GMRS Base Station Antenna selection

[W8HDU]

I wonder how the Antenna Specialist ASPD-701 would work. I still have a few of them from our old RPU system. I still think the Decibel Products DB-420 was better for coverage.

 

[prcguy]

An ASPD-701 would work great and better than the Laird FG4607. A DB420 is slightly better than an ASPD-701.

I wonder how the Antenna Specialist ASPD-701 would work. I still have a few of them from our old RPU system. I still think the Decibel Products DB-420 was better for coverage.

 

[WRFM426]

1.25" EMT is what I typically used. Cheap and works well. For a wall mount I'd typically pair it with an WM-4 mount or the larger one if I needed to get around an eve. Can't tell you how many control station setups I built like that...

 

[WRFM426]

A question of grounding..
My antenna will be at the top of the 10ft galvanized pole mounted with a WMD-12 onto the end of the house.
The electrical service line enters the house probably 50ft away. The main electrical ground rod is in the basement - set into the concrete floor…
I was planning on placing an 8ft grounding rod in the ground directly below the antenna, running a 6AWG bare copper wire to the grounding rod as a straight run (about 30ft) from the antenna pole.
In addition the lightning arrestor will be mounted on the outside wall 12ft from the antenna. From there the coax will enter the attic and thence to my office where the transceiver will be located.
The lighting arrestor will also be grounded to the grounding rod (about a 20ft run).
Lastly I will run a bonding wire from the antenna’s grounding rod over to the house electrical grounding rod (in basement).
Does that setup seem OK?
Btw, I’m reading the ARRL Grounding & Bonding book…..

 

[prcguy]

If you run a 6ga copper wire from any new ground rod to the main house ground rod, everything else sounds like it meets NEC. Just be aware that your GMRS radio, antenna and much of your home electronics will probably never survive a direct lightning strike to the new antenna.

A question of grounding..
My antenna will be at the top of the 10ft galvanized pole mounted with a WMD-12 onto the end of the house.
The electrical service line enters the house probably 50ft away. The main electrical ground rod is in the basement - set into the concrete floor…
I was planning on placing an 8ft grounding rod in the ground directly below the antenna, running a 6AWG bare copper wire to the grounding rod as a straight run (about 30ft) from the antenna pole.
In addition the lightning arrestor will be mounted on the outside wall 12ft from the antenna. From there the coax will enter the attic and thence to my office where the transceiver will be located.
The lighting arrestor will also be grounded to the grounding rod (about a 20ft run).
Lastly I will run a bonding wire from the antenna’s grounding rod over to the house electrical grounding rod (in basement).
Does that setup seem OK?
Btw, I’m reading the ARRL Grounding & Bonding book…..

 

[W8HDU]

What PRC said. You can never prevent lightning. What you can do is give it a choice of a better path to take. In my installation at home, the tower sits away from the house. (3) 12' ground rods are placed at the same angle as the tower legs from center of tower, and 6' away from the leg. Solid copper ground is a bad idea. Good for RF radials, bad for lightning. The best bet is to weave #16s or #12s using a drill, alternated directions, and take them off the leg to the rods.

If the antenna is at the top, there is little you can do to protect it, other than a plan for replacing it easily. I come off the antenna with a section of coax to the tower, or below the rotor, with one of these clamps. The the transmission line goes to the shack grounded at the base of the tower, and before it goes in the house. The clamp allows you to take off the antenna without having to take your line down. If the line needs to come down, that can also be disconnected and taken down. If the antenna is not at the top (bare top of tower), install a static cat to drain off as much charge as possible before taking a whollop.

I've had to deal with lightning on big broadcast towers, and small comm towers since I've been in the business. 1972 to present. If there is one given it's that if lightning can jump across 3 miles a sky, a Radio Shack arrestee or other cheap device won't help you. Lightning will hit where it wants to. But you can control it's path to a point.

Also, regarding towers in cement. Don't count on the bottom of the leg touching ground as your "ground". I've seen tower bases reduced to gravel because of steam explosions from the strike. Put in (3) rods away from the leg of the tower in different directions as mentioned above. That way the energy is more likely to take the best path, which is away from the base/cement.

If the mast is mounted to the house, think about where that energy will go if the antenna or mast gets hit. Most of the time it goes down the side of the house, ingressing where it can to electrical service.

