Have some questions about Putting up a antenna ....

Masonjeep

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I’m trying to setup a antenna I’m ordering...
This is the antenna I’m ordering.... D130NJ Diamond Super Discone Antenna | Scanner Master
This is the mount I’m thinking about getting.. https://www.neobits.com/rohn_products_1lg_universal_one_legged_mount_with_p2757162.html
I think I’m going to need about 75ft of cable was thinking about LMR400 what kind of connection will I need?
Also do I need to ground it?
Im a newbe so bare with me I don’t know a lot and another member here was kind enough to help me with programming K4EET thank you again...

So any suggestions thoughts or idea will be very appreciated I have a guy from the fire Dept that’s kind enough to put it up for me but he’s not a radio guy and I can’t do much due to a spinal injury.....
Thanks in advance

Mark M.
 

737mech

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The webpage says it comes with N Female connector so you need N Type Male on your coax and bnc on the other end for the scanner. Get it up high and yes LMR 400 is great cable for the feedline. Stay away from power lines. Use 3m "F4" tape just goole it also called uniwrap tape. That will weather proof the connectors.
 

K4EET

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Hi Mark,

It was my pleasure helping you get the scanner programmed. You'll be an expert in no time and helping others too!

As for the coax, here is the loss at 75 feet without connectors:

LMR-400 ----> 3.1 dB ---> Good
LDF4-50A ---> 1.7 dB ---> Better

From a cost versus loss viewpoint, I think LMR-400 is your best bet. Comments anybody?

You will need to ground the antenna where it enters the house with a ground rod. Having never worked with LMR-400 before, I do not know the best way to get the ground wire attached to it. You could put a PolyPhaser lightning arrestor in-line with the LMR-400 run just before it enters the house. That would have a bracket to bolt the ground wire to. Is there an alternative to the PolyPhaser? Comments anybody? Keep the ground wire run to the ground rod as short as is possible. Home Depot sells the ground rod, clamp and ground wire by the foot.

This is a question for somebody familiar with LMR-400, I am going to guess that a BNC connector does not attach directly to the LMR-400 cable. I suspect that there is a short jumper using RG-8X or similar. Am I correct? Comments anybody?

1/2 in. x 8 ft. Copper Ground Rod from Home Depot

1/2 in. Type-G Ground Rod Clamp for 10 SOL to #2 STR Wire

PolyPhaser IS-B50LN-C2 Lightning Arrestor
MSRP $74.52 ---> Street Price is less than $50.00

F4 Tape | Self-Fusing Silicone Tape

Since Mark would probably like to have all of the pieces available when his friend comes over to do the installation, what other pieces of the antenna system have been overlooked? Comments anybody?

Thanks in advance for helping Mark put together a reasonably priced outdoor antenna system. I have been out of the industry for over 15 years and have lost touch with what all is new out there. Additionally, I have a disability that affects my brain functions among other things and I admit I'm not the smartest cookie on the planet. :ROFLMAO: :ROFLMAO::ROFLMAO:

Dave
 

jonwienke

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You can connect BNCs directly to LMR400:

LMR 400 is stiff, and you may want a short N to BNC jumper for strain relief, but if you can route and support the LMR400 so it aims directly at the target connector, that may not be necessary.
 

mmckenna

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I’m trying to setup a antenna I’m ordering...
This is the antenna I’m ordering.... D130NJ Diamond Super Discone Antenna | Scanner Master
This is the mount I’m thinking about getting.. https://www.neobits.com/rohn_products_1lg_universal_one_legged_mount_with_p2757162.html
Those mounts will work fine. You can often find them free/cheap if you look around. Look for them at metal recyclers, flea markets, etc.

I think I’m going to need about 75ft of cable was thinking about LMR400 what kind of connection will I need?
LMR-400 is about the lowest level cable I'd use on a 75' run, and I'd encourage you to use something better.
-Yes- it'll work.

1/2" Heliax is a good option, but it's stiff and can be very difficult to run in a residential application. It's got a fairly large bend radius, so routing it through walls can be challenging. I've done it, it's possible, but it may very well kick your butt in the process.

LMR-600 might be a good middle ground. It's more flexible and has a tighter bend radius. It'll be a bit cheaper than the 1/2" Heliax, and will perform better than the LMR400 over that sort of length.

If you've never installed your own connectors, you may want to consider having them pre-installed for you. It'll save you some headaches.

