3 element UHF yagi--home brew

[mainetrunk]

Hey builder's, I've been searching for the UHF yagi formula for a long time. Bottom line, I re-fined my search, and came up with a design that is VERY similar to the 1 I've been staring at for 3 years... So, I just got done putting the finishing touches on the bnc, and BINGO.. I just got done with a VHF, and works perfect, now this.. The answer was HERE in R-R all the time, so here it is. Good luck builder's..
http://www.nt1k.com/files/n1bmx-gmrs-yagi.pdf
P.S-- Home Depot DID NOT have the correst spacer. I am using a black rubber fuel line, nore does ANYONE know what a shoulder washer is.. Had to buy big rubber washer's.. $5.00 total, I had the bolts,bnc, and tape...

 

[majoco]

There's a picture of a shoulder washer on the construction drawings. Obviously available from McMaster-Carr.

 

[mainetrunk]

I don't see it's use, I glued the elements in place. This this is the BULL'S @&%%'s... It is already in place doing well.

 

[majoco]

They're to insulate the elements from the boom, the reflector and the director. It works better if the boom is not part of the antenna. The small shoulder washers go under the driven element cable screws.

 

[mainetrunk]

oooops

Oh, WOW... I just saw the diagram again. Well, that may explain the good vhf reception.... Hmmmm. O.K, back to the drawing board--and PAY ATTENTION to detail. Glad I don't do this for a living, I'd be in debt... Thanks majoco--cheers to ya.

 

[mainetrunk]

I type in the search bar -- where to buy shoulder washers in N.H, and there's nothing near by. I'm thinking about using the leftover hose. That will separate them

 

[KevinC]

Not trying to get off-topic, but it's always amazing how well a random piece of metal works as an antenna.

And how much better a resonant one works...

 

[mainetrunk]

You are correct, look at satelite dishes, wires pointing at a peice of metal.
Back to it--- a DRILL PRESS is reccomended. Straight holes are a pain to make.

 

[mainetrunk]

Well, it is done. I used rubber hoses to be the insulator on all 3 elements. I see no difference between the 2. Well, I got what I wanted..

 

[majoco]

It would appear that the driven element is about 6" long, this would make it a quarter wave at about 500MHz. Why are you trying it at VHF? It says it is a GMRS antenna, I don't know what band that is on. Any other frequency would give it a high loss and a weird radiation pattern.

 

[mainetrunk]

GMRS band? That is uhf I beleive. And yes, I have to use the ATTENUATOR when doing vhf...
The next 1, I want to aim for 470 mhz thru 485. That's where the -action- is...

 

[majoco]

GMRS band repeater inputs 462.550 to 462.725, repeater outputs 467.550 to 467.725MHz.

 

[prcguy]

Thats backwards from GMRS in the US, repeater inputs are 467 and outputs are 462.
Prcguy

GMRS band repeater inputs 462.550 to 462.725, repeater outputs 467.550 to 467.725MHz.

 

[mainetrunk]

That's the formula i was taught 15 years ago, 465---469.9875 is input. Unless someone rewrote tx and rx . Any way, antenna's are done.. Next project-- cw

 

[majoco]

My apologies - I read it wrong. We don't have/need GMRS here, just a non-licence band around the same frequencies.

 

[mainetrunk]

I jusy wanna say- I built 2 of them, slightly modified, and works just as good.. I'm not doubting measurments to freqs, just saying-you can be off by a milimeter and still get good reception. I just built a 5 element yagi making hole where I -want-- It works better than the other 2, maybe better than the 1 I sold to MaineRadioMan. Dont tell him, lol