Repeater Range With Obstructions

[SeldomSeen]

I live in a valley in the foothills of the Rocky Mountains. My house is completely surrounded by hills and mountains that are anywhere from 400 to 1200 feet higher than my home elevation. The nearest GMRS repeaters are about a dozen miles away across those hills. I can hear repeater traffic on my scanner loud and clear. Does that imply that a good 4W HT or mobile radio used as a home base unit would be able to access those repeaters? I don't want to purchase until I can verify that this can happen.

[kidphc]

If you can hear it then you probably are going to be able to connect to it. Although, there is no guarantee till you try. Maybe get a friend/local to come over and hit the repeater.

 

As far as the 5w, that really isn't going to get you further out. It doesn't increase distance, but rather the punch the radio has to get through noise. Plenty of hams making some crazy contacts with .5 watts. Its more about elevation, line of sight and antennas more then anything else.

[rodro123]

I live in a valley in the foothills of the Rocky Mountains. My house is completely surrounded by hills and mountains that are anywhere from 400 to 1200 feet higher than my home elevation. The nearest GMRS repeaters are about a dozen miles away across those hills. I can hear repeater traffic on my scanner loud and clear. Does that imply that a good 4W HT or mobile radio used as a home base unit would be able to access those repeaters? I don't want to purchase until I can verify that this can happen.

If you order from Amazon it is returnable. Just my 2 cents.

[axorlov]

You probably hear repeater traffic because signal reflects from the hills around you. 4W HT may not have enough power for reflected signal to open repeater. Mobile radio might have enough power. It's impossible to know in advance. Directional antenna may help too.

[Riktar]

FWIW I live in an area that has some hills in and around me. While I am not in a geographic bowl as you are describing I do have some topography differences to deal with.

 

I have a repeater that is 30 miles away and another repeater that is 60 miles from me. Both are on the same linked system. Both are in totally different (nearly 180 degrees) directions.

 

In my car (mobile) and in my house (base) I use Kenwood TK-8180 mobile units. The house or "base" radio is the "H" model so it kicks out 45 watts. The car or "mobile" is not an "H" so it is pushing 30 watts. I may be switching those 2 radios around, but I digress....

 

The 30 mile repeater can be heard clear as a bell by the base unit. This repeater can hear me quite clearly as well now that I have ironed out "some" of my initial setup issues. The mobile unit can hear the repeater fairly clear and can communicate fairly clearly depending on where I park the car on the property. The handheld(s) I use when I am pedestrian on the property are really hit and miss with hearing the repeater. This doesn't concern me that much since their primary function is talking to the base unit.

 

The 60 mile repeater can be heard by the base unit but the static is about even with the voices being broadcast so while I can make out what is being said, it is hard to use. Just for grins I tried to broadcast and was told that while I was keying the repeater, nobody could make out what I was saying.

 

Anywho....

 

Chances are that if you can CLEARLY hear the repeater from your location, you should be able to talk to the repeater without much of a problem on a base unit in your house with an antenna setup that is (reasonably) proper.

 

If not, as was mentioned in an above post, Amazon is your friend when it comes to returns. 

[SeldomSeen]

I just received a Wouxun KG-805G HT with a mobile antenna, got the okay from the Front Range GMRS repeater group and programmed the radio (very simple both manually and with the computer interface). I got on the repeater this morning and asked for a signal report with just 4W. To my great surprise I actually got a response. The responder said my signal was fading in and out but he understood most of what I said. YAY!  Now it's tempting to get a 40W or so mobile unit and set it up as a base station.

 

A funny thing happened last night with the new rig. The magnetic antenna mount would not stay put on my 2017 Ford F250. It turns out that in order to save weight the body was made of aluminum. So I had to make due with my old Ford Ranger. 

[berkinet]

...I got on the repeater this morning and asked for a signal report with just 4W. To my great surprise I actually got a response. The responder said my signal was fading in and out but he understood most of what I said. YAY!  Now it's tempting to get a 40W or so mobile unit and set it up as a base station. ...

