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4/22/2019 5:32:20 PM
Posted: 3/14/2013 8:38:22 PM EDT
I'm looking for a solid but relatively inexpensive antenna switch for UHF / VHF. I need to connect to two antenna which have SO-239 inputs, and my radio on the other end has got an SMA female connection.

I'm imagining something like this:

SO-239 antennas > PL-259 to PL-259 cable > SO-239 switch > PL-259 to SMA male cable > my radio

Anyone know of any good switch like that (two SO-239 inputs and one SO-239 output)?
Link Posted: 3/14/2013 9:20:12 PM EDT
Link Posted: 3/15/2013 5:35:22 AM EDT
like this?
Link Posted: 3/15/2013 6:40:21 AM EDT
A duplexer would switch automatically:

http://www.universal-radio.com/catalog/hamantm/cduplex.html
Link Posted: 3/15/2013 6:42:14 AM EDT
OP what is the purpose of Two antennas?

Link Posted: 3/15/2013 7:15:45 AM EDT
[Last Edit: 3/15/2013 7:16:14 AM EDT by Elijah1]
Excuse my ignorance, but isn't loss a big concern with VHF and standard antenna switches?


To me VHF is anything 10m and above
Link Posted: 3/18/2013 12:34:33 AM EDT
Originally Posted By Mr_Harry:
OP what is the purpose of Two antennas?

I've got a GMRS antenna and 2-meter VHF antenna as well.
Link Posted: 3/18/2013 12:36:03 AM EDT
Originally Posted By wdlsguy:
A duplexer would switch automatically:

http://www.universal-radio.com/catalog/hamantm/cduplex.html


I don't understand ... do these things just select the best antenna for txing and shift all the power over there?
Link Posted: 3/18/2013 4:50:25 AM EDT
Originally Posted By Not_Yet_Begun2Fight:
I don't understand ... do these things just select the best antenna for txing and shift all the power over there?

Duplexer/Splitter/Combiner

Comet calls these "duplexers", but they are also referred to as combiners or splitters. They are basically band-pass filters, simultaneously passing RF in both directions through the common connector while the band-pass filters provide a high degree of isolation between ports.
* TX and RX from two radios at the same time into a dual-band antenna

* Combine a dual-band radio with separate outputs into a dual-band antenna

* Separate a single connector duplexed radio into separate antenna systems

* Allow a single coax run into two antennas at the top of the tower, and two radios at the bottom by using a duplexer at both ends of the coax run, avoiding cost and weight.

http://www.cometantenna.com/products.php?CatID=1&famID=6&childID=0
Link Posted: 3/18/2013 5:40:00 AM EDT
[Last Edit: 3/18/2013 5:42:17 AM EDT by ar-jedi]
Originally Posted By Not_Yet_Begun2Fight:
Originally Posted By wdlsguy:
A duplexer would switch automatically:
http://www.universal-radio.com/catalog/hamantm/cduplex.html

I don't understand ... do these things just select the best antenna for txing and shift all the power over there?

technically it's a diplexer, and it is a selective bandpass switch. the radio attaches to the common port. RF emissions which are in the VHF band (say, <300MHz) are passed to one port (A) and blocked at the other (B), and RF emissions which are in the UHF band (say, >300MHz) are directed in the inverse manner (passed at B, blocked at A).

see the fourth columns at
http://www.universal-radio.com/catalog/hamantm/cduplex.html

LPF = low pass filter
HPF = high pass filter

take the CF-4160N as an example.

the radio connects to COM.
the LPF is 1.3MHz to 170MHz. so 2m (~146MHz) will come out he LPF port, but GMRS (~450MHz) will not. attach 2m antenna here.
the HPF is 350MHz to 540MHz. so GMRS will come out of the HPF port, but 2m will not. attach GMRS antenna here.




all else being equal, get the diplexer with the lowest insertion loss (e.g. <0.25dB) and the highest isolation (e.g. >50dB).

note:
it is unlawful to transmit on GMRS frequencies using equipment designed, marketed, and FCC-approved for amateur radio frequencies.

ar-jedi
Link Posted: 3/18/2013 5:44:41 AM EDT
Link Posted: 3/18/2013 9:04:28 AM EDT
Originally Posted By ar-jedi:
note:
it is unlawful to transmit on GMRS frequencies using equipment designed, marketed, and FCC-approved for amateur radio frequencies.

Thanks for the detailed response! Also, just to clarify, the radio that prompted this is actually an approved GMRS / Marine VHF radio from Cobra (and I actually have a GMRS license!).
Link Posted: 3/18/2013 9:15:21 AM EDT
Originally Posted By Mr_Harry:
OP what is the purpose of Two antennas?



One tuned to GMRS frequencies and another one for VHF.

The radio comes with a rubber-ducky antenna that sucks. I thought I'd get better performance with one of each of the copper J-poles. I actually bought the GMRS one first, and am now getting the Marine VHF one. If I'd planned ahead, I probably could've got a decent dual-band antenna that would handle things well enough without all this switch / duplexer routine. Live and learn I guess ...
Link Posted: 3/18/2013 9:25:03 AM EDT
too little too late, but an arrow Jpole for $40 woulda saved the headaches, and dual coax, and mulitple ends, and x-plexers...
is it too late to back up and try another route?

Posted Via AR15.Com Mobile
Link Posted: 3/18/2013 9:42:55 AM EDT
Originally Posted By Not_Yet_Begun2Fight:
Originally Posted By Mr_Harry:
OP what is the purpose of Two antennas?



