Too much of a good thing?

[737mech]

Is there such a thing as having too much signals in a city area that you don't actually hear much? Here's my sitrep, city environment 4 miles from an airport 15 miles from an AF base. I was using a single antenna and 50 feet of coax 50 ohm from RS. I tried three antennas. First the 20-043 from rs. The the 20-176 also from rs. Then the st-2. The one difference I used the rg6 75 ohm with the st-2. Now I can basically see the base and airport tower from my roof top. The afb atis was coming in at two bars on the scanner signal meter with the 043 in the attic using 50 foot rg58. The rg6 with the 043 on the chimney I got less than a bar? similar results with the 176. The st2 I only tried the rg6 and it was also tried on the mast of the chimney. Here's where it gets wild, I tried a basic bnc tee connector with the rg58 and a 20-043 in the attic on one leg and the st-2 with rg6 on the chimney on the other leg pointed directly at the airport tower 4 miles away. I can now get the afb atis at four to five bars signal on the scanner? The afb tower transmits are clear. Why is this possible? From what I have read signal is lost by combining antennas in this manner? Supposedly I need a multicoupler to do this correctly? I feel like the info I have gathered here is reversed in a city environment? Can someone please explain this to me? OBTW I'm using a bct15 as a scanner.

 

[BlueMR2]

*Generally* speaking, the more "capture area", the better you will receive. If I'm understanding correctly, you increased the capture area by tying a couple of antennae together?

 

[blueangel-eric]

*Generally* speaking, the more "capture area", the better you will receive. If I'm understanding correctly, you increased the capture area by tying a couple of antennae together?

if the radio is desensing aka loosing sensitivty from strong signals like from broadcast towers then trying 2 antennas at the same time might cancel each other out or cutting the signal down a bit causing the radio to open up more. Usually it's not wise to hook 2 antennas together inline with out proper splitters or combiners or an antenna switch.

and there are filters out there for overloading signals.
Eric Burris

 

[DPD1]

Something sounds off, because any way you look at it... at that distance, with any kind of antenna outside, you should be getting the ATIS full strength... Even in an urban environment. Some airports do seem to have particularly weak ATIS setups, so that could be the problem. But normally you should get it better than that in most cases. I would double check all your connectors and make sure there isn't a short or something. If there's tons of stuff right around the antennas, then you're basically getting reflected signals. When that starts happening, things can get weird, because one spot may work and another may not work. And it doesn't always make sense which spots work.

Dave
www.DPDProductions.com
Antennas & Accessories for the RF Professional & Radio Hobbyist

 

[737mech]

What about the tuning of the 20-043?

I'm reading the instructions on the rs 20-043 and it says how to tune the antenna, so is that my solution? I'm basically trying to pull in 121.100 but I cannot hear the tower side of the conversation?

 

[mjthomas59]

Tuning is required when transmitting, but for receive only, as long as the antenna is designed for that band, you most likely won't see any benefit. I'm not going to say don't do it, but i wouldn't be too upset when the performance is unchanged.

It does sound pretty strange that by connecting 2 antennas in the manner you describe, that you are able to receive the signal at full strength, but when you only have 1 antenna you can't receive the signal at all. I would guess there is an issue with your coax or connections. I've never personally experienced what you are describing, but with 1 antenna you should be getting atleast a couple bars of signal. You might try the attenuate feature on your scanner and see if that does anything to improve your signal.

Something else i just thought of, what happens when you use the stock antenna? Can you get anything with that? Its possible the other antennas are causing overload as the 2 you described are designed to cover such a wide spectrum. The also make airband filters which could be of help to you as well.

