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The 102-inch whip in a perfect world and the real world

FiveFilter

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No, I'd disagree. After installing hundreds of NMO permanent mount antennas over the last 30+ years, I have not found a real downside.

The downsides that are often brought up are usually excuses by people that don't understand the importance of properly installed antennas, are too lazy to do a proper install, or are not permitted to do those sorts of modifications to a vehicle.

But the drawbacks are not physical or technical, they are perceived drawbacks.
Using the correct tools, parts and techniques does not have any "potential problems". I've never had a properly installed NMO mount leak. I've never had one fail.
I think it my career, I've had to partially drop a headliner once. I've never had to completely remove a headliner on any vehicle.
Routing wires is part of doing a good install. No professional would leave exposed wires. It's called being a craftsman. Maybe it's the difference between a hobbyist/amateur and a professional.

Often people will claim "resale value" as a drawback.
I've installed permanent NMO mounts on all my vehicles since 1990. Never, not one time, have I had it detract from the sale price of the vehicle. This goes back to doing a professional job and paying attention to details. The last vehicle I sold was a 2011 F150 with about 100,000 miles on it. It had 2 NMO permanent mounts on the roof. The dealer didn't care. Because I'd maintained the vehicle correctly, it was in good shape inside and out, and I'd looked after it, I received higher than blue book value for it. The dealer didn't care that it had two antenna mounts on top.



There's nothing to accommodate if the install is done correctly.

If someone doesn't feel like installing a permanent antenna, then fine, they should just say that. But magnetic mount antennas are not as good as a permanent install.



If that works for you, then great. Magnetic mount antennas are a reasonable solution for some users.

On the other hand, you could install a permanent mount NMO on all three vehicles. Buy two rain caps and one antenna. Swap antennas around as much as you want. Get the best of both worlds.

OK. I guess it's not possible for a pro who has made a career of radio applications and has drilled hundreds of holes for antenna installations to see the other side of the coin where some less-experienced folks reside.
 

mmckenna

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OK. I guess it's not possible for a pro who has made a career of radio applications and has drilled hundreds of holes for antenna installations to see the other side of the coin where some less-experienced folks reside.
No, I can appreciate what you are saying, but disagree.

Magnetic mounts are a solution that some choose. For hobby use, it may be a good solution for those that cannot or won't do a permanent install. It's up to the individual to decide. But you did suggest that permanent mounts had "disadvantages":


All good points. And you also might agree that there are also a few disadvantages to the alternative permanent mount in the roof, including having to punch a permanent hole in the roof and potential problems relating thereto, having to remove and/or otherwise deal with the headliner to make the install, having to route the wires in sometimes hard-to-negotiate places, et al.
I simply do not agree that they are disadvantages. The only disadvantage is that someone may not want to drill a hole in their car. I get it. It's hard doing the first one, been there, done that, but then I got over it. As I pointed out, I haven't had to drop a headliner in a very long time, so again, not a disadvantage. And you'll find that it's rare anyone doing a permanent install drops a headliner. It's usually not required.
And as more and more vehicles go to aluminum or composite body panels, magnetic mounts won't always be a solution.

I will agree that doing permanent installs is young mans work. Luckily I don't have to do installs frequently anymore. It is hard work contorting your body into strange yoga type positions to get under the dash board. But a cold beer when the job is done helps ease some of that pain.

Again, for hobby use, if the magnet mount does the trick for you, then go for it. But it doesn't really compare well to a permanent mount antenna. There's a lot more to it that just checking for low SWR and walking away.
 

FiveFilter

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Thanks for that MMcKenna. I appreciate your expertise in your field.

This is a story of two perspectives:

One from a profession who has made a living installing hundreds of permanent radio applications during the past 30 years.

The other from an amateur who has made a living entirely devoid of radio installations but who enjoys radio as a hobby.

I can see the reasons for professional installations that are permanent to a vehicle.

I also can see the reasons for an amateur not wanting such installations on their vehicles.

I can see the advantages and disadvantages of both approaches.

What I can't see is why some folks can't accept that.

It's nice to have a choice.
 

mmckenna

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I can understand using magnetic mount antennas. I keep one around for testing. Sometimes it's good to test a location on a vehicle before making it permanent.

