Jump to content

effective dual band yagi for gmrs


scottmckinney67
 Share

Recommended Posts

Hi guys and gals,

 

I'm looking to buy a directional antenna for GMRS that will also work on VHF when I get the tech license.  I've been looking at elk and arrow.  I love the portability but don't want to sacrifice too much performance.  Are these on par with say a cushcraft or some other brand of dual band yagi for GMRS?  Are there any specific antennas that you recommend?

 

I'm in a residential area and currently have 2 40 watt mobiles connected to midland 6dbi whips with ground plane plates.  Trying to talk simplex with my son that isn't far but we're marginal on height restrictions at his mom's house.  Right now we can talk, but it's pretty noisy and annoying. I used this calculator https://www.scadacore.com/tools/rf-path/rf-line-of-sight/ and it confirms we're on the edge height wise.  I will be able to raise his slightly, to maybe 3.5 meter height.  I'm around 8 meters high at my place in the attic.  I understand that height will trump pretty much everything but ex's rule in this case as far as my mounting at that location.

 

I'm hoping to keep antenna cost under 200.

 

Thanks!

Link to comment
Share on other sites

Most UHF beams only have 15MHz to 20MHz of bandwidth they are usable for. You are not likely to find one that is going to cover 50MHz unless all of the elements and spacing are tunable (which I have never seen). That's more than double the typical bandwidth coverage.

Link to comment
Share on other sites

First, I would forget about dual band Yagis. They tend to be a compromise at best, and most of them have minimal gain. Also if it's dual band, it won't be 2M and GMRS; it will be 2m and 440. Even if it happens to work somewhat on 462/467, it won't be ideal.

I would get a Larsen welded Yagi that is designed for 450-470 MHz, like this one: https://amzn.to/316dWOk

Those will last a very, very long time; and a pair of them pointed at each other will probably solve your problem.

Then when you get your ham license, get a dedicated antenna for that based on what you need it to do.

Link to comment
Share on other sites

Omni's fall into a similar issue.  While there are some dual-band 2m/70cm vertical antennas that cover from 440-470 MHz, the gain is very low.  As gain increases, the bandwidth narrows and so does the takeoff angle, impacting sensitivity between stations with elevation difference.

 

So, if you have the expendable income, you can test it.  However, don't be surprised if the lower gain of a broad band antenna doesn't help much.

 

I have to agree with RCM on getting two service-dedicated Larsen welded Yagis.  That's going to be your best bet, relating to both performance and price.

Link to comment
Share on other sites

Sorry to hear that.  I'm not sure what your goals are, but I have been a Ham for close to 18 years and GMRS is a fantastic service that I use regularly. The thing about radio service is to use the proper service for the comms you are trying to have.

I thought I stated my goal earlier, maybe that wasn't clear.  Based on the advice of other ham operators, who thought this wouldn't be an issue, I bought these small antennas and cheap radios and obtained a gmrs license.  It's not a gmrs issue, it's a line of sight and lack of gmrs open repeater issue in my opinion.  If you look at the link I posted and put in some antenna heights it gives what is a usable range based on some sort of path study parameters.  We're on the hairy edge.  I understand your mileage may vary when doing this but a few miles is kicking our butts at the moment.  

 

I do appreciate the advice.  We don't give up, so one way or another, we'll make it happen.  I just spoke to my son's mom and she's ok with an omni above the roof line.  I'm going that route with standard dual band antenna that has a relatively low swr on grms and we'll make due for now.  That doesn't work, tech licenses and I already have a diamond dual band mobile that I can stick in the attic after we get the licenses.

Link to comment
Share on other sites

Sorry... I misspoke.  I do realize that you have stated what your objectives are.  I guess I didn't understand why you are trying to get a multi-service beam or vertical.  After re-reading, if you are trying to get the most value per dollar, that makes sense.  Unfortunately, however, it doesn't work to our benefit very often.  Most multi-function devices accommodate convenience at the detriment of performance.

 

The map you shared is showing about 70 miles from point to point.  That is the very edge for 50 watts on a vertical.  Hopefully setting the antennas higher will do the trick.

 

Good luck with the Amateur radio test.  It opens up a whole new real of possibilities. 

Link to comment
Share on other sites

I would only opine that there is no magic that comes with a Technician license over GMRS. It's practically the same physics at play. I'm facing a different problem, but also physics related. I live in a dip that breaks LOS in the direction that I need coverage. GMRS focuses my solutions to the GMRS band, whereas the amateur solution spreads me over several bands, which equal more $

 

The only exception would be HF, which would do a better job at distance. 

 

Otherwise, I'm focused on doing GMRS really well as I can tune everything to be excellent at those frequencies. 

