mainetrunk
Member
Instead of me trying to type in what I am doing,
watch this
https://www.youtube.com/watch?v=MoQs3oPWsKc&feature=em-upload_owner
watch this
https://www.youtube.com/watch?v=MoQs3oPWsKc&feature=em-upload_owner
Details about building
- Thread starter mainetrunk
- Start date
- Status
I think you might be confusing two types of antennas, a dipole and a yagi (sometimes called a beam). Your two pipes mounted on the wood fed with a TV balun would be considered a dipole. They are too long however for 10 meters. Use the frequency/length formula to determine the correct length for each element. The other antenna (yagi or beam) has one reflector, one driven, and one or more directors (like a TV antenna). There are formulas and plans for the distance between each of the elements. The elements can be attached directly to the boom. The point where they connect to the boom is considered a zero reference point. The elements can also be insulated from the boom. Depending on which method you use will determine the actual lengths of the elements and their spacing. The American Radio Relay League sells a book called the "Antenna Book" which contains examples and "how to build" directions for many different types of antennas. The theory of building antennas can be complicated but building proven designs can be relatively easy and quite rewarding. Good Luck!
BB
BB
mainetrunk
Member
I know the types-yagi/dipole,
just--I seen yagi's with the split-element.. 1 side don't touch the other.
My main goal is to create a PERFECT 800 mhz antenna.
Yagi or dipole,
then 470--485 mhz, antenna.
Or maybe lo-vhf 1st.
I already made a 1:1 dipole for HF,
https://www.youtube.com/watch?v=nC8zyHE38vk
and the only problem is--
the -drop- wires ..
I want them higher, but not possible.
So, make a yagi or 2,
or dipole.
For now, you seen my toys,
now to build..
Thanx--I NEVER heard of the -antenna book- til now.
And I have been into antenna's for 4 years now.
I made a UHF yagi last year with that split element going on..
But, at the last minute,
drilled the wrong hole.
So, it is NOT perfect, but ok..
just--I seen yagi's with the split-element.. 1 side don't touch the other.
My main goal is to create a PERFECT 800 mhz antenna.
Yagi or dipole,
then 470--485 mhz, antenna.
Or maybe lo-vhf 1st.
I already made a 1:1 dipole for HF,
https://www.youtube.com/watch?v=nC8zyHE38vk
and the only problem is--
the -drop- wires ..
I want them higher, but not possible.
So, make a yagi or 2,
or dipole.
For now, you seen my toys,
now to build..
Thanx--I NEVER heard of the -antenna book- til now.
And I have been into antenna's for 4 years now.
I made a UHF yagi last year with that split element going on..
But, at the last minute,
drilled the wrong hole.
So, it is NOT perfect, but ok..
prcguy
Member
The video in the first post shows what looks like a Yagi, well sort of, but with a split boom and the two boom halves are fed with a TV balun?? Is that what I really saw?
prcguy
prcguy
mainetrunk
Member
Yes sir
mainetrunk
Member
I caught the hint--thank you.
So now, I opened up an RG5820,.
So the shield goes to 1 element,
and the wire goes to the other.
BIG difference. I even got the 470's tuned in.
Thank you Mass....
I got the 935's, vhf, and regular uhf real good.
DAMN, too bad our Radio Shack went out of bizz..
OK, we are getting somewhere, thanks.
As soon as I can get uhf/vhf/lo-vhf, and 935/800' tuned on 1 antenna,
I'll share it.
Thanks again
So now, I opened up an RG5820,.
So the shield goes to 1 element,
and the wire goes to the other.
BIG difference. I even got the 470's tuned in.
Thank you Mass....
I got the 935's, vhf, and regular uhf real good.
DAMN, too bad our Radio Shack went out of bizz..
OK, we are getting somewhere, thanks.
As soon as I can get uhf/vhf/lo-vhf, and 935/800' tuned on 1 antenna,
I'll share it.
Thanks again
prcguy
Member
Does than mean you took out the TV balun and connected coax to the two boom halves? With each half having an amount of smaller elements on it?
prcguy
prcguy
mainetrunk
Member
CORRECT SIR.
