Trying a homebrew yagi

[HomerBB]

I have begun to assemble a home made 3 element yagi.
I've started with the basic parts, and will be putting it all together in the next couple of days when I get time off from work.

Some photos of the start is here:

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[HomerBB]

In fairness regarding the construction materials, The pipe is all EMT (electrical conduit), for now, not aluminum. If the antenna proves worthy, I'll look into upgrading the cost to aluminum.

The PVC is to help with attachment to the top fence rail boom, and for easy adjustment of spacing. The radials can be slid in and out on the boom like a trombone movement to get my best performance.

I've looked at several matching methods, and am leaning toward this one:

[ external image ]
The DK7ZB

Any ideas forthcoming from you fellows will be discussed and considered.

Thanks,
Homer

[drdx]

Looks like a great start and I think that feed will work. The feed is always the biggest challenge as a gamma match is not the easiest thing to make at home. I don't know the spacing and element length you use, but from the pics it looks like you got some close math somewhere. For the reflector length on a 3 you should be in the 18 foot range for tube that size, about 16"8 for the director. Spacing will be in the 5 foot range optimally but many 3's only run an 8 foot boom as the simple yagi is very forgiving and almost "wants" to work. Being that it is under a full wavelength long boom wise, spacing is not overly critical as long as the elements are radiating, so uniform spacing is fine. I'd be curious if the pvc is strong enough esp. on the support but you'll soon find out. The front to back and fwd gain on a 3 is a great package for its size for sure.

For some cheap aluminum, I recently found a couple of aluminum walkers like the mobility challenged use. Many are all aluminum and can be easily cut up and made into elements. I found mine being thrown away, cheaper than buying anyday. You could also go all pvc with wire inside or a pvc structure and wire elements strung between like they did on early beams with bamboo.

What is the boom? Is it a fiberglass tent pole? or metal? Doesn't matter, just wondering.


-drdx

[HomerBB]

The boom is chain link top rail, 1 1/4" galvanized steel.

The dimensions I am starting with will be these (in the photo no elements are cut to length, yet):

Frequency = 27.185
Reflector length = !8' 1 3/8"
Driver length = 17' 2 1/2"
Director length = 16' 6 5/8"

Spacing:

Reflector to driver 7" 3"

driver to director 3' 7.5"


Remember that I said one reason for the 1 1/4" pvc nipples on boom holding the elements was so I could adjust the distances between all the elements by simply sliding them in and out.

[HomerBB]

For some cheap aluminum, I recently found a couple of aluminum walkers like the mobility challenged use. Many are all aluminum and can be easily cut up and made into elements. I found mine being thrown away, cheaper than buying anyday. You could also go all pvc with wire inside or a pvc structure and wire elements strung between like they did on early beams with bamboo.
-drdx

I'll be on the look out.

[drdx]

Good deal, measurements look good. It is great to see some homebrewing. The boom spacing in a book I have is the 5 foot range but I'm sure your information is newer than mine. The reflector to DE is wider spaced compared to most I've seen but your adjustability is nice and makes it easy to change. I just checked another book I have by Lawson and spacing using his math somes in a little over 5 feet for R to DE and a little under for DE to Dir. My Orr book calculates it to 5'4" for R to de and an even 5' for DE to Dir and that is at an even 27 mhz. I wrote that in the book long ago as I often freebanded down low so I made it with that in mind. Balance can be another issue and more evenly spacing can help there too. I'm not sure what your operating range is but the numbers you have there are for a nice broadbanded beam but should work fine from lower 26 mhz on up into the upper end of 27. If you operate within a narrow range of frequencies (like the regular 40, you can tighten up (shorter ref, longer director) the elements to where you operate for a little added performance, but I don't know if I'd bother as they work quite well even if set up to be wide banded. Try to make the elements telescopic so they like your boom have adjustability.

-drdx

[HomerBB]

Ok, I will look at that. Will poast a few more photos later (off to work).
I used an antenna program for these spacings, but will keep an open mind on the things you've offered. naturally, I'll need to get the match built and start trying it on for size, so to speak.

