RadioReference on Facebook   RadioReference on Twitter   RadioReference Blog
 

Go Back   The RadioReference.com Forums > Amateur Radio > Amateur Radio Antennas


Amateur Radio Antennas - For discussion of all amateur band designed antennas and related accoutrements. This includes base, handheld, mobile and repeater usage. For commercial antennas on the amateur bands please use Commercial Radio Antennas below.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #21 (permalink)  
Old 09-02-2018, 5:32 PM
RFI-EMI-GUY's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Dec 2013
Posts: 2,261
Default

That old low density foam Heliax cable could last forever. You cannot kill it. The problem with water intrusion was usually along the jacket because the spiral tended to create a gap around the outer jacket. Having AC inside the shelter tended to "pump" moisture into the cable jacket if it was poorly taped or had a nick.

The sealer I use is the stuff we call "monkey ****" a butyl product that stays sticky forever. I have a roll of that around that is 40 years old and still good.
__________________
"Have Spectrum Analyzer, - Will travel" "Going Green" ø
Reply With Quote
Sponsored links
  #22 (permalink)  
Old 09-02-2018, 8:03 PM
Member
   
Join Date: Feb 2007
Location: 175 DME, HEC 358° Radial
Posts: 5,587
Default

I'll try this again...

It doesn't call it "black death" (no one does), but there is a good description of "non-contaminating" coax here:

Davis RF Co. - Amateur Products

The discoloration in coax that is seen is polymers from the black PVC jacket leaching into the shield and center dialectric. It will eventually alter the characteristics of the coax (loss, VF) but you won't find anything definitive "out there" to quantify the degradation. You can count on this: If the shield has turned black from jacket contamination, it'll be harder to solder. If the center dialectric has darkened from jacket contamination, the velocity factor and loss of the cable has changed. It might still be perfectly usable for some applications (HF?), but it probably won't meet published specs. Do you really care if the line loss to your 14 MHz dipole is 0.27 or 0.57 dB? I sure don't.

Some coax does indeed age, and it doesn't always age well.
Reply With Quote
  #23 (permalink)  
Old 09-03-2018, 7:05 AM
rescue161's Avatar
KE4FHH
  RadioReference Database Admininstrator
Database Admin
Amateur Radio Operator
Amateur Radio
 
Join Date: Jun 2002
Location: Hubert, NC
Posts: 3,130
Default

Quote:
Originally Posted by RFI-EMI-GUY View Post
The sealer I use is the stuff we call "monkey ****" a butyl product that stays sticky forever. I have a roll of that around that is 40 years old and still good.
Same here! We called it "Monkey ****" or "B-Sealant." When I tried to purchase some, all of my "Monkey ****" and "B-Sealant" searches came up empty. I did find some though under the name Butyl tape. I was able to find the same 3.5" wide stuff that we used at work. Courtesy wraps are the name of the game as this stuff makes a huge mess once it gets applied.
__________________
Hams Against Magnetic Mounts
Reply With Quote
  #24 (permalink)  
Old 09-03-2018, 7:58 AM
MikeOxlong's Avatar
Forums Manager/Global DB Admin/Commie
  RadioReference Database Admininstrator
Database Admin
 
Join Date: Jun 2001
Location: Central Ontario
Posts: 10,219
Default

We call the sticky stuff bear ****. I've got a few dozen rolls of it because the riggers don't like to use it. Even with a courtesy wrap, the stuff is a pita.

The preferred method is to use Scotch 130C tape with a wrap of electrical tape over top.
__________________
Mike.

Sorry but I don't accept PM's. Please use email instead.
Reply With Quote
  #25 (permalink)  
Old 09-03-2018, 3:41 PM
majoco's Avatar
Member
  Shack Photos
Shack photos
 
Join Date: Dec 2008
Location: New Zealand
Posts: 2,817
Default

For receive only I like RG6 quad shield. My broadcast satellite antenna uses it and as far as I know it's been up there since the house was built in the late 90's - let's say 20years. I disconnected it 3 years ago to re-route it into the roof space and down a wall to a new location and it's still nice and pliable and the outer shows no sign of going powdery from the UV's which are supposed to be stronger here than anywhere else in the world. I had to chop the connectors off to get the cable down the wall and the copper both ends was bright and shiny.
In contrast, the RG57 to the FTA antenna was black and the outer cracked. That got replaced with RG6QS!

