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Car / Vehicle VHF radio

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2 hours ago, paulmbowers said:

At that point I'd probably be better off setting up with the Sena thing- interface the transceiver with phone, XM, etc. 

 

Big bike only, though. 

Yeah I think on a small bike it would be way overkill and pretty difficult to find a location. 

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Here is a nice compact lightweight setup

Heck this would probably fit on the 500

 

 

 

PICT3154.jpg

K7MDL%20June%202009%20VHF-CN98-6.jpg

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On 10/19/2016 at 8:23 PM, Sneeker said:

It's all about the antenna man.  A 5 watt radio with a good antenna can get out father than a 50 watt with a cheap antenna.  That's the bottleneck, so spend your money there first before you go high watt.  Make sure that the antenna is matched to the frequency/band you'll be using.

These by Baofeng are good if you want to get started on-the-cheap with a higher watt mobile rig.

Sneaker is correct. Get a good antenna, trim to length of freq. I have a waterproof kenwood VHF, 60 watt. I paid 30$ to open up the rest of the frequencies. Not that id ever use them. Try www.antennafarm.com tutorials. 

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3 hours ago, Reximus said:

Sneaker is correct. Get a good antenna, trim to length of freq. I have a waterproof kenwood VHF, 60 watt. I paid 30$ to open up the rest of the frequencies. Not that id ever use them. Try www.antennafarm.com tutorials. 

 

Please explain

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3 minutes ago, Goofy Footer said:

 

Please explain



There is a very specific optimum physical length for antennas, based on the frequency on which the radio operates. For example, the optimum quarter-wavelegnth antenna for the frequency 146.505 is 19.166581345346575 inches. For 145.000 it's 19.365517241379308 inches. That's a very small difference, but it IS a difference.

 

Most antennas are a compromise- they "cover the range" of VHF, with an optimum point set usually somewhere in the middle. 

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On 10/20/2016 at 10:24 AM, Sneeker said:

Whoops!   THIS ONE Works for the Baofeng UV5RE

(Fixed previous link too)

Wait, this antenna is more expensive than the actual Baofeng UV5RE handheld!  Is it noticeably better?

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Just now, Goofy Footer said:

Wait, this antenna is more expensive than the actual Baofeng UV5RE handheld!  Is it noticeably better?

Pretty much guaranteed, yes.

It's not that the antenna is expensive- it's that the radio is SO CHEAP.

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Last year I had a guy offer me a "better" antenna down at the Baja 1K. He said "longer is better bro!". The stock antenna came full lenth for around 138mhz. I had mine tuned for 150-something, our crew freq. Well, for receiving the radio doesn't care too much about length, but transmitting is huge. Millimeters make a massive difference. Goofy, the big antennas you see ontop of the front lifted bro trucks are mostly 5/8 wave antennas. People buy them because they believe that the longer antenna is better, and then fail to trim them to their main op freq (weatherman, baja pits, sdar, etc). The shorter ones are usually 1/4 wave. Those are the ones most commonly used on our big red work trucks. They typically have a wider freq range than the 5/8 ones. Also, the work trucks are tall and the antenna could get in the power lines. 

You can always carry two whips trimmed for respective freqs and swap them depending on your main op freq. 

Then there are "loaded" or gain antennas. Those are usually add a bit of recieving ability (+DB) to the antenna. Its an antenna base modification thingy.

Then, decide where you mount it. Antennas need a "ground plane". In very crude rudimentary laymen's terms, its like a platform for the radio waves to push off of when they leave the antenna. Please HAM guys I know this is not correct way to describe ground plane, but it works for this purpose, K, thanks. Anyways, the center of a big piece of metal is a great place to stick an antenna. Like the roof. Well, what if you have a canvas top jeep? Dont worry, there are no-ground plane antennas too. They can go anywhere. 

Ok, ya dig?

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Well- to his point- longer IS better- in the perfect increment- 1/4, 1/2, full wave. A properly tuned full-wave will outperform a properly tuned 1/2 wave.

 

But just something real long? Nope.

Now, real HIGH is another thing. A properly tuned 1/4 wave on top of Otay Mountain will outperform a full wave in a valley somewhere.

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This is why HAM is such a good hobby for old guys! So much to learn and tinker with from the safety of the garage .?

