Need Suggestions for a Relay Source
 

I'm looking for a source for small inexpensive 12VDC relays which are
usable for cold-switching ~200W of RF at frequencies up to 30 Mhz. The
relays would be used to remotely select several single-band antenna
tuners and several end-fed vertical wire antennas strung up into some
tall trees. The "tuners" would be link-coupled tapped parallel tank
ciruits, one tuner per band.

There would be two relays needed per band, one to switch the 50 ohm
coax from the shack to the specific tuner and the other at the output
end of the tuner to select the particular wire. At the input ends of
the tuners the RF voltage would be around 200V @ 2 amps. At the output
ends of the tuners (depending on the feedpoint impedance) the RF
voltage could go into the 2kV range at very low currents. So basically
I need some sort of relays which can handle 2kV of HF RF at 2 amps.
Single pole NO non-latching reed switches would do the job.

I know I can use surplus vacuum relays but at $35-40 a pop that ain't
gonna happen.

Any and all suggestions will be appreciated.

w3rv

"Brian Kelly" wrote in message
ups.com...
I'm looking for a source for small inexpensive 12VDC relays which are
usable for cold-switching ~200W of RF at frequencies up to 30 Mhz. The
relays would be used to remotely select several single-band antenna
tuners and several end-fed vertical wire antennas strung up into some
tall trees. The "tuners" would be link-coupled tapped parallel tank
ciruits, one tuner per band.

There would be two relays needed per band, one to switch the 50 ohm
coax from the shack to the specific tuner and the other at the output
end of the tuner to select the particular wire. At the input ends of
the tuners the RF voltage would be around 200V @ 2 amps. At the output
ends of the tuners (depending on the feedpoint impedance) the RF
voltage could go into the 2kV range at very low currents. So basically
I need some sort of relays which can handle 2kV of HF RF at 2 amps.
Single pole NO non-latching reed switches would do the job.

I know I can use surplus vacuum relays but at $35-40 a pop that ain't
gonna happen.

Any and all suggestions will be appreciated.

w3rv


Brian

Have you considered building your own coax relays? It is fairly easy to
construct a SPST coax relay with glass enclosed tube shaped reed relays.
Their performance may be acceptable to you, maybe not. But I have built my
own coax relays from regular relays and have gotten adequate performance.

Jerry

Brian Kelly wrote:
I know I can use surplus vacuum relays but at $35-40 a pop that ain't
gonna happen.

Hi Brian, the Omron LY series seem to handle 100w for me.
Perhaps you can contact Omron about their limits.
--
73, Cecil http://www.qsl.net/w5dxp

Brian Kelly wrote:
I'm looking for a source for small inexpensive 12VDC relays which are
usable for cold-switching ~200W of RF at frequencies up to 30 Mhz. The
relays would be used to remotely select several single-band antenna
tuners and several end-fed vertical wire antennas strung up into some
tall trees. The "tuners" would be link-coupled tapped parallel tank
ciruits, one tuner per band.

There would be two relays needed per band, one to switch the 50 ohm
coax from the shack to the specific tuner and the other at the output
end of the tuner to select the particular wire. At the input ends of
the tuners the RF voltage would be around 200V @ 2 amps. At the output
ends of the tuners (depending on the feedpoint impedance) the RF
voltage could go into the 2kV range at very low currents. So basically
I need some sort of relays which can handle 2kV of HF RF at 2 amps.
Single pole NO non-latching reed switches would do the job.

I know I can use surplus vacuum relays but at $35-40 a pop that ain't
gonna happen.

Any and all suggestions will be appreciated.

By coincidence, I was reading an electronics mag over breakfast today,
and saw this press release:

"Crydom has launched a high performance miniature reed relay boosting
carry currents by 33%. Fitting a full electrostatic copper screen that
completely enshrouds the relay coil, a reduction in power loss is
achieved. Lower loss means lower self heating – enabling an increase
in carry currents to an industry leading 4A RMS at 30MHz from the
miniature 30mm x 10mm package.

"The 6 Series is designed for next generation HF antenna couplers and
filter circuits where improved RF performance and higher packing
densities are required.

"The hermetically sealed high vacuum reed switch will isolate 3kV
minimum (DC or RF peak) making it suitable for a range of Test Equipment
and Electromedical applications where high voltage, high current pulses
are generated."

Without necessarily endorsing that particular product, there are a few
interesting points:

* Switching in HF antenna couplers and filters is now a recognized
market.

* Reed relays can handle this kind of service.

* Coupling into the coil can be a problem, which may suggest making your
own. Crydom use a shielded coil, and an alternative idea ISTR is to wrap
the glass relay tube in foil instead of the coil. (In both cases the
shielding would need to be overlapping but non-shorting.) Which is the
better would depend on the application, and how much shunt capacitance
it can tolerate.

More details and a data sheet at:
http://www.crydom.co.uk/Webpages/arc...d_rf_relay.htm


--
73 from Ian G/GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Jerry Martes wrote:
"Brian Kelly" wrote in message

.. . . .

