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Author Topic: New Ham Looking for Advice  (Read 11400 times)
KB1OJQ
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« on: August 05, 2010, 12:24:44 AM »

I am relatively new to the field of Ham radio, I studied electronics for 4 years so I have a strong background in electronics and my instructor is a fellow ham so I took the leap and got my Technicians license. Anyways I am need of some help. If anyone can give me some advice it would be very appreciated.

I just bought my first new rig and I needed some advice on the antenna and mounting. I purchased a Yaesu FT-7900R/E.

http://www.yaesu.ru/files/info/yaesu/ft-7900r-brochure.pdf

http://www.eham.net/reviews/detail/8280

I want to install it in my new car and hence the problem I have. I cant use my 2/70cm mag mount because that would scratch up and discolor the paint. I was thinking about looking into a hood mount antenna/ lip antenna, similar to that of a regular fm antenna placement on a car. The car is a hatchback so I can't use a trunk mount, and since its brand new I cant very well go drilling holes in the center of the roof.

Here's a picture of the car so you can get an idea of what I'm working with.

http://images.autobytel.com/web/carpicsviews/800pixelswide/CAC00POC312B0101.jpg

Anyone that has suggestions on what kind of mount I could use, model numbers, websites, would be tremendously appreciated. I want to get an antenna to go along with the mount, a 2m/70cm compatible with the antenna recommendations from you guys.

Thanks everyone

73, John
KB1OJQ
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W5LZ
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« Reply #1 on: August 05, 2010, 05:08:41 AM »

John,
I'm in the same boat, new car!  I know it isn't a 'thrilling' thought, but drilling the hole really is a better way of doing it.  The 'biggy' isn't the hole, but what's under it, head-liner and all that, or, in the case of 'hood' mounting an antenna, the typical two layers of metal in a hood.  There are mounting brackets that fit between hood/fender to hold an antenna, that's certainly one alternative.  Those 'lip' mounts depend on the number of screws holding them on, the more the merrier to some ridiculous degree.
A word about holes and scratched paint.  If the vehicle doesn't look like 'swiss cheese', lots of holes, those holes should make no difference on the worth of that vehicle.  They just are NOT that difficult/expensive to fill and repaint!  They do it all the time.  If it comes down to a hole or two 'making/breaking' a deal, find another dealer!
Paul

(Just went through that 'make/breaking' a deal thing with antenna holes.  Found another dealer, much better deal anyway, and nothing was ever said about filling holes.)
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K0BG
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« Reply #2 on: August 05, 2010, 06:18:15 AM »

You might want to visit my web site. After all, there is more to an install than just the antenna.
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VA3WXM
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« Reply #3 on: August 05, 2010, 08:27:40 AM »

There are hatchback lip-type mounts available from Comet and Diamond, if you're averse to drilling an NMO hole.  They clamp on using set screws.  The L-bracket option means your antenna will have to be mounted near the front of the car, closer to the engine (noise) and computers (RFI).

I bought my most recent car brand new and in less than 24 hours I had an NMO mount installed on the trunk lid.  There really is no better mount available for mobile VHF/UHF antennas.
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K0BG
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« Reply #4 on: August 05, 2010, 11:29:17 AM »

Jeff is very correct. Think about this. If all those Pacific Rim antennas were so good, why don't you see public service vehicles with them?
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WX7G
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« Reply #5 on: August 05, 2010, 01:06:04 PM »

Larsen KG-2/70-CX-PL on-glass antenna, $120 at HRO.

Eham reviews:http://www.eham.net/reviews/detail/1062
« Last Edit: August 05, 2010, 01:10:00 PM by DAVE CUTHBERT » Logged
K0BG
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« Reply #6 on: August 05, 2010, 02:34:47 PM »

The problem with a glass mount is the fact the vehicle in question has passivated glass. As a result, the performance of a glass mount will be very poor at best.

