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Increasing reception with a flat metal roof

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RenoHuskerDu

Longtime VFD, rusty old scanner
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We use FRS/GMRS handhelds in our family rural setting. We have some neighbors who are elderly and he became interested when he saw me easily qso with a son 800yds away. He purchased some handhelds too and would like to call us occasionally or call if they need help. I want to agree on a calling channel and add that to my old reliable RS 2067 scanner. I have a flat 30x40' carport metal roof attached to the house. I have a second carport metal roof on another side, 20x20' where I could install another antenna if the first one works well. Both carports have metal roof sections screwed together in numerous places. Both roofs are nearly flat, sloped just to collect rainwater for our cattle.

I recall that ground planes are generally Very Good. The metal roofs are ribbed but have large enough flat sections to easily install an NMO and vehicle antenna. I might just try an old 10m antenna from my CB days. There will be no trx, just receive. To answer if the elderly neighbors call, we'll step outside or go to a 2nd story window. In a related thread here I learned about proper grounding and surge arrestor. We get lighting in Central TX.

Finally come my questions:
  • Has anyone set up a similar scanner antenna with a metal roof as ground plane?
  • Is it worth getting a dedicated 2m scanner antenna? My hunch is that even an old CB stick would work.
  • If you suggest a 2m antenna, which has worked well for you?
  • Is RG8U still the best coax to use?
Thanks for any advice.
 

Rt169Radio

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In my opinion a mag-mount antenna in that setting would be fine, kinda like putting it on a metal coffee can (which I have done before)

Now a 2m scanner or ham radio antenna would be definitely be better reception wise instead of a CB antenna, any Diamond or Larsen brand 2m antenna would work good in my opinion

RG8U coax is still good but LMR-400 UltraFlex coax is even better
 

JoshuaHufford

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An antenna tuned to the frequency in use will always give the best performance, while others "may" work. But if you are going to the trouble of installing an antenna, why not install the proper one?

As far as coax it all depends on how long your run is, how much signal loss you can tolerate, sometimes the radius of bends you need to make, and sometimes your budget as well, there is no one "best" answer.

As far as installing an NMO mount in your carport, I don't see why that wouldn't work but others with more experience than me will probably chime in. Myself I'd probably install a small base antenna somewhere outside your home than drill into an expensive carport, and I have no problems drilling into the roof of an expensive car but you can't easily put a base antenna on your car.
 

WB9YBM

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If there's an easy way to do this, you might try to find a way to electrically connect the RF ground of the antenna (shield side of the coax) to the metal roof, as close as possible to the base of the antenna. Might help a bit.
 

FrensicPic

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If there's an easy way to do this, you might try to find a way to electrically connect the RF ground of the antenna (shield side of the coax) to the metal roof, as close as possible to the base of the antenna. Might help a bit.
Put an NMO (or similar) mount on the metal sheeting!
 

mmckenna

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Has anyone set up a similar scanner antenna with a metal roof as ground plane?

Pretty much ever mobile install is done this way. Large flat(ish) ground plane with an antenna mounted in the center of it. Doesn't matter if it's a car, truck or carport roof, having a ground plane under the antenna will provide the proper install the antenna wants.

Should work very well, however having the antenna down low (I'm guessing 10 feet or so above the ground) is going to result in less range than if you can get the antenna up higher. You'll see much better performance if you can get the antenna up as high as you safely can. Even mounting it on a roof peak with a ground plane will work. Something like this mounted on a pole and above your roof line will help quite a bit: https://www.theantennafarm.com/catalog/laird-technologies-mbc-1649

Is it worth getting a dedicated 2m scanner antenna? My hunch is that even an old CB stick would work.

It's worth getting an external scanner antenna designed for the frequencies you want to listen to.
It's worth getting an external 2 meter antenna if 2 meter band is what you want to listen to.
A CB antenna is going to "work" but it's really only going to work well on CB frequencies.

