[OKDXA] Coax Replacement

Tue, 17 Sep 2002 00:22:51 -0400

Thanks to all for the input on my feedline inquiry.  Nelson, your technical writing was especially interesting.  My RG213 still seems to be working fine just some age creeping up on my 10/15 meter yagi feeds.  I intend to keep in place my original line and switching arrangement while I get new feedlines, control cabling and switching for the multi-radio setup in place.  Since I'm going to the trouble to route and connect all the new stuff I wanted to consider best options for upgrades to cabling etc.  Coy, your comments on connections and protection of such is certainly correct.  No crimp style connections - all soldering - UV and proper weather proof sealing etc.  I'm running a new PVC tube for cabling to the second tower also.  Did a less than satisfactory job on the initial installation.  In fact the new pipe is a big part of my incentive.

This antenna stuff for DXing and contesting can be time consuming indeed.  Lightning protection for all the control cables and coax runs etc. in addition to the cable runs themselves.  Weather protection for all connections.  Doing it properly does pay off though as many a winter can be spent in the shack doing the part of the hobby I enjoy the most - operating.

73 - Jerry K5YAA

In a message dated Mon, 16 Sep 2002 10:43:54 PM Eastern Standard Time, [email protected] writes:

> 
> 
> Nelson,
> 
> Very fine job.  I was going to do something similar and you saved me a whole
> lot of time.  ;-)
> 
> And just for the record.   I have repaired ailing amateur radio stations
> around the world as well as long haul HF stations for the government.  Only
> on two occasions did I ever find the coax to be at fault and in one case it
> was the wrong coax for the use and in the other it had been manufactured
> wrong.  The first was easy to find.  Someone had installed RG-8 in a 300ft
> run to feed a UHF antenna.  (not good)  On the second, it was a tough
> problem to find and I wouldn't have if it hadn't been for a first class TDR
> that I applied to the line.  I paced off the number of feet to the problem
> area, cut through the 2 inch hard line to find that the center conductor was
> against the shield.
> 
> All of that having been said.  I have found many, many more problems with
> incorrectly installed or faulty connectors.  I would recommend spending much
> more time on the connectors than on the type of coax.
> 
> My 2 cents worth.
> 
> Coy
> ----- Original Message -----
> From: Nelson Derks <[email protected]>
> To: <[email protected]>
> Sent: Monday, September 16, 2002 9:48 PM
> Subject: Re: [OKDXA] Coax Replacement
> 
> 
> > Ok I have heard who like what type of coax but why did you select the coax
> > that you are using. PLEASE edumacate me.....
> 
> Ohhhh... Like we've never heard THAT before from The 'DLL...
> 
> By commercial standards, the original RG-8 coax was designed as a low-cost
> 50 ohm feed line in non-critical applications at moderate power levels. It
> uses a durable solid polyethylene dielectric with a service life in the five
> year range (really, look it up!). RG-213 is the mil-spec version with a
> non-contaminating PVC jacket that extends the service life closer to 10
> years. Old coax tends to go 'gooey' inside and will develop cracks in the
> sheath causing water migration problems and loss of efficiency. RG-213 is
> preferred, but there are cables sold as 'RG-213 TYPE' which isn't much
> better than RG-8 in terms of durability.
> 
> In most cases, the selection is based on cost and usage. RG-213 is good
> through 10 Meters for moderate run lengths and shorter runs up to 50 MHz. At
> 2 Meters and up, the loss characteristics become a factor and a foam coax
> like Belden 8214 becomes attractive... But, even a good foam coax like
> Belden has shortcomings in durability, heat resistance and impedance
> accuracy. 8214 doesn't like hot attics or sharp bends and isn't the first
> choice for phasing harnesses or tuned stubs, but, in a careful installation
> it works well. Some Hams will sacrifice a few dB for the greater service
> life of RG-213 over 8214, but, for a little more money, you can have it
> all...
> 
> Check out the specs at: http://www.timesmicrowave.com/products/commercial/
> for the LMR series from Times Microwave. These cables use a high silicone
> content outer sheath that's extremely abrasion resistant (compared to
> RG-213) and a high-density foam that approaches the crush resistance and
> impedance consistency of a solid dielectric cable, while maintaining
> superior loss characteristics. It's damn good coax and something you can
> install once and pretty much forget about for many years. Everything I do on
> 2 Meters and up is wired with an LMR cable and I've had very good luck with
> my VHF efforts. Part of that is due to the clean horizon on the slight ridge
> at my QTH, but I do believe some credit must be given to the coax. I have
> two runs that have been up five years and the outer sheath still looks new.
> 
> As for the model numbers, they come from the outside diameter of the cable.
> LMR-195 is .195" like RG-58, LMR-240 is a quarter inch cable like RG-8X, and
> LMR-400 is the equivalent of .405" RG-8 style cables. LMR-600 and up require
> custom connectors, but offer even lower loss characteristics approaching
> rigid Heliax style cables at a fraction of the cost. Visit the web page,
> it's worth the time...
> 
> Also, rumor has it Doug Xander uses nothing less than LMR-800 and enjoys
> superior results... I suspect you would too, if your QRP rig was running 10
> gallons and had a Continental Electronics logo on the front 
> panel, but
> that's another story.
> 
> - AC5UP
> 
> 
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