Link to comment
Share on other sites

Sorry... I misspoke.  I do realize that you have stated what your objectives are.  I guess I didn't understand why you are trying to get a multi-service beam or vertical.  After re-reading, if you are trying to get the most value per dollar, that makes sense.  Unfortunately, however, it doesn't work to our benefit very often.  Most multi-function devices accommodate convenience at the detriment of performance.

 

The map you shared is showing about 70 miles from point to point.  That is the very edge for 50 watts on a vertical.  Hopefully setting the antennas higher will do the trick.

 

Good luck with the Amateur radio test.  It opens up a whole new real of possibilities. 

No worries.  That map is just the link.  I'm literally less than 3.5 miles as the crow flies.  I think that's why my experienced buddies said it should be no problem.  When I place my antenna at 6 meters and my son's at 2 meters, the line shows red.  I go up to 7, it goes green.  I did get my antenna up to 8 meters high in my attic, drove to the area where my son's house is and we can talk, but the noise level is very high.  This is with the antenna on the roof of my honda accord, so probably close to 2 meters.  This is why I think the issue is terrain and elevation between us.  I bought the radios before finding that site and used the standard line of sight calculation and thought it would be no problem.  So I think even an antenna that's not exactly resonant on GMRS but close with a decent SWR a few meters off the ground will do the trick on his end.  Make sense?  I was looking at the yagi on his end to aim at me originally, but figured in the long haul, a comet, diamond, tran, omni would be a good choice since we plan on getting tech licenses.

Link to comment
Share on other sites

I would only opine that there is no magic that comes with a Technician license over GMRS. It's practically the same physics at play. I'm facing a different problem, but also physics related. I live in a dip that breaks LOS in the direction that I need coverage. GMRS focuses my solutions to the GMRS band, whereas the amateur solution spreads me over several bands, which equal more $

 

The only exception would be HF, which would do a better job at distance. 

 

Otherwise, I'm focused on doing GMRS really well as I can tune everything to be excellent at those frequencies. 

 

A tech license opens up some repeaters in my town.  Apparently there aren't any in Columbus Ohio, or the owners won't allow me.  I've asked and no response.

Link to comment
Share on other sites

Ah... I see what you are saying. Hmmm. So that distance shouldn't be too bad with a shade more height on his end. If mom is willing to have the antenna higher than the rooflines, then you should be good.

 

On the SWR side, there are some antennas that might be close. While high SWR means loss of radiated power... if you stay below 3:1, in theory nothing should break. I had run 180 watts pep on a setup that was 2.4:1 for 2 years, before I fixed the HF antenna. If you are going to throw the dice, try to find something that will be 2:1 or better.

 

Companies like Diamond offer antennas that are mostly fixed, with a small adjustable whip section. You can buy a base antenna and two adjustable whips. Cut one to GMRS and the other to Ham 440 band. Then you can just swap the inexpensive whip around depending on the service you want to use.

 

I haven't tried it at home, but I use that MO on my CR8900 on the Jeep. It works pretty well.

Link to comment
Share on other sites

Ah... I see what you are saying. Hmmm. So that distance shouldn't be too bad with a shade more height on his end. If mom is willing to have the antenna higher than the rooflines, then you should be good.

 

On the SWR side, there are some antennas that might be close. While high SWR means loss of radiated power... if you stay below 3:1, in theory nothing should break. I had run 180 watts pep on a setup that was 2.4:1 for 2 years, before I fixed the HF antenna. If you are going to throw the dice, try to find something that will be 2:1 or better.

 

Companies like Diamond offer antennas that are mostly fixed, with a small adjustable whip section. You can buy a base antenna and two adjustable whips. Cut one to GMRS and the other to Ham 440 band. Then you can just swap the inexpensive whip around depending on the service you want to use.

 

I haven't tried it at home, but I use that MO on my CR8900 on the Jeep. It works pretty well.

That's what I'm talking about!  I'd like to keep the antenna at 10 feet or less and I'll use fence top rail for a mast to clear the roofline.  I'd like to get a quality antenna that I can tune, then tune back after we get our licenses.  Any recommendations?  Also, if I drive the fence top rail 4 feet in the ground, would I need a separate ground rod?  I'm sure it's not up to code in some areas, but I don't want to start tying into her electric boxes or mess with her ground rod.  I have enough issues with her without being blamed for blowing her electric service :)  I would use a lightning arrester.  

Link to comment
Share on other sites

You should be able to get full-scale copy at 3.5 miles on less than 2 watts.  If you can't do it at 40 Watts, then lose those junk Midland antennas, and get a couple of decent UHF omni antennas mounted on the roofline.  Also run a heavy, large gauge coax cable designed for UHF...such as LMR-400.  If you have those Midlands with that thin RG-174 type coax, then that is exactly why you can't get 3 miles.  If you need to extend the coax, note that the CB coax extenders you buy at the truck stop will not work at UHF.