 

[WRFM426]

Laird FG4607 has (at last) arrived... Now looking to get grounding sorted out. Then to set it all up...
Plan (so far) is to have a grounding rod a couple of feet away from the end wall where the pole/antenna will be mounted. Ground the antenna to the rod, and ground the coax to the rod.
Coax from antenna to Polyphase at entry [point to house. Ground the polyphase to same grounding rod below.
Run bonding wire from grounding rod around side of house and then into house and attach to house electrical grounding rod in basement.
The antenna coax will go through the attic and then drop through the ceiling into an upstairs room where the radio will be located. Do I need to run another ground from the radio down to an external grounding rod, or is the electrical ground from the outlet sufficient?
If the former is required, then I'll add another grounding rod below the 'radio room', and run a bonding wire back around to the antenna grounding rod.
Does that sound reasonable? From what I've read, it seems to comply, but as I've not done this before, I'm seeking some wisdom from those that have..
Also: regarding grounding / bonding wire. I was planning on 6AWG bare copper. Is that OK, or would 8AWG be acceptable?
From what I've read, bare solid copper is a better option than bare copper multi-strand. Would you agree with that?
See attached pic..

 

[mmckenna]

Do I need to run another ground from the radio down to an external grounding rod, or is the electrical ground from the outlet sufficient?
If the former is required, then I'll add another grounding rod below the 'radio room', and run a bonding wire back around to the antenna grounding rod.

Ideally, you want the radio bonded to the same ground as the antenna system.
Relying on the negative power lead/chassis to the power supply chassis and through the house ground isn't a good idea.
A good way to do this is to put a grounding bar at your radio and bond all the radio equipment, power supply, etc. to that.
The ground wire in the outlet is for a safety, not for lightning or high static discharges.

Does that sound reasonable? From what I've read, it seems to comply, but as I've not done this before, I'm seeking some wisdom from those that have.
Also: regarding grounding / bonding wire. I was planning on 6AWG bare copper. Is that OK, or would 8AWG be acceptable?
From what I've read, bare solid copper is a better option than bare copper multi-strand. Would you agree with that?
See attached pic..

That sounds like a good plan. Conductor size will depend on the length of the run. 6 gauge is pretty safe.

 

[WRFM426]

The radio is a Wouxun KG-1000G Plus (Mobile/Base) - and is powered via a 13.8V power supply. The radio itself does not have a ground connection. Any recommendations on how I should ground the unit in this case?

 

[mmckenna]

The radio is a Wouxun KG-1000G Plus (Mobile/Base) - and is powered via a 13.8V power supply. The radio itself does not have a ground connection. Any recommendations on how I should ground the unit in this case?

Ground the chassis of the power supply.
Ground the chassis of the radio.

The power supply should have a means for grounding. If it doesn't use one of the chassis top screws.
The radio mounting bracket should screw directly into the side of the radio. If the radio isn't a cheap plastic box, it should be aluminum cast body. A ring terminal under one of the mounting screws should do what you need.

 

[prcguy]

As a coincidence to this thread, a couple of friends who had way too many antennas laying around brought me a nice perfect condition DB Products DB-408 for free which would have been an ideal antenna for the OP with 6.6dBd omni gain covering 450-470MHz. Now I need to find a new site for a local GMRS repeater using this antenna. Thanks BB and Jon, its a real beauty!

 

[W8UU]

The 408 is a great antenna.

 

[W8HDU]

I've got a DB420 sitting in storage, deciding if I want to put it up or stick with the ASPD701.

 

[prcguy]

I think there is about 3dB difference in gain favoring the 420.

I've got a DB420 sitting in storage, deciding if I want to put it up or stick with the ASPD701.

 

[W8HDU]

I think there is about 3dB difference in gain favoring the 420.

I think you're right. However I do know the beam off the array is quite narrow. When it was in use, I could work into our repeater from 8 miles away with a handheld. But walking around the neighborhood below the antenna (first 1/10th mile) nobody could hear me. When we swapped from analog to DStar it was more profound. Now the Dstar is off the air.

 

[Project25_MASTR]

I think you're right. However I do know the beam off the array is quite narrow. When it was in use, I could work into our repeater from 8 miles away with a handheld. But walking around the neighborhood below the antenna (first 1/10th mile) nobody could hear me. When we swapped from analog to DStar it was more profound. Now the Dstar is off the air.

