GMRS Base Station Antenna selection

[W8HDU]

@WRFM426 ... you might want to read the doc in the link below to plan what you want to do.

@mmckenna , has good info in getting a licensed electrician to walk through the project, but sometimes you can waste time or hit a dead end when what they recommend doesn't jive with what you planned to do.

The "STANDARDS AND GUIDELINES" book has a lot of good information.

This helped me in the planning of building (5) TV and communication sites, with towers > 500'. None have suffered equipment or building damage, even after multiple strikes.

 

[WRFM426]

I appreciate all the help shown here through the forum. I now have (yet) another question - pertinent to the Base Station antenna questions......
Yagi antennas.... There's a Repeater some 20 miles away which I'd like to connect with...
I was able to build a very useable J-Pole which - as probably mentioned before - is in the attic and acting as a stand-in until the new Laird FG4607 gets installed (getting there, but am getting an electrician to come and advise regarding grounding / bonding - as has been recommended here earlier..)...
I then decided to have a go at building a Yagi. It was moderately successful as a 5 element antenna, but I think I need to try another design - perhaps keep it simple and opt for a 3 element.. running it through my analyzer it appeared to have a main resonance at 504MHz, and at 467MHz - it had a SWR of around 1.9. I was hoping for a better result - hence I'm seeking a new design. If anyone has a good design for a 3 or 5 element GMRS antenna., please let me know..
The questions are threefold:
1. If I mount this Yagi in my attic - rather than outside on my roof-mounted pole - can I simply run suitable coax back to my antenna switch/radio, or do I need to ground it in another way - which, if it was outside, I'd presumably need to do (like I'll be doing with the 4607)..?
2. As a Yagi is going to add some significant gain, which would put the ERP over the 50W limit, do I need to reduce transmitting power accordingly in order to stay legal? BTW reading FCC Part 95 appears to state that for GMRS 'main channels' the transmitter power should not exceed 50W, whereas for interstitial channels ERP is the metric, not transmit power..
3. If my home-made builds are unsuccessful, are there brands that you'd recommend - along with whether I should opt for a 5 element, or 3 element? I know the 5 element will give greater gain, but is of course more expensive..
Your input is anticipated and welcomed..

 

[mmckenna]

The questions are threefold:
1. If I mount this Yagi in my attic - rather than outside on my roof-mounted pole - can I simply run suitable coax back to my antenna switch/radio, or do I need to ground it in another way - which, if it was outside, I'd presumably need to do (like I'll be doing with the 4607)..?

You should.
The roof isn't going to magically stop a lightning bolt if it decides that it likes the look of your antenna. That energy has traveled thousands of feet through the air (air is a pretty good insulator) and it's not going to be stopped by 1/2" plywood and some shingles.

Lightning blows hole through roof of home in St. George

A lightning bolt blew a four foot wide hole through the roof of a St. George home.

www.fox13now.com

The other reason is that even a nearby lightning strike that doesn't hit your antenna can induce enough energy into the antenna and coaxial cable to do damage.

Grounding and lightning protection is still a good idea.

2. As a Yagi is going to add some significant gain, which would put the ERP over the 50W limit, do I need to reduce transmitting power accordingly in order to stay legal? BTW reading FCC Part 95 appears to state that for GMRS 'main channels' the transmitter power should not exceed 50W, whereas for interstitial channels ERP is the metric, not transmit power..

For the primary GMRS channels, the rules only limit transmitter power output, not ERP. So, no, you don't need to lower your transmitter power output to stay below 50 watts ERP.

However, the FCC does like it when you lower your power to the point necessary to establish reliable communications, and no more. That lets other GMRS users utilize those frequencies.

3. If my home-made builds are unsuccessful, are there brands that you'd recommend - along with whether I should opt for a 5 element, or 3 element? I know the 5 element will give greater gain, but is of course more expensive..
Your input is anticipated and welcomed..

Pretty much any of the commercial name brand stuff will work fine. Laird, Larsen, Telewave, etc. Some get expensive, but they are good antennas.
I don't think you'd ever go wrong spending good money on the right antenna for the job.