Link to comment
Share on other sites

You should be able to get full-scale copy at 3.5 miles on less than 2 watts.  If you can't do it at 40 Watts, then lose those junk Midland antennas, and get a couple of decent UHF omni antennas mounted on the roofline.  Also run a heavy, large gauge coax cable designed for UHF...such as LMR-400.  If you have those Midlands with that thin RG-174 type coax, then that is exactly why you can't get 3 miles.  If you need to extend the coax, note that the CB coax extenders you buy at the truck stop will not work at UHF.

Thanks.  I am using the crap midlands with the light cable.  I could go with an omni uhf antenna but want one that will cover more than just gmrs as I don't ever want to not have a repeater option.  There are plenty of UHF repeaters in my area and no gmrs repeaters.  Go figure.

Link to comment
Share on other sites

Thanks.  I am using the crap midlands with the light cable.  I could go with an omni uhf antenna but want one that will cover more than just gmrs as I don't ever want to not have a repeater option.  There are plenty of UHF repeaters in my area and no gmrs repeaters.  Go figure.

Well, it won't cover 2 Meters, but if you want a good wide-band UHF antenna that will not be obtrusive, and very nicely cover both GMRS and the UHF 70cm ham band, then consider a quarter-wave on one of those Laird Ground plane kits that are being discussed in this forum on another thread.  (I'll post the link shortly) - now is shortly - https://www.theantennafarm.com/catalog/laird-technologies-mbc-1649

 

Quarter-wave antennas have no gain, but they do have extremely wide bandwidth, and better coverage in hilly terrain.  Since the antenna is very small and unobtrusive, you could mount it up higher on the top of the roof.  The added height, and a good coax will certainly beat what you've got running right now.

Link to comment
Share on other sites

You should be able to get full-scale copy at 3.5 miles on less than 2 watts.  If you can't do it at 40 Watts, then lose those junk Midland antennas, and get a couple of decent UHF omni antennas mounted on the roofline.  Also run a heavy, large gauge coax cable designed for UHF...such as LMR-400.  If you have those Midlands with that thin RG-174 type coax, then that is exactly why you can't get 3 miles.  If you need to extend the coax, note that the CB coax extenders you buy at the truck stop will not work at UHF.

 

I'm sure that your theory is valid, thanks.  But I think this map https://www.scadacore.com/tools/rf-path/rf-line-of-sight/ program is my core issue.  When I plug in my location and my son's I get red with my antenna less than 7 meters and his less than 2 meters tall.  I located my antenna in the attic at a little over 8 meters high on a 15 inch pizza pan for a ground plane.  When I test I'm in a honda accord with the antenna on the roof, which is probably very close to 2 meters high.  We can hear each other and understand most of what's said but it's noisy and can get garbled at times.

 

I'm going to get his antenna off the ground by a couple more meters first thing.  If that gets improvement, but not enough, I'll get him a taller antenna (still undecided on what) and better cabling.

 

My plan is to get our tech licenses and then broadcast vhf or uhf to a local repeater, which I can easily hit with my ladder line antenna and my baofeng.  So, knowing that, I'm trying to upgrade his antenna once, and not buy a GMRS specific base antenna.  Looks like Trams are tunable, but not sure about others at this point.  I originally had looked at elk and arrow because they seem to be pretty wide band and are directional.  I figured with those, I may be able to get away with one antenna buy for him.

 

Stay tuned for new results and keep the comments coming guys, I appreciate the help.

 

I am disappointed that there don't seem to be any open repeaters in Columbus Ohio.  When I checked the repeater section here, it showed 2.  Both say private only and one says its down.

Link to comment
Share on other sites

That's what I'm talking about!  I'd like to keep the antenna at 10 feet or less and I'll use fence top rail for a mast to clear the roofline.  I'd like to get a quality antenna that I can tune, then tune back after we get our licenses.  Any recommendations?  Also, if I drive the fence top rail 4 feet in the ground, would I need a separate ground rod?  I'm sure it's not up to code in some areas, but I don't want to start tying into her electric boxes or mess with her ground rod.  I have enough issues with her without being blamed for blowing her electric service :)  I would use a lightning arrester.  

 

Grounding rods are typically 6 feet deep and copper.  For proper protection, you would want to ground the mast and the cable at the mast side, and as close to the radio as possible, with the ground wire being as short as possible.  Use clamps for everything; don't solder.  Lightning will melt solder joints.  During times of the year when lightning occurs in any given operating area, most people disconnect the cables when the radio is not in service.  Proper grounding still doesn't fully arrest direct or near-direct strikes.

