OK. But one other VERY important thing. RG-numbers are generic. They used to be a spec, so they used to tell you what the cable was. That hasn't been true for at least 50 years. As an example, there
To add to Jim's post, anytime that you can use a higher impedance cable the loss will be less. If you have a 50 ohm and a 75 ohm cable with the same size conductors, the 75 ohm cable will have less l
This is *generally* true, if comparing all copper cables. But even in that case, the HF loss is not proportional to DC resistance when comparing different sizes of cable. And all bets are off when co
Rick, My point is that virtually all transmission line losses at HF are I squared R losses. What R is will depend on the materials, and how they are affected by skin effect. The equations on the LMR
That is not in dispute, but what is in dispute is the assumed proportionality of R to the square root of frequency. A copper plated aluminum cable that is better than an all copper cable at 50 MHz ma
Good information, but I need some suggestions. I will have a run of about 100 feet station to to the tower and then up 75 or so feet. I operate at 1 watt much of the time and need suggestions regardi
But Rick, I'm talking about loss at MF and HF, especially low HF (that is, 160M-40M), and to a lesser extent, 20-10M. Again, once you hit 5 MHz, skin effect becomes increasingly dominant. These data
Consider these cables that are spec'ed at 1 MHz: Type DC resistance RF loss Ratio DCR/RF loss 8214 2.3 0.1 23 8237 3.1 0.2 15.2 9913 2.7 0.3 9 9258 7.6 0.3 22.8 9913F7 2.9 0.4 11.6 Not a very good co
pessimistic, at least on the low end. Might be. I'm looking at hard copy of the 2006 edition. The graph shows 0.2 dB/100 at 1 MHz for 9913, 0.3 for 9913F7. The tabulated data shows 0.3 for 9913, 0.4
For what it is worth a number of years ago I found that the measured loss of various forms of new Belden cable at 440 Mhz was noticeably less (maybe 20 % or so if memory serves ?) than the published
This is quite interesting... It would be interesting to get a bunch of samples and test them. Tricky, because you need enough length so you're not trying to measure 0.001 dB differences. I wonder if
Author: "Marlon K. Schafer" <ooe@odessaoffice.com>
Date: Thu, 4 Feb 2010 21:03:03 -0800
Do you happen to be in Wa. state? I have a 1k spool of lmr400 I could let you take measurements from :-). Probably still have 200ish feet on my "small" roll. I've also got various hardline cable (5/8
Yes. 100 ft is sort of a minimum length, and more is better. My measurement setup is quite simple -- an HP generator and an HP spectrum analyzer. Nothing automated. To eliminate calibration errors in
No, I'm in the mountains above Santa Cruz. Maybe someone near you has the instrumentation and lab skills to do this. Short runs of hard line are probably not long enough to get good data. Thanks for
That's why you want to install the largest coax you can afford. 73 Roger (K8RI) _______________________________________________ _______________________________________________ TowerTalk mailing list
The ideal situation would be to be in some warehouse with several dozen different coaxes and your ANA. One would also want to figure out a reasonably fast way to make the connections. They don't have
Is it? the surface area of the shield is enormous compared to the center conductor. If both were solid copper, the relative contributions would be in the ratio of diameters. Z is about 138/sqrt(epsil
So, are we going to see articles in QST about "How to fabricate coax air line from thinwall 6" aluminum irrigation tubing" or " How I learned to stop worrying about rain on my openwire line and to lo
Not as ideal as you might think. The problem is that most coax is shipped on reels with access to only one end. To make a transmission loss measurement, you must unreel it to get a connector on both
No, see below See below I happen to own instrumentation that allows me to measure loss from one end; it's called an MFJ-259B. Cable loss is a built in function. As long as the far end is open, cable