 

[WRFM426]

You should.
The roof isn't going to magically stop a lightning bolt if it decides that it likes the look of your antenna. That energy has traveled thousands of feet through the air (air is a pretty good insulator) and it's not going to be stopped by 1/2" plywood and some shingles.

Lightning blows hole through roof of home in St. George

A lightning bolt blew a four foot wide hole through the roof of a St. George home.

www.fox13now.com

The other reason is that even a nearby lightning strike that doesn't hit your antenna can induce enough energy into the antenna and coaxial cable to do damage.

Grounding and lightning protection is still a good idea.



For the primary GMRS channels, the rules only limit transmitter power output, not ERP. So, no, you don't need to lower your transmitter power output to stay below 50 watts ERP.

However, the FCC does like it when you lower your power to the point necessary to establish reliable communications, and no more. That lets other GMRS users utilize those frequencies.



Pretty much any of the commercial name brand stuff will work fine. Laird, Larsen, Telewave, etc. Some get expensive, but they are good antennas.
I don't think you'd ever go wrong spending good money on the right antenna for the job.

@mmckenna
Appreciated.. makes sense..
If I go the ‘purchased Yagi’ route, I may as well mount it on the pole & and put a lightning arrestor in line. I’m also planning on mounting a grounding bar outside and below the pole to which the pole itself, the Omni antenna / lightning arrestor and the grounding wire (to the bonded grounding rod) will all be attached.
Any additional antennas (including the potential Yagi..) can therefore be grounded via their lightning arrestors mounted onto the same bar.
Does that seem reasonable?

While testing the home-made Yagi - or any antenna for that matter - (& disconnecting from radio after testing…), does it need to be grounded for effective usability.. or is the co-ax itself a sufficient ground?

 

[mmckenna]

Does that seem reasonable?

Yes, if you expect to be active in the hobby, planning for more is always a good idea. Doing it right the first time will always save you money.

While testing the home-made Yagi - or any antenna for that matter - (& disconnecting from radio after testing…), does it need to be grounded for effective usability.. or is the co-ax itself a sufficient ground?

For permanent installation, you want it grounded.
For testing, it doesn't need to be grounded in the sense of connecting it to a ground rod. Some antenna designs, mostly mobile type, do need a ground plane underneath them. Ground planes are part of the antenna, not part of the lightning protection system.

 

[prcguy]

Grounding a UHF Yagi and most any VHF/UHF antenna is only for safety and has nothing to do with performance.

@mmckenna

While testing the home-made Yagi - or any antenna for that matter - (& disconnecting from radio after testing…), does it need to be grounded for effective usability.. or is the co-ax itself a sufficient ground?

 

[W8HDU]

If I go the ‘purchased Yagi’ route, I may as well mount it on the pole & and put a lightning arrestor in line.

Just a word of caution. A "lightning arrestor" does little to mitigate a lightning strike and damage to home and equipment inside. Arrestors are for comfort only, as they do little to prevent the ingress of the lightning into the home.

Read mmckenna's post #63. If lightning can mile or more across the sky, do you think a 3" long "arrestor" will stop it from getting in?

Lightning can not be stopped nor discouraged. Lightning takes the easiest path to ground, and on arrestors it's usually along the shield of the coax and arrestor.

What you can do is give lightning a least path of resistance to ground away from the home and equipment. If it strikes the antenna, arrestor or 3-point grounding, the antenna is toast. But by keeping the lightning from entering the home you save the home and equipment inside.

 

[WRFM426]

Keep the run outside.
As for the gas line, I believe there needs to be some separation, but you need to talk to a licensed electrician regarding that. I'm not going to guess, and it is important to get accurate advice. Hobby sites like this aren't a good source.

Not sure I'm fully understanding you,
But, yes, all your grounding rods need to be bonded together. You can run multiple ground rods and connect them with your 6 gauge run on it's way back to the house ground rod. In fact, I think it's required/suggested(?) to have grounding rods along that length.

Again, a licensed electrician is a REALLY good investment, even if you hire the guy for an hour and have him walk the job with you.

