Can I use an existing TV antenna?

[johnnye]

Hi, I'm new to the hobby so pardon me if I'm asking an obvious question. I used search and google but couldn't come up with the right terms.

I have the pro-2096 and to start I'm trying to listen to the Metro DC 800mhz spectrum. I listen to the scanner in my computer room so I'd like to hook up an outdoor antenna. I have some sort of VHF/UHF antenna existing on my roof and I'm curious if that'll suit my needs temporarily till I find the spectrums I really want to tune in to. I can run new 50 ohm cable since I'll eventually have to do that anyway but I'm curious if I can save a buck temporarily since I spent a pretty penny on the 2096. The antenna is not in the greatest condition such as rust on the mounts etc, the aluminum doesnt look that oxidized though.

Thanks for your patience with a newbie

 

[wbruff]

TV antenna for scanners

TV antennas are 75 ohm and scanners are 50 ohms. Also TV signals and hence the antennas are horizontally polarized. It would work with those limitaions if you re-mounted the antenna so that the elements are arranged vertically. The difference in the 75 ohm impedance vs the 50 ohms would not be that big of a deal. Not perfect but better than nothing. Public saftey transmitters use vertically polarized antennas since most users i.e. police cars have vertical whip style antennas. So turn that antenna on its side and some "GOOD" 75 ohm cable like RG-6 and it should work.

 

[RevGary]

John - as wbruff mentioned, it's better than nothing, but remember that a TV antenna must be pointed toward the transmitting station to receive properly. A combination VHF-UHV TV antenna will have a section of shorter elements closer together at the end of the antenna. That is the section that will be utilized in your 800 monitoring, so make SURE that the small end of your antenna is pointing in the direction of what you will be listening to. Since the U-BOLT location for mast mounting will not align when you turn the antenna vertically, you will most likely have to drill 2 new holes in the main arm to accomodate the u-bolt. Measure carefully. Also, plug up the holes in the arm that will not be used any longer, in order to keep rain water out of the center of the arm. You can use silicone sealant in those old openings. You will also have to adapt the 'F' connector configuration for the 300 to 75 OHM matcher on the antenna to whatever cable that you are using and then to the input that your monitor uses - usually Motorola plug or BNC. You will be making a monitor antenna (beam) which will pretty much cover everything from 45 MHZ up to almost 900... good luck and let us know how it works out.

 

[Al42]

Whether the antenna will work at all, and whether it will work if you don't turn it, depends on where you are. I have no problem hearing the DC 800 MHz system from Fairfax County, with the antenna on my scanner. If you're close you should be able to hear it. If you need more antenna, try the TV antenna - whether it works or not, using it the way it is won't hurt anything, and might give you more signal than you're getting - especially if it's aimed at DC. If the signal still isn't strong enough, turning rhe boom so that the elements are vertical might help - or it might not, depending on how far you are from the system.

 

[SIMON11]

Anything is worth a try. I bought an indoor scanner aerial to use in the bedroom on my BNC scanner. I then bought a scanner with the SMA connection and temporarily could not connect the aerial. My scanner was in the bedroom and whilst I was laying in bed listening to a very weak signal I moved it near to the Metal bed frame and "WOW" a full clear signal far better than that on my other scanner connected to the aerial.
So throw all your antennas away and buy a metal bed frame.

 

[johnnye]

Basically I live on the first mountain heading west from DC. My computer room has a west facing window (I'm looking at the ridge) and the signal doesnt seem as clear as when I put it on the east facing window in my bedroom. East is the area I'm trying to receive so basically I'm trying to fix a position rather than strength problem. My roof has a complete line of sight of the eastern horizon so I'm betting that once I get up there I'll be fine.

Thanks everyone for your responses.

 

[trap5858]

If what you are attempting to listen to is DC off to the east- a fixed directional antenna like a YAGI will probably give you the best reception. The TV antenna with it's polarization changed will do this for you.

 

[dward42586]

TV UHF antenna for trunked systems

I have used a RS TV UHF antenna vertically polarized to receive TULSA/Oklahoma trunked system from about 35 miles with pretty good reception most of the time. Best possible coax and shortest length really make a big difference at these frequencies.

I'm now using the yagi that is provided for direct tv with excellent results.

 

[Randall]

also not all tv antennas are the same type, yagis are cut for certain frequencies or tuned by element lengths while a better tv antenna for scanners is the log periodic antenna which is not a resonant antenna and receives signals equally over its entire bandwidth which is much wider than a yagis.you can tell a log periodic by the way the transmission line connects to each sucessive set of elements, and the length of the elements.the transmission line will connect to alternating sides in a log periodic antenna so the the connections zig zag down the length of the boom to elements from alternating sides, and also the elements lengths change uniformly from shorter to longer while on a yagi each set must be a certain length to tune the driven elements or to focus the signal through the directors .

 

[kb2vxa]

Hi all,

Cutting through all the gobbledygook I'll give you the benefit of my experience. Depending on the type of antenna there are so many variables impossible to pin down but overall when mounted vertically it'll perform reasonably well as a beam within it's frequency coverage, about 50-220MHz VHF and 470-890MHz UHF.

One thing worth noting, a deep fringe corner reflector UHF antenna works exceptionally well on 470-890MHz, plenty of gain and reasonable directivity. 800 is no longer used for TV but it's not likely manufacturers would redesign the stamping dies they've been using for years.

You can use a balun at the antenna end of the RG-6U coax made specifically for the application (TV) but a run of heavy duty polyfoam dielectric TV twinlead has much less loss. Just hook up a TV balun backward with a short RG-6U jumper with the usual F connectors and an adapter to fit the scanner's antenna jack. Naturally with signals coming from more than one direction you'll need a small rotor.

Now Randall, what did I tell you about log periodics in another thread? To save you guys the trouble, simply stated they're not all you think they are. That's why I said there are so many variables, there's a huge difference between a log designed for a single frequency or somewhat narrow band than the broad band monstrosity that is a TV antenna. OK, I'll cut you some slack, my original statement was (slightly modified here) it (a log) will work reasonably well as a beam from 50 to 220MHz and gain increases with frequency starting with unity at 50MHz.

 

[kd5dga]

I use one that I modified myself with good success.Mine is not rotatable but It is pointed to Austin Texas and I get pretty good reception for a 60 mile hop. It was cheep and I like to experiment.