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  #21 (permalink)  
Old 08-18-2012, 6:38 AM
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A ground for that antenna is for safety, not for RF purposes. So, if you want a good safety/lightning ground, then a simple ground rod is not going to be even close to adequate. The National Electrical Code is a very good source for what's adequate for safety grounding, I'd definitely recommend reading the appropriate sections.
- 'Doc
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  #22 (permalink)  
Old 08-18-2012, 10:32 PM
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Originally Posted by Chauffeur6 View Post
Get a roll of 3M rubber splicing tape. Wrap all outdoor connections with the tape a few inches past the connectors, then wrap over that with some quality electrical tape like 3M Super 33+ vinyl.
This is what I do:
First a couple good overlapping wraps of 3M Super 88.
Then a couple good overlapping wraps of 3M 2242 rubber tape. Stretch the 2242 as you wrap it, enough that it turns gray. Then another couple good overlapping wraps of the 88 on top of that.
That's it, a good weatherproof connection. No Coax-Seal, no spray coating.
I have bought both of these tapes at Lowe's.

I can't take credit for this, it's from an article on the CD that comes with ARRL's Experimental Methods in RF Design book. It works great.
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  #23 (permalink)  
Old 08-18-2012, 10:57 PM
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i did it today before it rained
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  #24 (permalink)  
Old 03-17-2016, 2:52 PM
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What is everyone favorite source for Coax cable custom made? I would like double shielded but I'm not sure it's available. It must be Belden brand.
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Old 03-17-2016, 3:16 PM
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Always bond your ground rods together. If you don't the potential difference (volts) between the two different grounds can be substantial. Years back cable TV would put in their own ground and not bond. then nearby (many several hundred feet) lightning strike would cause a large voltage difference between the two grounds with the homeowners TV 'between' them (Bye Bye TV). The high potential difference is only for microseconds but that is all it takes -same thing can happen with Power system 'faults'.
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  #26 (permalink)  
Old 03-17-2016, 3:16 PM
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Why just Belden. Other manufactures such a Times Microwave, Davis and Jefa Tech make great coax.

I use Jefa Tech LMR 400 coax. Its great for CB and other frequencies. They can make you any length you want. The LMR 400 Flex coax is better suited for use as jumpers.

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Old 03-17-2016, 4:16 PM
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Why double shielded and why Belden? Belden makes great cable but so does many others as has been mentioned.

RG-214 is a typical RG-8 size double shielded coax but it uses older technology dielectric and is higher loss than more modern cables. Mil spec RG-214 also has dual silver plated shields and the price on that has gone through the roof in recent years. You will pay at least several $$ per foot of mil spec RG-214 and it will have the same loss as RG-8/U coax made in the 1950s.

The double braid doesn't buy you less loss and LMR type cables with full foil shield have superior shielding over dual braid types. In my opinion LMR-400 made by just about anyone should be the default cable for long runs or high power CB or amateur up through 1.5GHz.
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Quote:
Originally Posted by comoman View Post
What is everyone favorite source for Coax cable custom made? I would like double shielded but I'm not sure it's available. It must be Belden brand.
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  #28 (permalink)  
Old 03-18-2016, 2:04 AM
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When do you ground the shielding and not the radio? I saw a you tube ant vid where the guy says dont ground the shielding. Is this because it acts as antenna too? (Im ignoring lightning safety to make rf theory simpler in my question)
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  #29 (permalink)  
Old 03-18-2016, 6:31 AM
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Quote:
Originally Posted by BBB007 View Post
Why just Belden. Other manufactures such a Times Microwave, Davis and Jefa Tech make great coax.

I use Jefa Tech LMR 400 coax. Its great for CB and other frequencies. They can make you any length you want. The LMR 400 Flex coax is better suited for use as jumpers.

Get it here: JEFA Tech
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Originally Posted by prcguy View Post
Why double shielded and why Belden? Belden makes great cable but so does many others as has been mentioned.

