Roof-top TV antenna use with BCD 996T

[PiperPilot04]

Because I have a ranch house, which has no attic, I would like to know if there is such a thing as a matching transformer that would match my roof-top tv antenna to my bearcat bcd 996t radio. I do not want to punch holes through my exterior walls to run antenna cables.
Anyone with an answer to my delima?
Thank you in advance.

 

[RonnieUSA]

Because I have a ranch house, which has no attic, I would like to know if there is such a thing as a matching transformer that would match my roof-top tv antenna to my bearcat bcd 996t radio. I do not want to punch holes through my exterior walls to run antenna cables.
Anyone with an answer to my delima?
Thank you in advance.

Yes there is, it's in this search link>> https://www.google.com/webhp?hl=en&...cp.r_qf.&fp=5137c224b1c5d39b&biw=1366&bih=596

 

[WA1ATA]

Do you want to use the antenna for both the TV and the scanner at the same time?

Is the existing feedline 300 ohm twinlead (flat) or coaxial cable (round) ?

TV antennas are usually mounted with the antenna elements horizontal since broadcast TV is horizontally polarized. Most things you listen to on a scanner are vertically polarized and you would have better reception with the antenna elements mounted vertically (in other words, with the TV antenna rotated 90 degrees so the elements go up and down).

Luckily, most local police and fire departments have powerful repeaters and strong signals so most likely the TV antenna, even with the wrong polarization, will work for local signals.

My recommendation is to not worry too much about theory, and just hook the antenna up to the scanner and see if it works good enough to do what you want.

You will probably need to get some adaptors to go from the the BNC or SMA connector on your scanner to whatever sort of connector you have for your antenna system. For an initial attempt, I would not worry about the mismatch between a balanced 300 ohm twinlead and the unbalanced 50 or 75 ohm coaxial feed preferred by your scanner. It should only take a couple of minutes to connect the antenna to the scanner, even if only temporarily with bare wires stuck into connectors.

 

[KC4RAF]

About 20 years ago,

I experimented with TV antennas and matching transformers. Even without the transformers, receptions was great. The only problem is that the antenna is very directional, but hey, put a cheap rotator on it and all is nice. I was able to see a difference in horizontal and vertically polarized signals, plus front to back ratio. Just try it and you'll be pleasantly surprised.

 

[PiperPilot04]

using a rooftop tv antenna

Thank you for your advice. I thought I needed a balun coil to balance the RF TV cable impedence to the RF input of my scanner.
sincerely,
jim

 

[WA1ATA]

It's not that a balun isn't worth trying. It's just that you will get most of the improvement by switching from an inside antenna to a roof-mounted one, even if the matching isn't perfect.

If the connection to the antenna is 300 ohm twinlead, then a balun will probably help. One common type comes with an F-connector style output that can be connected to a short section of coax to feed the scanner (with an F to BNC adaptor at the scanner end).

See Push-On "F" Type Balun 180-025 as an example.

But the improvement would probably be a just barely noticeable 3 or 6 dB. I say "just noticeable" for the relatively large improvement of 3-6 dB because it really makes a difference you will find most signals either much stronger than needed, or so weak that they are not useable at all.

The dramatic improvement will be using an antenna on the roof as compared to a much lower one inside the house.