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Old 20-08-2013, 02:43   #1
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Antenna Switches

I am looking for a coax switch to switch between my VHF/UHF (not bought yet) ham radio and my AIS transceiver.

The problem is that all the switches I have been able to find, from Diamond, Alpha Delta, Ameritron, etc., etc., are all designed to switch multiple antennas from a single radio. Not multiple radios from a single antenna! The problem is that if you forget your radio is not switched to the antenna, you can fry it if you try to transmit.

This is not a problem for AIS transceivers as they are designed specifically (I think it's part of the specification) so that the transmitter is not damaged if it is switched on with no antenna connected. Alas, this is not true of regular radios.

Anyone struggle with this problem? Surely someone somewhere has made an antenna switch that will switch the unused radio onto a dummy load, or something.
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Old 20-08-2013, 03:56   #2
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Re: Antenna Switches

Something like this may be overkill Antenna matrix switch AMS-33 - Elad Online Shop .. Elad AMS-33 -Antenna matrix switch Elad Receivers at 224.95 | Ham Radio

Maybe cheaper just to invest in yet another ant.

ELAD make some good kit.
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Old 20-08-2013, 03:58   #3
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Re: Antenna Switches

added bit.... you could have a dummy load as one of the three available ants.

Oooops, I see it is only rated from DC to 150MHz......
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Old 20-08-2013, 04:30   #4
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Re: Antenna Switches

Shakespeare makes one that automatically switches between two radios and one antenna so no risk of frying the transmitter.

Shakespeare AS-2 Automatic Coaxial Switch

Not sure if there is any signal loss in the unit but I have one that is connected just behind my main VHF and if I have any problems can easily remove the switch and connect the antenna directly to the radio.
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Old 20-08-2013, 04:34   #5
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Re: Antenna Switches

By the way, Shakespeare makes a manual version as well which I used on a previous boat. Big surprise, I did forget to switch it at least once that I remember and try to transmit.

Even after 3-4 attempts to call another vessel before I remembered the switch the transmitter was fine. Not sure if I was lucky, if I didn't transmit long enough to cook the output section or just that the Standard Horizon model I had was good enough to put up with it but regardless I got away with it.
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Old 20-08-2013, 04:48   #6
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Re: Antenna Switches

Are you sure you want to use a Multiplex in a marine environment? (Not recommended!; contacts/corrosion issues.) When you build a network, make it a standard design so that anyone can use it; if you're not around someday, guess what's going to happen? I would build separate systems, if I was you! (No skimping/short cuts on a boat.)

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Old 20-08-2013, 05:09   #7
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Re: Antenna Switches

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Originally Posted by Teknav View Post
Are you sure you want to use a Multiplex in a marine environment? (Not recommended!; contacts/corrosion issues.) When you build a network, make it a standard design so that anyone can use it; if you're not around someday, guess what's going to happen? I would build separate systems, if I was you! (No skimping/short cuts on a boat.)

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I think the problem is that Dockhead already has so many antennas on his boat that the NSA is tracking him and the Russians are using his setup as a basis to design a new fleet of "fishing trawlers".
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Old 20-08-2013, 05:23   #8
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Re: Antenna Switches

Quote:
Originally Posted by skipmac View Post
I think the problem is that Dockhead already has so many antennas on his boat that the NSA is tracking him and the Russians are using his setup as a basis to design a new fleet of "fishing trawlers".
LOL. Correct. They were already referring to my boat in Cowes as the "Russian spy trawler".

Anyway, the mast is back in, so no more antennae! Enough already!
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Old 20-08-2013, 05:28   #9
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Re: Antenna Switches

Quote:
Originally Posted by El Pinguino View Post
Something like this may be overkill Antenna matrix switch AMS-33 - Elad Online Shop .. Elad AMS-33 -Antenna matrix switch Elad Receivers at 224.95 | Ham Radio

Maybe cheaper just to invest in yet another ant.

ELAD make some good kit.
Very cool device, and not at all overkill, I think.

Too bad it can't handle UHF, which eliminates it for my use.

The perfect device for me would be something just like that, just:

1. Will work through UHF frequencies
2. Type "N" connectors
3. Panel mount, at least control head

The other disadvantage of the Elad device is that despite its costliness, it is quite lossy -- 0.6dB at VHF (I suppose PLUS the insertion loss of the extra set of connectors -- ouch!) and reflection of 1.22:1 -- so degrading SWR quite a bit. I think the simple mechanical switches are much better in that regard.