Electrical tape? That sticky PVC stuff? The only thing is the self-amalgamating tape - and that comes second to the heatshrink tubing with the glue on the inside - that's a bit tricky to put on if your halfway up a mast on a cold winter's day though.....
__________________
Cheers - Martin ZL2MC - Palmerston North

Last edited by majoco; 09-03-2018 at 3:45 PM..
Reply With Quote
Sponsored links
  #26 (permalink)  
Old 09-03-2018, 7:39 PM
jeatock's Avatar
Member
  Audio Feed Provider
Audio Feed Provider
Amateur Radio Operator
Amateur Radio
 
Join Date: Jul 2003
Location: 090-45-50 W, 39-43-22 N
Posts: 571
Default

Okay. I typed ‘lighting’. Everyone else knew that I was referring to ‘lightning’ but I guess someone will sue me over the grievous, fatal typo that invalidated the entire post.

I put "mission critical" in the first sentence for a reason. That means public safety matter-of-life-and-death systems. Systems that aren’t allowed to fail.

Ever.

Murphy was an optimist. A site will fail at 4:00 PM on the Friday before Labor Day weekend or your wife’s family reunion, or when your tower crew is out of town. That often means "mission critical" service may not be restored before noon the following Tuesday. Maybe as soon as mid-day Saturday IF overtime, overnight courier freight and a whole lot of time in the dark with cold rain pouring down fixing the problem at great expense isn't an issue. And there are a couple hundred feet of 1-1/4" LDF and all the Sure-grounds, connectors, hoisting grips and the rest of the required items cached locally ready to install.

The dark and stormy night fail could be avoided IF you had planned, budgeted and prepared for replacement a year in advance, and picked a mild sunny day during a low traffic period to do the preventive work.

I sweep "mission critical" coax and antenna systems several times a year. They're mission critical systems. Failure is not an option.

It’s called preventative maintenance. You can't assume a reliable system will stay that way without it. I replace backup generator batteries every three years. It is not a contest to see how long you can make them last. They are mission critical, must start 100% of the time and still fail. Do I use a still-okay-take-out generator battery in my lawn mower? Yep. I have a charger and the grass can wait. Car tires are legal as long as Lincoln’s head disappears into the tread. Do I run tires that long? Maybe for a while on the car I only drive in town to the grocery store on sunny dry days. Should a police agency? No. A failure during a high-speed run in the rain could be catastrophic.

Do you replace your tires before they are no longer legal? Why? They are legal and shouldn’t be a problem. Murphy’s Law is over-rated.

Several years ago issues were reported at a five-year-old public safety site. Everything installed and grounded to R-56, including lavish bend radius, secure attachment, Sure-grounds with exothermic welds at the top, bottom and every 50 feet down the structure. Everything on the ground was tight and dry as a bone. It was still working acceptably so we scheduled repairs with the agency. It was only five years old, so it must be a simple loose connector up-top. Wind and other problems delayed climbing for a week. That made me nervous.

The site worked until the monsoon rain hit (at 11:00 PM on a Friday night of course). The site went deaf as a post and the transmitters went into auto-protect. Degraded the law enforcement, fire and EMS comms for a part of the county on a busy holiday weekend.

At 3:00 AM I found water inside the bottom N-Connector. At daylight (with the antenna disconnected) I checked the coax with my megger. The jacket was perforated in several places and would pass 1,000 volts to the structure. My tower guy could hear the snapping when I applied megger test voltage.

When we pulled the coax down hairline cracks became apparent in the upper sections. They were not visible until the coax was flexed, something you keep to a minimum with 1-1/4’ Times Microwave® LDF6. All weather-proofing was intact and dry. Removing the jacket from around the perforated sections revealed old corrosion mid-run. A combination of black and green death. This was a long-term slow-motion failure that waited until the worst possible time to rear its ugly head.

Did I bill the agency for the late night overtime weekend work? Only for materials. I have a fixed-amount monthly contract to make sure their mission critical systems don’t fail.

