Both RS scanners pick up pager transmitter sound

[Lexx333]

I am not sure if this is a RS scanner issue but I am getting some interference that sounds almost like a dial up modem. I believe from reading other posts in the forum that it is a pager transmitter? What exactly causes this and how can it be filtered away?

 

[jfhtm350]

I dont know what frequency your on or what scanner you have, but if you have a scanner that accepts pl or dc codes then you can program in the code and it will only open up the scanner if that code comes across.

 

[SCPD]

you will need a scanner with pl/dpl capability. its either data for a mdt, or a pager setup they use.

 

[Lexx333]

the particular scanner I am using when this happens is a Radio Shack pro 2051. I am usually in the 144.xx to 146.xx range.

 

[W8RMH]

You are monitoring the amateur 2 meter band. That is not interference and there are no pagers in this band. You are most likely receiving some type of packet transmission . There is no way to filter it out, you would have to lockout that frequency.

 

[kruser]

the particular scanner I am using when this happens is a Radio Shack pro 2051. I am usually in the 144.xx to 146.xx range.

Most likely intermod from a mix of two transmitters or a direct image from a paging site in the 152 or 158 MHz paging bands.
Setup a search from 152 to 153 MHz and 158 to 159 MHz and see if you hear the same type sounds.

The correct way to cure this is the use of a notch filter tuned for the true paging frequency. You can monitor the paging bands and find the true frequency using a 2nd scanner searching the paging bands and just match the sounds you hear. PAR Electronics sells them. One for each of the two bands. They work fantastic for these problems. The NOAA WX transmitters also caused this problem so they sell notch filters for that also.
Most of these problems were cured when they started selling better quality scanners using triple conversion IF circuits. The older dual conversion models were very prone to this problem. I'm not sure if the 2051 is dual or triple conversion.

Using PL or DPL squelch may keep the scanner from opening the squelch but if the ham repeater you are monitoring does not transmit a PL or DPL code, then that won't work. Also the paging noise will usually still come through when the scanner is receiving a signal with the proper tone squelch set and the paging transmitter comes on. If the intended signal is much stronger then the paging interference, using tone squelch may help as the real signal will mask the weaker paging signal.
If the intended signal is weaker than the paging signal, then you are SOL without some type of notch filter for the unwanted signal.

Edit: what W8RMH said is also a very possible cause. Packet radio or some other digital mode. All you can do for that is set your search around the noise or see if you can lockout individual frequencies while searching.
My bet is still intermod or an image from a VHF paging site. It is a VERY common problem with scanners.

 

[Lexx333]

You are monitoring the amateur 2 meter band. That is not interference and there are no pagers in this band. You are most likely receiving some type of packet transmission . There is no way to filter it out, you would have to lockout that frequency.

Thank you for the links in your response. That gave me some reading that was very beneficial. As you can probably tell I am just starting to dive a little deeper into the hobby.

 

[Lexx333]

Most likely intermod from a mix of two transmitters or a direct image from a paging site in the 152 or 158 MHz paging bands.
Setup a search from 152 to 153 MHz and 158 to 159 MHz and see if you hear the same type sounds.

The correct way to cure this is the use of a notch filter tuned for the true paging frequency. You can monitor the paging bands and find the true frequency using a 2nd scanner searching the paging bands and just match the sounds you hear. PAR Electronics sells them. One for each of the two bands. They work fantastic for these problems. The NOAA WX transmitters also caused this problem so they sell notch filters for that also.
Most of these problems were cured when they started selling better quality scanners using triple conversion IF circuits. The older dual conversion models were very prone to this problem. I'm not sure if the 2051 is dual or triple conversion.

Using PL or DPL squelch may keep the scanner from opening the squelch but if the ham repeater you are monitoring does not transmit a PL or DPL code, then that won't work. Also the paging noise will usually still come through when the scanner is receiving a signal with the proper tone squelch set and the paging transmitter comes on. If the intended signal is much stronger then the paging interference, using tone squelch may help as the real signal will mask the weaker paging signal.
If the intended signal is weaker than the paging signal, then you are SOL without some type of notch filter for the unwanted signal.

Edit: what W8RMH said is also a very possible cause. Packet radio or some other digital mode. All you can do for that is set your search around the noise or see if you can lockout individual frequencies while searching.
My bet is still intermod or an image from a VHF paging site. It is a VERY common problem with scanners.

Thank you for your response as well. My pro-96 doesn't seem to have this issue. I have started blocking out the frequencies. I will do some further investigating this weekend.

 

[kruser]

Thank you for your response as well. My pro-96 doesn't seem to have this issue. I have started blocking out the frequencies. I will do some further investigating this weekend.

The Pro-96 is triple conversion so that does point to the problem being intermod or an image then.
Some scanners (many really!) have very poor bandpass filtering built into them to keep the cost low. Triple conversion models can also have this problem, it's just not as bad as it was with the dual conversion models.