2 --- 4 inch elements.
1 element for the sheild--wiring,
and 1 element for the main wire.
At least, that is how it is --now--.
It is actually doing well on the 850's, and 935's, trunks..
That Radio Shack balun is -not- attatched to anything anymore.
2 --- 4 inch elements.
1 element for the sheild--wiring,
and 1 element for the main wire.
At least, that is how it is --now--.
It is actually doing well on the 850's, and 935's, trunks..
That Radio Shack balun is -not- attatched to anything anymore.
prcguy
Member
Ok, I still have a mental picture of what was in the YouTube video and that was not a Yagi. It was more of a fuzzy dipole with the thicker split boom being the dipole elements and the small diameter elements being the fuzz.
Can you post a pic of what you described? Does it look anything like the first white diagram in this link? Yagi Antenna
For 800-900MHz range the total end to end length of each element would probably be in the 5 to 6in range with the driven element split, insulated from the boom and coax attached something like you described.
prcguy
Can you post a pic of what you described? Does it look anything like the first white diagram in this link? Yagi Antenna
For 800-900MHz range the total end to end length of each element would probably be in the 5 to 6in range with the driven element split, insulated from the boom and coax attached something like you described.
prcguy
PC guy--I didn't think he understood the difference between a dipole and a yagi. And I didn't do a good job of explaining it. As they say "a picture is worth a thousand words".
mainetrunk--As PC guy stated get rid of the "elements (fuz)" on the dipole or get rid of the dipole and add elements to the boom for a yagi.
BB
mainetrunk--As PC guy stated get rid of the "elements (fuz)" on the dipole or get rid of the dipole and add elements to the boom for a yagi.
BB
mainetrunk
Member
Let's try this again
https://www.youtube.com/watch?v=BQUJC_C7k8s&feature=youtu.be
https://www.youtube.com/watch?v=BQUJC_C7k8s&feature=youtu.be
I saw a couple of things. You can't put a yagi on a dipole. A dipole has no elements perpendicular to the dipole. The small 3 element yagi on the piece of wood by itself is a yagi. On the yagi only the driven element is connected to the coax. The reflector elements and director elements are not connected to anything. You have all three connected together with pieces of wire. The director element and the reflector element are called parasitic elements and do not connect to the coax in any form. The center elements (called the driven element) are in the middle. You will notice that the driven element is really a dipole. One element is connected to one side of leads on your balun and the other element is connected to the other lead of the balun. The other end of the balun is connected to the coax. You can replace the wood boom with a metal boom. You can fasten the reflector and director elements directly to the boom (with through holes or on top or on the bottom of the mast). The driven elements are insulated from the boom and the coax would connect to them just like in your dipole example.
Remember that the element lengths are different for each element. The reflector element is slightly longer and the director element is slightly shorter than the driven element. The more director elements you have the more gain and the narrower the beam width. The antenna handbook has examples and dimensions of several different length of yagi antennas.
BB
Remember that the element lengths are different for each element. The reflector element is slightly longer and the director element is slightly shorter than the driven element. The more director elements you have the more gain and the narrower the beam width. The antenna handbook has examples and dimensions of several different length of yagi antennas.
BB
prcguy
Member
I watched the latest video and hear you want to make a Yagi antenna with some materials you already have. BTW, the small 3 element thing with wire attaching all elements and coax attached to the small element end is not a Yagi either. It could be a Log Periodic of sorts if you reverse the feed wires every other element but that's a separate conversation.
First make sure a Yagi is the thing you really want. They are very narrow band like covering only about 5Mhz at VHF or up to about 20Mhz at UHF but can have good gain and they also can reject signals from directions you don't want while bringing in signals from directions you do want.
With that said, you need to find a Yagi calculator on the Internet that will let you enter the size of the boom material you already have and also the element diameter. Looks like you want to build one where all the elements except the driven element are attached to the metal boom and grounded.
The dimensions of the elements will change depending on if you want to drill a hole through both sides of the boom and stick the element in to the half way point, or if you just want to put a screw or pop rivet through the center of the element and stick the screw or rivet in a hole in the boom. If you wanted to mount the elements in PVC pipe then the dimensions will change compared to mounting them on a metal boom.