I have no problem with what someone else chooses to do with their vehicles/antennas. It's a personal choice and no one is going to force anyone to drill a hole in their vehicle. If you are happy with your magnetic mount antenna, then that's perfectly fine with me. Enjoy the radio and be happy with your setup. If it works, it works.

You stated that: "And you also might agree that there are also a few disadvantages to the alternative permanent mount in the roof..."

And my reply was simply that I do not agree that there are any technical disadvantages to a permanent install.
On a site like this where others come looking for information, it's good to have multiple points of view on the different options. Your point of view regarding magnetic mounts is perfectly valid. Many choose to go that route. In fact, I'd bet that there are far more magnetic mount hobby users than those using permanent mounts. Probably by a large margin. I'm not trying to change that. Just pointing out that from a professional aspect, there's a lot of good reasons to do a permanent install.
But not everyone has the skill set or tools to do that. No shame in that.

Everyone can enjoy the hobby however they see fit. I'm happy that your antennas work well for you. That's what matters.
 

FiveFilter

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Thanks again. Yep, my magnet mount antennas do work very well for me. And the fact is, without mag mount antennas I never would have begun using short wave radios in my vehicles, nor would I have any today. They are that effective for me.
 

mmckenna

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If you want to read more, this topic has been pretty well beat to death over on this thread. Some good points of view from both sides:

 

FiveFilter

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If you want to read more, this topic has been pretty well beat to death over on this thread. Some good points of view from both sides:

Yeah, I believe I have a response in that thread; it's on page 10 if it is the long thread I'm thinking it is. I didn't see it until it was just about petered out.

That thread epitomizes how folks can exaggerate the negatives and ignore the positives when they take a side on a topic, and get all hot and bothered about it in the process.

It's almost like religion.

That thread starts off by showing some scratches on a guy's car that resulted because he used a magnet-mount antenna. Funny thing is, I've been using such antennas for decades now...decades...and have not experienced such scratches on my cars or trucks. Are my magnets better than his, or am I just smarter than him in taking care while putting them on and taking them off? And am I smarter than him because I use a small piece of tape to hold the coax in place if I see that the coax is moving enough in the wind to show a pattern in the wax before any scratches show up?

Speaking of damage resulting from antennas, I've seen pictures of permanently mounted antennas which have been ripped out of the sheet metal of their vehicles by objects hitting them. This may be happening more nowadays with the aluminum and paper-thin steel bodies gaining popularity due to weight concerns. The resulting damages from these antenna accidents had to be very expensive to repair. In contrast, a mag mount antenna would simply have been pushed off to the side in such an accident, possibly resulting in scratches, but scratches that could simply be buffed out.

I guess I just cannot understand why some folks continue to attack the preferences of others in their choice of antennas when there are truly two sides of the coin; pros and cons; positives and negatives.

A currently popular phrase for such a phenomenon is "haters will hate."

Read through that thread. It demonstrates it very well.

Addendum: I just read through that referenced thread, and indeed it is the one I remembered. I must admit to making one big mistake in my late response on page 10: I said tests have shown a 0.1 dB disadvantage to magnet mounts vs permanent hole mounts. The actual number is 0.2 dB. As you noted above, such an extra loss is not perceptible anyway.
 
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mmckenna

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I guess I just cannot understand why some folks continue to attack the preferences of others in their choice of antennas when there are truly two sides of the coin; pros and cons; positives and negatives.

A currently popular phrase for such a phenomenon is "haters will hate."

Read through that thread. It demonstrates it very well.

Yeah, I agree. The argument gets out of hand quickly when people get too passionate about what they believe. I'm a strong believer in permanent mount antennas, but I can see the benefit to magnetic mounts to those that choose them. I'm not the type to get upset due to someone else's choices.

As for the aluminum thing...
I've drilled a lot of holes in a lot of vehicles over the years. I've found that the aluminum body Fords are harder to drill. The type of aluminum they use is very hard and it takes longer to drill than a similar steel body truck.

