GMRS Base Station Antenna selection

[WRFM426]

New to this group, and fairly new to GMRS...
I live in a slightly hilly/wooded area of Massachusetts, and am looking to set up a GMRS Base Station to communicate with friends and family in the surrounding area. With an HT I get ~3miles from my house (ground floor) to a number of locations, so am thinking that a base station with a suitable antenna say 10ft above my roof should extend that reach.
Currently and specifically, I am looking a few antennas, such as:
- Laird FG4603 / 4605
- CommScope DB-404B
- DPD GMRS Vertical Outdoor Base Antenna
As a more general question too: what are the relative merits of a dipole vs a linear antenna?
Depending on how this part of the 'project' goes, I may consider later setting up a Repeater..
Your thoughts and assistance would be much appreciated..

 

[ladn]

Welcome to RR.
In addition to whichever antenna you choose, you'll need feedline (coax) to connect your transceiver to the antenna.
All coax cables have signal loss, but how much depends on the cable length and operational frequencies. GMRS operates in the 462/467 MHz area and the amount of signal loss in any given cable increases with frequency.

You'll need to figure out how long the cable run will be from the antenna to the radio and purchase your cable accordingly. My guess is that your run will be 50'-100'. You will want a decent quality cable, like Times LMR 400. Here's a link to the Times cable loss calculator: calculator - Times Microwave Systems. Buy genuine, quality cable, not some cheap, unbranded, stuff from eBay or Amazon. Times Microwave is an excellent brand. The Antenna Farm is a good vendor for cables and antennas.

Since this will be an outdoor installation, you will also need a lighting arrestor and a short run of flexible cable to connect to the radio as LMR 400, and similar cables aren't very bendy and tend to strain connectors.

There's a lot of info here on RR about cables, lightning arrestors antennas, installations and setting up your own repeater.

 

[prcguy]

Nearly all the performance of a GMRS base station is in the antenna system, which includes the antenna, the feedline and height. Of the three antennas you list I would say DPD, no. DB-408, expensive and no. Laird 4605 no, go bigger and get the 4607 rated 7dBd or 9.15dBi gain at the very minimum.

Many antenna gain figures are made up lies but I would trust DB Products and Laird. There are probably other suitable antennas but the Laird is ok, especially for the price.

For the feedline, with no repeater you can get away with LMR400 or larger but if a repeater is going to happen don't use LMR cable and go with Commscope Heliax like LDF4-50A for runs up to 50ft long or LDF5-50A for runs up to about 100ft. LMR cables have dissimilar metals and can produce IMD in a full duplex system which will introduce interference and degrade reception.

Where in MA are you? I'm typing this from the Boston airport trying to get home.

 

[WRFM426]

Welcome to RR.
In addition to whichever antenna you choose, you'll need feedline (coax) to connect your transceiver to the antenna.
All coax cables have signal loss, but how much depends on the cable length and operational frequencies. GMRS operates in the 462/467 MHz area and the amount of signal loss in any given cable increases with frequency.

You'll need to figure out how long the cable run will be from the antenna to the radio and purchase your cable accordingly. My guess is that your run will be 50'-100'. You will want a decent quality cable, like Times LMR 400. Here's a link to the Times cable loss calculator: calculator - Times Microwave Systems. Buy genuine, quality cable, not some cheap, unbranded, stuff from eBay or Amazon. Times Microwave is an excellent brand. The Antenna Farm is a good vendor for cables and antennas.

Since this will be an outdoor installation, you will also need a lighting arrestor and a short run of flexible cable to connect to the radio as LMR 400, and similar cables aren't very bendy and tend to strain connectors.

There's a lot of info here on RR about cables, lightning arrestors antennas, installations and setting up your own repeater.

Much appreciate the prompt response: yup, I was considering LMR400 as the main antenna feed.

 

[WRFM426]

Nearly all the performance of a GMRS base station is in the antenna system, which includes the antenna, the feedline and height. Of the three antennas you list I would say DPD, no. DB-408, expensive and no. Laird 4605 no, go bigger and get the 4607 rated 7dBd or 9.15dBi gain at the very minimum.

Many antenna gain figures are made up lies but I would trust DB Products and Laird. There are probably other suitable antennas but the Laird is ok, especially for the price.

For the feedline, with no repeater you can get away with LMR400 or larger but if a repeater is going to happen don't use LMR cable and go with Commscope Heliax like LDF4-50A for runs up to 50ft long or LDF5-50A for runs up to about 100ft. LMR cables have dissimilar metals and can produce IMD in a full duplex system which will introduce interference and degrade reception.

Where in MA are you? I'm typing this from the Boston airport trying to get home.

Thanks; good to know re the Laird.
I’ll take a look into the Heliax, as it might be worth biting the bullet now rather than another cable purchase later..
I’m in the town of Harvard - 35 miles west of Boston.

