Home » Public Forums » GMCnet » Recommended dual CB radio antennas for the GMC
| Recommended dual CB radio antennas for the GMC [message #292658] |
Mon, 21 December 2015 17:01  |
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Loffen
Messages: 1087
Registered: August 2013
Location: Norway
Karma: 1
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Senior Member |
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I just bought an old Delco AM/FM/CB radio for my GMC and would like a dual antenna setup, kind of old style with one antenna mounted to each outside mirror mount.
But this is not my field and I am kind of a newbe when it comes to CB radio's, does anyone have any recommendations ?
1973 23' # 1848 Sky Blue Glacier called Baby Blue and a 1973 26'-3 # 1460 Parrot green Seqouia Known as the Big Green,
And sold my 1973 26'-2 # 581 White Canyon lands under the name Dobbelt trøbbel
in Norway
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| Re: Recommended dual CB radio antennas for the GMC [message #292662 is a reply to message #292658] |
Mon, 21 December 2015 17:19  |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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"Dual" antennas may look cool, but unless you can get them about 9 feet apart, they will interfer with each other. You will have better results with 1 antenna mounted on your mirror base. Actually and ideally, you would want to mount it in the center of that big aluminum sheet that makes up the main roof panel. But, that is hardly practical. A mirror mount actually allows the GMC body to apply some directionally to your transmitted signal, concentrating the signal more up and down the direction of travel, front and back. You would seldom care about a signal comming from either side.
Mirror mounts are easy to find, less than $10. You will need to insure that the mirror mount actually goes to ground (GMC body/frame). The body represents the other half of your installed dipole antenna. No recommendation on an actual antenna by brand or name, a base loaded whip will work just fine. Do not be persuaded by big chome coils or advertising claims. RF is RF and the rules are simple. Go to your public library and find a copy of The ARRL Antenna Manual. This is the authority that is easily accessible and understandable.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: Recommended dual CB radio antennas for the GMC [message #292673 is a reply to message #292658] |
Mon, 21 December 2015 17:36 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Look around the truck stops, you might find one of the phasing harnesses that used to be available to get a pair of antennas to work properly. It can be done by playing with the length of cables feeding the two, if you're willing to a) do some arithmetic using information out of the ARRL book or others; and or b) play around with a signal strength meter at several locations around your coach some distance away from it - a couple hundred feet or so.
From a practical point of view, it's hardly worth the trouble. The best results will be gotten with a roughly 109" steel whip bolted to the rear bumper, next best and reasonably close in performance - and a hell of a lot less hassle - is any of the good loaded antennas, either bottom, continuous, or center, mounted conveniently. Center of the roof is best, on the mirror works - at least mine does.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Recommended dual CB radio antennas for the GMC [message #292709 is a reply to message #292658] |
Tue, 22 December 2015 06:16 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Do not waste your time, effort, or money on dual antennas for CB. A base loaded antenna in the aluminum part of the roof will work best if you have enough overhead road clearance. Second best would be a bumper mounted 108-109" whip.
As previously stated here, the steel body of the coach is 1/2 of the antenna system. The base of the antenna needs to be grounded. Unfortunately the mirrors of our coach are mounted in plastic/ fiberglass and not grounded.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Recommended dual CB radio antennas for the GMC [message #292715 is a reply to message #292658] |
Tue, 22 December 2015 08:21 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Loffen,
There are three real good RF guys ahead of me, and KenB finally got to the thing I was going to jump on....
My mirrors aren't grounded.
This will matter a lot, because an antenna system has two parts: The Radiating Element (the part that sticks up) and the Counterpoise (the other part sometimes just the earth and it goes the other way). Without both parts being correct, and in the case of a co-phase (what the two antennas do) being the correct spacing, the success of the system to radiate a signal may be poor.
If you want to put a co-phase on the mirrors because it looks cool, go ahead. Save the money and don't buy a co-phase harness.
