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Author Topic: MJF Antenna  (Read 1214 times)
JMD
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Posts: 17




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« on: October 18, 2005, 06:53:05 AM »

A friend of my dads a very nice gentlemen and long time ham operator gave me this antenna(still in the package) for passing my ham test.

I was very nice of him to do this, I was planning on buying a Larson mag mount set up.

My question is how does the MFJ 1729 Power Gain 144/440 mhz compare with the Larson NMO set up I wanted to get??

I see they go for about 70 dollars up here, and so far it seems to work well.

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N3ZKP
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Posts: 2008




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« Reply #1 on: October 18, 2005, 07:50:15 AM »

(1) you DON'T want to use a mag mount unless there is simply no other alternative. Mag mounts damage the paint on vehicles every time you put it on or take it off. Even worse, they WILL come off in a collision, and your vehicle's insurance will not cover any damage the flying antenna causes. If you are going to use an NMO mount, do it right and install it properly - in a 3/4" hole. Installed correctly they DO NOT leak and they NO NOT decrease the resale value of a vehicle.

(2) "gain" figures from the foreign antenna manufacturers, including the stuff that MFJ sells, are pretty much lies. The figures are compared to the typical rubber duck-type antenna, instead of an isotropic source. 5dB gain over an antenna that has 5dB loss (and most HT antennas are worse than that) is still unity gain - the same as a simple 1/4 wave whip.

(3) the Larsens are built to commercial standards and will last for years, despite collisions with tree limbs, garage doors and parking garages. The stuff from MFJ, Diamond and Comet will not withstand this kind of abuse.

I have a NMO270B that is six years old on the third vehicle and hits the cross beams in the BWI parking garage three or four times a month - not bent or otherwise damaged - not even to the black coating in the whip itself.

Lon
Baltimore, Maryland

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N3ZKP
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Posts: 2008




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« Reply #2 on: October 18, 2005, 07:51:54 AM »

BTW:

Since you say you have passed your exam, how about a name and a call sign?

Lon
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JMD
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Posts: 17




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« Reply #3 on: October 18, 2005, 08:58:14 AM »

Thanks for the info but drilling a hole in my car is a "no go" big time lol

I actually wanted the Larson and was about to buy it myself, when I was handed this gift, sooo I will have to use it for now, I would not want to hurt the persons feelings.

As far as name goes its Joe and the call sign is still pending.

Thanks to good old Canada Post Industry Canada has not received the documents regarding my test marks.

I have spoken to the gentlemen who tested me,(my father knows him) and he told me he sent the paper work off on Oct 4th, so he is now in contact with Industry Canada to resolve this.

I hope it happens soon.
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K5LXP
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« Reply #4 on: October 18, 2005, 09:08:02 AM »

As much as I'm a proponent of Larsen products, a free antenna in hand is hard to turn down.  Use it until it gives you a reason not to.  Won't get me to change my mind about drillin' holes though, HI.

Mark K5LXP
Albuquerque, NM
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N3ZKP
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Posts: 2008




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« Reply #5 on: October 18, 2005, 10:42:46 AM »

I agree, that since you already have it use it.

I would still find some other mounting method - trunk lip mount of something. ANYTHING but a mag mount for an antenna that big.

Why is the hole a no-no?

Lon

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JMD
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Posts: 17




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« Reply #6 on: October 18, 2005, 11:22:31 AM »

I agree a free antenna is worth using and to tell you the truth I hit a repeater almost 70 miles away with this set up, my father talked to a guy in Welland Ontario and I'm almost 70 miles (as the crow flies) from that area, so thats not to shabby.

However I have not been able to really test it out myself for obvious reasons, lack of a call sign.

As for why a hole in my car is a no go, well I have a mint VW Golf and I don't want to boar a hole in a perfectly good car, if I had a 10 year old beater then fine.

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JMD
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« Reply #7 on: October 18, 2005, 11:26:10 AM »

Also the antenna is quite small and light, it does however have a very powerful magnet.

I have a Larson CB antenna,(now collecting dust lol) separate mag mount, coil and whip.

About 140 dollars for this setup and this antenna towers over my dual band ham antenna and weighs a lot more.



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K5LXP
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« Reply #8 on: October 18, 2005, 03:10:14 PM »

>  I have a mint VW Golf and I don't want to [bore] a
> hole in a perfectly good car,

After what you see a mag mount does to the paint, you'll be wishing you drilled the hole...

It's enhancing the capabilities of the vehicle- makes it safer and more convenient to operate the radio and overall increases the pleasure of ownership. You make it sound like drilling holes is a bad thing.

Mark K5LXP
Albuquerque, NM

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JMD
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Posts: 17




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« Reply #9 on: October 18, 2005, 03:44:57 PM »


Mark it sounds like your taking this all too personal

For those who want to drill a hole........drill a hole, for those who choose to use the mag mount instead, use the mag mount.