I'm not sure about tear-out. I've seen photo's of it online, but I think it's very rare. I've hit my antennas on low objects without issue. Back a few years ago at a trade show in Las Vegas, me and my F-350 got into a parking garage under a hotel that got short pretty quick. Due to the big line of traffic behind me I couldn't stop and remove the antenna. I had to drive part way in to get to a wide space. The overhead was about 3-4" taller than the truck. I knew the antenna was hitting hard. I sort of figured I'd end up with some issues.
This was a permanent NMO mount on a 2018 F-350 with the aluminum body. Antenna mount was dead center in the roof.
Antenna was a stiff wide band quarter wave VHF with a spring at the base.

Zero damage to the truck or NMO mount.
Only damage was that the spring at the base had taken a permanent tilt to the rear. Antenna was fine and worked. I ordered a new spring just to satisfy my desire to have things look right.

Same thing with my work truck. 2017 F350. On an over grown site access road that hadn't see a truck in a few years. I had to beat my way up there in four wheel drive. Two NMO antennas on the roof, one VHF quarter wave wide band, like my personal truck. Other one was an 800MHz antenna.
There were many low tree branches. The headache rack behind the cab was hit and took some damage, bent it back enough that I couldn't get the top bin on the service body open. Same branches hit the antennas. No damage to those antennas or the mounts.

So, sure tear-out can happen, but it's not common, and in 30 years, I've never experienced it.

I have seen mag mounts get knocked off vehicles before. Did make some serious scratches, and it dragged down the highway for 1/4 of a mile. If the coax hadn't held, it would have been in the middle of the highway.
 

KA0XR

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I've seen a lot of casual antenna-performance comparisons on the Internet through the years, and the general results were that, inch-for-antenna-inch, the magnet-mounted antennas were as effective as those permanently mounted in a hole. The key seems to be the antenna length and where it is placed on the car, the best generally being in the middle of the roof. This is one recent example I ran into:

"Magnetic mounts (good quality ones anyway) have little significance on an antenna's performance, just as the Larsen PDF illustrates: a tiny loss of 0.2 dB with a magnetic antenna vs a permanently mounted antenna. That paper also states the minimum amount of effective ground plane needed for several frequencies; but, of course, CB @ 27MHz will require much more ground plane than 150MHz will, making it all the more detrimental to the signal pattern to have it on the fender of the vehicle instead of the roof. I've seen it many times in the real world too, where I could clearly hear a buddy of mine who has a magnetic roof-mounted antenna, but signals from others who had various non-roof-mounted antennas (most being non-magnetic) were not even detectable."

Where can this Larsen PDF that you mention be found? I didn't see a link posted for it in any of the previous replies.
 

RFI-EMI-GUY

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[URL

unfurl="true"]http://www.rfcafe.com/references/po...acement-popular-electronics-november-1966.htm[/URL]

FiveFilter sayeth:
"It's almost like religion." No it is actually science.

A lot of newbies appear here and either ask "what is the best antenna to install" or "why doesn't my xyz antenna tune properly" . In the former case the best antenna is likely to be recommended, an NMO mount antenna on the center of the vehicle roof. In the second case, the OP usually has recently purchased a "magic" antenna that purports to "require no ground plane, no mounting holes, no tuning and supposedly can be mounted virtually anywhere".

Usually that antenna in fact requires a ground plane, some sort of mounting facility, needs to be tuned, and won't work where the OP wants to mount it.

My advice is generally to send that "magic" thing back for exchange for a Larsen NMO and borrow a hole saw. Otherwise there is a lot of back and forth trying to figure out which of the many "magic parameters" is not working.
 
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slowmover

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Mag Mount plus cigar lighter = “CB Radio is dead. I just drove XXX miles and there’s nobody out there. I’m sticking it back in the attic”.

This is the reality of the temporary install:

1). Not very good antenna.
2). Questionable radio (unless details offered).
3). No external speaker.
4). Poor positioning of radio to be able to hear.
5). Likely overuse of Squelch, and not enough RF Gain.
6). Lack of familiarity with both radio AND how others are using it.

And so forth.

“Noisy Receive” is a topic we never get to try and help remedy. As the preceding problems are a huge obstacle. (“I’ve spent $136 and THAT’S IT!”).

