HF arial splitter
Submitted: Tuesday, Mar 07, 2006 at 21:10
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Member - Andrew W (VIC)
Seeing as i have am now a fully paid up member i reckon I can ask another question from all you wizz kids out there!
Messing about with arials on my GME TX4400 I can't find one that suits all the time, so is there such a thing as a spliier box that would allow me to have a 3db gain and a 9db gain fitted at same time, or do I have to choose one or the other? Currently using a 4.5 db gain which is fair for most situations but not ideal in any. I do a mix of flat country and mountain driving
Reply By: Member - Andrew W (VIC) - Tuesday, Mar 07, 2006 at 21:14
Tuesday, Mar 07, 2006 at 21:14
OOps - that should have the title of UHF splitter!!!
AnswerID:
159182
Follow Up By: Mike DiD - Wednesday, Mar 08, 2006 at 05:30
Wednesday, Mar 08, 2006 at 05:30
Splitting won't work - you would be sending half the power into each antenna. In fact the signals could interfere with other, so in certain directions you could have no signal.
Switching is the only practical solution to connect two different types of aerials.
Mike
FollowupID:
413790
Reply By: SA_Patrol - Tuesday, Mar 07, 2006 at 21:32
Tuesday, Mar 07, 2006 at 21:32
I know they are available for HF 27megs you could have RF loss on UHF range, unless something new out there which I don't know about
AnswerID:
159193
Follow Up By: Mad Dog (Australia) - Tuesday, Mar 07, 2006 at 22:04
Tuesday, Mar 07, 2006 at 22:04
Switches are available with an insertion loss of only .2 dB at 1500 MHz
FollowupID:
413726
Follow Up By: Mike DiD - Wednesday, Mar 08, 2006 at 05:26
Wednesday, Mar 08, 2006 at 05:26
I agree - Aerial switches using the standard connectors fitted to UHF CBs will do what you want. You will also need a cable with PL259 plug on each end to connect from switchbox to the CB.
Many years ago I bought an antenna where I could change the top to switch between low gain and high gain, but I don't know of any that are still avaialble now.
Mike R
FollowupID:
413789
Reply By: Wayne (NSW) - Tuesday, Mar 07, 2006 at 21:34
Tuesday, Mar 07, 2006 at 21:34
Andrew,
You can get them but when enquired about them the salesman said that he would sell me one but I would not be happy with it.
What you can do is to run the coax cable from the 3db and the 9db and even the 4.5db aerials and have them marked so you know which is which. When you want to change aerials just unscrew one aerial and replace it to the back of the radio.
A bit of mucking around but you wont be changing aerial every 5 min.
The other way is to have the same base and just change the aerial.
Wayne
AnswerID:
159195
Reply By: Old Scalyback & denny - Tuesday, Mar 07, 2006 at 21:36
Tuesday, Mar 07, 2006 at 21:36
hey andrew
now youre a paid up member you might get smarter answers
or dumber ones
lolololol
steve
AnswerID:
159197
Follow Up By: Member - Andrew W (VIC) - Tuesday, Mar 07, 2006 at 21:38
Tuesday, Mar 07, 2006 at 21:38
suppose that will depend on how dumb the question is!!
Sure as hell didn't start with a very smart one!!
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Follow Up By: SA_Patrol - Tuesday, Mar 07, 2006 at 21:47
Tuesday, Mar 07, 2006 at 21:47
Would that be smart answers from other paid members and dumber answers from guests.. :-) ... DOH
FollowupID:
413719
Follow Up By: Hairy - Tuesday, Mar 07, 2006 at 22:35
Tuesday, Mar 07, 2006 at 22:35
Whats this, a Victorian verses South Australian thing or something?
FollowupID:
413738
Reply By: Mad Dog (Australia) - Tuesday, Mar 07, 2006 at 22:00
Tuesday, Mar 07, 2006 at 22:00
What you want is a good quality coaxial switch. Pick one up from a Amateur Radio supplier such as Andrews communciations
http://www.andrewscom.com.au/
AnswerID:
159208
Reply By: Eric Experience. - Tuesday, Mar 07, 2006 at 22:27
Tuesday, Mar 07, 2006 at 22:27
Andrew.
The story about different antennas for different terian is a misunderstanding of the true situation. There is strong enough signal most of the time. the problem is the signal to noise ratio. if you get a change at all it is most likely to be atributed to a taller antenna being able to 'see' over the top of your vehicle. If you mount a 3db antenna up high towards the back of the vehicle it will work all the time, just like on a police car or ambulance. If you have the antenna low down on the front you are relying on reflections to pick up a signal from behind and you get a lot of niose from the motor. Eric.
AnswerID:
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Reply By: Mike DiD - Wednesday, Mar 08, 2006 at 05:22
Wednesday, Mar 08, 2006 at 05:22
A high-gain antenna focusses all the energy closer to the horizon - just like a lighthouse.
This works on transmit and receive.
If you use a high gain antenna when in a deep valley it focusses all the energy into the rocks.
A low gain antenna (low gain towards the horizon) means that there is still some signal at high angles to get out of the valley.
Mike
AnswerID:
159255
Follow Up By: Mike Harding - Wednesday, Mar 08, 2006 at 07:02
Wednesday, Mar 08, 2006 at 07:02
My experience with deep High Country valleys and VHF/UHF is that nothing gets out even with any of the dipoles or a long wire.
Mike Harding
FollowupID:
413791
Reply By: Member - Doug T (QLD) - Wednesday, Mar 08, 2006 at 07:54
Wednesday, Mar 08, 2006 at 07:54
Hi Andrew
I had 2 uhf antennae's for a while and used an Antennae switch ,1 coax in from the radio and 2 out , one to each antennae, I was using a 1/4 wave so it didn't get out to far but as still going 3 to 5 Ks , but yes a switch is ok , got mine from Dick Smith
AnswerID:
159267
Reply By: hl - Wednesday, Mar 08, 2006 at 08:00
Wednesday, Mar 08, 2006 at 08:00
I wouldn't bother. I doubt you would be able to tell the difference between the 2 aerials (if they are mounted at the same height). 5dB difference in gain does not make or break a signal.
Cheers
AnswerID:
159268
Follow Up By: kesh - Wednesday, Mar 08, 2006 at 16:22
Wednesday, Mar 08, 2006 at 16:22
I answered a similar sort of question on another
forum, it being along the lines of "why cant I hear the call from a vehicle which wants to overtake my caravan until that vehicle has passed"
My response was that with a low uhf antenna mounted on the bullbar with 5m. of metal behind it then a further 5-6m of aluminium van behind that how on earth is any signal either way going to penetrate that shield.
My philosophy is that uhf is line of sight. If the antenna cant "see" it, you wont hear or transmit to it.
I have my low (5dB) gain antenna mounted on the top bar of the truck canopy. In flat, open country communication up to 45km. is quite achievable.
kesh
FollowupID:
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