Base height and cable option

[WSFH518]

Hey all. I might be upgrading my mast height, and being a newb,  i have a couple questions. My existing height is 35' to the bottom of my antenna. I'm using a 50' LMR400 cable currently.(1000G Wouxun).

I have a chance to have a pole put in that will raise my height to around 55' to bottom of the antenna. Instead of splicing the LMR400 I was considering 65' of LMR600 to replace it. Is that a bad idea? A friend suggested Heliax but after researching it and the tooling I'd need for just a couple fittings I got sticker shock. 

I also noticed that some LMR600 has a braided center conductor which I'm not sure is better/worse. Any advice? Thanks

[SteveShannon]

32 minutes ago, WSFH518 said:

Instead of splicing the LMR400 I was considering 65' of LMR600 to replace it. Is that a bad idea?

Not at all. LMR 600 has even less loss than LMR 400.  Over 65’ the calculator at Times Microwave says that you’ll only attenuate 1.15 dB. 
https://timesmicrowave.com/calculator/

[WRUE951]

41 minutes ago, WSFH518 said:

Hey all. I might be upgrading my mast height, and being a newb,  i have a couple questions. My existing height is 35' to the bottom of my antenna. I'm using a 50' LMR400 cable currently.(1000G Wouxun).

I have a chance to have a pole put in that will raise my height to around 55' to bottom of the antenna. Instead of splicing the LMR400 I was considering 65' of LMR600 to replace it. Is that a bad idea? A friend suggested Heliax but after researching it and the tooling I'd need for just a couple fittings I got sticker shock. 

I also noticed that some LMR600 has a braided center conductor which I'm not sure is better/worse. Any advice? Thanks

Assuming you have a lightning arrestor and you should, place that as a splice point.   Heliax is always the first choice for performance but not your wallets performance..  I use about 65' of LMR 400 and doing fine.  Go with what you can afford.    I like the Heliax, but that's me talking with your money  

[WSFH518]

Thanks Steve. 

I'm still googling options and costs. I found 1/2" Commscope LDF4-50A on Antenna Farm for $2.19 per foot. I'd need two connectors obviously and I'm trying to figure out which I would need, and how difficult it would be to put on. According to some vids, not that big of a deal.

With the 1/2" being so stiff(LMR or Heliax) is it okay to use a short jumper? Or is that a no,no?

[WSFH518]

12 minutes ago, WRUE951 said:

Assuming you have a lightning arrestor and you should, place that as a splice point.   Heliax is always the first choice for performance but not your wallets performance..  I use about 65' of LMR 400 and doing fine.  Go with what you can afford.    I like the Heliax, but that's me talking with your money  

You posted while I was typing  YES! Price is a factor. I'm probably over thinking. But once that puppy is up 55', I can't change it. LOL

[SteveShannon]

7 minutes ago, WSFH518 said:

Thanks Steve. 

I'm still googling options and costs. I found 1/2" Commscope LDF4-50A on Antenna Farm for $2.19 per foot. I'd need two connectors obviously and I'm trying to figure out which I would need, and how difficult it would be to put on. According to some vids, not that big of a deal.

With the 1/2" being so stiff(LMR or Heliax) is it okay to use a short jumper? Or is that a no,no?

Almost everyone does use jumpers on both ends. 

[WSFH518]

10 minutes ago, SteveShannon said:

Almost everyone does use jumpers on both ends. 

Good to know. Never thought about a lightning arrestor. The pole will have a ground wire with a rod at the base(part of the install). I'm guessing I'd need an inline lightning arrestor for the cable. Correct? If so then that changes the amount of fittings and splices. Do I have that right?

 

Can I add the arrestor close to the radio, at the jumper to avoid a splice? Then run the ground outside?

[SteveShannon]

8 minutes ago, WSFH518 said:

Good to know. Never thought about a lightning arrestor. The pole will have a ground wire with a rod at the base(part of the install). I'm guessing I'd need an inline lightning arrestor for the cable. Correct? If so then that changes the amount of fittings and splices. Do I have that right?

 

Can I add the arrestor close to the radio, at the jumper to avoid a splice? Then run the ground outside?

Place the arrester outside the house right before the coax passes through the wall. Never invite lightning into your home. 

[WSFH518]

6 minutes ago, SteveShannon said:

Place the arrester outside the house right before the coax passes through the wall. Never invite lightning into your home. 

Okay. Then that does add two additional fittings. Thanks for the info Steve!