 

[WRFM426]

Nearly all the performance of a GMRS base station is in the antenna system, which includes the antenna, the feedline and height. Of the three antennas you list I would say DPD, no. DB-408, expensive and no. Laird 4605 no, go bigger and get the 4607 rated 7dBd or 9.15dBi gain at the very minimum.

Many antenna gain figures are made up lies but I would trust DB Products and Laird. There are probably other suitable antennas but the Laird is ok, especially for the price.

For the feedline, with no repeater you can get away with LMR400 or larger but if a repeater is going to happen don't use LMR cable and go with Commscope Heliax like LDF4-50A for runs up to 50ft long or LDF5-50A for runs up to about 100ft. LMR cables have dissimilar metals and can produce IMD in a full duplex system which will introduce interference and degrade reception.

Where in MA are you? I'm typing this from the Boston airport trying to get home.

Just a thought - as I only listed three antennas, and there are many others to choose from: what would recommend/suggest as preferred or better alternatives..?
BTW, I have been unable to find any online reviews of the FG series antennas..

 

[mmckenna]

Selecting an antenna involves a lot of individual decisions.
You need to consider your location in relation to where you want coverage. Is it something that an omnidirectional antenna will do, or do you need to focus coverage in certain areas? No point in blasting power into the side of a hill or in a direction you don't need coverage.
What's your budget? Good antennas for UHF can cost upwards of $2K. No point in someone recommending a $2000 antenna if your budget is $500.
What is your mounting situation? For some of the really good high gain antennas, you'll need a substantial mount to support it during a storm/icing.
What are your neighbors/wife going to let you get away with?

Spending 2 grand on an antenna you can only raise 10 feet above your home might be kind of pointless. You should look at what your coverage plots would look like with the antenna at various heights. 3 miles from a hand held is good, but if topology is going to keep you from having a clear view out past 3 miles, there's little point in putting in a high gain antenna and heating up the side of a hill.

But, it's really good to consider all your options now. A good antenna and good feedline will pay off in the long run. A lot of people start with a low budget, cheap antenna, cheaper coax, and then decide they should have purchased better equipment. Or, as they say "buy once, cry once".

 

[WRFM426]

Thx for the response..
I was considering antenna for under $500, with coax & connectors budgeted separately.
I’ll need omni rather than directional.
Thinking max of 10ft mounting pole on end of house or perhaps - if chimney - less than 10ft pole.

 

[mmckenna]

$500 limits you a bit, but you can still get some nice antennas for less than that.

I ran a Laird fiberglass antenna for many years on GMRS. I'm in a valley, so high gain wasn't called for. It was a unity gain, about 2 feet tall. Lasted year until I no longer needed it. Sold it off at some point.

Laird makes a 7dB version that's about 9 feet long that would probably be manageable, much larger and you're going to have issues supporting it. FG4609, I think. 7dB will focus more of your signal out to the horizon, so it should give you pretty good range out to the point that the topology gets in your way.

A 2 bay folded dipole would be nice, but you'd be hard pressed to find a new one under your budget.

Be careful with the Chinese/amateur/hobby grade antennas. The antenna is really important for your system, and you don't want to cut corners or install something that's going to fail after a few years. Especially if you are running a repeater.

There's probably some good used stuff out there, but you really need to know what you are looking at.

As for coax, not sure how long your run is, but if a repeater is in the long term plans, go with the Heliax now. It'll save you replacing a lesser cable down the road. In reality, most of the cost is in installation. I know, you'll install it yourself, but don't forget your time has value.

 

[WRFM426]

Again, I very much appreciate the time you’re taking on this..
I noticed that Digi-Key (https://www.digikey.com/en/products/filter/rf-antennas/875?s=N4IgTCBcDaIGIHMAsA2ADCAugXyA) has the FG4607 at a significantly lower price that elsewhere and shows the manufacturer as ‘TE Connectivity Laird’.. is this likely to be the ‘real deal’ product or a Chinese copy?

 

[tweiss3]

That appears to be a legit Laird. I had/have a Laird that was 1 model range above GMRS that I used for my repeater until the tower went up. They are good antennas.

 

[jeepsandradios]

You can get the 4607 from Antenna Farm for $210.

Antenna Farm Laird 4607

Remember mounting brackets are separate and run about $30.00. I have ordered alot of stuff over the years from this site.

 

[WRFM426]

You can get the 4607 from Antenna Farm for $210.

Antenna Farm Laird 4607

Remember mounting brackets are separate and run about $30.00. I have ordered alot of stuff over the years from this site.

Ah: good to know. Thanks for the tip..

 

[Project25_MASTR]

I'm with @mmkenna.