Even the best UV-Resistant jacket is not forever. That’s why it is marketed as ‘UV-Resistant’ and not ‘UV-Proof-Forever’. I have seen much coax fail simply because of the weather. Water is evil and patient, and I can guarantee it is silently doing everything it can to ruin your day. How do I waterproof connectors and mid-run Sure-grounds? Glue-lined heat shrink under self-vulcanizing tape under two kinds of vinyl tape. Overkill? No. Not for mission critical. Why do radome fiberglass antennas have drain holes in the bottom? Because after years of sun and wind they will draw water right through the coating. It’s inevitable. Why do the weep holes get plugged? Because Japanese Beetles are evil too, and learned everything they could from water.

Another inherited older site was hit by lightning. An observer said it was impressive. The Sure-ground waterproofing had leaked and corroded, and the lightning found an easier path by jumping through the outer jacket and carbon tracking down the water tower leg to a crack in the paint. The lightning had already traveled many thousands of feet through air, so blowing open an imperfection in the 1/8” jacket and running down a few feet of wet steel was easier than following the original installer’s suggested path to ground. Another finger of lightning found its way through the wet foam at the bottom and exploded the lightning protector.

A case of not being a problem until it becomes one.

Do I replace my own coax at home on a schedule? No. It’s for a hobby, and not mission critical. Do I go out in the rain to fix it? No. I confess to being crazy, not stupid. Did I buy all of it new? Nope, not all of it. Some of my hobby coax is used, but still sweeps good. It’s ‘good enough’ since my hobby is not ‘mission critical’. Pain in the rear when it fails, but nobody is going to die because of it.

Mission critical is another kettle of fish. Do I re-install used coax on mission critical antenna systems? No.

Mission Critical means it can’t fail.

Ever.


(Composed using Microsoft Word®, and spell-checked, twice.)


</rant> Ooooohhhhhmmmmm.
__________________
Public Safety Communications Consultant and Technician, Firefighter / COML, Interoperability Crusader and Slayer of Dragons (aka Proprietary Systems)
Reply With Quote
  #27 (permalink)  
Old 09-03-2018, 8:11 PM
Member
   
Join Date: Feb 2007
Location: 175 DME, HEC 358° Radial
Posts: 5,587
Default

Now, THAT sounds like the voice of experience.
Reply With Quote
  #28 (permalink)  
Old 09-03-2018, 11:02 PM
mastr's Avatar
Member
   
Join Date: May 2005
Posts: 207
Default

That was an impressive reply. That said, I cannot think of one instance in the last 30 years where I have replaced a run of Heliax cable merely because of its time in service.

My thinking is that failure is to be expected and alternate systems for use in that event provided. In other words, if you have a piece of equipment that cannot be "allowed to fail", you don't have enough equipment.
__________________
Disclaimer- all statements herein are my own and as such do not represent any official position or capacity.
Reply With Quote
  #29 (permalink)  
Old 09-03-2018, 11:17 PM
jeatock's Avatar
Member
  Audio Feed Provider
Audio Feed Provider
Amateur Radio Operator
Amateur Radio
 
Join Date: Jul 2003
Location: 090-45-50 W, 39-43-22 N
Posts: 571
Default

I agree with Mastr. Systems than cannot fail should have redundant backups.

Try and sell that concept to a public entity, where the price tag for a redundant backup to a system that (almost) always works is nearly the entity's entire annual budget. Not just for communications, there ENTIRE budget including heat, trash pickup, insurance and copy paper.

Grants (when they were available) got them started. After that the local budget takes over.

Poor people sometimes can only afford poor ways.
__________________
Public Safety Communications Consultant and Technician, Firefighter / COML, Interoperability Crusader and Slayer of Dragons (aka Proprietary Systems)
Reply With Quote
  #30 (permalink)  
Old 09-04-2018, 8:34 AM
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Aug 2015
Location: Santa Monica, Ca.
Posts: 326
Default Seal Coaxaint

I tape the connector with electrical tape, then paint it with clear coat paint.
Reply With Quote
  #31 (permalink)  
Old 09-04-2018, 8:42 AM
KevinC's Avatar
Moderator
  Premium Subscriber
Premium Subscriber
 
Join Date: Jan 2001
Location: Somewhere other than home :(
Posts: 3,762
Default

Quote:
Originally Posted by MikeOxlong View Post
We call the sticky stuff bear ****. I've got a few dozen rolls of it because the riggers don't like to use it. Even with a courtesy wrap, the stuff is a pita.