For a VHF Yagi if the elements are off by more than maybe 1/4" the performance will start to be degraded from what the design calls for. The higher in frequency you go the more critical the dimensions will be.
Then for simplicity you probably want to make a little insulator for the driven elements out of plastic or wood. After you do everything perfect you will still need to tune the driven elements using an antenna analyzer or a transmitter and SWR meter, etc, you will not be able to just cut them to length from a calculation because the coax you attach and any lead lengths will have an affect and detune it.
I'm not trying to talk you out of making one, just trying to point out all the things that can go wrong so you can be prepared and overcome them.
prcguy
First make sure a Yagi is the thing you really want. They are very narrow band like covering only about 5Mhz at VHF or up to about 20Mhz at UHF but can have good gain and they also can reject signals from directions you don't want while bringing in signals from directions you do want.
With that said, you need to find a Yagi calculator on the Internet that will let you enter the size of the boom material you already have and also the element diameter. Looks like you want to build one where all the elements except the driven element are attached to the metal boom and grounded.
The dimensions of the elements will change depending on if you want to drill a hole through both sides of the boom and stick the element in to the half way point, or if you just want to put a screw or pop rivet through the center of the element and stick the screw or rivet in a hole in the boom. If you wanted to mount the elements in PVC pipe then the dimensions will change compared to mounting them on a metal boom.
For a VHF Yagi if the elements are off by more than maybe 1/4" the performance will start to be degraded from what the design calls for. The higher in frequency you go the more critical the dimensions will be.
Then for simplicity you probably want to make a little insulator for the driven elements out of plastic or wood. After you do everything perfect you will still need to tune the driven elements using an antenna analyzer or a transmitter and SWR meter, etc, you will not be able to just cut them to length from a calculation because the coax you attach and any lead lengths will have an affect and detune it.
I'm not trying to talk you out of making one, just trying to point out all the things that can go wrong so you can be prepared and overcome them.
prcguy
mainetrunk
Member
OK, now we are talking.
No wonder why some stations come in that aren't close,
and others that are--bad reception...
I thought it was an easy build.
An----E with 2 sides the same,
how hard could it be?
Well, we now the answer to that stupid question..
O.K, I want a yagi for signal checking up on the hill, or 2..
UHF and VHF--also--470--485 mhz..( t-uhf )?
Sepparate antenna's if need be..
I bet a lo-vhf yagi is harder cause of the 20 mhz spectrum..30--50 mhz
OK, ---- next subject, the DIPOLE.
You saw the toy's,
dipole for 30--485 mhz?
1 or 2, or even 3 bands on the same antenna would be excellent.
No wonder why some stations come in that aren't close,
and others that are--bad reception...
I thought it was an easy build.
An----E with 2 sides the same,
how hard could it be?
Well, we now the answer to that stupid question..
O.K, I want a yagi for signal checking up on the hill, or 2..
UHF and VHF--also--470--485 mhz..( t-uhf )?
Sepparate antenna's if need be..
I bet a lo-vhf yagi is harder cause of the 20 mhz spectrum..30--50 mhz
OK, ---- next subject, the DIPOLE.
You saw the toy's,
dipole for 30--485 mhz?
1 or 2, or even 3 bands on the same antenna would be excellent.
mainetrunk
Member
OK,
I just did alot of reading.
Let me see if I got the lingo right.
A quarter wave antenna is what you see on a cops car--like for vhf
A halfwave is a dipole?
A fullwave is a LOOP?
If these are correct, then I just got rid of --1-- of my headache making mysteries.
thaks
I just did alot of reading.
Let me see if I got the lingo right.
A quarter wave antenna is what you see on a cops car--like for vhf
A halfwave is a dipole?
A fullwave is a LOOP?
If these are correct, then I just got rid of --1-- of my headache making mysteries.
thaks
Most antennas operate over a fairly narrow range of frequencies (0 to 10 MHz maybe). They can operate on several bands if the the bands are harmonics of the fundamental antenna frequency. A harmonic is a doubling or tripling of the fundamental frequency. As you get farther away from the design frequency the performance begins to decrease. Usually non-harmonic multi-band antennas work equally poor on all bands.