Assessing needed coverage areas versus wishful coverage areas and selecting antenna based on that is vastly more important in a lot of cases. One of my favorite examples is I used to go in and correct a ton of warehouse coverage issues in the 460 MHz range. 100% of the time, a previous shop had come in and put either a 3 dBd or 6 dBd antenna on the roof and just let a basic repeater with a notch only duplexer run at full power. Most of the time, I would end up installing a 0 dBd antenna such as an FG4500 (if budget were a concern) or a Telewave ANT450D, run new feedline (would sit down with customer and weigh pros and cons of LMR400 versus 1/2" corrugated) and pulling the repeater back to 10-15W of power and magically all of the coverage issues they had been dealing with since day one would be gone because I optimized the performance of the antenna system and selected an antenna that actually covered the area underneath were it was mounted instead of throwing most of it's energy towards the horizon.

So evaluate what you need and select your antenna accordingly. Trying to cover above or below your location (on a hill or in a valley/depression) a 0 dBd antenna works really well typically. Higher gain will concentrate more RF energy towards the horizon and limit the above/below coverage aspects.

 

[prcguy]

While low gain antennas have their place in saturating a vertically challenged area, in my experience with low level GMRS repeaters is you can't have too much gain at the horizon. The goal on this type repeater is to extend coverage as far as possible for everything from 2 watt HTs to 50 watt mobiles. I've experimented with many of these setups and in all cases going big on the antenna is what gave the best coverage, assuming no LMR cable and everything else is in good shape.

Usually these repeaters are on a house or some donated space that rarely extends above a 3 story building and if you are lucky its on a small hill. Coverage can be grim compared to high mountaintop or 500+ ft towers but these repeaters are often cobbled together with whatever equipment and real estate is available cheap or free.

Anyway, when I went through several different antennas on low level GMRS repeaters I got considerable distance on 7 to 10dBd gain types over ground plane and 3dB types. It really pays to go big and go as high as possible for low level repeater antennas that are not serving just a tall building or warehouse type environment. It also seems more than one post here is recommending the 7dBd gain Laird 4607, its not bad for the price.

I'm with @mmkenna.

Assessing needed coverage areas versus wishful coverage areas and selecting antenna based on that is vastly more important in a lot of cases. One of my favorite examples is I used to go in and correct a ton of warehouse coverage issues in the 460 MHz range. 100% of the time, a previous shop had come in and put either a 3 dBd or 6 dBd antenna on the roof and just let a basic repeater with a notch only duplexer run at full power. Most of the time, I would end up installing a 0 dBd antenna such as an FG4500 (if budget were a concern) or a Telewave ANT450D, run new feedline (would sit down with customer and weigh pros and cons of LMR400 versus 1/2" corrugated) and pulling the repeater back to 10-15W of power and magically all of the coverage issues they had been dealing with since day one would be gone because I optimized the performance of the antenna system and selected an antenna that actually covered the area underneath were it was mounted instead of throwing most of it's energy towards the horizon.

So evaluate what you need and select your antenna accordingly. Trying to cover above or below your location (on a hill or in a valley/depression) a 0 dBd antenna works really well typically. Higher gain will concentrate more RF energy towards the horizon and limit the above/below coverage aspects.

 

[WRFM426]

Looking at the specs of the FG4603 / 4605 / 4607, it seems that vertical beam angle is 33, 27, 26 degrees, gain is 3dB, 5dB, 7dB, and antenna lengths are 44', 60", 107" accordingly.
Bearing in mind that my location is not 'ideal' - i.e. towards the upper side of a hill but surrounded by trees (not too dense), how do I determine whether vertical beam angle or gain is the preferred characteristic?
The 'phase 1' part of my project was to install a base station then as a phase 2, convert base station to a repeater. If that is the end goal, is it better to have more gain and narrower vertical beam, or less gain and broader beam angle?
Ideally I want to make just a single purchase, rather than modify the antenna later on.
As mentioned before I can get approx 3 miles on HT to HT from my house to slightly lower elevations - to the West.
I'm at approx 370ft with hills up to ~550 ft a mile or so behind me (east), and a river Valley down at ~200ft to the West.
Also should I try to get as high as possible above my roof line? I was planning on a 10ft pole mount with antenna atop it..
If I went for the 4605 or 4607, then I'm a bit leery adding too much pole height as the brackets will be at the roof apex end wall of the house..

 

[WRFM426]

While low gain antennas have their place in saturating a vertically challenged area, in my experience with low level GMRS repeaters is you can't have too much gain at the horizon. The goal on this type repeater is to extend coverage as far as possible for everything from 2 watt HTs to 50 watt mobiles. I've experimented with many of these setups and in all cases going big on the antenna is what gave the best coverage, assuming no LMR cable and everything else is in good shape.

