I recently purchased a 1000 ft roll of Davis BuryFlex cable, planning on using it to replace old RG-213 cables on my 15M and 20M 3-stacks. I pruned one length of cable for an odd multiple of quarter
The VF of BuryFlex is published as 0.82. I think standard RG213 has a lower VF. --Original Message-- From: towertalk-bounces@contesting.com [mailto:towertalk-bounces@contesting.com] On Behalf Of R.Si
Wouldn't the different electrical lengths indicate that the cable manufacturing process is not consistent? Any spec on a cable has a tolerance and though they may wander in performance, it could stil
Actually, its well known that the velocity factor in a single run of coax can vary. You won't have this problem with Andrew Heliax (essentially). Whenever you use coax for phased lines, you need to c
The velocity factor in foam coax is the most difficult thing to control, since it is a function of the percentage of air bubbles in the dielectric. Some manufacturers specify it for a range of values
phase shift for each delay line of solid dielectric coax, if the application is critical. For HF, the delay is likely not critical. From reading the ARRL Antenna Book I understand phase errors up to
Indeed, phase errors of tens of degrees aren't going to have a huge effect, however, a transmission line length change of 30 degrees might have a radiated phase change much different. The reason is t
Note that the same change in bubble percentage that changes the velocity factor also changes the characteristic impedance, because they're both related to the effective permittivity (dielectric const
have a huge effect, might have a you're not just well matched load. tested by play. At the ohms, but both different, so the Unless I'm mistaken, the peak phase error caused by a line mismatch occurs
It's a bit tricky.. If the line matches the source (or the load), so there's only a mismatch at one end, then the phase error will be equal to the length error, because the matched (at one end) line
In terms of the phase of the current delivered to the load (what we care about when driving antennas), the current phase error won't necessarily be equal to the length error even if the source is mat
Turns out that there's a worst length, given a particular phase of mismatch, but that if you don't know the mismatch phase, and you assume they're all equally likely, then all lengths are the same. T
I would add that the Gore types have a very 'air-filled' Teflon tape dielectric that is very soft. It is so hard to keep coaxial that most of the good stuff requires armor to keep it working well. A
Peak phase error due to transmission line mismatch occurs with lines that are an odd number of 1/8th wavelengths long. The are no phasing errors due to mismatch when the lines are any multiple of 1/4
More like $5000.. at least for a pair of 1 meter test port cables, and that's if you get the inexpensive Megaphase stuff. _______________________________________________ See: http://www.mscomputer.co
This was best demonstrated by OH8OS in his paper about phasing his 2 x 3 array of 6L 20M KLMs -- 2 wide by 3 high, for a total of 36 elements on 20M. He had the capability of rapidly phasing the arra
with The any That's what I recalled. I looked at it again and that appears to be true for any condition. 73 Tom _______________________________________________ See: http://www.mscomputer.com for "Se