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80 mtr tuned to 160 mtrs

Jan 4th 2015, 19:38

KB3FFH

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Has anyone tuned a 80 mtr OCF antenna to 160 mtrs?
Jan 6th 2015, 21:08

NV2K

Joined: May 20th 2014, 01:06
Total Topics: 0
Total Posts: 0
I haven't, but I can work 40m using a 20m OCFD. It uses a balanced series stub to help with impedance matching, and my suspicion is radiation from this stub permits my tuner to match it on 7MHz.

I'd post a picture, but that does not seem possible in this forum.
Jan 7th 2015, 02:31

AA6E

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
You can post all kinds of formatted text on the forum, including images -- if they're findable through a web URL. Check https://www.phpbb.com/community/faq.php?mode=bbcode for all the options. (Not all codes necessarily work on this site.)

Example:

Avatars (self portraits, etc.) like mine at the left can be created through a free account at http://gravatar.com.

These are just a few ARRL secrets I've stumbled across. A pity that nobody actively runs these forums. :>

73 Martin AA6E
Jan 7th 2015, 02:33

W1VT

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

Running an EZNEC model of an 80M OCFD at 30 feet, I get 1 dBi of gain straight ip. With 50 ft of LMR-400, you can expect to lose 6 dB in the feedline and another 6 to 10 dB in the transmatch. In theory, you could reduce the transmatch loss to 1 to 2 dB by building a custom L network. 6 dB assumes a transmatch like the ATR-30 which has 500 pF tuning caps--the loss goes up significantly with smaller tuning capacitors and the usual T network.

The most practical 160M antenna for most hams is some sort of inverted L or top loaded vertical worked against a counterpoise or radial system. The tuning range of many tuners is limited on 160--ideas that work on 80 may not work on 160 because the tuner isn't up to it. If you put up an inverted-L you can use the horizontal wire to help in tuning--adjust the length for the most practical match.

Zack W1VT

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