If scanner listening is your goal, then get a scanner antenna:
This: https://www.theantennafarm.com/catalog/laird-technologies-mbc-1649
and This: https://www.theantennafarm.com/catalog/larsen-nmo150-450-758-8932
mounted as high as you can safely get it. Or, get a discone antenna up as high as you safely can.
And don't forget about proper lightning protectors and grounding.

If you suggest a 2m antenna, which has worked well for you?

Well, for mobile VHF use, I use a simple 1/4 wave antenna. But unless you plan on getting your amateur radio license, there's no need to limit yourself to the 2 meter amateur band. There are better antennas to use for scanner listening. See above...

Is RG8U still the best coax to use?

There are many grades of coax ranging from cheap thin coax designed for very short runs, to large 'hard line' coax that will cost you several dollars per foot. RG-8 is down near the bottom of the list. What you need depends on what you intend to do with it, how long the cable run is, and how big your budget is.
RG-8 is suitable for some applications, but from what you are talking about above, you can do better. Recommending a suitable coaxial cable will depend on exactly what you intend to do with it. There is no "one size fits all" when it comes to coaxial cable.
 

N4KVE

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Years ago, at the car dealership where I worked, the body shop manager knew I was into radios, & asked me how to improve the range on the cordless phone in his office to work anywhere on the property. I went to the local ham radio store, & got an antenna for the frequency of the phone, & some coax. For a ground plane, I had one of the workers throw a damaged Buick hood on the roof of the body shop office. I mounted the antenna on the hood, & soldered the coax to the base unit of the phone. Now the phone worked over the entire dealership, & the donut shop down the street.
 

mmckenna

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a damaged Buick hood on the roof of the body shop office.

Classic. I love solutions like that.

I once threw a mag mount on a piece of scrap sheet metal I found up on a roof for a temporary base.



Now the phone worked over the entire dealership, & the donut shop down the street.

Smells like a Part 15 violation.
 

lu81fitter

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Someone's favorite antenna might not have an NMO mount--just trying to cover all the bases.

While this is true, NMO mounts are an industry standard, professional grade, and the antennas on the mount can be easily changed out if circumstances require a different antenna or just for experimenting with different types of antennas to see what works best. I don't think anyone is saying the OP is limited to any one type of antenna. NMO just makes it easy to switch.
 

WB9YBM

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While this is true, NMO mounts are an industry standard, professional grade, and the antennas on the mount can be easily changed out if circumstances require a different antenna or just for experimenting with different types of antennas to see what works best.

Vehicles I dealt with at Motorola (while I worked there) all had NMO mounts--they're great if you want to easily & quickly change antennas. Unfortunately--at least at that time--I didn't find any 5/8 wavelength antennas (except for one ham radio antenna) that worked with an NMO mount. (Is it safe to assume that issue's been addressed since then?)
 

lu81fitter

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As mmckenna states, there are options available. There are also dual and tri-band antennas that cover a broad spectrum, although I'm sure there are drawbacks to them for transmitting. (I don't have any transmitting capabilities.)
I have a couple tri-band antennas that do pretty well, as well as a dual band that performs pretty good. All of them are NMO, and I use them just for receive purposes only.
 

lu81fitter

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To the OP, if you are just going to use the antenna for GMRS, you "could" use the roof as a ground plane and use a 1/4 wave whip (about 6") or some type of gain antenna (Length and price will vary). Height will be your friend. The higher you get it, the better your reception will be. If that is an option, a ground plane kit with an antenna is your best bet that is mounted above your roofline, as mmckenna posted above.
Will you be monitoring anything else with this setup?
 

RenoHuskerDu

Longtime VFD, rusty old scanner
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Bertram TX
To the OP, if you are just going to use the antenna for GMRS, you "could" use the roof as a ground plane and use a 1/4 wave whip (about 6") or some type of gain antenna (Length and price will vary). Height will be your friend. The higher you get it, the better your reception will be. If that is an option, a ground plane kit with an antenna is your best bet that is mounted above your roofline, as mmckenna posted above.
Will you be monitoring anything else with this setup?