Does the 6AWG bonding wire need to be one continuous length from antenna mounting pole, via external grounding bar, to first grounding rod, and thence to external electrical grounding rod, or can I use appropriate 6AWG lengths to connect each item. Thus one piece from mounting pole to grounding bar (where surge protector(s) are to be located) is/are mounted, and another piece from there to the grounding rod, and yet another (bonding wire) between grounding rods?
I have read that the grounding / bonding wire should not go through tight bends, rather sweeping wider radius turns, but presumably, normally the grounding wire to the antenna grounding rod will then take a 90 degree turn as it proceeds as bonding wire to the electrical grounding rod?
Question is therefore whether it's OK for the bonding wire to take sharp turns (Option 2), i.e. it is just the main antenna grounding wire that needs to keep wider radius turns (Option 1)?
See pic: Option 1 - radius / Option 2 - right angle

 

[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.

I purchased the Heliax (and the FG4607) - as recommended. A question now about routing of the Heliax...
After leaving the surge protector mounted on the grounding bar on the outside wall of the house, I will then need to get the Heliax in through the wall into the attic space.
As the Heliax can only cope with wide bends, is there a recommended wall-mounted box or conduit fitting that will allow me to get the Heliax through the wall in such a way to keep the weather (and bees & hornets..!) out and potentially allow for the passing through of other coax cable in the future..?
I'm having trouble finding something suitable.. Any ideas or recommendations ?

 

[ramal121]

Used at commercial sites...

Cable Entry Systems - Talley LLC - Top supplier of wireless and mobile products

Talley LLC - Leading supplier of wireless communications infrastructure and mobile products. Talley stocks a wide variety of infrastructure products.

www.talleycom.com

 

[mmckenna]

Does the 6AWG bonding wire need to be one continuous length from antenna mounting pole, via external grounding bar, to first grounding rod, and thence to external electrical grounding rod, or can I use appropriate 6AWG lengths to connect each item. Thus one piece from mounting pole to grounding bar (where surge protector(s) are to be located) is/are mounted, and another piece from there to the grounding rod, and yet another (bonding wire) between grounding rods?

One continuous length would be ideal, but not required.

I have read that the grounding / bonding wire should not go through tight bends, rather sweeping wider radius turns, but presumably, normally the grounding wire to the antenna grounding rod will then take a 90 degree turn as it proceeds as bonding wire to the electrical grounding rod?
Question is therefore whether it's OK for the bonding wire to take sharp turns (Option 2), i.e. it is just the main antenna grounding wire that needs to keep wider radius turns (Option 1)?
See pic: Option 1 - radius / Option 2 - right angle

Correct, sharp angles should be avoided since the energy might use that as a point to jump off to other paths to ground.
At the rod, that doesn't matter as it'll be right at the ground rod and at ground level.

If you can do one continuous run of conductor, that's ideal. If you need to run two lengths, your "option 2" should be fine.

 

[mmckenna]

Used at commercial sites...

Cable Entry Systems - Talley LLC - Top supplier of wireless and mobile products

Talley LLC - Leading supplier of wireless communications infrastructure and mobile products. Talley stocks a wide variety of infrastructure products.

www.talleycom.com

I've used a few of those items before. The work well and make life easy.

They tend to be designed for larger cables, so if you are only running 1/2" heliax, it might be a bit large for what is needed.

You can go to your local hardware store and get a short length of conduit to stub through the wall and a weatherhead to cover the entrance.
It should solve the bug access issues. You can also squirt some foam or conduit block in there to seal it up a bit better. Some have even used steel wool (use stainless or other suitable material if it gets humid/wet)

 

[WRFM426]

Gentlemen: thank you both..
I'm rapidly finding out that the radio transceiver ends up being but a small portion of the overall project costs...! Pole mount, antenna(s), Heliax / coax jumpers / connectors, grounding wire / rods, etc etc..! Anyway, your inputs are much appreciated!

