Home Brew Yagi

digitalanalog · #1 (**permalink**) 03-27-2009, 07:46 PM

o.k., so i could not find a antenna that i thought was worth the cost, to receive what i wanted, so i decided to build my own.

I built this antenna using a Yagi-Uda calculator i found on-line, there are a bunch of them available, i just picked one and went with it.

My main low reception area i am trying to gain signal on is 158.000 - 159.000MHz so i built this antenna using the calculator at 158.500MHz.

List of materials used to build this yagi:

1) 3/8" Rigid Aluminum Tubing, 3/8" O.D., .305" I.D, .035 Wall $5.52 ea. total = $11.04
2) Polythylene (LDPE) Rectangular Bar 1" x 1" total = $5.75
3) 1 1/2" Cush-O-Clamp $2.70
4) Rubber end caps FREE (from work)
5) 6/32 stainless hardware FREE (from work)
6) Small stainless hose clamps (for the driven elements) (free from work)

Total Cost of build = $19.49 (the stuff from work cost very little to buy even if i did have to pay for it myself)

If the weather holds off tomorrow i will be raising to 50' and see if it picks up my low receiving stations.
After checking the performance, I plan on building allot of my own freq, specific antennas, it much cheaper to build then to buy, as long as you pay attention to cutting length and spacing details, i guess i will find out how well i paid attention to details when i put this up.

Pics of the antenna up in the air will follow,as well as information as far as if it worked for what i built it to do.

So here is what it looks like.

mtindor · #2 (**permalink**) 03-27-2009, 07:57 PM

Thanks man... I'll be right over to pick it up! rofl.

Nice job. I'm anxious to hear how it performs for you. Looks very light - I'm sure the wind load will be nil.

Mike

digitalanalog · #3 (**permalink**) 03-27-2009, 07:59 PM

Quote:

Originally Posted by mtindor

Thanks man... I'll be right over to pick it up! rofl.

Nice job. I'm anxious to hear how it performs for you. Looks very light - I'm sure the wind load will be nil.

Mike

Weight is just under 2 lbs

rafdav · #4 (**permalink**) 03-27-2009, 10:19 PM

for low dollars. Let us know how she does on the VHF freqs. Congrats your way on a job will done.

Hoofy · #5 (**permalink**) 03-27-2009, 11:04 PM

Nice looking job.

Don't forget the coax !!!!!!!!!!!!!!!!!!!

knightrider · #6 (**permalink**) 03-28-2009, 12:08 PM

Antenna building is probably one of the cheapest things you can do in any of the radio hobbies, and make a difference. Your antenna looks very nice. It is said the antenna can make or break the system, and I have found that to be very true. Please follow up with your specs/measurements on building the antenna. I have a couple I have built that are an omni type. It is a simple dipole made of #10 electrical wire, placed inside of white PVC, and mounted vertical. Works great for receive. I have made and tuned a couple for fast deployment on 2m and 440 as well.

digitalanalog · #7 (**permalink**) 03-28-2009, 03:48 PM

Well antenna is up
No photo's of it, nothing exciting, only mounted at 20' on 1 3/4 galvanized pipe.

After about 2 hours of scanning, it's not picking up the 158.000 - 159.000MHz station
i built the antenna for, i think i will need an amplifier to grab the station i am so desperatly trying to receive.

But the performance of the antenna is GREAT, and it's as if it's an omni directional antenna, i am picking up everything from 150.000 - 450.000MHz.

And it's brought up many signals that were only giving 2-3 bars now at 4 or 5 bars, so i am very happy
with its performance, and only mounted at 20' i am really happy.

I used RG-6 cable, solid center to the upper driven element and outer braid to the bottom driven element.

Here is a screen capture of the program showing the spec's from which i built the antenna
all dimensions are within 1/32" from what is shown, i wanted it to work so i paid Very close attention to details.

All in all, i am very happy, even if i still can't receive the station i want, but maybe more height (sure do need it) and an amp will probably do the job.

Thanks to all for the comments.

smason · #8 (**permalink**) 03-28-2009, 05:12 PM

Looks pretty darned good, nice job!
My antennas always look like something the cat dragged in, but they do work...

James04TJ · #9 (**permalink**) 03-28-2009, 06:18 PM

Before adding an amp I would create another antenna with more elements (additional directionality and thus more gain) and possible upgrade the feedline. You may also want to consider placing the mount behind the reflector since in it's current configuration the mast may be altering the antenna's properties. Finally, you did not mention how long your feedline is but upgrading from RG-6 to something semi-rigid in a 1/2" or larger flavor may be something to consider if you have a 100+ foot run.

