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DIY 7-Element Yagi

RxDx

RxDx

Speaker collector
Well, I finally put something together. After buying a Channel Master CM-3671 and being disappointed by its performance, I felt I could do better.

This is the result:
build1-finished.jpg


I used pieces of the Channel Master. It had exactly what was needed for mounting elements. This hardware is hard to find otherwise.

Anyway, here is the whole saga. Preliminary testing looks good so far. Next it goes on the roof.
 
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So you're saying size matters? :)

For some reason, I couldn't access the saga. How did you determine element spacing?
 
musichal said:
So you're saying size matters? :)
Click to expand...

:-) This was build 1. Build 2 is a 12 element unit.

For some reason, I couldn't access the saga. How did you determine element spacing?
Click to expand...

Hmm. I tried a couple different ways and didn't have any trouble. Don't know what to tell you. I can post it here if you still can't get through.

Couple of ways I considered element spacing, one a stand-alone program (John Drew's Yagi Calculator), one a javascript (Martin E. Meserve's K7MEM.com). I went with the latter; I could use more elements (7 vs 5) on the boom I had, according to the model each presented.
 
Got it on the roof and noticed a few things :-)

It's a bit less sensitive than the thing it replaces. But that's not bad, comparing it to an antenna with a claimed range of 120 miles on FM. The model suggests almost 10 db.

It's definitely a narrower band antenna. I'm wondering if that partially explains being "down" on sensitivity. Can't just get "close enough" with the rotor now...

I'm happy with my first serious attempt at a killer antenna.
 
Help! I don't understand the spacing or the lack of a reflector. Eh?

The real beauty of a Yagi is not its gain, but its F/B ratio and pattern/beamwidth. I'm not getting this one. Help me understand.
 
No, you may have it right (that I have the last two elements reversed in function), but I can't get into K7MEM right now to check. Damn, you mean this thing might work even better?
 
Yes, reflector at the back. Always. Then driven element (connected to feedline). Then director(s) the the front.
 
G'day all, yes a reflector is indeed a part of every multielement yagi.

Place it about .15 to .25 of a wavelength behind the driven folded dipole element.

Its inclusion should dramatically improve the F/B ratio, as has already been mentioned. Regards, Felix (vk4fuq) aka catman.
 
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