BB
BB
Your lingo is pretty close. A dipole or loop is how the antenna is physically constructed. They could be 1/4, 1/2, 1, or 1 or 2 wavelengths long. These would have different feedpoint impedances and different radiation patterns. Another antenna is a Marconi (the 1/4 wavelength you mentioned on police cars). A Marconi is a vertical antenna that could also be 1/4, 1/2, or 1 wavelength long again with different feedpoint impedances. Another factor is the polarity of an antenna (vertical or horizontal). A dipole is typically horizontally polarized and a Marconi is usually vertically polarized. The transmitting and receiving antennas should be of the same polarity for maximum signal. However you can take a dipole (horizontally polarized) and turn it vertical to make it vertically polarized. So to summarize antennas can be constructed differently (dipoles, loops, vertical, horizontal) and have different wavelengths (1/4, 1/2, 1).
BB
BB
mainetrunk
Member
What have I gotten into?
This is a real challenge now. OK,
I got time..
I also wanna show you what a friend just sent me.
Unreal, talk about using your resources,even on an island
https://www.youtube.com/watch?v=9tIZUhu21sQ
I just wanna make something good for the upcoming winter.
I have no speciffic band chosen,
mostly UHF/VHF.
And by next spring, have 11.000---940 mhz coverred.
Sepparate antenna's for the trips to the hill,
and other high spots around here.
If you check your maps,
The only direction I have for no major hills in my way,
is towards Boston Mass.
I-O-W,
I am surrounded by hills, 140 feet above sea level.
Mt. Aggamenticus is a major hurtle.
Garrison Hill, Dover NH,
Rte 91 that goes to York Me, is way higher than me in some spot's.
But, I do receive them..
Only with my Ferret can I get signals further up than Kennebunkport.
After there, scratchy...
OK, time to re-think the ink----- ( Chris Farley, beverly hills ninja )
https://www.youtube.com/watch?v=U2xLzPxtaTA
Thanks again, and again, hahaha
This is a real challenge now. OK,
I got time..
I also wanna show you what a friend just sent me.
Unreal, talk about using your resources,even on an island
https://www.youtube.com/watch?v=9tIZUhu21sQ
I just wanna make something good for the upcoming winter.
I have no speciffic band chosen,
mostly UHF/VHF.
And by next spring, have 11.000---940 mhz coverred.
Sepparate antenna's for the trips to the hill,
and other high spots around here.
If you check your maps,
The only direction I have for no major hills in my way,
is towards Boston Mass.
I-O-W,
I am surrounded by hills, 140 feet above sea level.
Mt. Aggamenticus is a major hurtle.
Garrison Hill, Dover NH,
Rte 91 that goes to York Me, is way higher than me in some spot's.
But, I do receive them..
Only with my Ferret can I get signals further up than Kennebunkport.
After there, scratchy...
OK, time to re-think the ink----- ( Chris Farley, beverly hills ninja )
https://www.youtube.com/watch?v=U2xLzPxtaTA
Thanks again, and again, hahaha
mainetrunk
Member
Well, the good news is;
my Alinco DJ-11T has F-TUNE.
Which means, it grabs the nearest signal--in the antenna's band.
Every time I make a new 1,
I F-TUNE it,
and it tells me the range I am in.
Whether it was meant to be or not,
it works for me.
my Alinco DJ-11T has F-TUNE.
Which means, it grabs the nearest signal--in the antenna's band.
Every time I make a new 1,
I F-TUNE it,
and it tells me the range I am in.
Whether it was meant to be or not,
it works for me.
AC9BX
Member
Yeah, this split boom thing might work as "fat" dipole but probably not a very good one.
Perhaps the greatest challenge in antenna design is bandwidth.
Not going to happen.
