Old TV antenna troubleshooting

[bruderbell]

Hi all,
I've enjoyed perusing this site, gleaning what info I can understand. I like to think I'm pretty tech savvy, but I clearly don't understand antennas and RF as well as I'd like.

I purchased a home, and in the attic I found a TV antenna. It looks to be a pretty normal all-band tv antenna like shown here (http://www.homedepot.com/h_d1/N-5yc...?catalogId=10053&langId=-1&keyword=tv+antenna). Well, I got up there and checked it out, wanting to wire it up and use the old beast, but that's where I met my match. The antenna has two connection points on it and there was some really old cable hooked into the two points (I think I've gleamed that this is called "twin lead" as opposed to coaxial cable).

I built a little antenna once and so I have something that looks like this: http://www.amazon.com/Cabletronic-75-300-Antenna-Coaxial-Adapter/dp/B0041IG1AK

Since the antenna didn't have a connector for coax, I thought I better hook that into it and I figured I'd have a working rig...didn't work. It was working on my home-built rig, so I don't believe the adapter is bad.

Is there an existing walkthrough or something to that effect that i can study to figure out how to use this old antenna? I know I could buy a new one, but I'd rather learn how this works and have a go at it. I have a little digital multimeter, if that helps. I didn't see any obvious signs of abuse to the antenna - it's been in the attic after all, so it's seen zero wind and no animal damage sign is present.

Thanks in advance,
bruderbell

 

[wyShack]

Lets see where can we start? That type of antenna would probably hook up to 'twinlead'. (you can still get twinlead at radio shack or some hardware stores. or you can buy a matching transformer that converts the 300 ohm twinlead to the now standard 75 ohm coax. What do you wnat the antenna to 'do'? If you want to use it as a scanner antenna, remember that it is directional (point its shorter elements in the desired direction). Also for scanning the elements should be vertica; (it will be set up to mount horizontallly).

Enjoy

 

[bruderbell]

I'd like to be able to employ it as a broadcast TV antenna as the endgame.

Is there a difference between a balun and a matching transformer?

Currently the antenna is oriented horizontally, like those you see on the exterior of houses. I was able to find a website detailing the directionality of such antennae, and it is pointed in the proper direction.

 

[n5ims]

What you have works like you want, but is the wrong gender. It also isn't waterproof so it's not good to use on the antenna end (since your antenna is in the attic, this isn't critical, but still). What you need is more like this Indoor/Outdoor Matching Transformer : Antenna Transformers | RadioShack.com where the antenna attaches to the two ends and the coax screws into the connector.

 

[nanZor]

Is there a difference between a balun and a matching transformer?

Yes there is, but most commonly you'll find them housed together as one unit. This might be a bit much, but a nice reference with internal pics and measurements for some common ones: Measurements are for FM, but what goes on is applicable (other than loss figures at uhf for example) to what you'll find out there for the most part. The transformer part is about half-way down the page..

Baluns for 88–108 MHz

The problem these days is that nobody seems to make a decent one with everyone having a different opinion. What many do is to try a few and see if it makes a difference. Some are built better than others it seems, or have different frequency responses - especially at UHF. Some owners of huge TV arrays are dismayed to end up hooking their awesome antennas to a cheap balun/transformer with non-existent specs - leaving it up to the consumer to find out the hard way. Single channel applications can net you a good one, but finding one with a broad bandwidth AND low insertion loss is an endless search.

On a related note, If I owned an Antennacraft ST2 for scanning, and listened to UHF or especially 800mhz with it, I would DEFINITELY try a handful of different ones....

You may want to visit a forum for TV guys that might help as well:
Antenna Talk • HDTV Labs Forum