9:1 or 1:1 Balun?
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| Mar 23rd 2018, 04:33 | |
K4PDMTotal 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 2018, 09:13 | |
W1VTSuper Moderator 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 2018, 09:16 | |
W1VTSuper Moderator 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 |
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