So I keep looking.
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Old 20-08-2013, 05:38   #10
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Re: Antenna Switches

Quote:
Originally Posted by skipmac View Post
Shakespeare makes one that automatically switches between two radios and one antenna so no risk of frying the transmitter.

Shakespeare AS-2 Automatic Coaxial Switch

Not sure if there is any signal loss in the unit but I have one that is connected just behind my main VHF and if I have any problems can easily remove the switch and connect the antenna directly to the radio.
I'm aware of it. Yes, the functionality is perfect. Unfortunately, it can only handle 30 watts (ham VHF/UHF typically 50 watts, sometimes 75 watts), and it doesn't do UHF. Plus it's quite lossy.
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Old 20-08-2013, 05:43   #11
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Re: Antenna Switches

Quote:
Originally Posted by Dockhead View Post
Very cool device, and not at all overkill, I think.

Too bad it can't handle UHF, which eliminates it for my use.

The perfect device for me would be something just like that, just:

1. Will work through UHF frequencies
2. Type "N" connectors
3. Panel mount, at least control head

The other disadvantage of the Elad device is that despite its costliness, it is quite lossy -- 0.6dB at VHF (I suppose PLUS the insertion loss of the extra set of connectors -- ouch!) and reflection of 1.22:1 -- so degrading SWR quite a bit. I think the simple mechanical switches are much better in that regard.


So I keep looking.
Why not the Shakespeare AS2? Good up to 600 MHz or are you working higher than that? Other specs:

Frequency Range: up to 600 MHz
VSWR: Below 1.2:1
Power Rating: 30 W
Impedance: 50 ohms
Connections: SO-239 type
Power Supply: 12 vDC @ 200 ma
Sensing/Switching Time: Less than 100 ms

By the way, I have had one of these on my 18' open motor boat for 10 years to run my VHF and FM stereo off one antenna and still working fine.
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Old 20-08-2013, 06:00   #12
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Re: Antenna Switches

Quote:
Originally Posted by Dockhead View Post
I'm aware of it. Yes, the functionality is perfect. Unfortunately, it can only handle 30 watts (ham VHF/UHF typically 50 watts, sometimes 75 watts), and it doesn't do UHF. Plus it's quite lossy.
OK strike that one. What about their manual switch the CS2:

Frequency: up to 600 MHz
VSWR: Less than 1.2:1
Power Rating: Up to 1 KW (CW)
Impedance: 50 ohms
Insertion Loss: Less than 0.2 dB
Isolation: Greater than 50 dB

Has the power rating and claims a loss of <0.2 dB but still limited to the lower end of the UHF.

You could always hang a red tag on your transmitter when switched to the other radio.
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Old 20-08-2013, 06:11   #13
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Look up RF transfer relay, aka baseball switch. This is an example: http://www.pasternack.com/images/ProductPDF/PE7153.pdf

Likely you will not find this with SO-239 connectors but Type N is readily available. In US a popular vendor is Dowkey but also Amphenol and many others. You have to provide a dummy load or antenna for the fourth port.
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Old 20-08-2013, 06:34   #14
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Re: Antenna Switches

Quote:
Originally Posted by transmitterdan View Post
Look up RF transfer relay, aka baseball switch. This is an example: http://www.pasternack.com/images/ProductPDF/PE7153.pdf

Likely you will not find this with SO-239 connectors but Type N is readily available. In US a popular vendor is Dowkey but also Amphenol and many others. You have to provide a dummy load or antenna for the fourth port.
That looks like the perfect device!

$577 -- ouch!
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Old 20-08-2013, 07:53   #15
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Re: Antenna Switches

Quote:
Originally Posted by Dockhead View Post
I am looking for a coax switch to switch between my VHF/UHF (not bought yet) ham radio and my AIS transceiver.

The problem is that all the switches I have been able to find, from Diamond, Alpha Delta, Ameritron, etc., etc., are all designed to switch multiple antennas from a single radio. Not multiple radios from a single antenna! The problem is that if you forget your radio is not switched to the antenna, you can fry it if you try to transmit.

This is not a problem for AIS transceivers as they are designed specifically (I think it's part of the specification) so that the transmitter is not damaged if it is switched on with no antenna connected. Alas, this is not true of regular radios.

Anyone struggle with this problem? Surely someone somewhere has made an antenna switch that will switch the unused radio onto a dummy load, or something.
why use one of the several AIS splitters on the market,

dave
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