Television Antenna

[rmariotti]

I am attempting to adapt my TV antenna (in my attic) to use with my new 396T scanner. I've read a lot of posts that suggest turning the attenna 90 degrees which I plan to do. It's fed with an RG-59 cable that has been pre-run at the time the house was built and I'd like to keep using this cable.

My question is: Would I benefit (would the reception be significantly improved) by adapting this 75 ohm cable to the 50 ohm scanner? If so, how?

I've seen something on the internet that would convert 75-50 and had BNC connections on it. http://www.testpath.com/Categories.aspx?Category_ID=1105


Thanks in advance!
Ron

 

[W4KRR]

I've never heard of converting 75 ohm coax to 50 ohms. Not that there's no such thing, but...
With a scanner, the more important thing is having a cable that's low loss. Many people use RG-6 coax for scanner usage. It's 75 ohms, but it works fine because it has lower signal loss that RG-58 or RG-8, and no scanner will have a constant 50 ohms antenna impedance over such a wide receiving range anyway. You might try the setup that you already have, if it doesn't work well, you may want to try a lower loss cable like RG-6.

 

[KC8JPZ]

It is possible to adapt to coax. It is not easy though. It is done by inserting a section of coax of the required impedance in line with the 75ohm coax. The big problem is the availability of the impedance you desire. I have only seen this done one time by an antenna engineer friend. He used a section of 3/4" copper pipe as the outer shield and a brass rod that he machined to the diameter he needed as the center conductor. When this is done it's usually only a 1/4 wavelength section of coax or hard-line of desired operating frequency.

In other words, by the time you have done all the necessary calculations and machining. You could have just run a new line. If you fish the interior walls of your home you will be surprised at how easy it is.

If you have an interest in the line matching here is more info on it.
http://www.smeter.net/feeding/matchsec.php

 

[VernM]

No need to convert to 50 ohm feedline. The 75 ohm line will work just fine. Adapters are available for F to BNC connector. One source is www.thewireman.com

 

[rmariotti]

Thank you

Thank you good people. This setup seems to be working quite well. I believe I'll stick with this for a while.

I do have a discone antenna I bought from RS a while a go. I might try using that instead and see what happens. However, with my satallite tv system, I still need an external tv antenna.

Is it possible to combine the two signals (tv and discone) into the one cable?

 

[VernM]

Trying to put these two antennas into a common lead-in coax will cost you signal loss. to both scanner and TV. It will be better to run them independently.