[OKDXA] 20m yagi ez files

[Mark Beckwith]

All good.

If it was me I would create a smaller, easier to handle, 
computer-optimized 3 element yagi with similar gain and a better front 
to back ratio, all on a 13 foot boom.  I really don't feel any need to 
handle long yagis any more.  Short ones work fine for me.

That said, my friend Glenn K6NA turned his 204BAs into OWAs without 
lengthening the booms, and he is very pleased with them.  I have asked 
him for the dimensions.

Does this mailman list do embedded graphics or attachments?  I guess 
we'll find out.  If the images come across below, then we're good. If 
not, I can send to you directly or post to the web and email a link to 
the group.

Both screenshots ("screenshots" like I took a snapshot with my camera of 
my DOS antenna modeling screen) show a stock 204BA and a computer 
optimized 3 element yagi on a 13' boom.  Stock HyGain is red, Computer 
Optimized 3-elements on 13' boom is yellow.  Both are modeled one-half 
wave above ground.

I have not gone the EZ route, my modeling software is the old DOS 
program AO by K6STI.



BTW I have a massive boneyard of parts up here in Osage County if you 
need anything.

73 - Mark N5OT


On 2023-08-10 7:31 AM, Jeff Martin wrote:
> 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'..
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