From the Larsen web site. Notice the last paragraph:

Quote
Q: I purchased one of your KG series through glass mount antennas, specifically one for VHF 144-146 MHz. I installed the antenna according to your directions, and have obtained an SWR of 1.5:1. But, the antenna is "deaf", it receives poorly. I have tried another transceiver and changed the UHF connector on the fixed coax end, and my results are the same. Is there something I can do to make it work better?

A: Many factors can affect the performance of on-glass antennas. These include: Glass Thickness: KGs are designed for glass with a typical thickness of .0151 ± .002". Anything greater or less will result in a frequency shift. Most automobile manufacturers have side and rear glass panels within this tolerance. If the mounting surface is thicker or thinner, this value will change the dielectric constant and change the resonant frequency of the antenna.

Height on glass: The lower on the glass the antenna is placed, the greater the reflection from the roof. This will cause the VSWR to increase.

Tint: Various tints affect the dielectric constant causing a higher VSWR, poor reception or no performance.

Dielectric Constant: The couplers (inside / outside) function as a capacitor. The distance and glass material content between these two plates affects the capacitive value. If you are using a LLarsen GT Coupler (a glass tester for capacitive values), the galss may not exceed 3 pF of capacitance. Anything greater than 3 pF and FR will not pass through the glass.

UV Glass: Many newer vehicles are manufactured with UV resistant or passivated glass containing metal flakes which destroy the capacitive function. One way to tell if your vehicle has passivated glass is to look in the window for the manufacturers' stamp. If the brand has the word SOLAR in it, the glass is not adaptable for RF purposes.
« Last Edit: August 05, 2010, 03:05:01 PM by Alan Applegate » Logged

WX7G
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« Reply #7 on: August 05, 2010, 05:16:47 PM »

Larsen antenna website        http://www.larsen-antennas.com/techref_faqs.shtml

"How can I tell if the glass on my vehicle is suitable for on-glass antennas? First, look near a corner of a window for words that mean "sun", relate to sun, or refer to ultraviolet or other forms of radiation. If you find terms like "Soft-Ray", "EZE-Cool", "Solar-Coat", "Solar-Cool" or similar terms, your glass is probably passivated and won't work with on-glass antennas."

If the glass on this Pontiac Vibe is not passivated the on-glass antenna could work better than the hood mounted antenna (due to the increased height on the vehicle).

« Last Edit: August 05, 2010, 05:56:15 PM by DAVE CUTHBERT » Logged
KE5PPH
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« Reply #8 on: August 05, 2010, 07:52:35 PM »

Jeff is very correct. Think about this. If all those Pacific Rim antennas were so good, why don't you see public service vehicles with them?

Because the government will NOT, pay less than Too much.
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VA3WXM
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« Reply #9 on: August 06, 2010, 11:57:33 AM »

Because the government will NOT, pay less than Too much.

I'm not understanding.  Governments tend to be single-banded (or if on multiple bands they use multiple antennas).  A 1/4 wave whip is cheaper and much more durable than anything from Comet or Diamond.  Not knocking them, that's just a fact.
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KB1OJQ
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« Reply #10 on: August 06, 2010, 10:20:47 PM »

Hey guys can we keep this civil and on track please.
Alan I actually found your website a long time ago and it is an absolutely excellent website!
From everything that I have heard I want to stay away from window mounts at all costs.
I realize that there are some downfalls to using a lip mount bracket but let me ask this, if anyone could suggest some models to look at from them it would be much appreciated. I would also be open to looking into nmo mounts so if you guys want to I could look at a few of those that you could possibly put up here.

Thanks for all of the responses
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K0BG
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« Reply #11 on: August 07, 2010, 06:25:42 AM »

If it is just V/UHF, look at the Larsen NMOTLMB. This is just the mount, and coax cable. The matching dual band antenna would be NMO2/70B. AES, HRO, and most other amateur dealers should have both in stock.

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