The preferred method is to use Scotch 130C tape with a wrap of electrical tape over top.
One of my previous employers insisted on using Scotchkote...what a mess that stuff was.
__________________
Someone told me signatures are silly, so I got rid of mine.
Reply With Quote
  #32 (permalink)  
Old 09-04-2018, 10:43 AM
Member
   
Join Date: Feb 2017
Posts: 120
Default

UPDATE:

The dark dingy color of the copper shield in my coax seems to be superficial and due to the outside jacket as has been suggested.

When stripping back the jacket and inspecting the shield, it becomes obvious that the darkening is only on the outside. The inner side of the shield that faces the center conductor is still bright copper.

After stripping away the outer jacket, I used a Dremel tool with a nylon bristle wheel to remove the black stuff. It seems to remove about 70% of it and makes soldering much easier. The solder flowed quite nicely this time.
Reply With Quote
  #33 (permalink)  
Old 09-04-2018, 3:03 PM
mmckenna's Avatar
Member
   
Join Date: Jul 2005
Location: WTVLCA01DS0
Posts: 9,187
Default

Quote:
Originally Posted by KevinC View Post
One of my previous employers insisted on using Scotchkote...what a mess that stuff was.
But smells oh-so-good and makes the day just sort of fly right along….
https://www.youtube.com/watch?v=pl9dc5FhFYU
Reply With Quote
  #34 (permalink)  
Old 09-13-2018, 10:48 AM
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Apr 2003
Location: Cary, NC
Posts: 162
Default

A number of years ago at a commercial radio shop we got a couple spools of 'LMR-400 Type' coax, from a local vendor, who bought it from a U.S. manufacturer. Installation guys ran 2 long runs of it from dispatch on the 1st floor of a mall up to the roof, probably close to 100 ft. When I went out to test & bless the installation there was no kerchunk from the repeater they were supposed to access. Did the bottom & top wattmeter test - 50 Watts in at the bottom and absolutely nothing at the top. Zero Zilch Nada Gooseeggs Bupkiss.

Pulled apart the upper connection, cut the connector off & stripped back a bit. The surface of the inner conductor was almost as black as the outer jacket. Same at the bottom connector. Manufacturer must have had a process problem, something in the dielectric was corroding the copper plating of the inner conductor. Vendor took the unused cable back under warranty & replaced the material & such, but still a pain in the butt to run new lines.
Reply With Quote
  #35 (permalink)  
Old 09-14-2018, 12:48 PM
Lauri-Coyote's Avatar
Member
  Shack Photos
Shack photos
 
Join Date: Jun 2018
Location: Colorado/New Mexico and Washington DC
Posts: 163
Default

.
.
"Okay. I typed ‘lighting’. Everyone else knew that I was referring to ‘lightning’ but I guess someone will sue me over the grievous, fatal typo that invalidated the entire post."
.
.
.
Smiles, I knew it was 'lightning' but then I am a Smart A**
.
.
In my arena, when it comes to Mission Critical, having to decipher an incomplete message by filling in the blanks can be the failure determinate. My guys would have made a field day out of me if I had sent out a directive for something so cryptic.... (smiles)
.
All- in- all, my observation was not offer'd maliciously- I was just a being Coyote**
.
.
__________________________________________________ ________

.
.
** We had a long term project on the Navajo Reservation. There, a charming elder who was my liason to the tribal government, who, on learning this was my nickname (and radio call sign) delited in telling me many stories about Coyote.
.
When I told him how I had acquired the name he smiled and said "Yes, that fits you perfectly"
.
"We sometimes call him, or her in your case, Áłtsé hashké- the Story Teller, the little trickster, the Smart A**.... you are Coyote"
.
.
.
.
Lauri
__________________________________________________ ________________________
.

“The difference between the almost right word and the right word is really a large matter. ’tis the difference between the lightning bug and the lightning.”................. Mark Twain
.
.

