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Author Topic: Which Coax  (Read 3631 times)
KB1PXU
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Posts: 33




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« on: July 05, 2012, 01:37:58 PM »

I am getting prepared to put up a Mosley TA-63-N multi band antenna. The antenna will be mounted to a Glenn Martin roof tower.Still waiting delivery on both.  I had intended to use LMR400UF with a run of about 100 feet.  I have used LMR400 and 400UF previously for VHF and a HF windham all with excellent results.  Mosley recommends RX8 and 213 and not 9913 or equivalent.  I called them and asked why I should not use LMR400 and they said it was not designed for HF and they sometimes have customers who have anomalies on different bands when using LMR400.  I then said that many people use hard line when feeding large towers.  They really had no additional comments.

Just wondering what your thoughts are on using Belden RG-213 versus LMR-400UF.  Also I will need to to make a RF choke by winding 5 turns in a 6" diameter with the coax.  Just wondering if you think the 213 would be easier then the 400UF to coil or about the same. 

73
Will KB1PXU
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LA9XSA
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Posts: 376




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« Reply #1 on: July 05, 2012, 02:09:43 PM »

I'm not experienced with towers, but I don't quite understand. I thought LMR-400 would be good for HF; perhaps not cost-effective, but low loss. Perhaps somebody else could weigh in on this.
I'd understand if they discouraged any form of braided coax, and instead recommended heliax coax; that's good advice for remote commercial sites, since rusting coax braid can cause non-linearity, and thus intermodulation. However RG213 and RG-8X also have braided shields. Does the foil and braid in LMR cable start rusting and acting non-linearly before coax with just braid?
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KK5J
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Posts: 76




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« Reply #2 on: July 05, 2012, 02:28:52 PM »

I use LMR 400 with no problems. A while back there were suppliers of LMR400-like coax made overseas that wasn't very good quality. Perhaps that is the issue. Times LMR-400 has been excellent AND if it works at VHF well, it certainly should have few problems at HF.
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N4NOO
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Posts: 106




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« Reply #3 on: July 05, 2012, 05:09:31 PM »

What is wrong with Belden 9913?
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K0CWO
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Posts: 416




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« Reply #4 on: July 05, 2012, 06:39:08 PM »

Nothing
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K9KJM
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Posts: 2416




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« Reply #5 on: July 05, 2012, 10:24:55 PM »

What is wrong with Belden 9913?

Several of the early versions of Belden 9913 turned out to be just JUNK.   The early sprial air center would condense moisture inside EVEN IF PROPERLY SEALED, And the next few versions had major problems with the center conductor "migrating" out to the shield with the early foam dielectric versions.......
I, And most all commercial users I am aware of quit using 9913 and went to TIMES LMR400 many years ago.

They claim the latest versions of 9913 are now OK.  Could be. I just won't take a chance on it.

The ONLY reason someone could not suggest LMR400 for HF is because it is not nearly as "tough" as Belden RG213, Which you can run over with a truck.
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STAYVERTICAL
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Posts: 854




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« Reply #6 on: July 06, 2012, 12:23:41 AM »

I have just taken up 100 foot of RG213 which has been lying in the rain/sun and over part of a driveway where sometimes it was run over by a car.
I just took it up for a check after 5 years of service.
After a quick clean of the covering, I tested it with the antenna analyser, and it seems as good as new.

Cheap, tough, low loss, flexible - you would never notice the difference with a more expensive but fragile coax.
Making an air choke with it is trivial.
If you want to pay something extra get the milspec stuff.
Really, for HF ham use, RG213 is the logical choice on every measure I can think of.

The real point of failure are the terminations.
If you put a great deal of care into making sure water does not get in, you should be good for a long long time.
Next week my recycled 213 goes out again for its next 5 years in the weather.

73 - Rob

« Last Edit: July 06, 2012, 12:26:58 AM by STAYVERTICAL » Logged
KG4NEL
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Posts: 373




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« Reply #7 on: July 06, 2012, 05:37:24 AM »

'PXU -

If you're curious, plug some of your numbers into this: http://vk1od.net/calc/tl/tllc.php

There are other calcs available (Times Microwave has one, too)...but this has the Andrews cables as well as ladder line.

You're looking at less than a quarter of a dB difference between 400UF and RG-213. But I can't explain why Mosley told you what they did.