See my earlier comment about using a lot of Telewave ANT450D's professionally for just that reason, needing to cover the facility under the antenna and not so much towards the horizon.

 

[prcguy]

I've used a DB-420 on both a two story building near sea level and near the top on the side of an 1,100ft high hill and I had no close in dead spots except of course when the antenna was completely shielded due to wrapping around the hill. The two story building would saturate everything within a few miles around to handhelds and it would also get 30-40mi out to mobiles in unobstructed directions.

I can't see how you could have a dead spot 1/10mi away since you can unplug antennas and usually talk that far on UHF without an antenna.

I think you're right. However I do know the beam off the array is quite narrow. When it was in use, I could work into our repeater from 8 miles away with a handheld. But walking around the neighborhood below the antenna (first 1/10th mile) nobody could hear me. When we swapped from analog to DStar it was more profound. Now the Dstar is off the air.

 

[W8HDU]

I can't see how you could have a dead spot 1/10mi away since you can unplug antennas and usually talk that far on UHF without an antenna.

If you measure the field strength of the signal, which was at 443.62500, and then look at the profile of transmission from the antenna in the elevation plane per spec sheet, they track pretty darn close. With the DB408 the nulls were still there, just not as severe. Typically it's not too much of an issue since the loss in gain on the depression angle is somewhat overcome by the ERP of the transmission. But with the antenna up at 500' on the tower, both receive and transmission were compromised. Not unusual or unexpected.

Our TV pylon did the same thing, but it was a 32 gain antenna, and the power lobe didn't fall until about 4 miles from the site. Some viewers had to turn their antennas away from the station, picking up bounces off buildings and grain elevators for the best analog signal. When we went to digital in 2020, the new antenna is only a 6 gain, and it's elliptical polarization which corrects the artifact.

 

[WRFM426]

Ideally, you want the radio bonded to the same ground as the antenna system.
Relying on the negative power lead/chassis to the power supply chassis and through the house ground isn't a good idea.
A good way to do this is to put a grounding bar at your radio and bond all the radio equipment, power supply, etc. to that.
The ground wire in the outlet is for a safety, not for lightning or high static discharges.



That sounds like a good plan. Conductor size will depend on the length of the run. 6 gauge is pretty safe.

OK, so here's another thought.... If you look at the image I uploaded, it shows a planned ground wire bonding the Grounding Rod to the house electrical ground - with the 6AWG wire buried in the ground, going around the side of the house to the point where the electrical service enters... My new question is twofold: 1) if the bonding wire goes this route, it will cross a natural gas line that enters the house that side. Is that a problem? 2) as an alternative, is it acceptable to run the bonding wire from the Grounding Rod inside the house to the house electrical ground, rather than going buried around the outside ? Asa matter of principle, should I keep as much of the bonding wire outside and buried, rather than 'taking a short cut' to the electrical service grounding rod buy going through the basement ..?

Actually, there's a third question: if I place a second Grounding Rod outside / below the upstairs room where the radio will be located, I can drop a bonding wire to that rod, but presumably that second rod should be bonded to the first grounding rod at the base of the antenna - correct? Is it better to do that rather than run a bonding wire from the second grounding rod directly inside the house to the electrical ground?
Of course the antenna grounding rod will have already been bonded to the electrical grounding rod as outlined above..

 

[mmckenna]

OK, so here's another thought.... If you look at the image I uploaded, it shows a planned ground wire bonding the Grounding Rod to the house electrical ground - with the 6AWG wire buried in the ground, going around the side of the house to the point where the electrical service enters... My new question is twofold: 1) if the bonding wire goes this route, it will cross a natural gas line that enters the house that side. Is that a problem? 2) as an alternative, is it acceptable to run the bonding wire from the Grounding Rod inside the house to the house electrical ground, rather than going buried around the outside ? Asa matter of principle, should I keep as much of the bonding wire outside and buried, rather than 'taking a short cut' to the electrical service grounding rod buy going through the basement ..?

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.

Actually, there's a third question: if I place a second Grounding Rod outside / below the upstairs room where the radio will be located, I can drop a bonding wire to that rod, but presumably that second rod should be bonded to the first grounding rod at the base of the antenna - correct? Is it better to do that rather than run a bonding wire from the second grounding rod directly inside the house to the electrical ground?
Of course the antenna grounding rod will have already been bonded to the electrical grounding rod as outlined above..

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.