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View Full Version : Adding elements to FM Yagi



pluche
07-22-2008, 07:25 PM
And so I'm thinking... some of you might be able to answer this:

I bought an AntennaCraft FM6 a month ago and am not quite satisfied with it so I ordered an Winegard HD6055 8-element beam. Why the Winegard you ask? Because it's rated at 1 full dB extra and only 12-inch longer than the FM6 which pretty much fills up the space I have available for this without impeding on my ability to manoever. I can't affoard booms the size of the APS9 or APS13 at this location.

Without having any findings to support this, I'm wondering... would it be worth while to drill the boom of the Winegard beam and attach to it 3 or 4 elements of the soon-to-be defunct FM6, something in the order of two in the back and two up front???

I'm having all sorts of questions which all converge to the first one:
Are antennas built to optimum specs?
Is element spacing of such great importance?
Would adding a director (out back right-smack between two existing ones) improve gain?
Is there a minimum number of elements which can be safely added to improve the 7 dB figure published by Winegard?

and son on!!! Thanks for your imput.

KW4RZ
07-24-2008, 07:13 PM
I know of a modification to improve the Radio Shack / Antennacraft FM6 but not the Winegard. In my experience with a directional antenna you only have one reflector and multiple directors to increase forward gain. Driven elements in a FM antenna are in a log periodic fashion to cover the wide range of frequencies. Any modifications without proven efectiveness will probably disrupt and decrease your forward gain. Brian Beezley has a number of FM antenna modelling webpages that might be of help:

http://www.ham-radio.com/k6sti/

pluche
07-25-2008, 12:57 PM
Wow! Thanks a bunch for this link. I'll certainly give it a good read. 73. This is the kind of mid-summer project that sort of kicks in my mind in preparation of the late august-september peak Tropo season in the Montreal area.

73

John Wilke K9RZZ
07-31-2008, 06:30 AM
I don't think adding elements to the same boom is going to improve anything. I would imagine they are computer optimized (I could be wrong), but without going longer, I doubt you'll notice much improvement over the FM6 (a pretty good performer for it's size!) Longer booms = bigger performance. More elements does not always = better performance.