Novice Scanner Question

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rick1205

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Hello All,


I am new to RR and I am a novice when it comes to the scanner universe. I have a question about an antenna for a scanner, specifically a Uniden BCD996XT.



My question - Is it possible for me to use a vintage TV antenna with a 996XT to pick up digital, trunked systems in my county?



My situation – I purchased the scanner for my mother so that she could listen to the Fire/EMS/LE traffic in the county. I am setting the scanner up to do a simple scan of the channels without using all of the bells and whistles this complex piece of machinery has available. I am looking to get the best signal I can without having to put out a lot of money for an expensive antenna. I’ve read about the small Radio Shack 800MHz antenna and that may be an option but I figure an outdoor antenna would pick up signals better.


So, can I rig the old TV antenna to work with the 996XT?


Any feedback or suggestion would be appreciated.



Thanks in advance,
[FONT=&quot]Rick[/FONT]
 

rick1205

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Thank you for the reply. I appreciate the feedback. I'll give it a shot and see what happens.
 

LtDoc

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Can you use a TV antenna to receive signals with a scanner? Sure. It may not be the best in the world, but it'll certainly work, and no telling how 'well' it will 'work'. The best advice is to just try it and see how well it works for your particular situation. A simple length of wire thrown over the top of the house, or into a tree, can work amazingly well in some circumstances (also terrible in other circumstances).
There are limits, as with anything. I'd love to have an antenna 1/2 mile high, but that's sort of ridiculous, right?
Good luck.
- 'Doc
 

Blackink

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I'd love to have an antenna 1/2 mile high, but that's sort of ridiculous, right?

Lemme see if I can respond properly here.....

As someone posted just a short time ago...

....no telling how 'well' it will 'work'. The best advice is to just try it and see how well it works for your particular situation.

Doc, I think you answered your own question.....lolol
 

n5ims

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Most TV antennas cover the same general frequencies that are used by scanners (54 - 860 MHz) so that would indicate they may work OK.

One serious issue is that TV antennas are horizontally polarized (the elements go side-to-side) while what scanners listen to are vertically polarized (elements go up and down). This will cause the signals to be weaker, but if you can turn that antenna 90 degrees you can solve that issue.

The next serious issue is that many scanner antennas are omnidirectional (they receive just as well from all compass directions) while most TV antennas are directional (they're designed to receive from just one direction). A directional antenna may or may not be what you want. If everything you want to hear is in one direction it's a very good thing (you'll get stronger signals due to the gain of the antenna in that direction), but if you listen to signals from various directions (a city to the east, one to the south, and another to the north for example) you'll have to pick one to hear and miss out on the others).

The final minor issue is that a TV antenna is designed to feed either 300 ohm cable (that flat twin lead stuff of old) or 75 ohm coax like RG-59 or RG-6. Most often, there's a 300 to 75 ohm transformer to allow the use of coax. Scanners specify the use of 50 ohm coax for their antenna connection. I say this is a minor issue since most scanners will work just fine on either 50 or 75 ohm connections. There may be some additional loss using a 75 ohm connection, unless you have really weak signals, you should never notice the difference. Note that this information is specific to scanner installs (or more generally receive-only installs). If you try to transmit using the wrong impedance (that ohm thing) you could have some serious issues.
 

rick1205

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Most TV antennas cover the same general frequencies that are used by scanners (54 - 860 MHz) so that would indicate they may work OK.

One serious issue is that TV antennas are horizontally polarized (the elements go side-to-side) while what scanners listen to are vertically polarized (elements go up and down). This will cause the signals to be weaker, but if you can turn that antenna 90 degrees you can solve that issue.

The next serious issue is that many scanner antennas are omnidirectional (they receive just as well from all compass directions) while most TV antennas are directional (they're designed to receive from just one direction). A directional antenna may or may not be what you want. If everything you want to hear is in one direction it's a very good thing (you'll get stronger signals due to the gain of the antenna in that direction), but if you listen to signals from various directions (a city to the east, one to the south, and another to the north for example) you'll have to pick one to hear and miss out on the others).

The final minor issue is that a TV antenna is designed to feed either 300 ohm cable (that flat twin lead stuff of old) or 75 ohm coax like RG-59 or RG-6. Most often, there's a 300 to 75 ohm transformer to allow the use of coax. Scanners specify the use of 50 ohm coax for their antenna connection. I say this is a minor issue since most scanners will work just fine on either 50 or 75 ohm connections. There may be some additional loss using a 75 ohm connection, unless you have really weak signals, you should never notice the difference. Note that this information is specific to scanner installs (or more generally receive-only installs). If you try to transmit using the wrong impedance (that ohm thing) you could have some serious issues.
[FONT=&quot]
[/FONT]n5ims - [FONT=&quot]http://forums.radioreference.com/members/n5ims.htmlThank you for the feedback on my antenna question.
[/FONT]
[FONT=&quot]I checked the cable coming from the antenna and it appears to be a[/FONT][FONT=&quot] RG-59 or RG-6 with a screw-on type connector that you get with cable TV. That being the case, I’m assuming this means there's a 300 to 75 ohm transformer to allow the use of coax like you mentioned in your reply. Would it be better to change the connector at the end of the cable to a 50 ohm or 75 ohm? [/FONT]
 

SpectreOZ

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Would it be better to change the connector at the end of the cable to a 50 ohm or 75 ohm?
Changing the end connector won't change the impedance value of the feed line/cable, that said I use Rg6 quad shielded coaxial cable on my scanner feed line because it's signal loss is significantly lower than equivalent 50 ohm cable (including RG213) keeping in mind those losses increase with frequency.

So long as the cable isn't Rg59 you should be good to go, even if it is that nasty lossy Rg59 cable an external TV antenna will work to some degree as already indicated by previous comments.
 
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