If you want the radio signal to get out there, a 1/4wave on the rear bumper is the way to go. I had one and it worked well. But I put the radio by the drivers seat and Mary would never turn it on. So, after we got stuck in an hour long traffic jam that was on the CB, I ripped it out.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Recommended dual CB radio antennas for the GMC [message #292764 is a reply to message #292658] |
Tue, 22 December 2015 20:42 |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
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Hmmm...
The problem with a plastic roof is you have no ground plane.
I was thinking of making a dipole setup with the ground wire on one whip (left mirror) and the signal wire on the other whip (right mirror) on the other. You'd have to put the balun in the middle somewhere, under the front "hood" or something and include the run wire in the 102" total length of the antenna wire...
You could also get/build a 1/4 wave base station antenna for the top of the coach. It'd stick up an additional 8 ft on the roof, but what the hell, you don't drive a GMC into parking garages anyway.
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
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| Re: [GMCnet] Recommended dual CB radio antennas for the GMC [message #292775 is a reply to message #292769] |
Tue, 22 December 2015 23:18 |
TnS.GMC
Messages: 18
Registered: November 2015
Karma: 0
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Junior Member |
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> you don't drive a GMC into parking garages anyway
Bridges might be an issue tho.
A major antenna manufacturer (Shakespeare) made an antenna for the military
that was supposed to bend when hitting bridges and the like. When tested,
one lot snapped instead of bend. Shakespeare took the entire lot, chopped
the base off, added a handle, and gave them away at a trade show as walking
sticks. Sadly they were out by the time I realized it and got by their
booth.
--
Todd and Susan
'76 23' [X-]Birchaven
Alleged Mystery Machine
Melbourne, FL
--------- Original Message --------
From: gmclist@list.gmcnet.org
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Recommended dual CB radio antennas for the GMC
Date: 23/12/15 02:43
> Hmmm...
>
> The problem with a plastic roof is you have no ground plane.
>
> I was thinking of making a dipole setup with the ground wire on one whip
(left mirror) and the signal wire on the other whip (right mirror) on the
> other. You'd have to put the balun in the middle somewhere, under the
front "hood" or something and include the run wire in the
102" total length of
> the antenna wire...
>
> You could also get/build a 1/4 wave base station antenna for the top of
the coach. It'd stick up an additional 8 ft on the roof, but what the hell,
> you don't drive a GMC into parking garages anyway.
>
> --
> -Chr$: Perpetual SmartAss
> Scottsdale, AZ
> 77 Ex-Kingsley 455 SOLD!
> 2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
>
> Photosite: Chrisc GMC:"It has Begun" TT: "The Other
Woman"
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: Recommended dual CB radio antennas for the GMC [message #292800 is a reply to message #292658] |
Wed, 23 December 2015 11:44 |
Chris Tyler
Messages: 458
Registered: September 2013
Location: Odessa FL
Karma: 7
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Senior Member |
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Back in the 70s, my dad and I were big into CBs. I remember we spent a lot of time tuning the dual antennas on his pickup. Once it was right, we could really get out there. But until they were trimmed, they didn't work well at all.
I know a few truckers who use duals today. The feeling with them [which may be outdated now] is similar to the prevailing wisdom back in the 70s that the 'canoe' shaped pattern worked better on the road, up and down, and minimized the traffic from surrounding areas
My PO had been big on CBs as well, it came with duals. There were also ground wires which make sense now; didn't check it but I would have assumed the mounts were grounded... It came with a 70s/early 80s telephone type CB that I lusted after as a teen [this being waaaay before car and cell phones] that isnt working. Id like to try to fix it [hopefully just dryed out caps] but its prety far down on the priority list
He also placed a whip [spring loaded] antenna on the roof for FM reception that works very well with that big ground plane, and a Sirius antenna that I havent used.
Thing is, in recent years the CB culture had changed,and we have lots of other gadgets now. Plus, I'm not goung fast enough [usually] to worry about Smokey in the GMC. But, Im kinda going for that '70s custom van' look, and CBs were part of that.
"KNX7166, we gone"
76 Glenbrook
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