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Ameritron RCS-8V coax switch & AR-35 Rotator additions to the shack

dxhound

Active Member
Nov 17, 2006
783
58
38
I was thinking that using the coax in place of the board traces would help more with isolation issuesrather than power handling. Im sure the surface mil area of the trace is more if not equal to the surface area of a coax center conductor. Im sure at 1500watts that some mutual inductance occurs given the close natur of the traces and could cause false SWR readings as well as a small amount of RF to be placed on an unwanted source (i.e. other antennas)
 

Captain Kilowatt

Professional Amateur
Staff member
Apr 6, 2005
16,835
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Dxhound, I hear what you are saying but radiation from those traces is a function of frequencies used.It is not uncommon at all on AM broadcast frequencies to see heavy strap connections a foot or more long and the radiation from those is minimal. On HF there will in fact be very little.Any induced radiation into other antennas is overwhelmed by that from the active antenna,in fact the active antenna will induce more RF into the other nearby antennas than the leakage from those traces would.
 

dxhound

Active Member
Nov 17, 2006
783
58
38
I understand that the skin effect at these frequencies is almost non existant. My only concer would be the stray RF within the switch box would cause reactance issues and false SWR readings. Thats really my only concern with this design
 

Captain Kilowatt

Professional Amateur
Staff member
Apr 6, 2005
16,835
10,973
823
58
Nova Scotia,Canada
I understand that the skin effect at these frequencies is almost non existant. My only concer would be the stray RF within the switch box would cause reactance issues and false SWR readings. Thats really my only concern with this design


Well actually since we are dealing with RF the skin effect is VERY prevalent as it pertains to the portion of a conductor where the RF density is the greatest and has nothing to do with the length of the conductor whether shielded or not. Any reactance issues in a switch of this design are taken into account when the switch is designed and that is why they are rated for use on certain frequecies. A switch made for VHF or UHF is different than one made for HF because of the reactance issue. I mistakenly purchased an MFJ-1700B switch because I thought it was good to 6m as well as HF. I was wrong and since my FT-857 uses the same antenna port for HF as it does for 6m I had a problem with high SWR thru the switch on 6m but it was perfect on HF. I solved that issue by cutting out all the internal connecting wires and replacing them with RG-8X coax and grounding one end of the cable.this made it useable on 6m. Basically I did exactly what you suggested but not because of stray RF but rather reactances. Since the switch was only rated for HF everything was fine there but on 6m the reactances were too high since it was not rated for that band. It's just like anything else we buy and use. Run it within the manufacturer's specs and everything is fine.
 

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,034
1,335
283
Hi Mole,

just curious, is the switch working good still?

Thanks,
AP

Yep, still working. It would be interesting in the spring to get back on the roof and take a peek inside the switch to see how well it has held up under a season of rain...
 

airplane1

W9WDX Amateur Radio Club Member
Apr 15, 2005
1,051
32
58
Lebanon county PA
My son asked me what I would like for my birthday and I said money, LOL. I am going to buy one of these switches in spring. I hope to see Moe go up to the switch and look inside before I get one. Is it still working good this very cold windy winter so far?

AP
 

airplane1

W9WDX Amateur Radio Club Member
Apr 15, 2005
1,051
32
58
Lebanon county PA
Well ordered a remote switch from HRO yesterday for 159.95 free ship. It is going to be here today waiting for me when I get home from work.

I am going to hook it up and play with it to see how it works before putting it up on the tower.

AP
 

airplane1

W9WDX Amateur Radio Club Member
Apr 15, 2005
1,051
32
58
Lebanon county PA
Great news, I just did not get mine up yet, I got all my coax,antennas and whatnot to finish every thing but ran out of good weather. Hope spring is going to get here early.
 

airplane1

W9WDX Amateur Radio Club Member
Apr 15, 2005
1,051
32
58
Lebanon county PA
Got the switch on the tower at a hight I can reach with a 2 foot step ladder for easy access.

I am one that is never satisfied with things I buy and have to make them better in my little ways and this is a pic of my idea, I took the muffler style clamp and replaced it with a 1 1/4 inch dia.mounting block so it would not hurt my tower leg in any way as I tighten it down.

I am putting three antennas up in the next week or so and plan on taking pics and maybe some vids, a 4 element 10 meter home brew beam, Imax 2000 right above that and a OCF at 30 ft.
 

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KingCobra_CDX882

W9WDX Amateur Radio Club Member
Mar 30, 2005
2,035
48
58
The week link is that AR-35
Those are next to useless.

I have both those..
But removed the AR-35
( at best good for a medium tv or UHF antenna )
 

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,034
1,335
283
Just a quick update. 5 years in and relay 1 on the switch has failed. I had an open port, so I just moved the antenna there. One day I'll order the relay from Ameritron and replace it.
 

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,034
1,335
283
Another 5 year update on unit #2: The SWR on 2 of the 3 ports I use has gone sky high. I got on the roof and checked the relays, which are working. The contacts appear to be engaging, but clearly something is wrong. A visual inspection didn't reveal anything obvious so I may try using some fine sandpaper to remove any corrosion that might be there. Or I may just take it down and go a different direction with this antenna entirely. Seems like a good reason to explain to the wife why a new antenna is necessary :) :)
 

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