RG-214 is a typical RG-8 size double shielded coax but it uses older technology dielectric and is higher loss than more modern cables. Mil spec RG-214 also has dual silver plated shields and the price on that has gone through the roof in recent years. You will pay at least several $$ per foot of mil spec RG-214 and it will have the same loss as RG-8/U coax made in the 1950s.

The double braid doesn't buy you less loss and LMR type cables with full foil shield have superior shielding over dual braid types. In my opinion LMR-400 made by just about anyone should be the default cable for long runs or high power CB or amateur up through 1.5GHz.
prcguy
Because Belden is a quality brand and I've used it for year and like you guys using your preferred brand, I am familiar with Belden. I'm sure other brands are ok as well. I'm not against using other brand. I just did want any cheap cable like you can buy off the shelf of your local CB shops and Wally World. Double shielding really should need an explanation but double shielding is better than single as far as I know.

I just want some quality coax with quality PL259 connectors.
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  #30 (permalink)  
Old 03-19-2016, 1:49 AM
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Quote:
Originally Posted by comoman View Post
Because Belden is a quality brand and I've used it for year and like you guys using your preferred brand, I am familiar with Belden. I'm sure other brands are ok as well. I'm not against using other brand. I just did want any cheap cable like you can buy off the shelf of your local CB shops and Wally World. Double shielding really should need an explanation but double shielding is better than single as far as I know.

I just want some quality coax with quality PL259 connectors.
Foil or braid shielding? I would think foil would be better, its a solid shield. Wouldn't braiding not work as well at higher RF's? Also foil shielding doesn't snag like braiding can.

We are true believers of the foil in my house hold. Braiding is best done for my gf's African hair. Doesn't always block out some of the unwanted signals and noise coming from her mouth, maybe put an attenuator on her.



My idea: ground the bit of foil one inch (breaking continuity to the rest of the foil in the cab;e from the radio to a trusty ground rod, then wrap up the foil that goes up the feed line.
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  #31 (permalink)  
Old 03-19-2016, 7:33 AM
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Originally Posted by beamin View Post
Foil or braid shielding? I would think foil would be better, its a solid shield. Wouldn't braiding not work as well at higher RF's? Also foil shielding doesn't snag like braiding can.

We are true believers of the foil in my house hold. Braiding is best done for my gf's African hair. Doesn't always block out some of the unwanted signals and noise coming from her mouth, maybe put an attenuator on her.



My idea: ground the bit of foil one inch (breaking continuity to the rest of the foil in the cab;e from the radio to a trusty ground rod, then wrap up the foil that goes up the feed line.

I would prefer foil but copper braided shielding is ok as well. I don't really know why but I've never like the steel braided shielding. I realize there are lots of options but I'm not trying to re-invent the wheel here just buy some quality coax cable. I mainly wanted the best shielded because my coax is about 175 feet long and has a little db loss. I know the shield has little to do with db loss but I just want to take advantage of what ever is available that will give me the best performance for the money.
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  #32 (permalink)  
Old 03-19-2016, 8:29 AM
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Quote:
Originally Posted by beamin View Post
When do you ground the shielding and not the radio? I saw a you tube ant vid where the guy says dont ground the shielding. Is this because it acts as antenna too? (Im ignoring lightning safety to make rf theory simpler in my question)
If the radio is properly grounded.the.shield will also.be grounded. The same is true to some extant in reverse if the sield is grounded the radio is grounded.
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  #33 (permalink)  
Old 03-19-2016, 9:01 AM
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Quote:
Originally Posted by geartow View Post
If the radio is properly grounded.the.shield will also.be grounded. The same is true to some extant in reverse if the sield is grounded the radio is grounded.
Maybe you can explain this to me. I installed a new Stryker SR-89MC radio in my 2012 Jeep Wrangler. Using an ohm meter there is no resistance to ground from the radio. When the radio is turned on I get a 0.20k ohms reading.

What's up with that? No matter what I do I can't get the SWR's lower than 2.7 using my MFJ-259 analyzer.
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  #34 (permalink)  
Old 03-19-2016, 10:05 AM
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For your 175ft run LMR400 is the best option for loss vs price. With LMR400 you will have about 1.1dB loss in 175ft and about 77% of your power will reach the antenna. The same run in RG-213 or RG-214 would have about 1.7dB loss and about 67% of your power will reach the antenna.

