Antenna Switches

[transmitterdan]

You should be able to get something similar for less with a little digging. There are RF surplus sites that sell used items. They often have things like this for a lot less. Some ham stores sell less expensive ones. Trolling through some ham discussion groups may turn up something. Maybe even try using that new ham radio to reach out for advice on where to find used RF gear. If you can wait a while try to plan your schedule to be at the Dayton ham fest (Dayton Hamvention 2013 - DX Hamvention) next year. Bring a list of stuff you need and almost certainly someone will have the stuff you want.

[Dockhead]

Originally Posted by goboatingnow

why use one of the several AIS splitters on the market,

dave

They don't work at UHF frequencies; big insertion losses in any case.

[Dockhead]

Originally Posted by transmitterdan

You should be able to get something similar for less with a little digging. There are RF surplus sites that sell used items. They often have things like this for a lot less. Some ham stores sell less expensive ones. Trolling through some ham discussion groups may turn up something. Maybe even try using that new ham radio to reach out for advice on where to find used RF gear. If you can wait a while try to plan your schedule to be at the Dayton ham fest (Dayton Hamvention 2013 - DX Hamvention) next year. Bring a list of stuff you need and almost certainly someone will have the stuff you want.

Thanks!

[ka4wja]

Dockhead,
Commercial, hi-power, low-VSWR, low-loss, transmitter / antenna switch matrix (even just a 2 x 2) are VERY VERY expensive....(think thousands of dollars for even just a basic one!!)
But, these are not necessary here!!!


1) While I do know the exact product that you are looking for (see below), and I have been using these items for ham radio and commercial projects for close to 30 years (currently have a model 74 running on HF and a model 7422 on VHF/UHF at home....), I'm not sure they are actually necessary for your application....
But, below you'll find the details...




2) Most hams (and many commercial sites), simply use 1 x 4, 1 x 6, 1 x 8, etc. etc...switches to switch between multiple transmitters and a single antenna, and accept that they must select the correct position, before transmitting....

Originally Posted by Dockhead

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!

There is no effective difference between using these switches (Diawa or Alpha Delta are both good) for switching multiple antennas to one transceiver, or switching multiple transceivers to one antenna....
(I, myself, use Diawa's thru UHF....nice low-loss, hi-isolation, and never a worry....and use one on-board to switch between my backstay and a homebrew 12mhz / 14mhz dipole....)





3) Most modern solid-state transceivers (HF or VHF/UHF, etc.) do have transmitter VSWR protection built-in, that all but prevents final PA damage from transmitting into an open circuit...and many commercial / industrial / broadcast transmitters are designed/built to actually operate in quite high VSWR's (some will work at full power/full spec, into an infinite swr!)....

Originally Posted by Dockhead

The problem is that if you forget your radio is not switched to the antenna, you can fry it if you try to transmit.

In about 40 years of radio operating / installing, the only "blown finals" I've ever seen are from,
a) overheat / overload (usually driven beyond their saturation)...(did this with some friends decades ago, during a 160m contest....thank God for a spare radio!!)
b) lightning damaged...
While that's not to say that someone couldn't do something else wrong and damage their radio's PA, but I've never seen it....
And, I suspect that the stories get significantly exaggerated!!!

[EDIT:
I forgot....I have seen overvoltage (too high B+) damage as well...]

Besides, you should have an power/swr meter in the circuit, so that you always have a positive indication of your transmitter and antenna condition...
If you forget to "switch the switch", you'd see it quickly, stop the transmission, and place the switch in the correct position....so, having a "fail-safe" type switching arrangement is probably unnecessary....
But...
But, if you do desire it, see #4....




4) A Bird Model 72-R (and a small dummy load on one of the antenna terminals) is what will do exactly what you desire....
This would allow you to switch two radios to an antenna or to a dummy load, thereby always have a "load" (whether antenna or dummy load) attached to each transceiver....

The Bird specs are VERY conservative and are for 100% duty cycle, continuous operation....

---- Insertion loss is VERY VERY low....spec'd at < 0.02db at 100mhz, yes that is not a typo 0.02db (i.e 1/50 of a db)!!! (and < 0.09db at 1000mhz, etc...)
I have never been able to measure any insertion loss on mine...(the lowest repeatable measurement scale I have in my equipment is about 0.1 db...and even when doing this, cleaning connectors with denatured alcohol before the tests is required to maintain repeatability!!!)

---- Although "spec'd" at > 75db thru the microwave region, you'll find port-to-port isolation ("crosstalk") of > 85-90db on HF/VHF/UHF (I see >85db - 90db on mine, thru UHF)

---- Power handling is what is VERY conservative, spec'd at only 850 watts continuous on VHF.....
But, I've had my Bird switches running for many years with a few kw on HF and 1200 watts on VHF....and never an issue, ever!!!
Typically it is "accepted" that these switches are good for a couple kw thru VHF, etc...


See the Bird site for the exact specs and features of the Bird Model 72-R...
RF Coaxial Selector Switch | 72-R, Reversing | Bird Technologies

http://www.bird-technologies.com/~/m...s/921-72R.ashx



And, as I said I've had a Bird Model 74 (6-position, 1 x 6 switch) running at HF, w/ a few kw for years and years....and a Bird Model 7422 (2-position, 1 x 2 switch) running at VHF and UHF with up to 1200 watts for decades....
You can see one of them in the picture of my ham shack on qrz.com....
KA4WJA - Callsign Lookup by QRZ.COM
My Bird Model 74 is between the two rotator controls and just above my SP-7 speaker....(my 7422 is hidden)
And, here are the specs for my switches....
RF Coaxial Selector Switch | 74, 6 Position | Bird Technologies
RF Coaxial Selector Switch | 7422, 2 Position | Bird Technologies

Now, if you buy 'em retail, they'll set you back a few hundred dollars (about $400 - $500 USD, or so)....
But, if you buy 'em surplus, as I bought mine, you can get them for < $100 USD....(and, they will out live you and me, and still be working to spec!!!),





Now, how's that for an answer....the exact product you need, with a 100% fail-safe design, and uses NO electricity NO microprocessor, etc!!!
And, from someone who has been using a similar model (an almost exact model) for decades!!!
Enjoy!!



Fair winds...

John
s/v Annie Laurie

[Dockhead]

Wow!! What an incredibly thorough, helpful post! Exhaustively settling every aspect of the question. Wow, thank you extremely much, John. I'll look for one of those beauties. If I don't find one, I guess Ill take the alternative advice you gave. Problem solved. Cheers.

[El Pinguino]

Here you go.... 290960932282 eBay item number:

[Dockhead]

Originally Posted by El Pinguino

Here you go.... 290960932282 eBay item number:

Already on my Watch List. LOL

[poiu]

Instockwireless do great products and are efficient. I have a 3 to one combiner. Can do loads of antennas and automatically. No switch to fiddle with. Here's a big one if you want to simplify your installation:

[poiu]

Originally Posted by poiu

Instockwireless do great products and are efficient. I have a 3 to one combiner. Can do loads of antennas and automatically. No switch to fiddle with. Here's a big one if you want to simplify your installation:

Just looked again. Wrong frequency range as standard in their kit for your job. They may help with a special if you ask them.

[Dockhead]

Bought the Fleabay one. From a sailing ham, no less. Trying to figure out if he is secretly one of us.

[El Pinguino]

Wasn't me.....