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#1
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High voltage switch/relays for antenna?
TF3KX schreef:
Hello: I am contemplating constructing an antenna where a center-fed HALF WAVE will be bent in a loop, only to be isolated at the almost-touching ends by a relay or some other means of a remotely controlled switch. When the relay contacts are open I will have very high RF voltages between the contacts, probably "a few KV" or even more. Are there any suggestions on where I could find a relay, if any, for this? Or any other means for doing this? An additional constraint is that the switching device needs to be light and small (say, 1-2 oz or 20-50 grams). Some ideas I have come up with a - A small vacuum relay (supplier, type?). - A home-made relay, providing more contact spacing than usually available. - A DC-motor (toy-type) driven mechanism to open and close contacts. - A mercury switch that could be tilted to make or break the contacts. - A string-operated switch to open and close the contacts (would run up the antenna mast). Any comments or suggestions? 73 - Kristinn, TF3KX IMHO two high power relays would be an option, about 10 inches seperated from each other. 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! -- 73, Hans Remeeus (PA1HR) http://www.remeeus.eu Communication is about people, the rest is technology. |
#2
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High voltage switch/relays for antenna?
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 |
#4
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High voltage switch/relays for antenna?
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. |
#5
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High voltage switch/relays for antenna?
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 |
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