Im NOT a beleiver in the Yagi!

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Shortwavewave

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PLEASE GUYS Im not pointing fingers at you, and im not saying your wrong this is my OPINION

Why you ask? Yes I know I sound like I dont know WTH Im talking about, BUT proof Is always better than word of mouth.

Fisrt off let me just say I never beleived these things worked anyway BECAUSE, how in the heck does the Reflector "KNOW" its the reflector? what if the Directors think there the Reflectors? and whats keeping the signal from coming in at and ANGLE...nothing

I built a 800mhz Yagi...... directional? Yeah right How come when I point it the other way "BEHIND" a steel building I still can hear the stuff Im trying too.

Then again, this all could be becuase I built my own(not the best out there)
so untill I can spend money on a "REAL" professional Yagi.......

I will remain a disbeleiver on these objects

Please no flaming... if you want to CUS me out send me a email or PM
 

Airdorn

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Yeah, they don't work.

That's why there's millions of them everywhere, all pointed at their own very specific place to improve reception. :)
 

KC0QNB

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The antenna design dictates what element is what, the length of the elements also comes into play.
the reflector is longer by a certain amount than the driven element (the element the cable is hooked to)
the director are shorter than the driven element (DE) and proceed to become shorter as they go away from the DE by a certain amount the farthest director away from the DE will be the shortest of the set.
How are you feeding the DE? directly, through a balun, or a gamma match?
if you look at this picture you will see the the DE is actually split in two pieces and directly fed with coax (not the best way)
http://www.signalengineering.com/ultimate/yagiexp.jpg
now this one is connected via a gamma match (better)
http://www.echolinkradio.com/2m_beam_4el.jpg
Here is an article to read
http://www.hamuniverse.com/yagibasics.html
If you need more personal attention pm me, I am willing to help with what I know, which ain't much when it comes to yagis, I never needed one.
 

DPD1

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I think where you're going wrong is not so much what you built, but what you expect it to do. It's normal to get signal off the back and also off the sides. They will all do that to some extent, some more than others, depending on how it was designed. The signal should simply be strongest in the direction you're aiming... Assuming you are getting the actual signal unreflected. The more the antenna is in free space unobstructed, the more it will perform the way it's supposed to. The more you have objects around it, the more unpredictable the directional quality will be due to reflected signals.

Dave
www.DPDProductions.com
Antennas & Accessories for the RF Professional & Radio Hobbyist
 

Shortwavewave

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I guess your right, it didnt preform like I thought it would

Im just so fusterated because No matter what I try I cant seem to pick up my local 800systems well.

Also on a side note, do(or can) trunking radios talk simplex? reason I ask, Is beacuse on one agency I had been driving and came close to them and the reception was perfect, but back at home nothing....
 

ridgescan

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I run a VHF yagi w/4 elements; a driven, a reflector and 2 directors. I have it pointed south by southeast to bring in peninsula activity. The funny thing is that I also bring in Highway Patrol from the north on VHF low, and Coast Guard base and oftentimes the ships from the northeast and northwest respsctively. So it is somewhat omnidirectional. All this within a 10 mile radius though...the intended direction gets up to 40 miles down the peninsula:)
 

jon_k

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I'm not offended by anything anyone can say on this forum. In fact I love threads like this that leave it wide open for debate. Threads with debate are interesting and keep me coming back. It's not until people start using cusswords and calling people names that a thread gets to the point of cesspool where it's not worth monitoring.

On to the debate.

Yagi's have been around for years and they are quite proven technology. Amateur operators have been building them longer than I've been alive.
I'm sure there is a good reason.

Fisrt off let me just say I never beleived these things worked anyway BECAUSE, how in the heck does the Reflector "KNOW" its the reflector?
The directional field is configured due to the longer elements being on back, and they get shorter along the boom of the antenna, thus directing the signal outbound when Txing.

I built a 800mhz Yagi...... directional? Yeah right How come when I point it the other way "BEHIND" a steel building I still can hear the stuff Im trying too.
A piece of metal is a piece of metal. Why when I get a twist tie that came with my garbage and poke it in my scanner do I pick up 144mhz-800mhz really no worse than my stock rubber ducky? Metal is metal man!

The Yagi will pick up weak signals in a direction it is pointed at. However, being it is metalit will pick up any signal from any direction.

I don't believe you can really understand the full effect from a yagi unless you are using it to transmit. This is when this design becomes kick ass hands down. A field will be established BEHIND the Yagi for a couple dozen yards -- but in the direction it points the field will be established for miles and miles and miles.