 

Paul is correct, longer is better. Somewhere I heard wider is better but thats for something completely off topics l. I can hit catalina and Santa barbara repeaters from the top of san miguel on 5 wattS with a Uv5r. 

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Okay as an old guy and a ham guy I'll jump in here and try to elaborate. You guys are on the right track. The typical mobile antennas will be either 1/4 wave, 1/2 wave or 5/8 wave. Any of them will outperform the standard HT antenna by a wide margin IF PROPERLY MATCHED. The antenna length must be appropriate for the frequency you are using. Sometimes the antenna will come pre-cut to the correct length for a specific band. Many antennas come with a "cut-chart" that lists the correct length for the frequency you want to use. Alternatively you can use a SWR meter to adjust the antenna length. Most typical VHF antennas have a band width of around 6 Mhz though there are some wide band variations. That means it will perform well within +\- 3 Mhz of the frequency it is tuned for. An example  would be an antenna tuned for 150 Mhz will perform well from 147 - 153 Mhz. Outside that range and the performance starts to drop off pretty quickly. Also 1/4 and 5/8 wave antennas must be mounted on a ground plane. Most of the time this will be the roof or body of a vehicle. A half wave antenna is the only antenna which can be used with or without a ground plane however without a ground plane it will perform as a quarter wave. What's this mean? In a nutshell a quarter wave will perform much better than the standard HT antenna, a half wave (with ground plane) will perform better than the 1/4 wave and the 5/8 wave will perform slightly better than the half wave assuming they are all properly matched to the frequency being used. 5/8 wave is a very popular antenna for mobile apps. If you don't have a good ground plane the 1/2 wave is a good choice.

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The ARRL Antenna book has some really good information on antennas.  I still have my copy from 1976 in my office along side a newer 20th edition as well as a handful of other antenna engineering / design books.  The ARRL books do a great job of simplifying the explanation of how antennas work and are what I usually pull out when trying to explain something on the topic to a new engineer.

Here we're talking about antennas that are a fraction of a wavelength, whereas the antennas I typically work with are many multiples (like 150 or more) of a wavelength.  But the principles are the same.  Generally, the larger the effective area of an antenna, the greater the gain.  The gain over what, you might ask?

The gain of an antenna is typically referenced to a standard like an isotropic source or an ideal half-wave dipole in free space.  An isotropic source is one which radiates equally in all directions like a sphere.  It's an ideal reference that isn't physically possible in real life.  It is possible to get closer to the ideal half-wave dipole so for wire antennas that are a fraction of a wavelength or maybe a few multiples, the half-wave dipole is a common reference.

Gain is often expressed in dB form, typically with a suffix to indicate the reference to which it is being compared, such as dBi for an isotropic source or dBd if the gain reference is to a half-wave dipole.  The dB form of gain is simply the logarithm of the numeric gain multiplied by 10.  If the antenna you are looking at has a gain of 5 x that of a half-wave dipole, it will have 10 log(5) = 7 dBd gain in dB form.  By the way, a half-wave dipole has a gain of 2.15 dBi, or 1.64 times that of an isotropic source.  Helpful to know so you can make an apples to apples comparison when people are throwing out different gain numbers.

You can look through antenna design books all day long, but at the end of the day, the antennas we're talking about for use on motorcycles with a handy talky are generally going to be a compromise at best.  Keep in mind that a 1/4 wavelength at 146 MHz is 2.05 m divided by 4 or 0.51 m give or take, which is 20.2 inches.  That's a lot longer than the little rubber ducky that comes with the radio, right?  How's that work then? Antennas need to be a given electrical length to work right, but they can be physically shortened by use of a loading coil that basically winds the extra length into a more compact form.  That's how they get the rubber ducky so short.

I do have a 5/8 wave antenna for 2 m that is coiled up in my backpack that I have pulled out a few times on the trail and made some comparison contacts switching between the rubber ducky and the 5/8 wave antenna.  Not a huge difference and most of the time not noticeable.  The only time is when I'm on the extreme limits of being able to get into a repeater.  I've found that simply walking to a better location further up a hill usually makes a much bigger difference.

Short of going with something like amgems showed in his post or packing up my Cushcraft 15 element beam, most of the time I'm happy to just live with the rubber ducky.

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