Usually these repeaters are on a house or some donated space that rarely extends above a 3 story building and if you are lucky its on a small hill. Coverage can be grim compared to high mountaintop or 500+ ft towers but these repeaters are often cobbled together with whatever equipment and real estate is available cheap or free.

Anyway, when I went through several different antennas on low level GMRS repeaters I got considerable distance on 7 to 10dBd gain types over ground plane and 3dB types. It really pays to go big and go as high as possible for low level repeater antennas that are not serving just a tall building or warehouse type environment. It also seems more than one post here is recommending the 7dBd gain Laird 4607, its not bad for the price.

Apologies: I missed your post recommending the higher gain 4607.
It may make redundant my post below.
How high can I safely go on a pole mount - assuming that I twill use two brackets for the end wall perhaps space 2ft apart - meaning that there could be nearly 3ft of pole below the roof apex on the end wall..

 

[tweiss3]

Looking at the specs of the FG4603 / 4605 / 4607, it seems that vertical beam angle is 33, 27, 26 degrees, gain is 3dB, 5dB, 7dB, and antenna lengths are 44', 60", 107" accordingly.
Bearing in mind that my location is not 'ideal' - i.e. towards the upper side of a hill but surrounded by trees (not too dense), how do I determine whether vertical beam angle or gain is the preferred characteristic?
The 'phase 1' part of my project was to install a base station then as a phase 2, convert base station to a repeater. If that is the end goal, is it better to have more gain and narrower vertical beam, or less gain and broader beam angle?
Ideally I want to make just a single purchase, rather than modify the antenna later on.
As mentioned before I can get approx 3 miles on HT to HT from my house to slightly lower elevations - to the West.
I'm at approx 370ft with hills up to ~550 ft a mile or so behind me (east), and a river Valley down at ~200ft to the West.
Also should I try to get as high as possible above my roof line? I was planning on a 10ft pole mount with antenna atop it..
If I went for the 4605 or 4607, then I'm a bit leery adding too much pole height as the brackets will be at the roof apex end wall of the house..

If you look at the datasheet, it shows elevation pattern:

For the 4607, you get 7db of gain towards the horizon (because there is 0 degrees of downtilt). That gain width is about 27 degrees. Look at the pattern above.

 

[prcguy]

I've had past conversations with at least two different antenna mfr application engineers and they all agree a 10dBd gain antenna is good for up to about 1,000ft AGL. I doubt if your on a hill that approaches that height, so a 7dBd gain antenna should have no problems with weak or dead zones around the base of a hill. The 33deg 1/2 power beamwidth on the 7dBd gain Laird FG4607 means that at 16.5 degrees above and below the horizon the gain will have dropped by half or 3dB. Those would be the 4dBd gain points of the antenna at those extreme up and down angles.

The more gain an omni antenna has the narrower the half power beamwidth will be, but that doesn't mean it cuts off sharply and there is no signal at all above or below those half power points. An antenna has a main lobe, which is what is advertised and there lots of smaller lobes with lower gain that fill in the areas outside the main lobe to some extent. If I were in your type of terrain I would try and find a 10dBd gain stick, but those can be hard to find at a good price and I would be satisfied with a 7dBd gain model which is more affordable. That's why I have a couple of new ones in the garage along with a dozen other types for those pop up repeater projects.

Looking at the specs of the FG4603 / 4605 / 4607, it seems that vertical beam angle is 33, 27, 26 degrees, gain is 3dB, 5dB, 7dB, and antenna lengths are 44', 60", 107" accordingly.
Bearing in mind that my location is not 'ideal' - i.e. towards the upper side of a hill but surrounded by trees (not too dense), how do I determine whether vertical beam angle or gain is the preferred characteristic?
The 'phase 1' part of my project was to install a base station then as a phase 2, convert base station to a repeater. If that is the end goal, is it better to have more gain and narrower vertical beam, or less gain and broader beam angle?
Ideally I want to make just a single purchase, rather than modify the antenna later on.
As mentioned before I can get approx 3 miles on HT to HT from my house to slightly lower elevations - to the West.
I'm at approx 370ft with hills up to ~550 ft a mile or so behind me (east), and a river Valley down at ~200ft to the West.
Also should I try to get as high as possible above my roof line? I was planning on a 10ft pole mount with antenna atop it..
If I went for the 4605 or 4607, then I'm a bit leery adding too much pole height as the brackets will be at the roof apex end wall of the house..

 

[tweiss3]

Apologies: I missed your post recommending the higher gain 4607.
It may make redundant my post below.
How high can I safely go on a pole mount - assuming that I twill use two brackets for the end wall perhaps space 2ft apart - meaning that there could be nearly 3ft of pole below the roof apex on the end wall..

I have 10' of mast from the top of my repeater tower at my house. I would say 10' its pretty much the max without guy wires.