[BC] RG-8

[Mike McCarthy]

What Times doesn't say is LMR series cables introduce IM between the braid 
and foil.  Thus artificially raising the noise floor.  In very sensitive 
applications, the raising of the floor 3-6 dB could be unacceptable.

Andrew makes a LDF-1, a 1/4" cable for last foot applications.

MM

At 11:07 PM 4/3/2008 -0600, Gregory Muir wrote
>Choice of cabling is often found out to be inadequate after the job has 
>been completed.  It tales careful consideration before you start to choose 
>the cable for your application.  If you look closely at cellular sites you 
>will often find 214 in use within the building.  Then it is Heliax up the 
>tower. The same applies to trunking sites.  But there I have even seen RG8 
>in use.
>
>LMR400 is effectively solid.  It's a foil tape covered with a tinned 
>copper braid.  Times touts shielding effectiveness 50 dB greater than 
>single layer braid.  In the past I have had 100% success of its use at 
>co-located sites. And I currently have tenants at one of my sites 
>utilizing both RG214 and LMR400 on their receive sides in the presence of 
>several high power LMR and digital paging systems plus my two 100 KW FMs, 
>a 50 KW FM and a 35KW television transmitter with no problems at 
>all.  Turn out the fluorescent lights when you leave and they stay 
>lit.  That tells me about the RF presence at that site.
>
>One must also use care in terminating smaller cables.  The "quick-spin" 
>cable stripping tools nearly always cut off a significant amount of shield 
>strands reducing the contact area with the connector outer 
>shell.  Variation in crimp pressure can mean the difference between good 
>and bad when putting crimp connectors on cable.  I have performed 
>post-mortems on trouble cables and found that excessive pressure literally 
>pinches the braid connection to a point where it breaks off inside the ferrule.
>
>Andrew Heliax cable is excellent.  Although it would be great to do, I 
>would have a problem trying to use it in 100% of my applications in light 
>of the numerous cables and tight spaces they are located in.  Besides, I 
>would hate to have to adapt from Heliax down to BNC and SMA connectors on 
>the equipment.
>
>Greg
>
>
>----- Original Message ----- From: "Broadcast List USER" 
><Broadcast at fetrow.org>
>To: <broadcast at radiolists.net>
>Sent: Thursday, April 03, 2008 7:23 PM
>Subject: Re: [BC] RG-8
>
>
>>Really, double shielded or quad shielded cable is CRAP!
>>
>>You should only use 100% shielded cable, like LDF-4.
>>
>>I have built all kinds of combined land mobile sites, and they all  bitch 
>>about the 100% shielding requirement until it is on the air.   100% 
>>shielding is really great, and makes the sites work well.
>>
>>RG-8 really blows.  So does 213, 214, and LMR-400.  If it isn't  solid, 
>>it isn't 100%.
>>
>>--chip
>>
>>On Apr 3, 2008, at 6:00 AM, broadcast-request at radiolists.net wrote:
>>>Message: 11
>>>Date: Wed, 2 Apr 2008 23:31:49 -0700
>>>From: tony dinkel <tonydinkel47 at hotmail.com>
>>>Subject: Re: [BC] RG-8
>>>To: <broadcast at radiolists.net>
>>>Message-ID: <BAY127-W48C4B2CB93108F2D10145DC1F70 at phx.gbl>
>>>Content-Type: text/plain; charset="iso-8859-1"
>>>
>>>
>>>Agree with the LMR comment.  I am using LMR-400 cable where ever 
>>>I  would spec RG-8 or 213 now.  RG-214 is mandatory for more 
>>>critical  situations that involve flexing or full duplex mode.  And if 
>>>you  think 214 is expensive, try RG-393.  A customer had me replace 
>>>all  of his jumpers in a tx rack not too long ago.  Really expensive 
>>>and  stiff stuff but its double shielded, silver plated everything 
>>>and  teflon dielectric.  Not good for areas with UV exposure 
>>>though,  unless you give it a good 50% overlap wrap with Scotch 
>>>88.  Done  that too but not for a run to a tower!
>>>
>>>td
>>>wb6mie
>>>microwave frequency services
>>>
>>>
>>>>If you have the inclination to use a more inexpensive grade cable as
>>>>compared to Andrew products, you might try looking at the Times Microwave
>>>>LMR series cables.  They have an overall foil shield (100%  coverage) 
>>>>and are
>>>>very robust for most applications at a much cheaper cost.  The  only minor
>>>>problems is that it is a significantly stiffer cable as compared  to 
>>>>RG8 and
>>>>that it possesses possess a foam internal insulation which is a  bit tricky
>>>>to manage at times if you need to solder the center conductor.  RF
>>>>Industries makes crimp-style connectors for this cable (again at reasonable
>>>>prices) but, after attending a RF connector symposium at NIST, I  still
>>>>solder the center conductor contact in lieu of crimping whenever possible.
>>>>
>>>>But if you want a super high-grade RG8 braided shielded cable, go  with
>>>>RG-214 which has a double silver-plated braid shield and will put  you 
>>>>in the
>>>>poor house before your project is completed.
>>>>
>>>>Greg
>>
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>
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