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Old 01-07-2016, 13:35   #16
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Re: VHF / AIS Antenna Separation

Don,
The answer to your question is, yes there are coaxial switches made that do exactly what you desire...but, they are pricey!! (MSRP is about $2000 USD.....yes, you read that right Two Thousand Dollars....but, you can find 'em on the shelf in commercial radio supply houses, new, for about $750 - $1000, and new on e-bay for about $400....and used are typically about $250.....I bought my 72 and 74's used for about $100 each)
RF Coaxial Selector Switch | 72-R, Reversing | Bird Technologies

Not sure if that's the answer you were looking for....but there you go...

BTW, your question reminds me of the best answer I ever heard for problems like this...given to me > 40 years ago (in another context)....
"Absolutely, yes you can have 'fast', 'reliable', and 'cheap', just pick two!"
I know, sort of like henry Ford's "you can have a model T in any color you want as long as you want black"....


Don, bottom line....if you don't want to spend the money (~ $120) and use two manual switches (Daiwa CS-201's) and their associated cables, and/or are not comfortable remembering to switch them correctly...
Then you options are limited...
a) swap the cables manually...
b) install the Vesper SP-160 ($240)
c) buy a Bird 72-R, or equiv.


I do hope this helps..

John
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Old 01-07-2016, 13:39   #17
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Re: VHF / AIS Antenna Separation

HUH? A switch that does this for HF frequencies is less than $30, but the same kind of switch for VHF frequencies costs $2,000. Seriously? What am I missing?
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Old 01-07-2016, 14:04   #18
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Re: VHF / AIS Antenna Separation

Gosh, Don...read what I wrote again...
Its MSRP is $2000...
And, you can buy 'em for $400...
Not sure how else to write it...

As for what you're missing....honestly I don't have the time to write a treatise on switch design, isolation, coaxial switch design, switch VSWR/return loss, etc. etc...

As I wrote earlier...
"Absolutely, yes you can have 'fast', 'reliable', and 'cheap', just pick two!"


But, if you want a layperson's explanation, here you go...
--- Your application (reliable, low-loss, high-isolation VHF transfer switching) is like driving thru the Alps on a windy spring morning, maybe with a few snow flurries...
--- Your mention of MFJ, is like a 20+ year old Yugo with bald tires...
--- My notation of the "proper" device (the Bird 72-R) is like recommending an Audi A6 or Range Rover Discovery, etc. for the drive, rather than that old Yugo...

And, I'm being generous when I compare the MFJ switch and the Bird switch to Yugos and Range Rovers....the difference is even bigger...


And, FYI....
Just so you know I'm not blowing smoke here....I DO own and use Bird products a LOT....including a Bird 74 switch and a Bird 72 switch, in my ham shack at home....
Here is a picture showing one of them (the Bird 74)....it is the black knob, between the two rotor control boxes, on the shelf, just above the speaker...






Fair winds...

John
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Old 01-07-2016, 21:16   #19
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Re: VHF / AIS Antenna Separation

Thanks to all, especially John.
I will check the coax all the way, which means I must go up the mast. This makes sense in terms of my constant intermittent TX and RX problems. Maybe I will try bypassin the AIS first.

When I pulled the AIS out the boat was on the hard so I didn't test the VHF only.
I have raised anyone or the test numbers on a DSC call.

Can I realistically monitor the current draw, as John mentioned above, by watching the current draw through my Xantrexshunt monitor?

I am grateful for your helpful ideas,
Fair seas


This is the second replacement AIS250!
My e7 plotter had to be replaced 3 months old under a general recall!
The Remote microphone unit was also replaced from new as defective!

The plotter, autopilot, sensors, i70 displays all work excellently now, but what a load of bxllxx it has been the past few years working through it all.
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Old 01-07-2016, 21:19   #20
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Re: VHF / AIS Antenna Separation

Another question- other than a visual inspection, is there some way I can check the continuity of the coax?
PS I have a VOM
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