— Self-fulfilling prophecy of timidity + quick rejection.
 

slowmover

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Mag Mount plus cigar lighter = “CB Radio is dead. I just drove XXX miles and there’s nobody out there. I’m sticking it back in the attic”.

This is the reality of the temporary install:

1). Not very good antenna.
2). Questionable radio (unless details offered).
3). No external speaker.
4). Poor positioning of radio to be able to hear.
5). Likely overuse of Squelch, and not enough RF Gain.
6). Lack of familiarity with both radio AND how others are using it.

And so forth.

“Noisy Receive” is a topic we never get to try and help remedy. As the preceding problems are a huge obstacle. (“I’ve spent $136 and THAT’S IT!”).

— Self-fulfilling prophecy of timidity + quick rejection.
Do you want to know what CB can really do? It’s gonna run you $500 and the labor is yours.

$50/year for ten years of use.

.
 

FiveFilter

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[URL

unfurl="true"]Antenna Placement Does Make a Difference!, November 1966 Popular Electronics[/URL]

FiveFilter sayeth:
"It's almost like religion." No it is actually science.

A lot of newbies appear here and either ask "what is the best antenna to install" or "why doesn't my xyz antenna tune properly" . In the former case the best antenna is likely to be recommended, an NMO mount antenna on the center of the vehicle roof. In the second case, the OP usually has recently purchased a "magic" antenna that purports to "require no ground plane, no mounting holes, no tuning and supposedly can be mounted virtually anywhere".

Usually that antenna in fact requires a ground plane, some sort of mounting facility, needs to be tuned, and won't work where the OP wants to mount it.

My advice is generally to send that "magic" thing back for exchange for a Larsen NMO and borrow a hole saw. Otherwise there is a lot of back and forth trying to figure out which of the many "magic parameters" is not working.
RFI Guy, your taking my quote out of context about religion makes you look like an MSNBC reporter, or maybe CNN :)

That reference to religion was about those who go out of their way to throw shade on the nonbelievers who choose to use a magnet to hold their antennas on instead of drilling a hole through the roof. This holier-than-thou activity has been done to the point of religious zealotism; usually by hams, but not necessarily.

My point in the threads containing that "religion" reference is that there are pros and cons to both approaches. I'm saying that those with the hole-istic "religion" refuse to see that, and they can't hold themselves back from criticizing the nonbelievers.

I'm not disparaging your hole-in-the-roof advocacy. I'm just saying that there are valid reasons for both approaches. I won't take the time or space to repeat all that here.

And about the "science" you refer to, seeming to claim I am denying science: I abundantly recognized in those threads that "science" has determined that there is a performance penalty to the magnet mount antenna, and that it's around 0.1dB of additional loss. I also acknowledged that this fact can give the just-drill-the-damn-hole guys the right to say the mag mounts aren't as efficient. But only zealots would say this difference is significant. The loss of such a miniscule amount of energy cannot be detected by the human ear in any practical way. That, too, is science.

Addressing some other points in your post: I make no claim to any "magic" involving magnetic mounts. Nor do I say a mag mount doesn't need a ground plane. Nor do I say a mag mount doesn't need to be tuned. Any such statements are wrong and misleading.

Wow. This just keeps on and on. Amazing.
 

prcguy

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I'll dip my big toe in this for a moment just to stir things up a little more because I like it. The stated 0.1dB additional loss using a mag mount can be true at UHF and possibly other frequencies depending on mag mount size, shape and some other factors. I've tested some of my mag mounts at VHF and UHF compared to a hard mounted NMO and don't see enough difference to not use them. At 27MHz the loss is much more depending on mag mount size and lower frequencies get much worse. This is due to the capacitive coupling between the mag mount and vehicle body.

I've also done some testing at HF, mostly 3.8MHz, 7MHz and CB using a mag mount and a copper sheet 8.5 X 11 inches with some thin refrigerator magnet material attached and 2" of wide braid attaching the sheet to the mag mount ground. This raises the capacitive coupling of the mag mount from maybe a few hundred pf to many thousands of pf and seems to equal a hard grounded mount on all frequencies I tested.

