Hello
I had not hooked up my Pro-96 to an outside antenna until recently. When I did I noticed that reception was down on VHF. Since the radio with the rubber duck works very well I was a bit puzzled. I wondered about the attenuator so I hit the ATT button and the VHF station that was very noisy came in full quieting. I played with it bit more, finding stations that were at the squelch level and found that when the ATT was enabled they were readable. Of course this isn't acceptable since the unit is carried almost every day, and to have to go through and disable/enable the attenuator would be a pain.
I live in a rural area, and intermod is a non issue. but I figured something was getting in to the front end. I switched to a emergency antenna I have in the attic with lousy feed line and the attenuator worked as it is supposed to.
I decided to try and find the problem, so I started searching different slices of spectrum. While searching the AM aircraft band I heard music. It was all up and down the band. I figured out which radio station it was, a local FM transmitting on 103.5 located approximately 3 miles away from my house.
I figured that I would try and reduce the level of the FM station, so I decided to try a tuned stub. I attached the antenna connector to one side of a BNC "T" connector. I attached the male end of the "T" on the scanner, and cut a piece of RG-58 coax cable with a length of one quarter wave length of the FM stations frequency.
234 / 103.5 = 2.2608
converting that to inches 2.2608 * 12 = 27.13
Also the cable was left open on the end (not shorted).
This completely notched the FM station from the front end of my radio. The scanner receives as it should on VHF, and the attenuator also works as it should, reducing the received signal, not enhancing it.
This might not work if you are bombarded with different signals, but I would think that if FM radio stations are your problem you should be able to reduce the interference with this method.
I called a friend who has a Pro-97 and asked him to check his on an external antenna. While mobile in Springfield IL he experienced the same problem. When he heard VHF stations weaker than he thought he should, he hit the ATT button and they also came in much better. I don't know if his was FM radio overload or not, but it seems that the Radio Shack portables are prone to this interference when they are on a base or mobile antenna.
Hope this helps someone.
Flip N9AZZ
I had not hooked up my Pro-96 to an outside antenna until recently. When I did I noticed that reception was down on VHF. Since the radio with the rubber duck works very well I was a bit puzzled. I wondered about the attenuator so I hit the ATT button and the VHF station that was very noisy came in full quieting. I played with it bit more, finding stations that were at the squelch level and found that when the ATT was enabled they were readable. Of course this isn't acceptable since the unit is carried almost every day, and to have to go through and disable/enable the attenuator would be a pain.
I live in a rural area, and intermod is a non issue. but I figured something was getting in to the front end. I switched to a emergency antenna I have in the attic with lousy feed line and the attenuator worked as it is supposed to.
I decided to try and find the problem, so I started searching different slices of spectrum. While searching the AM aircraft band I heard music. It was all up and down the band. I figured out which radio station it was, a local FM transmitting on 103.5 located approximately 3 miles away from my house.
I figured that I would try and reduce the level of the FM station, so I decided to try a tuned stub. I attached the antenna connector to one side of a BNC "T" connector. I attached the male end of the "T" on the scanner, and cut a piece of RG-58 coax cable with a length of one quarter wave length of the FM stations frequency.
234 / 103.5 = 2.2608
converting that to inches 2.2608 * 12 = 27.13
Also the cable was left open on the end (not shorted).
This completely notched the FM station from the front end of my radio. The scanner receives as it should on VHF, and the attenuator also works as it should, reducing the received signal, not enhancing it.
This might not work if you are bombarded with different signals, but I would think that if FM radio stations are your problem you should be able to reduce the interference with this method.
I called a friend who has a Pro-97 and asked him to check his on an external antenna. While mobile in Springfield IL he experienced the same problem. When he heard VHF stations weaker than he thought he should, he hit the ATT button and they also came in much better. I don't know if his was FM radio overload or not, but it seems that the Radio Shack portables are prone to this interference when they are on a base or mobile antenna.
Hope this helps someone.
Flip N9AZZ