 

 

ETA: Once knew a gal nicknamed "lightning". I guess the one time you invite it in 

[SteveShannon]

12 minutes ago, WSFH518 said:

ETA: Once knew a gal nicknamed "lightning". I guess the one time you invite it in 

It all depends on how she got the nickname!  Did she burn down a house?

[WRYZ926]

Okay, let me see if I got the information correct. 

You are currently running 50 ft of LMR400

Your mast is 35 ft and you want to go to 55 ft

That means you will go from 50 ft of coax to 70 ft of coax.

I ran the numbers on the kv5r coax calculator 

You will be fine even with LMR400 if you are running an antenna with at least 4-5 dBd of gain.

You definitely want to use lightning arrestors right before the coax enters your house. Also make sure they are connected to a close ground rod too. Lightning arrestors won't do much good if they aren't grounded.

You can use LMR400 Ultra Flex, RG8 or even RG8X for short jumpers. Loss will be very minimal even with RG8X if the jumpers are kept to 6 ft long or shorter.

[WSFH518]

41 minutes ago, WRYZ926 said:

Okay, let me see if I got the information correct. 

You are currently running 50 ft of LMR400

Your mast is 35 ft and you want to go to 55 ft

That means you will go from 50 ft of coax to 70 ft of coax.

I ran the numbers on the kv5r coax calculator 

You will be fine even with LMR400 if you are running an antenna with at least 4-5 dBd of gain.

You definitely want to use lightning arrestors right before the coax enters your house. Also make sure they are connected to a close ground rod too. Lightning arrestors won't do much good if they aren't grounded.

You can use LMR400 Ultra Flex, RG8 or even RG8X for short jumpers. Loss will be very minimal even with RG8X if the jumpers are kept to 6 ft long or shorter.

Just saw the like button. Oops. 

Thanks so much! I probably should have asked for layman's term type advice like yours. I have an general idea of the basics, but I can also see how easy it is to miss something simple. Thanks everyone! ETA- 11dbi gain antenna. Element

Edited October 20, 2025 by WSFH518
More info

[WRYZ926]

Most coax loss calculators use gain listed in dBd. To go from dBi to dBd, subtract 2.15 from the gain in dBi. So your antenna with 11 dBi go gain is actually 8.85 dBd.

Most manufacturers market their antenna gains in dBi to make them look better. My calculations posted above was using an antenna with 5 dBd of gain.

Here are the numbers using 8.8 dBd of gain.

 

You will be fine sticking with LMR400 if you want to.

[WSFH518]

Got a new question. The pole being set will have a ground attached to it, down to the ground rod(part of the install). Is it okay to attach the arrester ground wire to that ground? Or does it need its own ground wire and rod?

Also. Are there quality compression fittings for LMR600? Seems I'm finding crimp on mostly. Trying to avoid buying $75 crimpers for four fittings, unless that's the best way to go.

[SteveShannon]

10 minutes ago, WSFH518 said:

Got a new question. The pole being set will have a ground attached to it down to an ground rod(part of the install). Is it okay to attach the arrester ground wire be attached to that ground? Or does it need its own ground wire and rod?

Also. Are there quality compression fittings for LMR600? Seems I'm finding crimp on mostly. Trying to avoid buying $75 crimpers for four fittings, unless that's the best way to go.

You certainly can use that ground but it has to be connected “bonded” to your service ground, as does any other ground. See this article for more information: https://reeve.com/Documents/Articles Papers/Reeve_AntennaSystemGroundingRequirements.pdf

Messi and Paloni make excellent compression fittings for coax. I’ll be back with a link. 
Never mind; they only go to .500”

[WSFH518]

1 minute ago, SteveShannon said:

You certainly can use that ground but it has to be connected “bonded” to your service ground, as does any other ground. See this article for more information: https://reeve.com/Documents/Articles Papers/Reeve_AntennaSystemGroundingRequirements.pdf

Messi and Paloni make excellent compression fittings for coax. I’ll be back with a link. 

Well that changes things. My meter is on the opposite end of shop.. I'm off to look at your link..

[WRYZ926]

Per the link that Steve posted, you want to have ground rods every 8 feet and have everything bonded to the service ground. 6 gauge wire is the minimum for grounding per the NEC. I highly suggest reading the article he linked.

I actually prefer crimp on connectors as I don't have to worry about ruining the dielectric inside the coax. I bet someone in a local radio club will have crimpers and will probably be willing to help. It never hurts to ask.