I don't know how well these are for the receiving end, but for transmitting they can take a signal that would go a mile and at the same output power accomplish 4-5 miles. I've seen installations that have increased WIFI range bigtime. Just set two yagi's at point A and B and you'll get great internet miles and miles away.

Im just so fusterated because No matter what I try I cant seem to pick up my local 800systems well.
You either didn't build your Yagei right, or more easily the case you are not pointing it in the right direction. Depending on the frequency and Yagi design, the "beam" of reception may be very thin, almost as much as a laser beam depending on how many elements the Yagi has. (I've seen 32 elements on a Yagi for 32 mile coverage and the beam I was told was the size of a laser beam.) One inch off... and you might as well pick up the signal from the backside or side of the Yagi. Make sure that thing is pointed in the right direction of the receiving end so the waves hit it head on.
 
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DPD1

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I guess your right, it didnt preform like I thought it would

Im just so fusterated because No matter what I try I cant seem to pick up my local 800systems well.

Also on a side note, do(or can) trunking radios talk simplex? reason I ask, Is beacuse on one agency I had been driving and came close to them and the reception was perfect, but back at home nothing....
For starters, there are many towns right now that have spent millions on radio systems, and their own people can't even hear as well as they'd like. So I wouldn't feel too bad. But when you say local, are you referring to the actual town you live in? Or is this a county thing, or perhaps the next town over or something? Because if this is the actual city you live in, there should be no problem at all. In fact, a yagi could even be detrimental in that situation. If it's your town you can't hear, then you might have a problem in your system somewhere. You would want to use something like a yagi if you're going for the next town over or something. But if that's the case, it may just simply mean that the other town's system was designed too tightly for their area and it's just not getting enough signals outside that area. You might also be better off investing in going higher with good cable, rather than focusing so much on the antenna. Often times you can get larger leaps in performance that way. Also make sure that you aren't getting TOO much signal. I had a guy a while back say he kept on having his local PD cut out and have poor reception. Turns out his handheld was actually overloading and cutting out from too much signal.

Dave
www.DPDProductions.com
Antennas & Accessories for the RF Professional & Radio Hobbyist
 

Shortwavewave

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Yes its the town I live in and I know Im only inbetween 5 to 10 miles of the repeater, I had a Pro97 about a year ago and had the same problem but had to sell it due to money.

I have quad shield 75ohm cable, and I know its not my scanner Ive picked up fine on the road, unless the BCT8 is that much of a dud? Or I could be in a dead spot...
 

jon_k

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I have quad shield 75ohm cable, and I know its not my scanner Ive picked up fine on the road, unless the BCT8 is that much of a dud? Or I could be in a dead spot...
Bad spot possibly. So you say mobile you pick stuff up. You said you're frustrated nowhere in your area can you pick anything up.

Your Yagi has been tested outside, correct? Are there other buildings and things in the way? 800mhz will bounce off buildings and stuff fairly well, but they could cause odd dead zones in certain areas.

Tell us about your area. Is it almost line of sight to the towers you want to pick up?
 

rescue161

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I live in a weak spot for reception of the local 800 system. Even Motorola handhelds have difficulty out here. My scanners were even worse. I bought an 800 MHz Yagi on this board. It is a commercial unit. I hooked the 396 to it and walked around my yard. Reception was that of the rubber duck until I started turning in place. It went from 1 bar to full scale, but quickly went back to 1 bar as I kept turning. So I double checked in several areas of my property. Sure enough, the "sweet spot" where I was getting full bars was always in the same direction. Yes, Yagis do work very well. This antenna is only 3 elements, but it brings in the signal on 800 VERY well. I mounted it in the attic pointed in the direction of the tower and never looked back. I used to get dropped/lost signal on UniTrunker, but not now it is always at 100%.

Get yourself a commercial Yagi and you'll see.
 
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jon_k

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I live in a weak spot for reception of the local 800 system. Even Motorola handhelds have difficulty out here. My scanners were even worse. I bought an 800 MHz Yagi on this board. It is a commercial unit. I hooked the 396 to it and walked around my yard. Reception was that of the rubber duck until I started turning in place. It went from 1 bar to full scale, but quickly went back to 1 bar as I kept turning. So I double checked in several areas of my property. Sure enough, the "sweet spot" where I was getting full bars was always in the same direction. Yes, Yagis do work very well. This antenna is only 3 elements, but it brings in the signal on 800 VERY well. I mounted it in the attic pointed in the direction of the tower and never looked back. I used to get dropped/lost signal on UniTrunker, but not now it is always at 100%.