Thanks, great info.

Homer

[HomerBB]

Got the elements cut and set to the spacings outlined above. Have it set to a 45* angle and just ned to get the matching system made and mounted, raise it up higher and begin to test it.

Photos:

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[HomerBB]

Added my version of the match system.

Tested SWR:

ch 01 1:7

ch 19 1:4

ch 40 1:2

with no further tuning than the match on the antenna as shown.

All the time I had to fool with it so far. Will try to get better reports than truck drivers saying, "It's workin' driver"

I'll try to get a few field strength numbers, too. I need to get it up into the air a little.

photos:

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[drdx]

Cool cool cool, you should be proud it was that close the first run. If you have no other method, get a junk radio and deadkey it from the house and drive around in and out of the intended signal path and test it. Now, if this thing has promise in the structural and ruggedness departments then you'll be hailed as a home depot antenna specialist.

-drdx

[HomerBB]

I am happy so far. Now I have a SWR meter that also has a field strength meter on it with a little wire antenna that inserts into the top of it. i've never used it, as it was recently given to me. Would that be better to use than the radio, or both?

[Double D]

Ok, I will look at that. Will poast a few more photos later (off to work).
I used an antenna program for these spacings, but will keep an open mind on the things you've offered. naturally, I'll need to get the match built and start trying it on for size, so to speak.

Thanks, great info.

Homer

What program did you use? BTW, what are the diameter of those elements? I'd like to run your dimensions through one of my programs but without the diameters, it's a guessing game.

[HomerBB]

I used an antenna program for these spacings...
Homer

What program did you use? BTW, what are the diameter of those elements? I'd like to run your dimensions through one of my programs but without the diameters, it's a guessing game.

KA5WNX's Antenna Workshop II

This program offers 27 different antenna designs, but it doesn't give any data on performance, nor adjustment of things like spacing, length, etc.

Anther choice that does is for Yagi antennas only is QUICKYAGI

When put through Quickyagi I found I disliked the results.

The diameter of the elements is 1/2" conduit, or actual 5/8" OD or 0.625".

[Double D]

I used an antenna program for these spacings...
Homer

What program did you use? BTW, what are the diameter of those elements? I'd like to run your dimensions through one of my programs but without the diameters, it's a guessing game.

KA5WNX's Antenna Workshop II

This program offers 27 different antenna designs, but it doesn't give any data on performance, nor adjustment of things like spacing, length, etc.

Anther choice that does is for Yagi antennas only is QUICKYAGI

When put through Quickyagi I found I disliked the results.

The diameter of the elements is 1/2" conduit, or actual 5/8" OD or 0.625".

Okay, here's the results if the antenna was placed 1 wavelength over average ground:

R=25.81
X=-25.53
Gain=12.71 DBi
Front to Back=30.53 DB

Pretty good numbers for a 3 element. I have Quickyagi too, but all the numbers are freespace, so that really doesn't really tell you much about the antennas performance over ground.

[HomerBB]

Okay, here's the results if the antenna was placed 1 wavelength over average ground:

R=25.81
X=-25.53
Gain=12.71 DBi
Front to Back=30.53 DB

Pretty good numbers for a 3 element. I have Quickyagi too, but all the numbers are freespace, so that really doesn't really tell you much about the antennas performance over ground.

Much better than I thought. I guess I need that program. Does it have a name?

Thanks.

PS. When the final construction is done (I took it down to redo it with lighter materials and to improve my mast. Too much wind here) it will mount at one wavelength height. One thing also I've gotto do is put on a gamma match, or use it flat. The mast negatively influences my otherwise good SWR.

[Double D]

Much better than I thought. I guess I need that program. Does it have a name?

The program is called MMANA. You can get it here: [Please login or register to view this link]

[HomerBB]

Much better than I thought. I guess I need that program. Does it have a name?

The program is called MMANA. You can get it here: [Please login or register to view this link]

Thanks

[Double D]

No problem. One thing, everything is in metric so be ready to do a lot of converting.

[HomerBB]

No problem. One thing, everything is in metric so be ready to do a lot of converting.

No problem.