Hans Remeeus wrote:
For example Titanex (www.titanex.de) sells good High Power Ceramics
Relais for this purpose:
http://www.titanex.de/frames/acc.html#UB6-9 (HPRL) with power handling
of 5 kW each.

Palstar in the US use high power relais in some of theire antenna
tuners, but those relays are not ceramic.

Good luck!


I would say good luck also if I assumed a relay could actually be rated
for a certain number of "kW".

A relay that easily takes 50kW in a 50 ohm system could fail at 100
watts in an application like this, so it is foolish to even look at
power ratings in other applications.

In this case when the relay is open he will have very high voltages
across the contacts even with very modest power. When the relay is
closed he will have a few amps of current at low power up to 5 or 10
amps at kilowatt levels.

Not only will he have high voltage between contacts, he will have high
voltages from the contact to ground.

That virtually excludes conventional relays, and it even excludes many
types of vacuum relays. The popular ceramic vacuum relays normally have
too low of coil to contact breakdown plus the terninal spacing is much
less than 1/2 inch.

He probably can get by with a conventional ceramic vacuum relay like an
RJ1A (about $50 US surplus) at low power levels (normally considered a
"5kW relay, whatever that means) , but if he runs more than a few
hundred watts and especially if there is moisture in the air he will
need a HV glass vacuum with opposing terminals for contacts and a long
insulation bar on the transfer solenoid bar.

Power levels depend on the application, and he has picked about the
toughest application I can think of.

73 Tom

wrote:
In this case when the relay is open he will have very high voltages
across the contacts even with very modest power. When the relay is
closed he will have a few amps of current at low power up to 5 or 10
amps at kilowatt levels.

I performed this same function in Arizona with a $5 relay.
There is a surplus store beside the freeway in South Phoenix.
They carry surplus relays from the local power company. Some
of those relays are high voltage rated. I choose a SPST relay
that had four contacts. Two contacts were about an inch apart
and, when energized, were shorted by an insulated shorting bar.
When not energized, there was a total of at least one inch of
air gap in the contact path, maybe more. The contacts were
about 1/4" in diameter.

I was running 100 watts. I borrowed a differential high voltage
scope and measured the peak to peak voltage between the ends of
my loop to be somewhat less than ~2500 volts. This was a full
wave 40m loop broken in the middle and tuned to resonance on 80m.
I tested it in increasing increments of 10 watts all the way to
100 watts with no problem. It was before the monsoon season so
the humidity was low. A couple of months later, a severe
thunderstorm broke my upper 2x2 support and brought the whole
thing tumbling down.
--
73, Cecil, http://www.qsl.net/w5dxp

schreef:
Hans Remeeus wrote:
For example Titanex (www.titanex.de) sells good High Power Ceramics
Relais for this purpose:
http://www.titanex.de/frames/acc.html#UB6-9 (HPRL) with power handling
of 5 kW each.

Palstar in the US use high power relais in some of theire antenna
tuners, but those relays are not ceramic.

Good luck!


I would say good luck also if I assumed a relay could actually be rated
for a certain number of "kW".

A relay that easily takes 50kW in a 50 ohm system could fail at 100
watts in an application like this, so it is foolish to even look at
power ratings in other applications.

In this case when the relay is open he will have very high voltages
across the contacts even with very modest power. When the relay is
closed he will have a few amps of current at low power up to 5 or 10
amps at kilowatt levels.

Not only will he have high voltage between contacts, he will have high
voltages from the contact to ground.

That virtually excludes conventional relays, and it even excludes many
types of vacuum relays. The popular ceramic vacuum relays normally have
too low of coil to contact breakdown plus the terninal spacing is much
less than 1/2 inch.

He probably can get by with a conventional ceramic vacuum relay like an
RJ1A (about $50 US surplus) at low power levels (normally considered a
"5kW relay, whatever that means) , but if he runs more than a few
hundred watts and especially if there is moisture in the air he will
need a HV glass vacuum with opposing terminals for contacts and a long
insulation bar on the transfer solenoid bar.

Power levels depend on the application, and he has picked about the
toughest application I can think of.

73 Tom


Hello Tom,

I know that, but you forgot to quote an important part of my text:

"IMHO two high power relays would be an option, about 10 inches
seperated from each other."



--

73,
Hans Remeeus (PA1HR)
http://www.remeeus.eu
Communication is about people, the rest is technology.

Hans Remeeus wrote:
Hello Tom,

I know that, but you forgot to quote an important part of my text:

"IMHO two high power relays would be an option, about 10 inches
seperated from each other."

That does nothing for breakdown voltages to control cables unless the
relays are a certain construction and wired a certain way. It can help
with antenna end-to-end breakdown voltage.

73 Tom