[TowerTalk] Fan Dipole

[Gene Smar]

Don:

     Add two feet to the 40M antenna and get on the air.  DX is awaiting.


73 de
Gene Smar  AD3F



-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Don W7WLL
Sent: Friday, September 29, 2017 4:30 PM
To: Towertalk <towertalk at contesting.com>
Subject: [TowerTalk] Fan Dipole

To begin, I have zero experience with a fan dipole. I’ve read what I could find but see there are a number of variables to consider and not all are in agreement (not unusual) on feedpoint arrangement and separation.

Wanted to try one, so put together an 80/40, hung it off the 70 foot tower in an general inverted V configuration.

The 80 is at about a 150 deg spread angle and the two ends are around 30 feet off the ground. It now has minimum SWR at 3.760.

The 40 is connected to the same point as the 80 (at a MFJ-918 balun I had). It is at about a 100 degree spread with the ends about 20 feet above ground. Shows minimum SWR at 7.350.

Both currently are in same general plane (vs ‘at right angles’). 

Obviously the 40 will have to be lengthened to get it down to where I want to go.

Can I presume that the 40 should be lengthened to the freq I want first, and trim the 80 last (then back and forth until close enough)?

What should I expect if I decrease the distance between the 80 and 40 wire ends (i.e. open the 40 up), What is the ‘best’ distance before they become to close?

Also I have the room and also was considering adding a set of 160 wires but at a wider spread (180-190 deg).

I have the option of adjusting both the spread angles and the end wire heights.

Words of wisdom from those familiar and having experience with fan dipoles would be appreciated.

No fancy anaylazers available, just the 269C.

Don W7WLL
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