 

[737mech]

Results with one antenna

I tried lots of ways to get what I want. First config RS 20-176 with Rs rg58 50 foot mounted in the attic. Result not bad about 2-3 bars from Nellis AFB Atis (270.100) but nothing fom KLAS atis (132.4). Then I replaced the 20-176 with a 20-043 disconne same coax. Not much better still can't hear 121.1 ground tower transmits. Then I tried a ST-2 with supplied RG-6 thru a f to bnc connector mounted on my chimney. Nellis got better but still no atis or ground from KLAS. Then I tee fitted the st-2 with rg-6 from the chimney and the 20-043 rg58 from the attic and I got Nellis atis five bars and clear. Still no 121.100 at all? Then I took my pro-2051 and tried the same antenna setup no positive results. Wierd thing though, I can use a magnet mount antenna with rg58a/u 12 feet or so on my truck in my driveway with the Pro-2051 and hear both sides of the conversation? I tried this with the bct15 set only to 121.1 and no reception? I checked the attenuator is off for that freq. I also programmed the bct15 modulation from auto to am only. I'm four miles from KLAS but also five miles from a radio antenna farm atop a mountain to the south of my location. As another note I can receive Ramp Control (both sides of conversation) on 129.1700. I would like to hear 119.900 and 121.100 but I feel my configuration is somehow deaf in those bands? Any help or suggestions? Also I bought a roll of rg6 quad coax from home depot, might give it a try?

 

[jerk]

I tried lots of ways to get what I want. First config RS 20-176 with Rs rg58 50 foot mounted in the attic. Result not bad about 2-3 bars from Nellis AFB Atis (270.100) but nothing fom KLAS atis (132.4). Then I replaced the 20-176 with a 20-043 disconne same coax. Not much better still can't hear 121.1 ground tower transmits. Then I tried a ST-2 with supplied RG-6 thru a f to bnc connector mounted on my chimney. Nellis got better but still no atis or ground from KLAS. Then I tee fitted the st-2 with rg-6 from the chimney and the 20-043 rg58 from the attic and I got Nellis atis five bars and clear. Still no 121.100 at all? Then I took my pro-2051 and tried the same antenna setup no positive results. Wierd thing though, I can use a magnet mount antenna with rg58a/u 12 feet or so on my truck in my driveway with the Pro-2051 and hear both sides of the conversation? I tried this with the bct15 set only to 121.1 and no reception? I checked the attenuator is off for that freq. I also programmed the bct15 modulation from auto to am only. I'm four miles from KLAS but also five miles from a radio antenna farm atop a mountain to the south of my location. As another note I can receive Ramp Control (both sides of conversation) on 129.1700. I would like to hear 119.900 and 121.100 but I feel my configuration is somehow deaf in those bands? Any help or suggestions? Also I bought a roll of rg6 quad coax from home depot, might give it a try?

Try moving the antenna four feet to the left or right or both and check results. I'm sure you'll see an improvement. The truck is outside away from obstacles and interference.

 

[737mech]

Tried that

Check my previous post, I tried the 20-043 on the chimney no obstructions line of sight to the KLAS tower. The only difference was I used the rg6 from the st-2.

 

[jerk]

Check my previous post, I tried the 20-043 on the chimney no obstructions line of sight to the KLAS tower. The only difference was I used the rg6 from the st-2.

Based on experience try moving the antenna. There are no obstructions on your end... but what about between the airport and you.

Heck, just moving a scanner around a room with the back of the set antenna sometimes yields amazing results. I can move my truck 4 feet and pick up a system with full bars... and move back to the original spot and receive absolutely nothing.

 

[737mech]

The scanner dance

That's what I call it, the scanner dance. I hooked up the st-2 with the rg6 that came with it and mounted it on a camera tripod. I tried several locations both inside and outside my house. You're right, it matters where the scanner is and where the antenna is. I can't explain it, I can get way cool strong signals and way weak ones depending on where I am a few feet this way or that way who would have thought? Problem now explaining to my wife that my shack is now going to be in the livingroom. Maybe I try some stuff with the antenna and new coax, different locations. Thanks a bunch for the help!!!!

 

[jerk]

That's what I call it, the scanner dance. I hooked up the st-2 with the rg6 that came with it and mounted it on a camera tripod. I tried several locations both inside and outside my house. You're right, it matters where the scanner is and where the antenna is. I can't explain it, I can get way cool strong signals and way weak ones depending on where I am a few feet this way or that way who would have thought? Problem now explaining to my wife that my shack is now going to be in the living room. Maybe I try some stuff with the antenna and new coax, different locations. Thanks a bunch for the help!!!!

A very much oversimplification.. but think flashlight and light waves, sometimes they bend, sometimes they don't... it's very comparable to radio waves. They sometimes do the strangest things.