 

I would guess that your transmit issues are not caused low power, but by a poor antenna or poor installation of the antenna.  You note you are using a mag mount antenna, there is one issue already.  If you cannot, or really do not want to, drill a mounting hole in your truck, take a look at an antenna design that does not require a ground plane. There are several such designs so I won't go into them here.

 

For a base station you'd have even more options. First choice would be to get the antenna up high. Then, depending on your needs, using a "gain" antenna would probably help, especially a directional antenna.

[Riktar]

Your comment on the mag mount mobile antenna has me thinking. I did get a permanent NMO antenna mount in a used TK-8180 package I purchased and was considering installing it on my 2007 Trailblazer since I will (most likely) be the last person owning it until it goes to the bone yard. Right now I am using a Midland mag mount for my MNO antennas and have the antenna fairly centered on the roof. If I went with the "permanent" mount I would have to shift it back a couple of feet because of the moon roof option the vehicle has. In your opinion, does the change to a permanent over a magnetic mount have benefits that outweigh the need to place the antenna in a less centered position on the vehicle? As I understand it, the trailblazer body is acting as the ground plance which is why I tried to center the mag mount as close to dead center as possible.

 

Because as it stands now I can still hit the repeater in my area with the mobile but because I am on the fringe of the repeaters range the connection is sometimes a bit sketchy. So any measure of performance improvement would be welcome.

 

 

I would guess that your transmit issues are not caused low power, but by a poor antenna or poor installation of the antenna.  You note you are using a mag mount antenna, there is one issue already.  If you cannot, or really do not want to, drill a mounting hole in your truck, take a look at an antenna design that does not require a ground plane. There are several such designs so I won't go into them here.

 

For a base station you'd have even more options. First choice would be to get the antenna up high. Then, depending on your needs, using a "gain" antenna would probably help, especially a directional antenna.

[berkinet]

... If I went with the "permanent" mount I would have to shift it back a couple of feet because of the moon roof option the vehicle has. In your opinion, does the change to a permanent over a magnetic mount have benefits that outweigh the need to place the antenna in a less centered position on the vehicle? As I understand it, the trailblazer body is acting as the ground plane which is why I tried to center the mag mount as close to dead center as possible....

Well, as is the answer to a lot of radio questions, it depends. If you are using a 1/4 wave dipole antenna, then you need a ground-plane. You should have 1/4 wave (~6.5") ground around your antenna. If there is less than 1/4 wave ground in one direction you will get some, relatively minor, directionality. If you still have problems after permanently mounting the antenna, you can, as I noted above, switch to a gain antenna. If you really do have ground-plane issues, the gain antenna will likely address that as well. Typical gain for UHF no-ground-plane antenna, without ground-plane, would probably give you ~3db of omni-directional gain - the equivalent of doubling your power.  If you have a ground-plane, the gain would likely be higher.

 

Here are a couple of sites listing UHF no-ground antennas...

https://www.theantennafarm.com/catalog/antennas-191/mobile-antennas-192/380-512-mhz-uhf-196/no-ground-uhf-antennas-215/

https://www.arcantenna.com/shop-antenna-frequencies/400-490-mhz-uhf/no-ground-plane-ngp-uhf-antenna.html

[Lscott]

If you cannot, or really do not want to, drill a mounting hole in your truck,

I would think very carefully about doing this. Besides going to aluminum to save weight the sheet metal gauge is likely reduced too. With an NMO mount there isn't that much metal area to resist the bending moment of the antenna. I've read more than one account where the roof was damaged, roof area bent or the mount just plain ripped out, when the antenna hit a small tree branch or driving at highway speeds. At least with a magnet mount it will just knock it off the roof most likely with little to no damaged being caused.

 

If you do go with a NMO mount research first for a good way to reinforce the roof are around it before doing the install.

