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Old 29-12-2018, 14:30   #1
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SSB Antenna Question - GTO-15 Connector?

I recently replaced the backstay on my Alberg 35 and, rather than putting insulators in the backstay, I procured a GAM Split Lead SSB antenna that "wraps around" the backstay. The antenna is fed with GTO-15 cable, which is a high-voltage cable that resembles (in appearance and size only) a spark plug wire you'd find on a motor.

I regularly transit the canal system in New York, which means I have to drop the mast on an equally regular basis. I'd like to avoid having to empty the lazarette and then crawl into it to disconnect the GTO-15 feed line from the tuner and then thread it up past the thru-deck fitting and back every time the mast goes up and down. I'd like to put a connector a foot or so above the deck to make this a cleaner operation, but I cannot find any connectors that are specific to this cable or its application as an RF feed line.

I suppose an SO-239/PL-239 combination could be used, but I'm concerned this might introduce a significant impedance mismatch in what is effectively the radiator in the antenna system as well as not being very waterproof.

Has anyone done anything similar? If so, what type of connector did you use?

Thanks!
Tom
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Old 29-12-2018, 15:27   #2
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Re: SSB Antenna Question - GTO-15 Connector?

Most any simple connector will work as long as you isolate or insulate it to avoid unintended grounding or RF burn hazard. The -239 connectors will work ok... just don't ground the shell and there will be no issue with impedance mismatch.

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Old 29-12-2018, 15:30   #3
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Re: SSB Antenna Question - GTO-15 Connector?

The length of any connector you are likely to use is very short relative to HF wavelengths, so there will be almost no effect on the antenna impedance as long as there is an excellent electrical connection. You don't even need to use something designed for RF, and it would probably be best not to anyway since you probably want something both waterproof and reasonably small and light weight.
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Old 29-12-2018, 20:32   #4
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Re: SSB Antenna Question - GTO-15 Connector?

Use a MILLEN high-voltage connector. Cf.:

https://www.ebay.com/i/352551407159?chn=ps

https://www.rfparts.com/connectors-h...ge/37001b.html

https://www.ebay.com/sch/i.html?_nkw...&ul_noapp=true

You'll have to invent your own weatherproofing.
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Old 30-12-2018, 19:20   #5
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Re: SSB Antenna Question - GTO-15 Connector?

You can use a butt connector. Just cut it out and re-splice as needed. Leave a longer GTO wire as it and your antenna will be a cm shorter each time.
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Old 30-12-2018, 20:44   #6
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Re: SSB Antenna Question - GTO-15 Connector?

Hi Alley


There are no weatherproof connectors in widespread use that are ideal for that situation, but there is much that can be adapted.


Perhaps the simplest thing would be to just use a pair of N connectors (for coaxial cable) and use only the center pin leaving the shield connection unconnected. These are weatherproof connectors that are insulated for the sorts of voltages that will be present. The solder-type connectors may be the easiest to use.


A PL-239 arrangement will also work but these are generally not weatherproof. The impedance mismatch should not be a factor. In a dry environment many people would use a banana jack and plug instead.



As suggested upthread you can just use a crimp-on splice or perhaps an automotive "bullet" connector. These will not be officially rated for the voltage but in many situations will work out fine in practice. You can use a short piece of 1/2" pvc pipe with holes/slots/whatever cut in it as a standoff so that the splice is an inch or more away from the backstay.
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Old 30-12-2018, 21:45   #7
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Re: SSB Antenna Question - GTO-15 Connector?

A little bulky, but fairly light and waterproof would be a male and female pair of MC4 connectors as used commonly in solar panel installations. The GTO-15 might be a bit thick for the gasket where it enters the connector, but you can always wrap with something like Scotch Rubber Splicing Tape 23 to form a water tight seal. You could easily waterproof almost any simple connector by encasing in this or some other self-fusing tape.
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Old 03-01-2019, 23:27   #8
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Re: SSB Antenna Question - GTO-15 Connector?

I would not use a Millen connector under any circumstance. Its a poor connector design that is very dangerous. Worst of all is that the material that they use to make this HIGHVOLTAGE connector is hydroscopic, meaning that it absorbs water and will arc over.



Quote:
Originally Posted by continuouswave View Post
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Old 03-01-2019, 23:38   #9
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Re: SSB Antenna Question - GTO-15 Connector?

Search out of type HN Amphenol connectors. These are proper high voltage connectors. If you mount it on a insulated support and fill it with Dow Corning DC4 dielectric grease you will never arc this connector out. if you get a decent Amphenol grade it uses beryllium copper connections so will mate thousands of times without going faulty. Just ignore the Epay crap which is utter garbage.



If you do want a plug and play proper connector that will withstand high voltages that will typically be encountered when doing a tuning cycle you can try and buy whats called a Alden connector these can be bought from 15kv ratings right upto 50kV. You can buy them as connectors alone or with some high voltage pigtails that have better specifications than GTO wire. Theres a few dealers like Mouser and RF parts that sells these Alden connectors. You can try Surplus Sales of Nebraska which has an excellent selection of hard to get high voltage connectors. But watch their prices.



The ultimate high voltage connector is whats called a LEMO high voltage connector. The LEMO Y connector can bought with 70kv ratings. They are very expensive.


If you want a good safety margin and want to use a heavy duty screw coupling try using a MALE AND FEMALE 7/16 DIN connector. These connectors are built like a tank and have heaps of insulation around the center pin. Again fill them with with silicone Dow DC grease and they will never break down.



I use these connectors everyday designing XRAY and MRI machines and they have never failed in the thousands of machines that we have shipped.




Quote:
Originally Posted by alley View Post
I recently replaced the backstay on my Alberg 35 and, rather than putting insulators in the backstay, I procured a GAM Split Lead SSB antenna that "wraps around" the backstay. The antenna is fed with GTO-15 cable, which is a high-voltage cable that resembles (in appearance and size only) a spark plug wire you'd find on a motor.

I regularly transit the canal system in New York, which means I have to drop the mast on an equally regular basis. I'd like to avoid having to empty the lazarette and then crawl into it to disconnect the GTO-15 feed line from the tuner and then thread it up past the thru-deck fitting and back every time the mast goes up and down. I'd like to put a connector a foot or so above the deck to make this a cleaner operation, but I cannot find any connectors that are specific to this cable or its application as an RF feed line.

I suppose an SO-239/PL-239 combination could be used, but I'm concerned this might introduce a significant impedance mismatch in what is effectively the radiator in the antenna system as well as not being very waterproof.

Has anyone done anything similar? If so, what type of connector did you use?

Thanks!
Tom
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Old 04-01-2019, 10:09   #10
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Re: SSB Antenna Question - GTO-15 Connector?

Quote:
Originally Posted by plebian99 View Post
I would not use a Millen connector under any circumstance. Its a poor connector design that is very dangerous. Worst of all is that the material that they use to make this HIGHVOLTAGE connector is hydroscopic, meaning that it absorbs water and will arc over.
Hello--in connecting the antenna to its single wire feed line there won't be any difference in voltage.

Yes, it is not designed to tolerate being underwater, but if one end of your antenna is underwater, you will have more problems than the connector possibly failing to maintain good insulation.

I don't think the connector is particularly dangerous. It has been in use for decades to conduct very high DC voltages, albeit the design is a bit old-school.

As for the material, the connector is made in two versions. One is mica and the other is plastic. I'd use the plastic version. I am not aware that plastic absorbs liquids. Plastic drink containers seem to be rather good at not absorbing the contents of the bottle.

But, as always, any internet discussion thread with more than five replies will contain completely contradictory recommendations. Feel free to sort this out yourself.
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