Original OTA Build-It-Yourself Antennas & Gear (Now Closed)

[Bam]

I’m all for that. I can give you alot of good input on OTA experiments I’ve been doing to increase gain like my newest experiment with a homemade Balun I'm about to test.. The Balun’s that come with most Antennas have a very high insertion loss on UHF frequencies, up to 80%. It's easy to make your own tuned to just the channels you want with low loss from what I found out. Here is how..

http://www.kyes.com/antenna/balun.html



Half Lambda Coax Matching Section calculator,

http://n-lemma.com/calcs/dipole/balun.htm

[weblurker]

Originally Posted by stampeder

You could do that, but it wouldn't work.

TV and radio signals operate at very specific wavelengths (and frequencies, but we're not discussing those right now) so an antenna must be designed to capture those particular wavelengths while rejecting as many of the unwanted ones as possible. VHF and UHF antennas have quite different appearances and behaviours because the wavelengths are quite different in size, with UHF's being smaller.

That's quite an interesting question, do the antenna elements have to be one specific length or can they be multiples of a minimum length?

I thnk UHF wavelengths range from 10 to 100cm (newbie alert, I don't know what I'm talking about here). Would a 20 to 200cm set of antenna elements work better than a 10 to 100cm set of elements or would more than 8 elements get more signal? More length or more elements? Could you build your own 16 or 32 element antenna? You'd have some 'splainin to do to the neighbours if you put up 32 bowties on the back of your house. ;->

I suspect there are only a small number of antenna design experts around these days, but I'll try to find a forum or newsgroup to ask about this.

[JohnnyG]

The elements are indeed a specific length, and then the spacing between the bow-ties is very specific as well, as is the spacing of the mesh in the reflector.

I bought a book on antenna design from Radio Shack years ago. Not sure where it is, but it's probably in a box somewhere in the house. Um...unless the ex-wife that got box!

[stampeder]

Originally Posted by weblurker

Could you build your own 16 or 32 element antenna? You'd have some 'splainin to do to the neighbours if you put up 32 bowties on the back of your house. ;->.

I like your can do attitude! Here's a couple of links that directly answer your questions:

http://www.hdtvprimer.com/ANTENNAS/16bay.html
http://www.hdtvprimer.com/ANTENNAS/32bay.html

and make sure you read the part about "why it might not work" to save yourself some trouble. Also I can save you some wandering around the web looking for antenna technology info. This site is packed with everything you need:

http://www.hdtvprimer.com/ISSUES/erecting_antenna.html

Originally Posted by weblurker

I suspect there are only a small number of antenna design experts around these days, but I'll try to find a forum or newsgroup to ask about this.

They are working in R & D for military contractors, mobile phone manufacturers/vendors, wifi, scientific research, and a variety of other things. Antenna technology lives on! Where I work the antenna guys are using such instruments as spectrum analyzers, field testing, and anechoic & em-neutral test chambers to get more and more into and out of antennas of tomorrow's mobile phone products.

[HDTV101]

Originally Posted by JohnnyG

I bought a book on antenna design from Radio Shack years ago.

My dad had a book from RS about installing TV antennas..... way back when I was a kid in the 1970's. Might have been the same book?. I helped my dad install a UHF antenna from RS and we found all these extra channels back in the mid 70's. I liked WUTV 29 from Buffalo because they had all these great Sci-Fi movies and my dad like channel 79 (city TV back then) for the blue movies that had on late at night!

It looked something like this... but didn't have such a long boom. It was $9.95 from what I remember and we wired it up with the old flat twin lead.

[JohnnyG]

The edition of the book I have has pictures and part number for currently-available Radio Shack items, but aside from that, I bet they are largely the same. The science really hasn't changed since then.

[stampeder]

http://www.digitalhomecanada.com/for...5&postcount=21

[HDTV101]

Originally Posted by stampeder

http://www.digitalhomecanada.com/for...5&postcount=21

No it wasn't anything like that ARRL HAM book. It was a simple little book that covered different TV antennas that RS sold and how to install them.
Had a section on CB antennas too... something else we put up on the roof. Had one in the car... like everyone in 1976

Breaker-one-oh …… XM4252816 is 10-8 10-10 on the side of this one….
Hay good buddy what’s your 10-20 there?

[stampeder]

Wow, what a list of antenna types:

http://users.pandora.be/educypedia/e...tennatypes.htm

[TelSat]

Does anyone have the measurements of the CM-4228?
I want to build one I just need the length of the bowtie and the separation between them. I have seen a picture and I think I can make it.
If anybody is willing to take measurements I could draw the plans and directions on how to make it.
I have made antennas before but never bowties and I can't find the formula to cut the elements. I also would like to have the separation between elements.

Thanks

[Yaamon]

Telsat if you are in the Markham area feel free to drop by my office.

I have 3 Cm4228 in boxes for friends there you can measure what you need.

[tricky]

36"x39.5"x5" Just a little too big to strap on my motorcycle when I was in Illinois and saw them on sale for $39 US grrrr
http://www.warrenelectronics.com/antennas/4228.htm

[stampeder]

Originally Posted by tricky

36"x39.5"x5" Just a little too big to strap on my motorcycle when I was in Illinois and saw them on sale for $39 US grrrr
http://www.warrenelectronics.com/antennas/4228.htm

You would have lost about 10mph carrying one of those too!

[TelSat]

Originally Posted by Yaamon

Telsat if you are in the Markham area feel free to drop by my office.

I have 3 Cm4228 in boxes for friends there you can measure what you need.

I actually can figure the measurements from your pictures the only thing I can't see is the separation between the bowties and the mesh.
I went to Rona and saw the mesh but it seems that they only sell it in big rolls. I have to shop around I am assuming the size of the holes on the wire mesh to be 1 by 2 inches from the pictures.
I would make a 4 elements or 4 bowties antenna to start since I made a bowtie on a piece of wood just to test and got 4 TO stations no CFTO even though it scanned as 9-1 but I also got ABC from Buffalo and the signal was 83%.

CBC
CFTO no picture
CBC French
CITY
Toronto One
ABC Buffalo I can remember the call letters

This is with the small bowtie in the piece of wood inside the apartment.
I am moving at the end of the month so I have to put it aside for now but the plan is to install an antenna at the new location.

Stampeder i will let you guys know as soon as I get into it. I'll try to post pictures. I think this homemade antenna is doable.

TelSat

[stampeder]

Originally Posted by TelSat

I actually can figure the measurements from your pictures the only thing I can't see is the separation between the bowties and the mesh.
I went to Rona and saw the mesh but it seems that they only sell it in big rolls. I have to shop around I am assuming the size of the holes on the wire mesh to be 1 by 2 inches from the pictures.

TelSat, all the power in the world to ya, but keep in mind that the grille on the 4228 is designed so that signals on very specific wavelengths are reflected to the bowtie elements. I think you really need to check out Yaamon's CM4228 in person with a very accurate gauge. Let us know how you do!