Mostly just MURS and GMRS freqs, for local family comms, and the eventuality of EMS, prep, defense needs as society decays. There are elderly nearby who bought HTs to contact us if in need. Our county only has 2 Deputies on duty any given night shift and response time can be 45 minutes depending on where they are. We're all trained as first responders, and two of our kids are VFD. I talked him into a GMRS lic so he can be legal.

I found a mag mount 6dB gain 144/440 antenna from The Antenna Farm which is just about 70cm tall, imagine that. It seems to work well. My boys were 7 miles away on 462.7125 in rolling hilly terrain, and the trusty old Pro-2067 on the new roof mount picked them up before the 15" whip on my HT did.

I do have lightning concerns. Central Texas is in general lightning country, and our home is near a gentle peak in 3 directions. It's stuck close twice in 2 years, killing our Huge Satellite modem (good riddance) and another time a nearby oak. So I'm more comfortable with that mag mount down at least 10' below the nearest tree and the peak of our roof. Our elderly neighbors come booming in now, 500 yds away but under their metal roof, which is why their cell service is so bad. And 8 miles to the cell tower.
 

mmckenna

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I found a mag mount 6dB gain 144/440 antenna from The Antenna Farm which is just about 70cm tall, imagine that. It seems to work well. My boys were 7 miles away on 462.7125 in rolling hilly terrain, and the trusty old Pro-2067 on the new roof mount picked them up before the 15" whip on my HT did.

If you are going to be using GMRS and MURS, you may want to consider a commercial dual band antenna that will resonate closer to the frequencies you are using. The ham antennas are going to under perform since they are designed for spectrum lower in the VHF and UHF bands.
 

WB9YBM

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Yes. 1/4 wave, 1/2 wave and 5/8 wave are all available.

the 1/4 wave & 1/2 wave I knew about (already in existence when I was at Motorola); glad to hear about the 5/8 wave. Is the 5/8 wave available in different bands? Who makes it?
 

mmckenna

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the 1/4 wave & 1/2 wave I knew about (already in existence when I was at Motorola); glad to hear about the 5/8 wave. Is the 5/8 wave available in different bands? Who makes it?

All the big antenna manufacturers make 5/8 wave mobile antennas for VHF and higher frequencies. Motorola even sells them now.
VHF: https://www.theantennafarm.com/cata...-vhf-antennas-457/high-gain-vhf-antennas-208/

UHF: https://www.theantennafarm.com/cata...0-512-mhz-uhf-196/high-gain-uhf-antennas-214/

800: https://www.theantennafarm.com/catalog/laird-technologies-b7603r-6542
 

JoshuaHufford

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Mostly just MURS and GMRS freqs, for local family comms, and the eventuality of EMS, prep, defense needs as society decays. There are elderly nearby who bought HTs to contact us if in need. Our county only has 2 Deputies on duty any given night shift and response time can be 45 minutes depending on where they are. We're all trained as first responders, and two of our kids are VFD. I talked him into a GMRS lic so he can be legal.

I found a mag mount 6dB gain 144/440 antenna from The Antenna Farm which is just about 70cm tall, imagine that. It seems to work well. My boys were 7 miles away on 462.7125 in rolling hilly terrain, and the trusty old Pro-2067 on the new roof mount picked them up before the 15" whip on my HT did.

I do have lightning concerns. Central Texas is in general lightning country, and our home is near a gentle peak in 3 directions. It's stuck close twice in 2 years, killing our Huge Satellite modem (good riddance) and another time a nearby oak. So I'm more comfortable with that mag mount down at least 10' below the nearest tree and the peak of our roof. Our elderly neighbors come booming in now, 500 yds away but under their metal roof, which is why their cell service is so bad. And 8 miles to the cell tower.


Not trying to get too off topic but if you want to help them with cell reception a cell booster can work wonders in that situation.
 
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