Personally if I looked at a car for sale and saw that a hole had been drilled in it for an antenna, I would walk away from the car and not buy it, there are others out there that would buy it.

Drilling a hole is not a bad thing if it’s what you want to do.

Personal preference my friend, I will never drill a hole in the surface of my car for an antenna.

Also I have used a mag mount Larson (CB) for several months and I have removed it carefully on many occasions, and the paint and finish are just fine.

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K0BG
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« Reply #10 on: October 18, 2005, 04:38:08 PM »

Joe, Mark isn't taking it personally I'm sure. Lon, Mark, and I are all long-time amateur operators, and all of us have had a lot of mobile experience. We know that for the best performance, hard mounting is preferred. The difference is noticeable even without fancy equipment.

I have drilled holes in every car I have owned (24), and every company car I have had (7). Only once have I been ask what the mount was, and when I said it was for the cellphone, the dealer appraiser said, "Oh".

I always use a good quality NMO mount, and I always leave it on the vehicle when I trade it in.

There is one insidious aspect of mag mount antennas; they come off in a crash! There has been one reported death, and 7 injuries from flying mag mounts in the last 18 months. There's probably more that have gone unreported.

Lastly, most insurance companies will not provide liability coverage for devices not permanently attached to the vehicle. All else being equal, this would convince me.

Alan, KØBG
www.k0bg.com
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JMD
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« Reply #11 on: October 18, 2005, 06:49:48 PM »

I do agree Alan that a permanent mount is preferred however I don't see it as being a must do thing.

Yes mag mounts can come off in a crash, so can so many other things on a car however I would be more concerned about a 3000 lb car impacting me than a small mag mount antenna.

One death in 18 months ? there must be millions of vehicles in Canada and the USA using mag mounts for ham,CBs just to name a few so from a safety stand point I don't see mag mounts as being a cause for urgent concern when it comes to accedents.

I'm supprised mag mounts are still selling or allowed to be sold if they are a cause for consern
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KE3HO
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Posts: 235




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« Reply #12 on: October 18, 2005, 08:45:45 PM »

I have heard all sorts of ideas for how you can use a mag-mount without screwing up the paint. I have not heard one yet that I believe. Even if you find a procedure that allows you to install and remove the magmount without chiping the paint, I can tell you from experience that the magmount will cause damage to the paint. Every time it rains, or every time there is dew on the roof of your car, water will get under the magmount. It can't be avoided. I don't know about Canada, but in my area dew on the roof is a daily thing for about a quarter to half of the year. Add raid days to that and it adds up quickly. Every time water, even a little bit, gets under the magnet, you have to take it off and dry it (both the magnet and the spot on the roof were it was sitting). It is a royal pain to say the least. I tried applying a heavy layer of wax before putting the magmount on, but this did not help much. The wax turned milky white from the water soaking into it and the water still go into the paint (after rubbing off the wax I could still see a milky circle in the clearcoat).

My feeling is, the best thing to do with a magmount is to give it to someone you don't like :-)

Drill the hole and put the NMO mount in the roof and you will have less damage to the car than any magmount.

73 - Jim
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K0BG
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« Reply #13 on: October 19, 2005, 07:25:24 AM »

As a new amateur you have a lot to learn. A mag mount capacitively couples to the surface under the antenna. Even at VHF frequencies, there is added loss when compared to the exact antenna mounted solidly in sheet metal. That fact is irrefutable. This doesn't address the accident consequences, or the eventual paint damage.

You may scoff at what you've been told by four different amateurs; that's your privilege. Sooner or later, if you're really intent on learning about RF theory and practice, you will discover why the aforementioned is true.

You seem to be taking this as a personal vendetta, which it isn't. As impolite as it may sound, your rebuttal exemplifies your lack of knowledge on the subject. Unless you're willing to listen to experience, your travels through life are going to be difficult, to say nothing about amateur radio.

Alan, KØBG
www.k0bg.com
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WB2WIK
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« Reply #14 on: October 19, 2005, 08:26:48 AM »

JMD good luck with the antenna, the car and getting your license in the mail!

And everybody else: There are people who will never be convinced to punch a hole in their car, no matter what -- just like there are people who buy homes having CC&Rs and then wonder why they can't put up antennas; and there are people who both start out and finish their ham radio careers on VHF-FM without ever having operated HF.

I'm very happy to be in the group that tries everything, and I've punched holes in the roofs of every car I've ever owned or leased since 1969, usually the same day the car came home from the dealer.  For me, it takes less time and effort to make the hole and run the cable all inside the vehicle where nobody can see it than it takes most people to think about whether they should so this or not.

I like the hole because the resulting installation not only works better and lasts longer, but looks neater and is less likely to be stolen.

But some will never be convinced -- don't try.

WB2WIK/6
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