Last question (for now...): is Browning a reputable Yagi antenna manufacturer?
I'm looking at a Yagi (Browning BR-6355) to hit a distant Repeater, but I have no idea of this antenna's quality. Looks like Radio Research Inc. in NY has this for $92, which struck me as a reasonable price..
The Laird Y4505 runs at double the price - around $189.. Does the Laird represent twice the value?
If any quality issue relates to weather resilience, could I not simply mount the Yagi in my attic to protect it? Would there be a significant signal degradation attic-mounted rather than say externally mounted? Obviously the extra 10 feet if mounted on a pole may well help, but regarding roof shingles / wood, etc, are they going to be much of a hindrance to the Yagi's reception / transmission?

 

[mmckenna]

Gentlemen: thank you both..
I'm rapidly finding out that the radio transceiver ends up being but a small portion of the overall project costs...! Pole mount, antenna(s), Heliax / coax jumpers / connectors, grounding wire / rods, etc etc..! Anyway, your inputs are much appreciated!

On a commercial/public safety system, it is not uncommon to spend as much on the antenna system as you would on the repeater/base station itself.

You've learned something valuable that many fail to pick up on. Too many hobbyists will spend $500 on the latest and/or greatest radio, and then toss a $20 Chinese mag mount antenna on the roof and call it good.
Shortly later, they are trying to figure out why their $500 whizz and/or bang radio works like it has a $20 Chinese antenna connected to it.

Last question (for now...): is Browning a reputable Yagi antenna manufacturer?
I'm looking at a Yagi (Browning BR-6355) to hit a distant Repeater, but I have no idea of this antenna's quality. Looks like Radio Research Inc. in NY has this for $92, which struck me as a reasonable price..
The Laird Y4505 runs at double the price - around $189.. Does the Laird represent twice the value?
If any quality issue relates to weather resilience, could I not simply mount the Yagi in my attic to protect it? Would there be a significant signal degradation attic-mounted rather than say externally mounted? Obviously the extra 10 feet if mounted on a pole may well help, but regarding roof shingles / wood, etc, are they going to be much of a hindrance to the Yagi's reception / transmission?

Tram/Browning are in the Cheap Chinese Antenna category. Similar to the Cheap Chinese Radios.
They work fine for some, but you won't normally see them in a commercial/public safety application.

It may work fine for you.

A lot of their products appear to be knock-offs of legit brands. I wouldn't be surprised if they are made in the same Chinese factories.
I've tried one or two of their products, and was not impressed.

If reliability is a concern, and budget isn't, the Laird would be worth the extra cost. You'd probably get a lot longer useful life out of it than the Tram/Browning.

Mounting it in the attic can work if there isn't any RF opaque building materials in the way. Keep in mind that "line of sight" is important on these higher frequencies, so getting the antenna up higher and in the clear can make a difference.

 

[WRFM426]

On a commercial/public safety system, it is not uncommon to spend as much on the antenna system as you would on the repeater/base station itself.

You've learned something valuable that many fail to pick up on. Too many hobbyists will spend $500 on the latest and/or greatest radio, and then toss a $20 Chinese mag mount antenna on the roof and call it good.
Shortly later, they are trying to figure out why their $500 whizz and/or bang radio works like it has a $20 Chinese antenna connected to it.

Tram/Browning are in the Cheap Chinese Antenna category. Similar to the Cheap Chinese Radios.
They work fine for some, but you won't normally see them in a commercial/public safety application.

It may work fine for you.

A lot of their products appear to be knock-offs of legit brands. I wouldn't be surprised if they are made in the same Chinese factories.
I've tried one or two of their products, and was not impressed.

If reliability is a concern, and budget isn't, the Laird would be worth the extra cost. You'd probably get a lot longer useful life out of it than the Tram/Browning.

Mounting it in the attic can work if there isn't any RF opaque building materials in the way. Keep in mind that "line of sight" is important on these higher frequencies, so getting the antenna up higher and in the clear can make a difference.