Brian

Have you considered building your own coax relays? It is fairly easy to
construct a SPST coax relay with glass enclosed tube shaped reed relays.
Their performance may be acceptable to you, maybe not.

I don't worry much about coax feedline impedance bumps at HF
frequencies.

But I have built my
own coax relays from regular relays and have gotten adequate performance.

I've done that a number of times with $5 Potter & Brumfield open frame
relays and never had a problem. In 50 ohm circuits. My big concern is
switching HF kilovolts with $5 relays which is a whole different
problem.

Tnx


Jerry

w3rv

Cecil Moore wrote:
Brian Kelly wrote:
I know I can use surplus vacuum relays but at $35-40 a pop that ain't
gonna happen.

Hi Brian, the Omron LY series seem to handle 100w for me.
Perhaps you can contact Omron about their limits.

OhYeah, that's what I've been looking for. Tnx Cecil! I Googled 'em and
landed on the Mouser web page which lists the Omron LYs. They're good
for 10-15 amps @ 2 kV AC and for only $6-7 each. Should work fine
although I'd like to have higher voltage ratings. Not much to lose by
trying a couple of them to find out if they arc in the 110% humidity we
occasionally get around here.

--
73, Cecil http://www.qsl.net/w5dxp

w3rv

Brian Kelly wrote:
OhYeah, that's what I've been looking for. Tnx Cecil! I Googled 'em and
landed on the Mouser web page which lists the Omron LYs. They're good
for 10-15 amps @ 2 kV AC and for only $6-7 each. Should work fine
although I'd like to have higher voltage ratings. Not much to lose by
trying a couple of them to find out if they arc in the 110% humidity we
occasionally get around here.

The LYs are designed to minimize humidity problems. The
air gap is replaced by some sort of plastic separator.
--
73, Cecil, http://www.qsl.net/w5dxp

Ian White G/GM3SEK wrote:
Brian Kelly wrote:

.. . . .

I need some sort of relays which can handle 2kV of HF RF at 2 amps.
Single pole NO non-latching reed switches would do the job.

I know I can use surplus vacuum relays but at $35-40 a pop that ain't
gonna happen.

Any and all suggestions will be appreciated.

By coincidence, I was reading an electronics mag over breakfast today,
and saw this press release:

"Crydom has launched a high performance miniature reed relay boosting
carry currents by 33%. Fitting a full electrostatic copper screen that
completely enshrouds the relay coil, a reduction in power loss is
achieved. Lower loss means lower self heating - enabling an increase
in carry currents to an industry leading 4A RMS at 30MHz from the
miniature 30mm x 10mm package.

"The 6 Series is designed for next generation HF antenna couplers and
filter circuits where improved RF performance and higher packing
densities are required.

"The hermetically sealed high vacuum reed switch will isolate 3kV
minimum (DC or RF peak) making it suitable for a range of Test Equipment
and Electromedical applications where high voltage, high current pulses
are generated."

They sound like they'd definitely do the job but so far I can't find a
U.S. source for them.

Without necessarily endorsing that particular product, there are a few
interesting points:

* Switching in HF antenna couplers and filters is now a recognized
market.

* Reed relays can handle this kind of service.

Exactly. They're showing up everywhere in recently-designed ham
equipment - to the 2kW level and beyond. Big amps, big autotuners, etc.


In prior times the coax could be remotely switched but the only relays
which could handle high RF voltages were pricey vacuum relays. It's the
recent advent of these inexpensive new type reed relays which led me to
reconsider using end-fed half-wave verticals.

* Coupling into the coil can be a problem, which may suggest making your
own. Crydom use a shielded coil, and an alternative idea ISTR is to wrap
the glass relay tube in foil instead of the coil. (In both cases the
shielding would need to be overlapping but non-shorting.) Which is the
better would depend on the application, and how much shunt capacitance
it can tolerate.

I don't understand the shielding/loss problem. I wouldn't be using
these relays inside equipment where shielding as such might matter. How
how significant are these losses? I'm switching the bottom ends of more
or less resonant wires from wire to wire and from tuner to tuner in
some arramgement or another TBD. All of it out the yard where I hope I
radiate as much RF as possible.

More details and a data sheet at:
http://www.crydom.co.uk/Webpages/arc...d_rf_relay.htm

Nice specs, I'll continue the hunt for a source.

--
73 from Ian G/GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Thanks Ian.

w3rv

Cecil Moore wrote:
Brian Kelly wrote:
OhYeah, that's what I've been looking for. Tnx Cecil! I Googled 'em and
landed on the Mouser web page which lists the Omron LYs. They're good
for 10-15 amps @ 2 kV AC and for only $6-7 each. Should work fine
although I'd like to have higher voltage ratings. Not much to lose by
trying a couple of them to find out if they arc in the 110% humidity we
occasionally get around here.

The LYs are designed to minimize humidity problems. The
air gap is replaced by some sort of plastic separator.

Neat. Even if they do arc the barrier could always be replaced with a
bigger and better homebrewed barrier. Off to the relay store and pass
the epoxy . .

--
73, Cecil, http://www.qsl.net/w5dxp

w3rv