On Mon, 7 May 2012 19:17:58 -0500 Mike Waters <[email protected]> wrote: >it would be interesting to >experiment with some > CAT5/6 sometime, just for the fun of it. :-) > I did that. I was testing a small dual-feed DHDL loop (-50 dBi gain) using twisted pairs removed from a CAT 5 cable. On the bench the twisted pair showed 100 ohm of impedance and a loss of about 2.8 dB at 1.8 MHz on a 100' run. (I also tried CAT 6. The results were the same. The difference between CAT 5 and CAT 6 is that the CAT 6 pairs' twists are more precisely controlled, which results in a more uniform impedance and lower losses at the upper end of the spectrum.)
I was running two 16 foot lenghts of twisted pairs, one from each element, into a phasing/combiner box, which had carefully designed balanced-transformer inputs. The twisted pairs had #31 common mode chockes every 4 foot. While the twisted pairs worked, despite the balanced arrangement, there was more common mode (BC and noise) pick-up than the same runs using (non-balanced, but grounded) RG-179 cables. The RG-179 cables had the same #31 chokes as the twisted pairs. I attribute the performance difference to the fact that the shields of the coax cable were grounded, while the twisted pairs were "floating". I believe that if one wants to use a balanced arrangement, twinax may be the ultimate solution. Otherwise, just stick with good quality RG-6. 73, George _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