 

As far as antennas go, if you are looking at 2m/70cm/GMRS specifically, I have a Diamond X50a on my house.  It has a 1.8:1 SWR on 462 MHz and a 1.6:1 SWR in 467 MHz.  Those are your baseline frequencies for GMRS simplex and repeaters (respectively).  Those are about $100 each.

 

There is another Diamond that could work... but I have zero experience with it and I don't know anyone who has used one.  Keep in mind, multipurpose tools like an all-bander antenna will work, but there will be a compromise on performance compared to dedicated antennas. That said, there is a Diamond Super Discone (like the D130J) that are somewhat of an all-bander antenna, for about $100 each.  For the D130J, specifically, on VHF and UHF its rated for 200 watts.  Below 144MHz, its only rated for 20 watts on FM and 50 watts on SSB.

 

You would want to either buy or borrow and antenna analyzer to dial it in.  Also, order some quality coax cable. 

Link to comment
Share on other sites

Grounding rods are typically 6 feet deep and copper.  For proper protection, you would want to ground the mast and the cable at the mast side, and as close to the radio as possible, with the ground wire being as short as possible.  Use clamps for everything; don't solder.  Lightning will melt solder joints.  During times of the year when lightning occurs in any given operating area, most people disconnect the cables when the radio is not in service.  Proper grounding still doesn't fully arrest direct or near-direct strikes.

 

As far as antennas go, if you are looking at 2m/70cm/GMRS specifically, I have a Diamond X50a on my house.  It has a 1.8:1 SWR on 462 MHz and a 1.6:1 SWR in 467 MHz.  Those are your baseline frequencies for GMRS simplex and repeaters (respectively).  Those are about $100 each.

 

There is another Diamond that could work... but I have zero experience with it and I don't know anyone who has used one.  Keep in mind, multipurpose tools like an all-bander antenna will work, but there will be a compromise on performance compared to dedicated antennas. That said, there is a Diamond Super Discone (like the D130J) that are somewhat of an all-bander antenna, for about $100 each.  For the D130J, specifically, on VHF and UHF its rated for 200 watts.  Below 144MHz, its only rated for 20 watts on FM and 50 watts on SSB.

 

You would want to either buy or borrow and antenna analyzer to dial it in.  Also, order some quality coax cable. 

 

I did buy an analyzer, its the AURSINC Vector Network Analyzer 10KHz -1.5GMHz HF VHF UHF.  Do you know of any videos of how to tune the diamond x50a?  I assume that I'd cut the 70cm section slightly?  Cut radials also?  With the SWR that low, I'd think I'm safe for not blowing up my radio, I may buy that and give it a try as is.  The added height may be all that I need...

Link to comment
Share on other sites

...lose those junk Midland antennas...

 

I have no idea how, but I have talked to a couple of people using the Midland 6db gain antennas on the mag mount, stuck to cookie sheets and they sound great.  I have never gotten that to work with any service.

 

I am using Comet and Diamond antennas for most of my mobiles.  I only have one Midland antenna left, and its going bye-bye very soon.

 

While the midland antenna seems to work okay for me RF performance wise, after less than a year, 2 of the 3 I have broke mechanically.  One, the bottom section snapped off, requiring the antenna to be re-soldered and glued back together (ended up in the trash later anyway).  A second one, the center loading coil broke in half and the top section of the antenna disappeared while cruising down the highway.  The last one I have left has only seen about 2,000 miles in the wind and it looks like a boomerang.  The metal whip sections are not standing up to highway speed winds.

 

So, yea... they are junk.

Link to comment
Share on other sites

I did buy an analyzer, its the AURSINC Vector Network Analyzer 10KHz -1.5GMHz HF VHF UHF.  Do you know of any videos of how to tune the diamond x50a?  I assume that I'd cut the 70cm section slightly?  Cut radials also?  With the SWR that low, I'd think I'm safe for not blowing up my radio, I may buy that and give it a try as is.  The added height may be all that I need...

 

The X50a is pre-tuned.  There is nothing to adjust.  For me it just worked well for GMRS as well as 2m and 440. 

 

The CR8900's are mobile... which I did tune manually.  I would avoid trying to use them at home, though.

Link to comment
Share on other sites

IMHO - you don't have an antenna problem. You've got a radio problem. 3.5 miles with 40 watts in relatively flat terrain in mid Ohio is not a line of sight problem.

 

Those Midlands are quite honestly garbage. You are going to spend a lot of time (and money) trying to make those units perform like actual radios should. Go buy some used Kenwood/Motorola/Vertex radios programmed to GMRS (which will end up costing half as much and work three times better).

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use and Guidelines.