When attempting to reel in a distant station, every dB helps. With that said, you made one very fine looking antenna.

digitalanalog · #10 (**permalink**) 03-28-2009, 06:49 PM

Feedline is only 50', so the RG-6 may not be ideal, it should be satisfactory.

Yes, my next plan is to make a much larger antenna, and possibly using the same program making a 20 element antenna, i did some math on it and it will be very large yet very reasonable cost wise, when considering what they want for something like a Crate or other popular log type yagi's.

More antenna's will be in the future, that's for sure.
There cheap
Fairly easy to construct
and it's a great feeling when it works as well as this one does.

But i do think i will need an amp, i live in a rural area and i live down in a valley, so all things(line of site or other reception situations) are not in my favor.

James04TJ · #11 (**permalink**) 03-28-2009, 08:25 PM

You could also consider (rather than a 20 element design on a single boom) creating two separate antennas in a stacked array configuration. Take a look at the Cushcraft 26B2 for some ideas: http://www.cushcraft.com/comm/suppor...4WB%2013B2.pdf You should be able to net near 20dBi if you play your cards right.

digitalanalog · #12 (**permalink**) 03-28-2009, 08:33 PM

Quote:

Originally Posted by James04TJ

You could also consider (rather than a 20 element design on a single boom) creating two separate antennas in a stacked array configuration. Take a look at the Cushcraft 26B2 for some ideas: http://www.cushcraft.com/comm/suppor...4WB%2013B2.pdf You should be able to net near 20dBi if you play your cards right.

20db gain would be great, i will take this design into consideration that's for sure.
thanks.

kb0nly · #13 (**permalink**) 03-31-2009, 01:57 AM

I see it was already mentioned, but i will add another vote for mounting it behind the reflector, get the mast out of the equation. The omni like performance is a combination of things, first of all it doesn't have enough directors to make it really directional, and putting the mast that close to the driven element in the same vertical plane might also be affecting its tuning more than anything.

But a darn nice looking antenna!! Where did you find the poly bar stock by the way??

Another consideration, if you go a lot bigger that poly is bound to sag and move around in the wind. You can easily alter the design to use an aluminum tube for the boom and have the driven element electrically connected, it wouldn't have to be insulated if you used something as simple as a Gamma Match on it. Easy to make and adjust. I can maybe post some pictures tomorrow to show some of the ones i have made if i get time. I usually take a piece of aluminum sheet about 1/2" wide and whatever length i need and then form it around two pieces of rod the same size as the match and element, then a couple screws to tighten the loops to the element and match.

Do a search for Gamma Match and you will see plenty on the subject. Last one i built i took an aluminum block and drilled two holes in it then sawed it in half on a band saw, that made a super looking shorting strap.

AlmostHandy · #14 (**permalink**) 03-31-2009, 02:23 AM

Hey digi, check out this yagi program by VK5DJ. It is really amazing.

Not only does it have a really nice yagi calculator in it, it also has calcs for baluns, stacked arrays, gain, SWR, Impedance, and a cool calc that lets you reverse engineer a pre-existing antenna into a design guide for a duplicate.

Great stuff.

digitalanalog · #15 (**permalink**) 03-31-2009, 07:03 AM

Here is the tubing used
McMaster-Carr

Here is the Poly Rectangular bar used
McMaster-Carr

Here is the mast mounting clamp i used.
McMaster-Carr

kb0nly · #16 (**permalink**) 03-31-2009, 05:32 PM

Ok, cool. $2.30 per foot on the square poly? Ouch! I guess for small antennas its no big deal, but i can get various grades and sizes of aluminum tubing for far less and it should prove to be more durable, just have to alter the design a bit for the driven element to be installed without being insulated.

drumstick · #17 (**permalink**) 04-01-2009, 11:33 AM

Nice antenna !! I may be wrong, but wouldn't RG58 cable (50-ohm) be better than RG6 (75-ohm) for antenna use ?? I know that both will work, but the 50-ohm cable is usually used for antennas.

Fast1eddie · #18 (**permalink**) 04-01-2009, 01:50 PM

Very nice and excellent craftsmanship. Maybe build a corner reflector since you are in a valley w/pre-amp. Thanks for posting the links-found them very interesting and joined up. Outside of Pittsburgh here, in the western suburbs.

DDan · #19 (**permalink**) 04-01-2009, 02:11 PM

Quote:

Originally Posted by drumstick

Nice antenna !! I may be wrong, but wouldn't RG58 cable (50-ohm) be better than RG6 (75-ohm) for antenna use ?? I know that both will work, but the 50-ohm cable is usually used for antennas.

Nope. On a scanner the impedance is as varied as the frequencies listened to. The RG6 is a lower loss solution for a scanner.