Author: "John E. Cleeve" <g3jvc@jcleeve.idps.co.uk>
Date: Mon, 18 Feb 2013 08:03:36 -0500
Good afternoon gentlemen, A 100 metre(325ft)drum of 75ohm, 25mm(1 inch) diameter coax, and the appropriate connectors, has been donated to my GM project, for which I am very grateful. I am considerin
nope, go for it! Good afternoon gentlemen, A 100 metre(325ft)drum of 75ohm, 25mm(1 inch) diameter coax, and the appropriate connectors, has been donated to my GM project, for which I am very grateful
If the antenna has an impedance of 50 Ohms, and the coax is close to a quarter-wave or odd multiple long, you'll see an SWR(50) of 2.25:1 at the shack end instead of 1:1. 73, Steve G3TXQ A 100 metre(
Cut the coax to a common multiple of 1/2 wave length for as many bands as you can. You can easily get 20-10 with the length you have without losing too much coax and maybe 40-10. It won't help the lo
Author: "John E. Cleeve" <g3jvc@jcleeve.idps.co.uk>
Date: Mon, 18 Feb 2013 09:14:59 -0500
Thank you, David, Steve and Stan, I have always ensured that when using co-ax for transmitting, it has been cut a multiple of electrical half wave lengths at the lowest frequency to be used on the or
On 2/18/2013 5:47 AM, Stan Stockton wrote: Cut the coax to a common multiple of 1/2 wave length for as many bands as you can. You can easily get 20-10 with the length you have without losing too much
Yet another way of attacking this problem, or if you have a bit more SWR than you would like, is to build a "line flattener" box. I made one with three lengths of 50 ohm coax - 2,4 and 8 feet long, w
Author: "John E. Cleeve" <g3jvc@jcleeve.idps.co.uk>
Date: Mon, 18 Feb 2013 14:38:23 -0500
Thank you Jim and Gene, For your advice and also pointing me towards AE6TY and SimSmith. My aim for my GM project is to be able to switch between HF aerials without the use of tuner units, it looks a
If the antenna has an impedance of 50 Ohms, and the coax is close to a quarter-wave or odd multiple long, you'll see an SWR(50) of 2.25:1 at the shack end instead of 1:1. 73, Steve G3TXQ Jim VE7RF __
The vswr on the coax is 75/50 with a perfect 50R load. Measuring with a 50 ohm vswr meter will show vswr from 1:1 to 2.25:1 depending on the line length. 73, Gerald K5GW In a message dated 2/19/2013
Another point with respect to loss in that coax. Because its diameter is quite large, loss is MUCH lower than the RG8-size coax we usually use. It is also lower because the loss in ANY coax at HF is
On 2/19/13 6:21 AM, Jim Thomson wrote: Another point with respect to loss in that coax. Because its diameter is quite large, loss is MUCH lower than the RG8-size coax we usually use. It is also lower
You guys are saying the same thing! ie, agreeing; not disagreeing. 73/K5GW In a message dated 2/19/2013 8:58:32 A.M. Central Standard Time, jimlux@earthlink.net writes: Sure it would. as long as the
Sometimes folks don't read very carefully, especially when the ideas expressed are different from their preconceptions. When I started in ham radio 57 years ago, most hams fed dipoles with 75 ohm co
Author: Anthony R. Gold <ham-radio-mail-lists@ahjg.co.uk>
Date: Tue, 19 Feb 2013 17:10:52 +0000
A good thought, and if you use a 75 ohm VSWR meter you can measure that. _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTa
The SWR on the 75 Ohm line will be 1.5:1, but if the line is a quarter-wave or odd multiple long, the 50 Ohm load impedance is transformed to 75*1.5 or 112.5 Ohms - that's an SWR(50) of 2.25:1. In fa
In fact any line length between 0.15 wavelength and 0.35 wavelength will transform the load impedance to produce an SWR(50) greater than 2:1. My, my -- some of us do work pretty hard to find worst ca
Yes, BUT -- signal to noise on receive on the MF and HF bands is nearly always determined by band noise (that is, noise picked up on the antenna), not circuit noise in the RX. VHF/UHF is a very diffe
The Op asked a simple question: "... would I notice any serious difference in the aerial matching etc, between the use of 50 ohm and 75 ohm coax at HF" I gave him a factual answer: if he has an anten
A rather pessimistic one and a rather limited one, considering the great usefulness of 75 ohm coax if you know how to use transmission lines and take the time to do the design work. I gave him a far