antenna problems

[prophead]

Hi all,

I have a Maycom ar-108 scanner that i have been using to listen to aircraft. I have recently bought an external antenna and mounted it on the roof. The thing is i cant pick up anything. not even the stuff i can with the rubber antenna that came with the scanner. I have tried it on the local moors before i fitted the antenna and it worked fine there. It also worked fine all the way home in the car until i was on my street. With the rubber antenna i get a signal strength of 5 and pick up the local airport. with the external antenna i get a full signal strength but just white noise. There is a large transmission antenna on the hill above my house which looks like an electricity pylon bristling with aerials and dishes. I presume this may be the cause, but then why is the rubber aerial ok. If this is the cause is there anything i could get that would block out that interference.

Regards

Prophead.

 

[N_Jay]

Hi all,

I have a Maycom ar-108 scanner that i have been using to listen to aircraft. I have recently bought an external antenna and mounted it on the roof. The thing is i cant pick up anything. not even the stuff i can with the rubber antenna that came with the scanner. I have tried it on the local moors before i fitted the antenna and it worked fine there. It also worked fine all the way home in the car until i was on my street. With the rubber antenna i get a signal strength of 5 and pick up the local airport. with the external antenna i get a full signal strength but just white noise. There is a large transmission antenna on the hill above my house which looks like an electricity pylon bristling with aerials and dishes. I presume this may be the cause, but then why is the rubber aerial ok. If this is the cause is there anything i could get that would block out that interference.

Regards

Prophead.

It all depends how much you want to spend.

What type of extenal antanna did you buy?

Do you care about any band besides Aircraft?

How long is the cable run?

 

[prophead]

I didnt want to spend too much. Im only interested in airband at the moment.

The antenna i bought was a sky scan airbase which is a vertical white pole with 4 metal thin poles going out the bottom which go diagonally down. thats the best way a can describe it. it looks like an upside down Y shape.

The cable is 4M long

 

[N_Jay]

I didnt want to spend too much. Im only interested in airband at the moment.

The antenna i bought was a sky scan airbase which is a vertical white pole with 4 metal thin poles going out the bottom which go diagonally down. thats the best way a can describe it. it looks like an upside down Y shape.

The cable is 4M long

I don't know anything about that antenna (Anyone?, Anyone?, Beuler?)

4 M of cable shoudl be insignificant at 120 MHz.

I would start with an attenuator. A filter to reduce the signals from outside the band you are interested in would be better, but more expensive.

 

[LarrySC]

First rule of thumb when installing antenna. Check with OHM meter from scanner connector to receive element on antenna. If you get a full scale reading then install it. Be sure coax is 50 to 75 ohms. Double check connectors for proper fit. It does sound like signal overload. If there is no way to cut down incoming signal in radio then look for an attenuater for your coax at a local TV shop. Good Luck

 

[prophead]

Will an attenuator do the job. I enquired about this in Maplins and they said it would only reduced the strength of all the signals so i would get the same results but with all round lower strength (including the stuff i want to hear).

 

[N_Jay]

Will an attenuator do the job. I enquired about this in Maplins and they said it would only reduced the strength of all the signals so i would get the same results but with all round lower strength (including the stuff i want to hear).

It depends on the particular problem.

A receiver front end is not linear. It does not react to signal differences the same at all power levels.

Often by reducing the total energy it has to deal with you will allow it to better receive the desired signal.

If the problem is noise ON the desired frequency, then an attenuator may not help.

If the problem is noise well outside the band, then a filter does an enven better job, but you are into a lot more money.

 

[prophead]

ive just bought a notch filter but that has made no difference at all.

 

[N_Jay]

ive just bought a notch filter but that has made no difference at all.

What are you notching?????

The problem with hit-or-miss solutions is that most of the time you miss!

 

[prophead]

I really dont know!!

I went into a radio shop and explained the problem and the guy told me i neede a notch filter. The way he described it was a box that would accept the airband frequencies but none others. However he didnt have one, so i went to another shop which did have one and bought that. This one has a dial on it which from what i can work out will take out a certain frequency. The problem is i think i need to take out all frequencies apart from the airband range. Can i get something like this.

Am i right or totally wrong, i dont know much about radio theory i just need to listen to the airband to help with my pilot training.