Bob, and the gang, I added a random length of LMR400 coax between the output of the coupler and the 1:1 balun. Iam guessing Im tuning the coax and not so much coupling energy into the doublet. But no
That's good news. The length of coax is some portion of an electrical wavelength. It simply adds some value of reactance which then the tuner is able to match. Just for curiosity, have you tried to m
How much coax did you add? The main idea of open wire line is it is much less lossy than coax at high SWR's. You therefore want to keep the coax portion is short as practical. The SWR on the feedline
Interestingly, when using *short* lengths of coax the loss can be lower at high SWR than when it's matched. For example, 10ft of RG213 has a matched loss at 1.9MHz of 0.03dB; but terminated with 500
That's a new one on me. How could loss be less with high SWR on a short length of coax? It makes no sense. Carl Moreschi N4PY 58 Hogwood Rd Louisburg, NC 27549 www.n4py.com On 11/9/2013 5:07 PM, Stev
Sure it does! The losses in feedline at HF are overwhelming due to I^2R copper losses. If you look at the current distribution along a matched line it's flat; for example, flowing 50W into a matched
This is an interesting point, and Steve has recently made a believer out of me! The primary transmission loss component at HF, and even more at MF, is IR loss. With high SWR on the high-impedance sid
Correct! In the example I gave, had the 10:1 SWR been caused by a 5 Ohm load rather than a 500 Ohm load, the current would have been a maximum at the load (3.16A) and the loss/unit length at that poi
True - but in the situation being discussed the high SWR on the short length of coax is being caused by the load at the balun/ladderline. Arguably that high SWR is more likely to be a high impedance
I say it's 50-50 whether it's a high impedance or low impedance at the coax connection point. We don't know how long the open wire line is so the high SWR line could have rotated to anything that wou
No, I havent, but thats a darn good idea. The wife is sick, so I have plenty of time to play radio on a cold saturday night. Ill put the MFJ on it and see what it shows Mike Bryce wb8vge prosolar@sss
I didnt measure it, but took a hunk I had in the shack and put some ends on it. Im guessing but between ten and fifteen feet. Mike Bryce wb8vge prosolar@sssnet.com ___________________________________
That's a new one on me. How could loss be less with high SWR on a short length of coax? It makes no sense. The loss in coax at HF frequencies is not that high, and the additional loss due to high SWR
If you use coax for an 80 meter dipole and run it on 40 meters with coax, the loss will be very high. That's because the additional loss from a high SWR (around 100 to 1 in this case) is huge. If you
Actually, if you "do the sums," you find that dielectric loss is barely beginning to be a factor well above 500 MHz in most cables that aren't "broken" -- for example, full of water. 73, Jim K9YC ___
Steve asked me to post the following message for him. (he is having trouble getting his post to go through) -Rick -- I say it's not 50:50 :) The impedance will "rotate around" a Smith Chart centred o
Here's the rules that apply: The longer the feed line on a given line......the more loss. The higher the SWR on a given line.......the more loss. The higher the frequency on a given line.....the more
I have a 253 Auto coupler and MFJ 989B. The MFJ998RT in the shop for repairs from abuse. Non of these tuners will tune 160M on their own. Each of these I had to add an inductor L network for 160M. Ev
Jim, for Antenna Analyzer BCI from nearby station, find a loopstick or other similar old AM coils and make as series circuit of it and a 365 cap to ground on antenna input of analyzer. It will trap o
My inductors are about 25uH in series and 25uH to ground. Best that I can calculate from online calculators. Jim K9TF -- Jim K9TF _______________________________________________ TenTec mailing list T