I'd recommend doing an N male connector at the antenna end and an N male at the radio end. But do not connect it directly to the radio. It's heavy cable (same for LMR-400, heliax, etc) and you'll put a lot of strain on the connector. Instead use a short jumper for something like RG-58 with a female N connector on one end and the other end to match your radio. This short jumper won't have any noticeable loss, and will take the strain off the radio's antenna jack. That'll save you a repair down the road.
At the antenna end, you can do the same thing, or you can carefully support the cable where it attaches to the antenna to make sure it doesn't strain the antenna base. On the professional side, it's common to use a short jumper of more flexible cable to make the final connection.

Also do I need to ground it?
National Electric Code says yes, you do need to ground it. Common sense says yes. Doing the right thing says yes. Doing the job safely says yes.
An inexperienced hobbyist/ham will tell you "no".
You decide, but hopefully you'll do the job right.

The antenna mounting bracket needs to be grounded.
You need to ground the coax shield and you need to provide lightning protection (yes, even if you don't get much lightning in your area, or your buddy tells you it will never get hit, or if someone tries to convince you that a wrap of electrical tape will magically stop a several million volt surge that has traveled thousands of feet through the atmosphere…)
Use a Polyphaser installed at the point where the coaxial cable enters your home.
So, you'll need an LMR-600 jumper from the antenna with a male N connector long enough to reach from the antenna to where the coaxial cable enters the house. Leave a drip loop (google that, keeps water from running down the cable into the house).
The Polyphaser will provide the lightning arrestor function to help protect what's in the house, and it will ground the outer shield of the jacket. From the Polyphaser, you'd run your cable from there to the radio.
Grounding may be best left to a professional electrician if you have concerns, but here's what you'd need:
Ground wire (6 gauge is what I would run) from the mounting bracket straight down to a ground rod directly below the antenna. Keep any bends/turns in the cable gentle and sweeping, lightning likes to jump off sharp points and sharp bends in wire.
You'll also need a ground wire (6 gauge again) from the Polyphaser direct to the ground rod.
On the professional side, it's not uncommon to install a ground bar near the Polyphaser and ground the mounting bracket/Polyphaser to that and then run a single wire down to the ground rod.

If you can use an existing ground rod at your homes electrical panel, if it's near the antenna mount, that's acceptable.
If that's not possible, then you'll need to install a new ground rod (at least one) and bond that to the house ground rod. No exceptions.


So any suggestions thoughts or idea will be very appreciated I have a guy from the fire Dept that’s kind enough to put it up for me but he’s not a radio guy and I can’t do much due to a spinal injury.....
Thanks in advance

Mark M.
Done right, this should work just fine. Just make sure he's aware of the NEC requirements for grounding. If unsure, get an electrician to do that part for you.

And as others said, DO NOT(!!!!) ignore proper waterproofing on ALL the exterior coaxial cable connections. Quickest way to destroy all this work is to skimp on the waterproofing.
 

K4EET

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As an FYI, here is how the coax loss stacks up at 75 feet for 900 ~ 1,000 MHz:

LMR-400 ----> 3.1 dB ---> Good (Times Microwave)
FSJ4-50B ----> 2.6 dB ---> Good (Andrews 1/2 inch Heliax SureFlex)
LMR-600 ----> 1.9 dB ---> Better (Times Microwave)
LDF4-50A ---> 1.7 dB ---> Better (Andrew 1/2 inch Heliax)
LMR-900 ----> 1.3 dB ---> Best (Times Microwave)
 

mmckenna

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As an FYI, here is how the coax loss stacks up at 75 feet for 900 ~ 1,000 MHz:

LMR-400 ----> 3.1 dB ---> Good (Times Microwave)
FSJ4-50B ----> 2.6 dB ---> Good (Andrews 1/2 inch Heliax SureFlex)
LMR-600 ----> 1.9 dB ---> Better (Times Microwave)
LDF4-50A ---> 1.7 dB ---> Better (Andrew 1/2 inch Heliax)
LMR-900 ----> 1.3 dB ---> Best (Times Microwave)
Yep.
To the OP, there will likely be a noticeable difference between the 3.1dB loss of LMR-400 and the sub-2dB of the others. LMR-600 is easier to work with if you are installing it in a residence, compared to the 1/2" heliax. Unlikely you'd be able to "hear" the difference between the 1.9dB of the LMR-600 and the 1.7dB of 1/2" heliax. .2Db would make minimal impact on your reception except on the very fringes. At that point, you'd probably want a band specific gain antenna, though. For a ~0dB gain discone, you want to use decent coaxial cable.

