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Author Topic: Another idea/question re: Corvette antenna  (Read 2530 times)
KD5GR
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Posts: 62




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« on: July 18, 2012, 08:01:30 PM »

I started a thread in the antenna forum about a 2-meter/70cm antenna for a Corvette and got some great information.  I'm pretty sure I know what I'm going to use, but I saw a thread that's interesting.  One of the posts talked about using copper tape on a windshield as a 1/4 antenna and that has me wondering about doing something like that inside the rear cap on my Corvette.

I could use copper tape too, or even bond a 1/4 wave rod to the inside of the rear cap.  I'm not sure how to handle grounding, but if this configuration would theoretically work, it would be a good stealth antenna for the 'Vette.

I'd appreciate any opinions or suggestions.

Thanks,
Chas.

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WB6BYU
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Posts: 12773




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« Reply #1 on: July 18, 2012, 08:34:01 PM »

Sure, you can use copper tape or wire inside the fiberglass body, either as a full dipole
if you have enough vertical space, or a quarter wave vertical with a couple of radials.
You can even fold it around a bit if the space isn't big enough.  You can put it inside
a fender, door, trunk, a seat back, or anywhere else that is mostly enclosed in fiberglass.

It's not uncommon, for example, for an aircraft to put their VHF antenna inside a
fiberglass tail section.

How well it works on the inside of the windshield will depend to some extent on
whether the car has passivated glass.  In any case, being in close proximity to
different dielectric materials (even if they are non-conductive) will change the
required antenna length, so some adjustment will be required.
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KA4POL
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Posts: 1766




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« Reply #2 on: July 18, 2012, 10:19:19 PM »

This could become a problem depending upon the transmit power. Most modern cars do give limits in their manuals as the electronics do not like high RF levels.
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K1CJS
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Posts: 5516




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« Reply #3 on: July 19, 2012, 05:10:26 AM »

You could also just bond four simple 19" lengths of wire to the inside of the rear cap in an X configuration with the antenna mounted at the middle of the X and have the 1/4 wave antenna perform well.  73!
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KD5GR
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Posts: 62




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« Reply #4 on: July 20, 2012, 12:31:27 PM »

This could become a problem depending upon the transmit power. Most modern cars do give limits in their manuals as the electronics do not like high RF levels.
I need to check on this; I never gave that a thought.

Thanks,
Chas.
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KD5GR
Member

Posts: 62




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« Reply #5 on: July 20, 2012, 12:36:19 PM »

You could also just bond four simple 19" lengths of wire to the inside of the rear cap in an X configuration with the antenna mounted at the middle of the X and have the 1/4 wave antenna perform well.  73!
Everything will have to be installed/bonded in the vertical so I don't have the option of radials, if I understand you correctly.  I had someone suggest hanging a simple 1/4 wave from  the roof panel on the inside, but that would put the antenna about 10 inches from my head!  I've lost enough hair over the years and with 50+ watts, I don't want to cook what I have left.

This set up would really be just an experiment for use in town.  I already know what I'm going to do for a more serious antenna installation for road trips.

Thanks for the input guys,
Chas.
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K1CJS
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Posts: 5516




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« Reply #6 on: July 21, 2012, 08:55:13 AM »

Chas,

What i was referring to is gluing wires under the deck where a car trunk usually is--the inside of the rear cap.  I don't know if that is feasible since I don't own a Corvette, but that has been done many times in vehicles where the top or the trunk lid is fibreglass.

...I had someone suggest hanging a simple 1/4 wave from  the roof panel on the inside, but that would put the antenna about 10 inches from my head!  I've lost enough hair over the years and with 50+ watts, I don't want to cook what I have left....

Don't worry about that.  VHF radio systems that put out 100 watts or more have been around for years--usually in Police cars--with the antennas mounted on the trunk.  There has yet to be an instance reported where any harm has come to those police officers from the use of the radio units in those cars.  Any harm from RF at those frequencies is an old wives tale--specters of harm coming from the government and personal injury attorneys.  You get greater radiation and harm coming from strong sunshine than you do from VHF RF radiation.
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WB6BYU
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Posts: 12773




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« Reply #7 on: July 21, 2012, 10:55:13 AM »

Quote from: KD5GR

...I had someone suggest hanging a simple 1/4 wave from  the roof panel on the inside, but that would put the antenna about 10 inches from my head!  I've lost enough hair over the years and with 50+ watts, I don't want to cook what I have left...



Then don't run 50 watts.  If you're around town talking through a local repeater then you
shouldn't need that much power.  I rarely run my mobile rigs above 5 or 10 watts unless
I'm out in among the hills where I'm shielded from the repeater.


But just about anywhere on the car that is fiberglass and you can get access to it you
can stick a dipole or quarter wave vertical with two or more radials using burglar alarm
copper tape or thin wires attached to the inside of the body with tape (for temporary
testing), glue, etc.  You can bend the top of the vertical wire if you don't have quite
enough height.  You just have to look at your car and see where it will work.

I also saw an article where someone used a wire hanging down from the bottom of
the car as his antenna.  There are lots of possibilities, but they will have to be
custom designed for your specific situation.
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W4FID
Member

Posts: 119




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« Reply #8 on: July 29, 2012, 06:23:17 AM »

For many years I traveled extensively for business. Even back then -- MUCH worse now -- airports don't like a 5/8 whip and mag mount in your briefcase. So I used two wrist straps to hang the HT from the rear view mirror. That puts the rubber duck in the windshield. Used a speaker mic. Used a cigar lighter plug. In 15 seconds I had a "mobile" in a rental car that was fine for urban use. True; not worth a darn in rural settings; but you said local use was your goal. My Icom 02AT had about 250,000 miles on it in about a dozen years and was fun in hundreds of cities where I met lots of nice hams. A J-pole hung from the curtain rod in the hotel window completed my "ham on the go" life.

Same line of thinking could work in your Vette. No permanent vehicle modifications. Not unreasonably ugly. Easy to remove/hide if you're concerned about drawing yet another level of attention (as if the Vette wasn't criminal bait enough in its own right) where you park.

Don't forget when 2M FM became popular a 10 watt xtal controlled rig was de regular and repeaters were much fewer and further between yet we all had lots of QSOs and fun. It's even easier now with so many repeaters and a dual band HT will double your fun -- so it's a workable strategy.
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