The attic has decent elevation and thus pretty good line of sight. With the 'right' weather conditions, I can hit the Repeater in question even with my home-made J-Pole (also in the attic..)
I learned this valuable lesson (product quality / you get what you pay for..) many moons ago, and have often been criticized for it. (For the record, I was leaning towards the Laird anyway...)
Short story: once, when we first came to the USA, I was in search of a 'decent' grip wrench - something akin to the quality UK/German/Swedish tools... When I was told that the store version was a 'bargain' at $9.99, I asked whether they had anything more expensive. The store person was bemused... I explained that often (not always) price correlates with quality. The store had nothing that looked like it was a quality product, so I looked elsewhere..
Other parallels: putting a cheap cartridge on your expensive record deck (that might date me somewhat...), putting a cheap 'scope on your expensive rifle, putting a cheap lens on an expensive camera body... putting a cheap hifi preamp in front of a decent power amp...one could go on..

 

[mmckenna]

The attic has decent elevation and thus pretty good line of sight. With the 'right' weather conditions, I can hit the Repeater in question even with my home-made J-Pole (also in the attic..)

Should work just fine.

Other parallels: putting a cheap cartridge on your expensive record deck (that might date me somewhat...), putting a cheap 'scope on your expensive rifle, putting a cheap lens on an expensive camera body... putting a cheap hifi preamp in front of a decent power amp...one could go on..

Cheap tires on your car.
Cheap boots on your feet.

If it's something that you are going to rely on and use frequently, it's almost always worth putting the extra effort into it.
However, some things are overpriced but do not have the quality to match.

 

[prcguy]

I would search for a used Phelps Dodge/Celwave or DB Products or Laird or Cushcraft or Antenna Specialists or Kathrein Scala or Motorola or Comtelco or similar 7 element 10dBd gain Yagi on eBay. They come up all the time for good prices like $35 with some shipping.

On a commercial/public safety system, it is not uncommon to spend as much on the antenna system as you would on the repeater/base station itself.

You've learned something valuable that many fail to pick up on. Too many hobbyists will spend $500 on the latest and/or greatest radio, and then toss a $20 Chinese mag mount antenna on the roof and call it good.
Shortly later, they are trying to figure out why their $500 whizz and/or bang radio works like it has a $20 Chinese antenna connected to it.



Tram/Browning are in the Cheap Chinese Antenna category. Similar to the Cheap Chinese Radios.
They work fine for some, but you won't normally see them in a commercial/public safety application.

It may work fine for you.

A lot of their products appear to be knock-offs of legit brands. I wouldn't be surprised if they are made in the same Chinese factories.
I've tried one or two of their products, and was not impressed.

If reliability is a concern, and budget isn't, the Laird would be worth the extra cost. You'd probably get a lot longer useful life out of it than the Tram/Browning.

Mounting it in the attic can work if there isn't any RF opaque building materials in the way. Keep in mind that "line of sight" is important on these higher frequencies, so getting the antenna up higher and in the clear can make a difference.

 

[WRFM426]

I would search for a used Phelps Dodge/Celwave or DB Products or Laird or Cushcraft or Antenna Specialists or Kathrein Scala or Motorola or Comtelco or similar 7 element 10dBd gain Yagi on eBay. They come up all the time for good prices like $35 with some shipping.

Good advice..! I am awaiting the arrival of a used Laird Y4505 which cost $30 on eBay..

 

[prcguy]

The Y4505 is a 7dBd antenna but you got it at a great price. It takes at least 7elements to reach 10dBd gain.

Good advice..! I am awaiting the arrival of a used Laird Y4505 which cost $30 on eBay..

 

[WRFM426]

The Y4505 is a 7dBd antenna but you got it at a great price. It takes at least 7elements to reach 10dBd gain.

the distance from my radio to where I'm going to place the Yagi is approx 20ft. Is RG8X good enough for that distance or should I go with 9913 or LMR400? Will there be a noticeable difference?


Similarly, my J-Pole is up in the attic approx 45-50 feet away, and current coax is also RG8X to that. Again, would replacing it with either 9913 or LMR400 make a noticeable difference?

Once the FG4607 is mounted, I'll be using Heliax for that (approx 60 feet away..)..