my recently
> > christened h/b 8877 amplifier.
> > Something didn't seem right with the amp tuning and I quickly discovered
> > that the SWR was terrible. A continuity check on the TX feedline in the
> > shack showed a dead short. Today I climbed up the tower with my
> > multimeter and quickly discovered that the relay was the culprit. Some
> > slightly blurred photos below (too many Molsons' last night hihi !).
> >
> > http://home.cogeco.ca/~va3to/Relay/Relay1.jpg
> > http://home.cogeco.ca/~va3to/Relay/Relay2.jpg
> >
> > I thought the Dow Key transfer relay was good for 1700W at 144MHz
> > according to the datasheet but evidently not.
> >
> > So I'm looking for a replacement...doesn't have to be a transfer type.
> > A SPDT would suffice but it must be capable of handing at least 1500W
> > with a 12V or 28V coil.
> > I can pay using Paypal. Anyone ?
> >
> > Merry Christmas & Happy New Year to all !
> > Hugh VA3TO
> >
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