Last edited by Lauri-Coyote; 09-14-2018 at 12:57 PM..
Reply With Quote
  #36 (permalink)  
Old 09-14-2018, 12:58 PM
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: May 2015
Location: Hammond, IN
Posts: 1,620
Default

Quote:
Originally Posted by kb4mdz View Post
A number of years ago at a commercial radio shop we got a couple spools of 'LMR-400 Type' coax,
That single word is a huge "red flag" in my experience. I should have thought the person who put the connectors would have noticed the problem...
__________________
Bill
N4GIX - Ham / WQWU626 - GMRS
VV-898, TK-840(N), 2xTYT-7800, 2xUV5R v2+, HP1, BCD436HP, TMV7A, Ritron RRX-450 Repeater, MD-380, XPR7550, 2xCS800, Bridgecom BCR-40U Repeater, Elecraft KX3 + PX3
Reply With Quote
  #37 (permalink)  
Old 09-14-2018, 3:02 PM
RFI-EMI-GUY's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Dec 2013
Posts: 2,261
Default

Quote:
Originally Posted by N4GIX View Post
That single word is a huge "red flag" in my experience. I should have thought the person who put the connectors would have noticed the problem...
Weasel Wording. I see similar in Baofeng spec sheets when they talk of modulation. You have to read spec sheets carefully these days because nobody seems to pay attention to or care about meeting established standards. If it can be made extremely cheaply there is a market ready for it and Amazon has no concept of quality. Just cheap and fast.
__________________
"Have Spectrum Analyzer, - Will travel" "Going Green" ø
Reply With Quote
  #38 (permalink)  
Old 09-14-2018, 5:15 PM
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Apr 2003
Location: Cary, NC
Posts: 162
Default

Quote:
Originally Posted by N4GIX View Post
That single word is a huge "red flag" in my experience. I should have thought the person who put the connectors would have noticed the problem...
Yes, you're right, the installing crew should have noticed; the guy doing connectors was new enough to da biz that he hadn't learned that 'fine point' of coaxial cable installation. He did a nice job on installing the connector, but not yet what makes a good connection. :-( It was a learning experience for several people.
Reply With Quote
  #39 (permalink)  
Old 09-14-2018, 6:55 PM
bill4long's Avatar
Member
   
Join Date: Aug 2012
Location: Earth
Posts: 561
Default

Quote:
Originally Posted by W9BU View Post
I used to have some jumpers made from an RG-8X that used a clear PVC jacket. Over time, the copper braid in the shield oxidized and turned green...which you could clearly see through the jacket. I threw those jumpers in the trash. They may have still been good, but they sure looked ugly. Not exactly a black death, but a green sickness that proved terminal.

Bailey Quarters was played by Jan Smithers. I think I would have married her, given the opportunity. For a time, she was married to James Brolin who made a name for himself as Dr. Steven Kiley, M.D., on the Marcus Welby. M.D., TV program. He was a bit of a stud in his day, so I'm sure Ms. Smithers would have been more interested in him than me.
Me too.

Current pic:

https://i.pinimg.com/originals/d5/73...88139b1ce0.png
__________________
This space for rent
Reply With Quote
  #40 (permalink)  
Old 09-14-2018, 6:57 PM
bill4long's Avatar
Member
   
Join Date: Aug 2012
Location: Earth
Posts: 561
Default

Quote:
Originally Posted by Murphy625 View Post
Read this in another post where a member was discussing a J pole he built and was having issuess. He said his coax had some "black death"

Tried googling but of course google thinks I'm interested in music.

Can someone tell me what this means?

I've been wondering about some coax I have laying around myself. Its a Columbia RG8 /U (.405 diameter) and when I strip it back, the copper shield isn't brightly colored.

My copper shield is a dingy darker color although the center conductor looks fine. The shield is copper and you can see the copper color, but there's a dark oxidation taking place.

Is that what black death is? Is my coax going bad?
Throw it away and get some RG-213, which is the modern equivalent.

Are you transmitting or just receiving, and which band(s)?
__________________
This space for rent
Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 4:58 PM.


Powered by vBulletin® Version 3.8.2
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
All information here is Copyright 2012 by RadioReference.com LLC and Lindsay C. Blanton III.Ad Management by RedTyger
Copyright 2015 by RadioReference.com LLC Privacy Policy  |  Terms and Conditions