Dual band antenna

bob1857 · Post by **bob1857** » Thu Apr 27, 2006 9:27 am

I got a UHF and VHF radio and looking to use dual band antenna. Don't know much about them yet, what else would I need to complete install. Thanks

va3wxm · Post by **va3wxm** » Thu Apr 27, 2006 9:58 am

You'll have to find a dual-band antenna that covers both frequencies you want to use.

You'll also need a diplexer to combine the two radios into one antenna.

And of course the associated mount and coax.

bob1857 · Post by **bob1857** » Thu Apr 27, 2006 9:59 am

knew there was something else.

kb0nly · Post by **kb0nly** » Thu Apr 27, 2006 5:18 pm

I used a triplexer to put a lowband, VHF, and UHF on one triband antenna. Look here for some examples of diplexers.

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

I use a Comet CF-4160 which is the same as the CF-416A shown on that page except it doesn't have the pigtails, just three SO-239's the CF-4160K shown has a SO-239 and two fixed PL-259's and is really intended for use with dual band radios that have pigtails with SO-239's off the back of the radio. I use the CF-4160 to combine a X9000 VHF and UHF to a dual band base antenna at home.

I use the CF-514 in the mobile. You can see pictures of that install here.

http://frontiernet.net/~kb0nly/mobile.htm

I highly recommend the Comet diplexer's and triplexer's. The dual band unit only runs around $40-$50 and is a good investment.

bob1857 · Post by **bob1857** » Thu Apr 27, 2006 5:44 pm

Thanks, I was having a hard time locatiing diplexer on-line. They look like just what I need.

kb0nly · Post by **kb0nly** » Thu Apr 27, 2006 6:17 pm

Universal Radio has some of the best prices lately on Comet gear. You won't be dissapointed with one of their diplexer's. I have put 250W through one with no ill effects, they are rated for much more!

va3wxm · Post by **va3wxm** » Fri Apr 28, 2006 4:41 am

bob1857 wrote:Thanks, I was having a hard time locatiing diplexer on-line. They look like just what I need.

Sorry, I suppose I should've said duplexer as well.

Problem is when I hear that word I think of the BpBr "cans" used in repeater installations to isolate the transmitter from the receiver.

Post by **firemed9** » Fri Apr 28, 2006 5:38 am

A couple of quick questions about diplexers, as I have always went 1 radio = 1 antenna. If you use a diplexer, will both radios still recieve at the same time? If I am transmitting on one, you cant transmit on the other, right? If am transmitting on one, will the other receive?

The reason I ask these is here we use both vhf and uhf. If I am running command with a partner in my vehicle, right now, i am able to talk to my vhf people while my partner can talk with our uhf people. If I wanted to go to a diplexer, I want to know if this is still possible.

kb0nly · Post by **kb0nly** » Fri Apr 28, 2006 7:16 am

A diplexer can do all of the above. Both receiving, one receiving one transmitting, both transmitting, etc. I have used them for crossband repeat with a dual band antenna.

Also near here we have a site with a UHF and VHF repeater, they both have duplexers, the output of which go to a diplexer, and then hardline to the dual band antenna. Two repeaters, one antenna. Works beautifully.

In my mobile i have lowband, VHF, and UHF, going into a triplexer. Same applies here as well, all three radios could transmit if necessary, though highly unlikely... lol

Just think of a diplexer as a duplexer but with a different band on each side, rather than two frequencies in the same band.

va3wxm · Post by **va3wxm** » Fri Apr 28, 2006 8:33 am

kb0nly wrote:In my mobile i have lowband, VHF, and UHF, going into a triplexer. Same applies here as well, all three radios could transmit if necessary, though highly unlikely... lol

Yeah, I would think the electrical system in your van would melt down if you did so!

But to re-affirm, the duplexer will allow you to transmit on V and still hear and/or transmit on U without difficulty.

kb0nly · Post by **kb0nly** » Fri Apr 28, 2006 8:42 am

Yeah no kidding, three 100w transmitters at once, about 90amps give or take a few.

I have briefly transmitted with both the VHF and UHF with the van running, it grunted a bit and the engine speed picked up due to the computer adjusting idle speed for the load on the alternator. This was only done to quickly run some interference and wiring checks.

Now the radios are turned down a bit, 75w on VHF, 75w on UHF, and 80w on the lowband. After one of the local repeaters gets fixed and is hearing better again i might take the VHF down another notch to 60w since it's the farthest repeater i use and everything else locally can be had with 50w easy enough. The UHF will stay where it is for now, not much UHF around here, need all the power i can get to tickle the ones we have. The lowband only gets used on 6m simplex for the time being, there isn't any 6m repeaters around here. I do love keying up with 80w on the lowbander and interfering with various things.. lol

bob1857 · Post by **bob1857** » Fri Apr 28, 2006 10:23 am

I just got a little confused, with a vhf and a uhf radio, I'll need a diplexer, duplexer or both ?

kb0nly · Post by **kb0nly** » Fri Apr 28, 2006 10:48 am

All you need is a diplexer to put two radios on one antenna, that is when they are both different bands.

Sorry to confuse, was just trying to make an analogy but it caused more confusion than it solved i guess!

bob1857 · Post by **bob1857** » Fri Apr 28, 2006 11:23 am

By the way..what are the down sides to using a dual band antenna ? Signal loss ?

va3wxm · Post by **va3wxm** » Fri Apr 28, 2006 11:28 am

Basically it's a compromise. It'll work okay for both bands just not outstanding on either one.

One advantage for us hamsexy types is most of our bands are harmonically related so it's relatively easy to build a multiband antenna that works well.

One antenna per band is the ideal way to go but it's not always practical.

bob1857 · Post by **bob1857** » Fri Apr 28, 2006 11:35 am

I Thank you very much for clearing the air !

kb0nly · Post by **kb0nly** » Fri Apr 28, 2006 11:39 am

Yep, just like marriage, it's a compromise.. LOL

A good dual band antenna and your set. Remember, the radios are only as good as the antenna they are connected to!

60A · Post by **60A** » Fri Apr 28, 2006 4:05 pm

That's really interesting! I would not have imagined it was that simple or cheap!

kb0nly · Post by **kb0nly** » Fri Apr 28, 2006 7:05 pm

The diplexer's are a lot cheaper than they used to be. I can remember a couple years back when i bought the first one i use at home, still have it, that was in the $80+ range, now they can be had for around $40-$45.

SCLarmon · Post by **SCLarmon** » Sat May 27, 2006 10:44 am

What's a good VHF/UHF antenna to use with the diplexer. I need a trunk lip mount (can't drill any holes unfortunately). VHF is mostly about 155 mhz and UHF is around 470, but listen to 450-s - 503 mhz. Don't want anything over 20 inches if possible. I'm assuming VHF with be unity and UHF may be around 3 db with a decent antenna ?

How much range would I use compared to using separate unity gain antennas??? I put out about 45 watts on VHF and 40 on UHF.

All help appreciated.

Dual band antenna

Dual band antenna

Thanks..

Dual Band

Re: Dual Band

diplexer or duplexer

No problem

Thanks