[WRXB215]

In addition to Steve's link, here is a good discussion about grounding and bonding. 

 

[WRTC928]

FWIW, I'm feeding a Comet CA712efc antenna (6.85 dBd gain) from a 50 watt GMRS repeater with 75' of LMR400. Running it through the coax loss calculator shows 30.5 watts to the antenna with 147.5 watts effective radiated power. Going to LMR 600 would result in an ERP of 175.7 watts. Is the additional 28.2 watts worth the additional cost of the cable and connectors? Only you can answer that. For me, it wasn't. To the west, my range is limited by a hill and no practical increase in power is going to change that. To the south, east, and north, I get 15-17 miles of coverage and that's more than enough to fill in the gap between the repeaters to my northeast and south. 

[WRTC928]

On 10/20/2025 at 8:04 PM, WRYZ926 said:

Most coax loss calculators use gain listed in dBd. To go from dBi to dBd, subtract 2.15 from the gain in dBi. So your antenna with 11 dBi go gain is actually 8.85 dBd.

Most manufacturers market their antenna gains in dBi to make them look better. My calculations posted above was using an antenna with 5 dBd of gain.

Here are the numbers using 8.8 dBd of gain.

What antenna has 8.8 dBd of gain? I'm fine with what I have for now, but I may want something different in the future.

[SteveShannon]

13 hours ago, WRYZ926 said:

Per the link that Steve posted, you want to have ground rods every 8 feet and have everything bonded to the service ground

Just a tweak to this. A lot of times people say every eight feet. I even had an inspector tell me that. But it’s not that simple. Ground rods should be spaced at intervals of twice their length. So four foot ground rods should be eight feet apart but eight foot ground rods should be spaced 16 feet apart. Nothing is gained by spacing them closer. 

[WRYZ926]

20 minutes ago, WRTC928 said:

What antenna has 8.8 dBd of gain? I'm fine with what I have for now, but I may want something different in the future.

The OP stated his antenna has 11 dBi of gain which equals  8.85 dBd of gain.

Quote

Thanks so much! I probably should have asked for layman's term type advice like yours. I have an general idea of the basics, but I can also see how easy it is to miss something simple. Thanks everyone! ETA- 11dbi gain antenna

Look at the numbers posted. Any antenna with 11 dBi of gain will have 8.85 dBd of gain. It's simple math. subtract 2.15 from the gain given in dBi to get the gain in dBd.  I just rounded it to 8.8 for simplicity.

[WRYZ926]

21 minutes ago, SteveShannon said:

Just a tweak to this. A lot of times people say every eight feet. I even had an inspector tell me that. But it’s not that simple. Ground rods should be spaced at intervals of twice their length. So four foot ground rods should be eight feet apart but eight foot ground rods should be spaced 16 feet apart. Nothing is gained by spacing them closer. 

You are correct. But most will tell you every 8 feet as that is what most people go with. Nothing is gained by placing them 8 feet apart but it won't hurt anything either.

My ground rods are space between 8 and 15 feet as that is what I had to do to avoid concrete steps, and the concrete pad that the AC condenser sits on. I wanted to keep everything close to the foundation.

[WRTC928]

10 minutes ago, WRYZ926 said:

The OP stated his antenna has 11 dBi of gain which equals  8.85 dBd of gain.

Look at the numbers posted. Any antenna with 11 dBi of gain will have 8.85 dBd of gain. It's simple math. subtract 2.15 from the gain given in dBi to get the gain in dBd.  I just rounded it to 8.8 for simplicity.

Sorry, I missed that. Yes, I understand how you got dBd by calculating from the stated dBi. With that much gain, I probably wouldn't bother with the extra expense and hassle of using something better than LMR400, but sometimes people just want the very best, and I have no problem with that if it's their money. In some areas, I'm that way myself.

[SteveShannon]

24 minutes ago, WRYZ926 said:

You are correct. But most will tell you every 8 feet as that is what most people go with. Nothing is gained by placing them 8 feet apart but it won't hurt anything either.

Actually it does diminish the returns by having them spaced too closely together, even though the costs increase linearly. Placing two eight foot rods eight feet apart is not as good as putting them sixteen feet apart. You lose some of the effectiveness of having the second ground rod. In fact NEC even specifies a minimum spacing of six feet because of that. 

[WRYZ926]

I placed my ground rods no closer than 8 feet and no farther than 15 feet apart in order to get around obstacles. Yes ideally they would all be the same distance apart and closer to 16 feet if I could have done so.