If your really hard core you could go bigger to LMR600 and get about .7dB loss and 85% of your signal to the antenna but it will cost more.

Or you could shorten the run to your antenna and use a less expensive cable. Bottom line is your coax run is going to be a substantial investment and there is no good way around loss in 175ft of cable, unless you find a really good deal on LMR600 like I did, as in the last 200ft on the end of a wooden spool for free.

The LMR series of cables has an aluminum foil shield that provides way more shielding than even double braid coax and it also has a heavy braid for strength and solid attachment to the connector.
prcguy

Quote:
Originally Posted by comoman View Post
I would prefer foil but copper braided shielding is ok as well. I don't really know why but I've never like the steel braided shielding. I realize there are lots of options but I'm not trying to re-invent the wheel here just buy some quality coax cable. I mainly wanted the best shielded because my coax is about 175 feet long and has a little db loss. I know the shield has little to do with db loss but I just want to take advantage of what ever is available that will give me the best performance for the money.
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  #35 (permalink)  
Old 03-19-2016, 11:13 AM
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Quote:
Originally Posted by prcguy View Post
For your 175ft run LMR400 is the best option for loss vs price. With LMR400 you will have about 1.1dB loss in 175ft and about 77% of your power will reach the antenna. The same run in RG-213 or RG-214 would have about 1.7dB loss and about 67% of your power will reach the antenna.

If your really hard core you could go bigger to LMR600 and get about .7dB loss and 85% of your signal to the antenna but it will cost more.

Or you could shorten the run to your antenna and use a less expensive cable. Bottom line is your coax run is going to be a substantial investment and there is no good way around loss in 175ft of cable, unless you find a really good deal on LMR600 like I did, as in the last 200ft on the end of a wooden spool for free.

The LMR series of cables has an aluminum foil shield that provides way more shielding than even double braid coax and it also has a heavy braid for strength and solid attachment to the connector.
prcguy
Thanks for the feedback. Unfortunately my 62" Rohn tower is cemented into the ground and would be difficult to relocate.

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  #36 (permalink)  
Old 03-19-2016, 11:22 AM
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Yeah I can see where relocating would certainly cause issues..LoL
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Old 03-19-2016, 12:44 PM
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Personally I'd spend the money for Comspec 1/2" heliax. It may be buried below the frostline, has the absolute minimal loss (0.625 dB @30 MHz), and runs $1.99' from Antenna Farms.
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Old 03-19-2016, 1:18 PM
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I'll second the Heliax.. Antenna farm will make up custom lengths with connectors.. You're looking at another $50 for the connectors plus whatever they charge to install them.
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Old 03-19-2016, 1:25 PM
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Quote:
Originally Posted by jwt873 View Post
I'll second the Heliax.. Antenna farm will make up custom lengths with connectors.. You're looking at another $50 for the connectors plus whatever they charge to install them.
$26 for the labor including shrink wrap for proper sealing.

UHF Male is $36.95

I'd suggest UHF Female for the tower end, so you can use a more flexible jumper from the heliax to the antenna, and avoid a SO-239 barrel connector. The fewer components to introduce loss is best!

The two most important items in any radio system is #1 antenna, and #2 the feedline. Spending the money now for something that will last for the next three or four decades is a wise investment.
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  #40 (permalink)  
Old 03-19-2016, 2:56 PM
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So the 175ft run in LMR400 has about 1.1dB loss and cost maybe $148 + $5 in connectors and your recommending Heliax that will cost $348 + $75 in connectors and more for connector installation to save less than .5dB?

Plus 1/2" Heliax is not the absolute minimal loss in feedline. A 175ft run of 600 ohm open line including the loss in 2 transformers will beat the pants off 1/2" Heliax at 27MHz.
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Quote:
Originally Posted by N4GIX View Post
Personally I'd spend the money for Comspec 1/2" heliax. It may be buried below the frostline, has the absolute minimal loss (0.625 dB @30 MHz), and runs $1.99' from Antenna Farms.
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