Not plugging these guys, but The Antenna Farm will do custom coax builds for you. You can spec' out the cable, connectors, length etc. and get exactly what you want. I'd recommend the -real- LMR-600 (beware of "equivalent" type cable). https://www.theantennafarm.com/catalog/times-microwave-lmr-600-1491
Order one cable the length you need to get from the antenna to the Polyphaser, and another to get from the polyphaser to your radio.
Opt for the heat shrink option on the connectors. That helps with strain relief and a bit with waterproofing (although you still need to properly waterproof the connections outside).
-Dual Fittings, same connector.
-Spec' N male connectors on both ends.

Polyphaser:

Short jumper to get from the radio end of the LMR-600 to your radio:
Again, add the heat shrink to the connectors, helps with strain relief.
Spec a Female N connector on one end and the other end to match your radio.

Grounding wire, ground rod, clamps, etc will all depend on your specific install, but most of it can be picked up at Home Depot.
 

n1das

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If you can use an existing ground rod at your homes electrical panel, if it's near the antenna mount, that's acceptable.
If that's not possible, then you'll need to install a new ground rod (at least one) and bond that to the house ground rod. No exceptions.
How would this be best accomplished when the antenna feedline entrance and the house electric panel ground rod are at opposite corners of the house? Installing one or more new ground rods isn't a problem but bonding to the house ground rod would be a problem. I live in a tri-level house and this is the situation I would have if I were to put up an antenna for a scanner or a ham repeater.
 

prcguy

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In that case you would be better off without the second ground rod and run a ground wire from the antenna across the roof to your electrical panel ground. NEC specifies 10ga copper wire for this but for runs longer than about 30ft you would need to upsize the wire. Check NEC article 810 for details.

How would this be best accomplished when the antenna feedline entrance and the house electric panel ground rod are at opposite corners of the house? Installing one or more new ground rods isn't a problem but bonding to the house ground rod would be a problem. I live in a tri-level house and this is the situation I would have if I were to put up an antenna for a scanner or a ham repeater.
 

mmckenna

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Yeah. With lightning, you want as straight and direct a path as possible to ground. That's best accomplished by a downlead from the antenna/protector straight down to a rod. You can route cables a bit, but you'd have to make sweeping turns, no sharp edges, etc. That gets to be a problem on most residential houses since no one wants to see it.

In some cases, depending on soil conductivity, more ground rods may be necessary to get the low resistance needed.

But NEC requires the ground rods to all be bonded. That way there's no voltage differential between the grounds at the electrical outlet and the ground on the coaxial shield.
A long time ago I used to install telephone and fiber optic cable. When running shielded phone cable or fiber between buildings, the metallic parts of the jacket needed to be grounded at each end. It was often possible to see a voltage between the shield of one end of the cable and its local ground point.
 

prcguy

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Its probably not possible for the OP to ground his new antenna to survive a lightning strike, that would require lots of $$ and it would still be questionable after that. Its better to ground to meet code for human safety and realize that a direct hit would be disastrous and disconnect any antenna cables during a storm and toss them outside.

What is worse, an antenna ground that you hope will save you but it cannot, or knowing it can't and you take other precautions?

Yeah. With lightning, you want as straight and direct a path as possible to ground. That's best accomplished by a downlead from the antenna/protector straight down to a rod. You can route cables a bit, but you'd have to make sweeping turns, no sharp edges, etc. That gets to be a problem on most residential houses since no one wants to see it.

In some cases, depending on soil conductivity, more ground rods may be necessary to get the low resistance needed.

But NEC requires the ground rods to all be bonded. That way there's no voltage differential between the grounds at the electrical outlet and the ground on the coaxial shield.
A long time ago I used to install telephone and fiber optic cable. When running shielded phone cable or fiber between buildings, the metallic parts of the jacket needed to be grounded at each end. It was often possible to see a voltage between the shield of one end of the cable and its local ground point.
 

mmckenna

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Absolutely.
But doing it to NEC is the right step. If one wanted to take it further, Motorola R56 is a well respected resource.

Both are better than the approach that many have where they don't ground anything.
 

K4EET

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Ahh... Ye ole Motorola R56! When I was a Microwave Product Consultant/Two-Way Radio Engineer for Motorola back in the early 1980s, that was the gold standard for microwave and two-way repeater sites. What a bear to meet though! But you knew things were done right!
 

Masonjeep

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Sorry guys my internet is going in and out thanks for the answers I’ll read everything when it stays on....

mark m.
 
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