Scantenna Mounting

[Chevyman22360]

I have my scantenna mounted on a 60 foot tower and am very unhappy with the results, do you suppose the antenna is mounted to close to the tower, would that be the reason? I took a picture below. I am planning on putting a tv antenna above, and maybe a diamone discone 130 above that if I can't get this scantenna to work.

 

[jonny290]

It seems as though that's about a foot away from the tower, which will severely hinder operation.

I would suggest getting it out on a fiberglass or PVC pole, get it 4 to 5 feet out there. Get a solid mount and clamps and you won't have to worry about it breaking at all.

What coaxial cable are you using?

 

[Chevyman22360]

What coaxial cable are you using?

I am using LMR 400 cable and is tested 100%

 

[tbharper]

did you install the tower yourself and if you did how did you ho it ? i know its a stupid question

 

[scansomd]

I have mounted my scantenna close to a tower with no problems whatsoever.

I would take a close look at the balun and make sure it is installed correctly and is making a good connection.

Did you purchase this antenna new or inherit it from somewhere?

I have my scantenna mounted on a 60 foot tower and am very unhappy with the results, do you suppose the antenna is mounted to close to the tower, would that be the reason? I took a picture below. I am planning on putting a tv antenna above, and maybe a diamone discone 130 above that if I can't get this scantenna to work.

 

[Chevyman22360]

I have mounted my scantenna close to a tower with no problems whatsoever.

I would take a close look at the balun and make sure it is installed correctly and is making a good connection.

Did you purchase this antenna new or inherit it from somewhere?

TBHARPER,
I did put up the tower myself using a gin pole, pretty slick unit, but very hairy!!!

I have used different baluns installed them different ways so am sure that is not the problem. I actually bought new new antennas, thinking the first one had a problem, because had the same problem with that one. Am about ready to give someone a heck of a deal on a couple antennas!!

 

[jonny290]

I realize it's a colossal pain in the butt to climb towers to test antennas, but I would take signal readings across a band, then build a vertical dipole or ground plane antenna for that band, install it in the same spot as the Scantenna with the same LMR-400, and see how it compares. If it's _worse_ than a dipole or ground plane, you have problems.

My guess is that you may be seeing front end desense from having such a _good_ antenna, picking up a nearby signal. I'd search for all signals in a 1 or 2 mile radius from your location.

1: visit http://world.maporama.com/idl/maporama/drawaddress.aspx, type in your address and find your coordinates at the bottom of the map
2: visit http://svartifoss2.fcc.gov/reports7/lat_long.cfm?accessible=NO, select "Point Radius" and try first a 1km, then a 1mi, then a 2mi search.

This will take you some time but power levels are listed on each licensee's page, if you find a pager or digital site that's spitting out a few hundred watts near you that could overload your radio and desensitize it across the board. To test suspect frequencies, program them in and see if you can receive them inside the house with no antenna, or if they come in full-scale with a paper clip in the BNC jack or something ridiculous like that.

 

[Chevyman22360]

I realize it's a colossal pain in the butt to climb towers to test antennas, but I would take signal readings across a band, then build a vertical dipole or ground plane antenna for that band, install it in the same spot as the Scantenna with the same LMR-400, and see how it compares. If it's _worse_ than a dipole or ground plane, you have problems.

My guess is that you may be seeing front end desense from having such a _good_ antenna, picking up a nearby signal. I'd search for all signals in a 1 or 2 mile radius from your location.

1: visit http://world.maporama.com/idl/maporama/drawaddress.aspx, type in your address and find your coordinates at the bottom of the map
2: visit http://svartifoss2.fcc.gov/reports7/lat_long.cfm?accessible=NO, select "Point Radius" and try first a 1km, then a 1mi, then a 2mi search.

This will take you some time but power levels are listed on each licensee's page, if you find a pager or digital site that's spitting out a few hundred watts near you that could overload your radio and desensitize it across the board. To test suspect frequencies, program them in and see if you can receive them inside the house with no antenna, or if they come in full-scale with a paper clip in the BNC jack or something ridiculous like that.

I am not sure this is the problem, the reason I say this, I built a J-Pole for the 150-160 mhz band which covers the South Dakota statewide TRS System, I have this leaning against a wall in the house and I can recieve 99% modulation on three towers off the control channel about a 30 - 40 mile radius, this is why it seems so strange to me, why spend all this money buying expensive antennas and cable and get better with a cheap j pole. There are other frequencies I am trying to pull in, that is the reason for the outdoor antenna, and a avid hobbyist.

 

[timmer]

There is a chance that you are overloading your reciever. What receiver/scanner are you using? Does it have a attenuator, and if so, turn it on and see what that does. I have a discone mounted up about 45 feet, and it does great when used with my ar 3000, but overloads the heck out of my BC 780 and Pro 97. Just way too much signal for them to handle.

 

[Chevyman22360]

I am using a Radio Shack pro-96, I never have done anything with the attenuator, could be a possibility I suppose.

 

[ampulman]

I built a J-Pole for the 150-160 mhz band which covers the South Dakota statewide TRS System.

Just curious. TRS's in the 150 - 160 mhz range?

AM

 

[SAR923]

I am 100% certain that your Pro 96 is suffering from desense. Mine does exactly the same same thing with just a 1/4 wave groundplane mounted in the attic. If you use the attenuator, you will see a big improvement in VHF signals. For an even better solution, spend $20 and get a combination high pass/FM notch filter. You can find them at Scannermaster.com and other electronic outlets. It will knock out most of the signals that are causing the front-end overload problem.

 

[Chevyman22360]

I am 100% certain that your Pro 96 is suffering from desense. Mine does exactly the same same thing with just a 1/4 wave groundplane mounted in the attic. If you use the attenuator, you will see a big improvement in VHF signals. For an even better solution, spend $20 and get a combination high pass/FM notch filter. You can find them at Scannermaster.com and other electronic outlets. It will knock out most of the signals that are causing the front-end overload problem.

How do I know what channels to use the attenuator on, I tried the attenuator on a couple of the TRS channels and they dissappered.

 

[SAR923]

The desense generally affects VHF from the air band through about 165 MHz. The first place I'd test would be the NWS channels and see if reception improves with the attenuator on. If not, you either need a notch filter or you've got a bad balun or bad antenna.

 

[scubasky]

Thank you! Turning on ATT fixed mine! I was getting so worried that I wasted a couple hundred bucks on a scantenna and a mast!

 

[Chevyman22360]

Thanks for help!!!

Yes, the attenuator fixed it, I always wondered what the button was for, now I know.
Thanks for all the response!!!
Merry Christmas and Happy New Year!!!