If it were me, and I've done stuff just like this, I would use:
Tilted Terminated Folded Dipole (this is a pair of parallel dipoles made of wire connected at the ends separated by the appropriate distance for the frequency range, a terminating resistor in the middle of one and feed in the middle of the other, generally sloping in the air - this is for HF, useful for shortwave listening and up to perhaps 50MHz. It's not very efficient but amazingly wide band and quiet. It requires a balun to match to coax or use a parallel wire feed.
I'd use a discone or biconical for VHF and UHF. Because they can be quite large at VHF it might be wise to use a simple vertical or "ground plane" for 150MHz and then the discone for 450 and higher which would cover everything pretty well up to about 1GHz. A Log-Periodic Dipole Array is a great choice for wideband with directional gain. It has less gain and wider beam width than the Yagi but a "neater" pattern. The Yagi is a great beam antenna but has a very narrow bandwidth. However, building a log-periodic with ideal parameters for best performance makes them much larger than if you sacrifice and they get quite large too for lower frequencies.
A TV balun may not be a good choice (even for TV). Any such device has practical limits to its useful frequency range. In addition that style which looks like the molded plastic one's Radio Shack and others sell is a rather poor device. They are also impedance matching, in particular to convert a 300 ohm antenna to 75 ohm coax, a 4:1 conversion. If your antenna whatever it is is not 300 ohms then using this balun will not be good for 75 ohm coax. A Yagi (without a design to compensate such as a folded driven element or gamma match) typically has a low impedance, around 15 Ohms. Using a 4:1 balun to reduce that, ... that's a losing proposition.
WA0CBW brings up some good points. Harmonics can be useful, or as stated equally bad everywhere.
A naturally resonant half wave antenna for example will also work fairly well at 3 times the design frequency. At twice the impedance is way off. A 100MHz antenna will work at 300 but not at 200. It would also work at 33.3MHz but with reduced signal because it just isn't big enough. This is oversimplified but shows the idea.
A dipole is a directional antenna on one axis, in the other it's omni. So if you used a dipole in the vertical orientation you get omnidirectional coverage.
Perhaps the greatest challenge in antenna design is bandwidth.
Not going to happen.
If it were me, and I've done stuff just like this, I would use:
Tilted Terminated Folded Dipole (this is a pair of parallel dipoles made of wire connected at the ends separated by the appropriate distance for the frequency range, a terminating resistor in the middle of one and feed in the middle of the other, generally sloping in the air - this is for HF, useful for shortwave listening and up to perhaps 50MHz. It's not very efficient but amazingly wide band and quiet. It requires a balun to match to coax or use a parallel wire feed.
I'd use a discone or biconical for VHF and UHF. Because they can be quite large at VHF it might be wise to use a simple vertical or "ground plane" for 150MHz and then the discone for 450 and higher which would cover everything pretty well up to about 1GHz. A Log-Periodic Dipole Array is a great choice for wideband with directional gain. It has less gain and wider beam width than the Yagi but a "neater" pattern. The Yagi is a great beam antenna but has a very narrow bandwidth. However, building a log-periodic with ideal parameters for best performance makes them much larger than if you sacrifice and they get quite large too for lower frequencies.
A TV balun may not be a good choice (even for TV). Any such device has practical limits to its useful frequency range. In addition that style which looks like the molded plastic one's Radio Shack and others sell is a rather poor device. They are also impedance matching, in particular to convert a 300 ohm antenna to 75 ohm coax, a 4:1 conversion. If your antenna whatever it is is not 300 ohms then using this balun will not be good for 75 ohm coax. A Yagi (without a design to compensate such as a folded driven element or gamma match) typically has a low impedance, around 15 Ohms. Using a 4:1 balun to reduce that, ... that's a losing proposition.
WA0CBW brings up some good points. Harmonics can be useful, or as stated equally bad everywhere.
A naturally resonant half wave antenna for example will also work fairly well at 3 times the design frequency. At twice the impedance is way off. A 100MHz antenna will work at 300 but not at 200. It would also work at 33.3MHz but with reduced signal because it just isn't big enough. This is oversimplified but shows the idea.
A dipole is a directional antenna on one axis, in the other it's omni. So if you used a dipole in the vertical orientation you get omnidirectional coverage.
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