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On Sun, 11 Dec 2005 05:39:27 +0000, Wes Stewart *n7ws*@ yahoo.com
wrote: I wasn't going to go that far, and I realize it's probably not common in ZL but I've bought lengths of LDF5-50 at ham flea markets. The last purchase, claimed to be about 10 meters worth, but by my estimation at least twice that long, and new and unused, cost me $10 U.S. Most of this stuff is leftover or removed from commercial two-way or cell phone use and shows up all of the time. LDF4-50 is even more common. I often buy short pieces that have been cut down, just for the connectors that are still on one end. I find it curious that Andrew cable is seen so often at these events and yet I've -never- even seen a piece of Davis cable, dispite the claims that miles of it are in commercial use. I agree with Ian's comments, the larger sizes are often available here as they are less attractive to hams. But if you buy 3 or 4 lengths of LDF5 or LDF6 and use connectors to join them, you will run into big $ unless the connectors come very cheap. Andrews has some braid+foil / foam coax, and they perform roughly similarly to LMR400, BuryFlex and 9913. To my mind LDF4-50 would be acceptable in this configuration, and the great advantage is that if water gets in somewhere, it doesn't wick right down the cable. I haven't handled BuryFlex, and I saw the claim it is waterproof, but I suspect it is not as waterproof as Heliax type cable where the closed cell foam dielectric is bonded to the inner and outer conductor with an adhesive, and there is no braid to form a natural wick. I am in the throes of replacing feedline on a HF dipole to repair damage by birds. The birds don't seem to eat PE irrigation tube, so I have fitted RG6 with a W2DU style balun inside 13mm PE tube to defeat the birds. The birds have attacked the LDF4-50 on the VHF/UHF antennas, but even if they make a hole in the copper, it doesn't seem to affect cable performance measurably, probably because the water can't travel up and down the cable from the hole. Still, parts of ZL have Keas, and they will eat anything, especially rubber or plastic! So I feel for our ZL friends running coax over 60m of ground. BTW, I added BuryFlex to my online line loss calculator, 9913 and C2FP were already there. I still like the open line option, but it will be real important to use effective baluns to adequately ensure balance. It used to be common commercial practice when HF Radio was used more widely for international telephony / telegraphy. Owen -- |
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