ARRL

Secure Site Login

Forum Home - Rules - Help - Login - Forgot Password
Members can access, post and reply to the forums below. Before you do, please first read the RULES.

9:1 or 1:1 Balun?

Mar 23rd, 04:33

K4PDM

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
I'm using a 250 foot inverted vee fed with window line, and I'd like to know which balun I should be using...the 1:1 balun built into my MFJ 989D tuner, or a commercial surplus 9:1 balun.

Most experts nowadays say to use a 1:1 balun with a long doublet fed with 450 ohm line, but my analyzer shows lower untuned SWRs with the 9:1 external balun. It seems the tuner doesn't have to work as hard to match, with the 9:1 balun.

Even though current thought favors the 1:1 balun, in my case since the match is easier to achieve with the 9:1 balun, should I be using it instead?

73 Paul K4PDM


Mar 23rd, 09:13

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

Perhaps. But, SWR doesn't provide the whole picture. You may want use an non-contact IR thermometer to see which balun gets hotter after transmitting. You may also want to see which balun provides the best signal to noise ratio on receive. Just because a balun is commercial made doesn't insure that it has a lot of common mode rejection on the frequencies you want.

Zak Lau W1VT
ARRL Senior Lab Engineer
Mar 23rd, 09:16

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

Perhaps. But, SWR doesn't provide the whole picture. You may want use an non-contact IR thermometer to see which balun gets hotter after transmitting. You may also want to see which balun provides the best signal to noise ratio on receive. Just because a balun is commercial made doesn't insure that it has a lot of common mode rejection on the frequencies you want.

To get a complete picture, you would want to use your analyzer measurements to calculate transmission loss as well as tuner loss.

Zak Lau W1VT
ARRL Senior Lab Engineer

Back to Top