Get yourself a commercial Yagi and you'll see.
I'm sure with a bit of fiddling he could accomplish the same goals. I imagine he went out, waved it about and threw it down in frustration. Easy to do, especially when you're not too sure if you made your antenna correctly.

I've never made a Yagi but the construction is simple, finding the parts is the hard part.

If the measurements work his should work just as well if not better than a commercial Yagi. In fact, coat hanger rods work great.

I think all shortwavewave needs to do is go out and have patience and aim for a while to find the correct angle and direction. Being directional antennas, they tend to be a bit, uh directional. ;-)

I've not needed a Yagi for my own purposes yet, though I may build one with a friend of mine so we can talk on amateur simplex frequencies. He's about 30 miles away and has trouble even hitting some of the repeaters.
 

Shortwavewave

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Tell us about your area. Is it almost line of sight to the towers you want to pick up?
I live in Midwest City, OK 5miles east of Oklahoma City
Well I live in an Apartment and have a outside porch type thing to put antennas "yes Im allowed"

For the longest time Ive Used a 20ft Dia loop 5ft each side, about 12ft high "cant go any higher than that", It worked for everything, Literly I was even able to DX 160meters, to pick up my local police on 460.125, untill I finnaly got a Trunking scanner I know I will keep.

Im sort of in a "vally" because Im in the lowest spot in town, plus with building all around me.

This is where the tower is I want to pick up http://www.radioreference.com/apps/db/?action=siteInfo&siteId=7869
Im right where the "city" above HWY 3, is in Oklahoma City
 

K4DHR

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Physical height of the antenna in relation to surrounding terrain is a HUGE factor in RF reception. I monitor some RR data that comes in in the 890 MHz range that I can't even receive a transmitter maybe a mile and a half away from my home. I drive UP the hill (I live on the downslope between two hills) about 1/4 mile in either direction and I start picking up not only that station, but two or three more within a 5-6 mile radius.

I'm planning on mounting an omni-directional antenna with some gain on about a 10' mast on our chimney in a few weeks that should improve things somewhat, but I'm still going to be stuck with our poor geographic location unless I set up a 50'+ tower in the back yard to overcome the terrain.
 

Shortwavewave

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I uploaded some Pictures to my profile page of a "new yagi design" than the first one i made, this has 5 Directors.
http://www.radioreference.com/forums/album.php?albumid=5

I might have had a "bad" connection some where, I hooked this one up and now I can pick up stations with out static and distortion.

I used coat hangers, and a dowel. Have a stand for it for now till i can get a rotatable mount for out side, and some more high quality coax.

I still want a professional/commertial like the one from DPD1's website

ANd please I wasnt trying to prove you guys wrong.
 

jon_k

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I might have had a "bad" connection some where, I hooked this one up and now I can pick up stations with out static and distortion.
Happy you got it working!

I used coat hangers, and a dowel. Have a stand for it for now till i can get a rotatable mount for out side, and some more high quality coax.

I still want a professional/commertial like the one from DPD1's website
It's all looks man. A self-made one will work just as well and in some cases better, depending on how cheap the mass-produced parts are.

I've got a HAM friend who made an HD TV antenna that picks up signals better than a $95 amplified antenna set he had purchased at first, all he got was fuzzy picture quality. He threw it out and made one out of coathangar and wood. Added a balun at the end and the quality is better than any store-bought antenna I've seen.
 

kb2vxa

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I'll skip right to the heart of the matter and tell you the hard truth; you have a LOT to learn about the Yagi-Uda antenna. Second, even if you fashioned it correctly (and from what you said I doubt this very much) you are expecting far more than it's capable of delivering. A parallel study for further understanding is learning about polar patterns and what those lines on the chart mean.

The long and short of flaming is don't flame until and unless you know what you're talking about. That goes for antennas too and at this point by the soot on your face it looks like you had a bit of a backdraft.
 

zz0468

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Those director elements just look way too small.
Not only do the director elements look too short, the boom is too thick for those elements, and the way they taper in length, it looks like you were trying to make a log-periodic array, not a yagi.

Where did the dimensions come from? When you duplicate the dimensions of a yagi from someone else's work, you need to duplicate the boom, and the element diameters, too. About the only wiggle room you get is in how you feed the driven element. And even that's critical.
 
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