 

Many mobile antennas are fairly stiff and don't give much if they are flexed so an antenna strike goes straight to the mount. Some antennas are available with a spring located at the antenna base. These will reduce the chance your vehicle roof and or antenna will suffer damage from a low tree branch strike or other low obstruction contact.

[Radioguy7268]

Our company has done more than 50 installations on Aluminum body F-series trucks. I can tell you that there is no issue with the thickness of the roof, or any "weakness" in the aluminum as compared to a steel roof.

 

There is some validity to the idea that an aluminum roof isn't going to be as easy to repair as a steel roof when some idiot runs under a roof/tree/overhead obstruction with less than 2" to spare above the roof line. I can tell you that one reason I'm a BIG fan of the basic 1/4 wave hatpin for roof mounted antennas is that the antenna will shear off in nearly every circumstance before the roof itself is damaged. 

 

I'd also tell you that a spring loaded antenna is MORE rigid at the base, and is more likely to suffer damage to the roof compared to the hatpin. Balance the cost of buying a few spare hatpin antenna whips (Current retail is around $8.75) versus a body shop repair of your roof.

 

If you can't tell - I dislike mag mount antennas. Drill the hole. Use a 1/4 wave UHF hatpin, carry a spare. 

[Riktar]

Maintaining 6.5" around the antenna mount, magnetic, permanent or otherwise is no problem. I was wondering if moving it away from the center of the car would still cause a bias in transmit/receive performance. IE: where the mount currently is, I have (approx) 2 feet of "ground plane" to the sides and 4 feet to the windshield and the back hatch. If I go with a permant mount I would maintain the 2 feet to the sides but the fore and aft would change from 4 feet in both directions to 3 feet from the back and 5 feet to the front.

 

And just an FYI: I have 2 antennas I will employ on the vehicle: One is a Larsen LP450NMO antenna. This is a unity gain antenna that does require a ground plane. This is teh antenna that I will use around the property since it is REALLY low profile so no worries about low hanging branches and it will also come in handy when going through carwashes. 

 

The other antenna is a Browning BR-450 (No ground plane needed) that will be my "open road" antenna since I want maximum range on the road and I will net be concerned with low hanging branches on the interstates.

 

Are you saying that as long as I have the 6.5 inches around the mount (for the ground plane needed antenna) the remaining roof placement would not make that much difference?

 

As always, thank you for the info!

 

Well, as is the answer to a lot of radio questions, it depends. If you are using a 1/4 wave dipole antenna, then you need a ground-plane. You should have 1/4 wave (~6.5") ground around your antenna. If there is less than 1/4 wave ground in one direction you will get some, relatively minor, directionality. If you still have problems after permanently mounting the antenna, you can, as I noted above, switch to a gain antenna. If you really do have ground-plane issues, the gain antenna will likely address that as well. Typical gain for UHF no-ground-plane antenna, without ground-plane, would probably give you ~3db of omni-directional gain - the equivalent of doubling your power.  If you have a ground-plane, the gain would likely be higher.

 

Here are a couple of sites listing UHF no-ground antennas...

https://www.theantennafarm.com/catalog/antennas-191/mobile-antennas-192/380-512-mhz-uhf-196/no-ground-uhf-antennas-215/

https://www.arcantenna.com/shop-antenna-frequencies/400-490-mhz-uhf/no-ground-plane-ngp-uhf-antenna.html

[berkinet]

...Are you saying that as long as I have the 6.5 inches around the mount the remaining roof placement would not make that much difference?...

that is exactly what I am saying.

[Riktar]

Thanks berkinet! 

[SeldomSeen]

The pristine newish F250 is basically my wife's. Drilling a hole in the roof would not be in my best interests.   I chose the Midland mag mount for the convenience of using it in some of our other vehicles. That 32" antenna would sure look funny on top of my '72 Alfa Romeo GTV.

[berkinet]

... That 32" antenna would sure look funny on top of my '72 Alfa Romeo GTV.

Best car I ever owned was a '72 Giulia Super.