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KB1PXU
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Posts: 33




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« Reply #8 on: July 06, 2012, 06:37:18 AM »

Perplexing that Mosley was not able to provide a fuller explanation other than it was not designed for HF.
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K7KBN
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Posts: 2763




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« Reply #9 on: July 06, 2012, 08:58:48 AM »

The guy at Moseley is the former manager at the local Radio Shack.  Cellphones are too small for LMR-400.  Cellphones use RF.  Therefore, LMR-400 is not recommended for RF.  Simple syllogism  Grin Huh Roll Eyes
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73
Pat K7KBN
CWO4 USNR Ret.
K5KNE
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Posts: 65




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« Reply #10 on: July 06, 2012, 08:19:27 PM »

LMR 400 will work fine - if you have it on hand or can get some easily.  I use Belden 9913 for my runs up the tower and one run goes to my tribander. I just had 9913 and decided to make all the runs up the tower with it.  RG-8U will work fine for the HF bands and LMR 400 and 9913 are both overkill because they are made for VHF and UHF.

I don't like putting on n connectors, but I use them.  PL-259s with RG-8U is sure a lot easier for me.

73   Walter  K5KNE
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K3VAT
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Posts: 701




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« Reply #11 on: July 07, 2012, 04:27:24 AM »

I am getting prepared to put up a Mosley TA-63-N multi band antenna. The antenna will be mounted to a Glenn Martin roof tower.  73 Will KB1PXU

Will, The Mosley TA-63-N is a pretty big antenna (7 ft^2 @ 60 lbs) for a roof-mount system.  However, the Glenn Martin RT936 or 1832 should accommodate it (so I trust that you've ordered one of these).  Additionally, with this size of antenna the actual roof tower mounting system (design & materials) is very important and, IMHO, the key to safe & long life of this arrangement.  Roof pitch, roofing materials, size and spacing of roof trusses, access to underside of the roof are all important parameters.  Hopefully, you (or better yet, engineer consultant) have worked all these factors out; but, if not, then there are a number of good postings on this forum to assist.  Finally, I believe that Norwalk, CT requires a building permit for roof mounted towers, is that correct?

GL, 73, Rich, K3VAT
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KB1PXU
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Posts: 33




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« Reply #12 on: July 07, 2012, 05:39:13 AM »

I am getting prepared to put up a Mosley TA-63-N multi band antenna. The antenna will be mounted to a Glenn Martin roof tower.  73 Will KB1PXU

Will, The Mosley TA-63-N is a pretty big antenna (7 ft^2 @ 60 lbs) for a roof-mount system.  However, the Glenn Martin RT936 or 1832 should accommodate it (so I trust that you've ordered one of these).  Additionally, with this size of antenna the actual roof tower mounting system (design & materials) is very important and, IMHO, the key to safe & long life of this arrangement.  Roof pitch, roofing materials, size and spacing of roof trusses, access to underside of the roof are all important parameters.  Hopefully, you (or better yet, engineer consultant) have worked all these factors out; but, if not, then there are a number of good postings on this forum to assist.  Finally, I believe that Norwalk, CT requires a building permit for roof mounted towers, is that correct?

GL, 73, Rich, K3VAT


Rich -

Thanks for all your suggestions.  Everything already handled.  Still have a remaing question about why not to use LMR400UF for the feedline.

73 Will KB1PXU
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K3VAT
Member

Posts: 701




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« Reply #13 on: July 07, 2012, 09:58:07 AM »

Rich -
Thanks for all your suggestions.  Everything already handled.  Still have a remaing question about why not to use LMR400UF for the feedline.  73 Will KB1PXU

Very good Will!
You can certainly use LMR400UF for the feedline.  I've used this at my previous station and it worked great.  Many consider LMR coax to the the best performance-vs-price, especially as there are good dealers who can install the exact connectors that you require (such as http://therfc.com/ or http://www.davisrf.com/).  If you want an expert's opinion on coax, give Joel a call at the RFC.

GL, 73, Rich, K3VAT
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KC4MOP
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Posts: 729




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« Reply #14 on: July 07, 2012, 05:50:22 PM »

The Orion Wire Company:
Stacey Jones
Accounting Manager
Orion Wire Co., Inc
ph: 603-787-2200
fx: 603-787-2221

I bought 150 feet with PL259 connectors installed for $156.35 delivered. 1.1dB loss/100 feet at 50mhz.

Has an extremely flexible and reasonably priced version of LMR400. Can even be used right at the antenna. My concern was losses at 6M. But even 10M needs to be watched for losses.
HF systems with high SWR can get lossy.
Fred
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