[OKDXA] 20m yagi ez files

[Mark Beckwith]

Oh well.  The JPG didn't come through, so I have posted it here: 
http://n5ot.com/okdxa.jpg

Anyway, at age 65 and doing my own antenna work still, I like shorter 
lighter antennas when possible.

73 - Mark N5OT



On 2023-08-10 7:35 PM, Mark Beckwith wrote:
> 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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