Icom R8600 Searching For New Signals Help

[MDScanFan]

I have been using the R8600 to search for and save for new frequencies. The receiver is designed to skip a frequency after it has been found and continue to look in the designated scan range for more signals. The issue I am having is that it saves frequencies that are slightly off the center frequency of the real signal. For instance, on the rail band, let’s say the signal it found is on 160.230 MHz. It saves that frequency and then skips it and keeps searching. When that signal transmits again the R8600 ends up stopping on and saving the unwanted frequencies of 160.225 and 160.235.

Has anyone else experienced this issue? Is there a way to remedy it?

 

[prcguy]

I have not done any signal searching like this but I do know you must use the same frequency step as the channel spacing of the service you are searching because really small steps will allow the radio to receive a signal slightly off frequency. If you are searching in say 1KHz steps the radio will lock onto a frequency possibly a few KHz away from center as it approaches but if you search in the channel spacing like 15KHz or 12.5KHz, etc, the radio will stop right on the active channel since it will be too wide of a step to receive an off frequency signal.

I have been using the R8600 to search for and save for new frequencies. The receiver is designed to skip a frequency after it has been found and continue to look in the designated scan range for more signals. The issue I am having is that it saves frequencies that are slightly off the center frequency of the real signal. For instance, on the rail band, let’s say the signal it found is on 160.230 MHz. It saves that frequency and then skips it and keeps searching. When that signal transmits again the R8600 ends up stopping on and saving the unwanted frequencies of 160.225 and 160.235.

Has anyone else experienced this issue? Is there a way to remedy it?

 

[MDScanFan]

Agreed. I should have mentioned that in the example above I was using a step size of 5 kHz, which is appropriate for the railband. I have seen the same issue for other VHF FM searches with appropriate scan steps. I believe I also encountered it for VHF airband.

In all cases the issue seems to occur for moderate signals and stronger. Probably around -60-70 dBm or greater from what I recall. I does not show up for weak signals, which I suppose makes sense.

I have not done any signal searching like this but I do know you must use the same frequency step as the channel spacing of the service you are searching because really small steps will allow the radio to receive a signal slightly off frequency. If you are searching in say 1KHz steps the radio will lock onto a frequency possibly a few KHz away from center as it approaches but if you search in the channel spacing like 15KHz or 12.5KHz, etc, the radio will stop right on the active channel since it will be too wide of a step to receive an off frequency signal.

 

[prcguy]

I think 5KHz in FM mode is narrow enough where the radio will sense a signal that much off frequency and stop scanning. For the RR band I think 15KHz would be a better choice.

Agreed. I should have mentioned that in the example above I was using a step size of 5 kHz, which is appropriate for the railband. I have seen the same issue for other VHF FM searches with appropriate scan steps. I believe I also encountered it for VHF airband.

In all cases the issue seems to occur for moderate signals and stronger. Probably around -60-70 dBm or greater from what I recall. I does not show up for weak signals, which I suppose makes sense.

 

[MDScanFan]

Ah, my mistake, you are right. I mistakingly thought the rail step size was 5 kHz based on the frequencies I was seeing. 15 kHz is what I should be using and would remedy this issue. I will revisit what I was using for the other search bands as well. Thank you!