The antennas were first tested and tuned on the hard grounded mount then moved to the mag mount in the same basic location. Without the ground coupling copper sheet the antennas at 3.8 and 7MHz were out the window on tuning plus there was a lot of RF on the coax due to the mag mount coax becoming a ground radial and performance was down. Adding the big capacitive sheet brought the tuning back exactly where it was with the hard grounded mount and performance came back.

So a mag mount can work the same as a hard grounded mount if it has sufficient coupling to ground.

RFI Guy, your taking my quote out of context about religion makes you look like an MSNBC reporter, or maybe CNN :)

That reference to religion was about those who go out of their way to throw shade on the nonbelievers who choose to use a magnet to hold their antennas on instead of drilling a hole through the roof. This holier-than-thou activity has been done to the point of religious zealotism; usually by hams, but not necessarily.

My point in the threads containing that "religion" reference is that there are pros and cons to both approaches. I'm saying that those with the hole-istic "religion" refuse to see that, and they can't hold themselves back from criticizing the nonbelievers.

I'm not disparaging your hole-in-the-roof advocacy. I'm just saying that there are valid reasons for both approaches. I won't take the time or space to repeat all that here.

And about the "science" you refer to, seeming to claim I am denying science: I abundantly recognized in those threads that "science" has determined that there is a performance penalty to the magnet mount antenna, and that it's around 0.1dB of additional loss. I also acknowledged that this fact can give the just-drill-the-damn-hole guys the right to say the mag mounts aren't as efficient. But only zealots would say this difference is significant. The loss of such a miniscule amount of energy cannot be detected by the human ear in any practical way. That, too, is science.

Addressing some other points in your post: I make no claim to any "magic" involving magnetic mounts. Nor do I say a mag mount doesn't need a ground plane. Nor do I say a mag mount doesn't need to be tuned. Any such statements are wrong and misleading.

Wow. This just keeps on and on. Amazing.
 

mmckenna

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and they can't hold themselves back from criticizing the nonbelievers.
Honestly? None of us really care what you do.
If you want to install a magnetic mount antenna on your own vehicle, then go right ahead, none of us will mind one bit. Trust me, I will not lose any sleep over it.

But as prcguy pointed out, there's more to it than just the 0.1dB difference.
 

prcguy

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Here is one of my capacitive ground sheets using 8.5 X 11" of copper foil on a thin magnetic sheet that has a self adhesive side. This one has a slightly longer braid connection to fit a tri or quad magnet mount that will hold up big HF antennas. Its easy to make with components off Ebay and I recommend this sheet goes towards the rear of the mag mount so if the wind picks it up the braid will catch it and it won't try to fly away.

1619636948347.png


Edit: Here is a piece of expensive crap from Diamond antenna that tries to do the same thing, but its only about 3 X 7.5" in size and it costs a lot. Although it probably improves things its much too small for the lower bands like 40 and 80m and its ground connection is a very thin wire and should be a short wide strap. You can make a much larger and more effective one for much less.




I'll dip my big toe in this for a moment just to stir things up a little more because I like it. The stated 0.1dB additional loss using a mag mount can be true at UHF and possibly other frequencies depending on mag mount size, shape and some other factors. I've tested some of my mag mounts at VHF and UHF compared to a hard mounted NMO and don't see enough difference to not use them. At 27MHz the loss is much more depending on mag mount size and lower frequencies get much worse. This is due to the capacitive coupling between the mag mount and vehicle body.

I've also done some testing at HF, mostly 3.8MHz, 7MHz and CB using a mag mount and a copper sheet 8.5 X 11 inches with some thin refrigerator magnet material attached and 2" of wide braid attaching the sheet to the mag mount ground. This raises the capacitive coupling of the mag mount from maybe a few hundred pf to many thousands of pf and seems to equal a hard grounded mount on all frequencies I tested.

The antennas were first tested and tuned on the hard grounded mount then moved to the mag mount in the same basic location. Without the ground coupling copper sheet the antennas at 3.8 and 7MHz were out the window on tuning plus there was a lot of RF on the coax due to the mag mount coax becoming a ground radial and performance was down. Adding the big capacitive sheet brought the tuning back exactly where it was with the hard grounded mount and performance came back.

So a mag mount can work the same as a hard grounded mount if it has sufficient coupling to ground.
 
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