One tuned to GMRS frequencies and another one for VHF.

The radio comes with a rubber-ducky antenna that sucks. I thought I'd get better performance with one of each of the copper J-poles. I actually bought the GMRS one first, and am now getting the Marine VHF one. If I'd planned ahead, I probably could've got a decent dual-band antenna that would handle things well enough without all this switch / duplexer routine. Live and learn I guess ...


I was gonna suggest seeing if you could fine tune a ham dual band antenna to see if you couldn't get it to work for Marine/GMRS. I know what you mean though. I have a 5/8 wave VHF antenna on my dd as well as a UHF 5/8 wave up on my roof. Two separate radios, and the dual band didn't have the bandwidth for jumping back and forth between ham and business so I added another antenna to the roof.
Link Posted: 3/18/2013 10:56:52 AM EDT
Originally Posted By Not_Yet_Begun2Fight:
Also, just to clarify, the radio that prompted this is actually an approved GMRS / Marine VHF radio from Cobra (and I actually have a GMRS license!).

the diplexer i posted above, and several others from that link, will work in your situation.

ar-jedi

Link Posted: 3/18/2013 10:57:08 AM EDT
Originally Posted By Not_Yet_Begun2Fight:
Originally Posted By Mr_Harry:
OP what is the purpose of Two antennas?



One tuned to GMRS frequencies and another one for VHF.

The radio comes with a rubber-ducky antenna that sucks. I thought I'd get better performance with one of each of the copper J-poles. I actually bought the GMRS one first, and am now getting the Marine VHF one. If I'd planned ahead, I probably could've got a decent dual-band antenna that would handle things well enough without all this switch / duplexer routine. Live and learn I guess ...


Perhaps not. You're talking about one of these, right? How would you expect it to perform vs two dedicated antennas? Just as good? 90%? 75%?

P.S. Sorry for all the dumb questions, I'm a frickin' noob.
Link Posted: 3/18/2013 11:58:49 AM EDT
Originally Posted By Not_Yet_Begun2Fight:
Originally Posted By Not_Yet_Begun2Fight:
Originally Posted By Mr_Harry:
OP what is the purpose of Two antennas?



One tuned to GMRS frequencies and another one for VHF.

The radio comes with a rubber-ducky antenna that sucks. I thought I'd get better performance with one of each of the copper J-poles. I actually bought the GMRS one first, and am now getting the Marine VHF one. If I'd planned ahead, I probably could've got a decent dual-band antenna that would handle things well enough without all this switch / duplexer routine. Live and learn I guess ...


Perhaps not. You're talking about one of these, right? How would you expect it to perform vs two dedicated antennas? Just as good? 90%? 75%?

P.S. Sorry for all the dumb questions, I'm a frickin' noob.


not sure if it was directed to me, but I did post the mention of the arrow

FWIW: I have one, I LOVE it. it works like a champ for my purposes. I'm a noob too, but have to believe it's broad enough to work with what you are intending within reason. I've used it with base and HT's and it performs!



Link Posted: 3/18/2013 3:27:03 PM EDT
Originally Posted By SCWolverine:
not sure if it was directed to me, but I did post the mention of the arrow

FWIW: I have one, I LOVE it. it works like a champ for my purposes. I'm a noob too, but have to believe it's broad enough to work with what you are intending within reason. I've used it with base and HT's and it performs!

Yeah, I apparently can't quote right either.

One more question on this subject:

Arrow offers two models that appear promising:

A) "Dual Band 155/460 MHz - Search & Rescue" <-- is 460 close enough to GMRS and 155 close enough to Marine VHF?
B) "Dual Band GMRS & MURS - 152/462 MHz" <-- is 152 close enough to Marine VHF?

Which one would you go with?

Technically that's three or four questions, but I guess I'm really trying to figure out this: how close does my antenna have to be tuned to the frequencies I want to work with for it to be "good"? How for off of the listed frequencies will these antenna suffer a SWR > 1.5:1?
Link Posted: 3/18/2013 3:57:36 PM EDT
[Last Edit: 3/18/2013 3:57:44 PM EDT by ar-jedi]
Originally Posted By Not_Yet_Begun2Fight:
Technically that's three or four questions, but I guess I'm really trying to figure out this: how close does my antenna have to be tuned to the frequencies I want to work with for it to be "good"? How for off of the listed frequencies will these antenna suffer a SWR > 1.5:1?

for a VHF antenna of about unity gain (meaning -3dbi to about +6dbi), the typical 2:1 bandwidth is about 5 MHz.
the more gain and the more elements, the narrower the 2:1 bandwidth will be.

ar-jedi

Link Posted: 3/18/2013 6:18:28 PM EDT
Originally Posted By Not_Yet_Begun2Fight:
Arrow offers two models that appear promising:

A) "Dual Band 155/460 MHz - Search & Rescue" <-- is 460 close enough to GMRS and 155 close enough to Marine VHF?
B) "Dual Band GMRS & MURS - 152/462 MHz" <-- is 152 close enough to Marine VHF?

Which one would you go with?

I'd see if he can make one tuned to Marine VHF and GMRS for you.
Link Posted: 3/19/2013 5:36:29 AM EDT
The Ed Fong PVC Jpole can prolly be purchased tuned to your specs. He mentions that in his description. I have one of these at the barn (shack) and Dig it as much as my Arrow.
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