[OKDXA] 20m yagi ez files

[Jeff Martin]

Hi Dan,
   Regarding the EZ files, a standard 204BA to start with would be nice, 
then any mods that someone has suggested would also be good...
   I'm not looking at a major over-haul. I will stick with the stock 26 
foot boom length. The original had the spacing laid out for weight 
balance on the boom. A more updated computer design would have the 
driven element closer to the reflector and dir 1  just barely in front 
of the boom to mast mount. I have some measurements for spacing that 
would probably work.
Refl      0"
Driven 85"
D1       72"
D2     149"

   These spacings came out of both the 1994 Antenna book and the 2007 
Antenna Book.

   Some kind of weight compensator will be needed out on the boom toward 
the D2 end.

   The differences between the two books are in the tip element lengths. 
The refl and driven elements are a couple inches different. Also it says 
nothing about whether these dimensions are for CW or phone or whatever. 
Guess I can just try it and see. Was just looking if someone had some 
experience or documentation or EZ files...

Tnx...
73,
Jeff - K5WE

------ Original Message ------
>From "dan edwards" <w5xz at att.net>
To "Oklahoma DX Association" <okdxa at mailman.qth.net>
Date 8/10/2023 7:03:20 AM
Subject [OKDXA] 20m yagi ez files

>jeff, how many eznec files for 20m yagis would you like to see? < grin >
>jim lawson, w2pv, was right; there is no magic, yagi gain is largely defined by boom length. roughly, double the boom length, pick up 2 dB..
>kim, n5op, is also right; a 40' 4 el version was fairly successful, and klm, now m^2, still makes one.
>later on, it was found that adding elements in the right places could improve the pattern and / or match across a broader range of frequencies..thus, the 'OWA' arrays found favor ( optimized wide-band array ). Asymmetric element spacing makes the things tend to 'wind vane' when the breeze picks up.
>So, w6nl, in 'Physical Design of Yagi Antennas' described a way to add vestigial elements ( like pvc ) to torque balance the things..
>but to me, more elements = more cost, weight, wind loading...usually, i'm looking for best bang for the buck, rather than unlimited budget, anyway.. and, w5dc, also sk, convinced me 'dont use a gamma match'..insulated driven element feed, slightly shortened from resonance, and matched with shunt inductance, is efficient and foolproof..
>as always, JM2C...73, dsw, w5xz, dan
>the last model was what we put up at w5wmu, fixed on europe..the 'death ray', ha! even komrad veektor, n8oo, said 'dan, this i like'..