Nice of G3TXQ to so liberally quote my work:-)
I have a problem with W7FG recommending 4:1 baluns.
(http://trueladderline.com/all-baluns/) I suspect the thinking is that because
the line is high impedance, the balun should be an impedance step up. With a
non-resonant dipole fed with open wire, the input impedance is just as likely to
be lower than 50 Ohm and a 1:1 is more appropriate.
No need for me to elaborate, W8JI does a fine job:
https://www.dxengineering.com/techarticles/balunsandfeedlinechokes/baluns-choosing-the-correct-balun
N7WS
On 12/11/2017 6:04 PM, Grant Saviers wrote:
It seems there is a good solution to a single common mode choke for balanced
lines over all of HF. See the article in November 2017 RadCom (RSGB) "An
effective, easily made HF Balun". G3LNP describes a 4:1 balun for all band
doublets fed with REAL open wire feeders, with CM rejection on the order of 40db.
Additionaly, consider G3TXQ's measurement of punched ladder line losses.
http://www.karinya.net/g3txq/wet_ll/
I evangelize using real open wire, easy to make or buy. Examples:
http://trueladderline.com/w7fg-design-600-ohm-open-wire-feedline/
http://www.73cnc.com/product_p/ls100.htm
Grant KZ1W
On 12/11/2017 16:15 PM, Bert wrote:
We're talking about a common mode choke, not a balun/transformer.
Bert, VE3NR
On 12/11/2017 7:08 PM, Wes N7WS wrote:
Actually that's not true. A lot of baluns are wound with balanced
transmission line.
Wes. N7WS
Sent from my iPhone
On Dec 11, 2017, at 3:49 PM, Bert <balmemo@sympatico.ca> wrote:
Hi Bill,
Choking the window line is not a good idea - you'll choke the signals too.
Common mode chokes are mainly used for coax cables and multi-conductor
cables. I'm sure you'll get many more detailed replies from the experts.
Good Luck!
Bert, VE3NR
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|