ATS, bandwidths and sensitivity . . .

[KB2GOM]

Recently, I saw a claim on YouTube that, if you are using ATS (automatic tuning system such as on CCrane Skywave SSB), and you narrow the bandwidth, you will make the search more sensitive, that is, you will get more "hits" that if you used ATS on a wider bandwidth.

Does that line up with radio theory . . . that a narrow bandwidth is more sensitive than a wider bandwidth?

 

[Boombox]

I've read that much on various radio forums. Some guy who claimed to design radio circuitry stated that it works that way. Personally, I don't really know.

 

[ka3jjz]

Searching and scanning per se on HF is a crapshoot. Any noise level that exceeds a threshold will stop the scanning. There are ways to do this, but not on a consumer radio such as the CCrane.

Mike

 

[MDScanFan]

Recently, I saw a claim on YouTube that, if you are using ATS (automatic tuning system such as on CCrane Skywave SSB), and you narrow the bandwidth, you will make the search more sensitive, that is, you will get more "hits" that if you used ATS on a wider bandwidth.

Does that line up with radio theory . . . that a narrow bandwidth is more sensitive than a wider bandwidth?

Yes, that is correct. The sensitivity of a receiver is dependent on bandwidth. The wider the filtered bandwidth the more noise power that is received and the stronger the desired signal needs to be in order to be detected. As the bandwidth is narrowed the received noise power reduces. So it makes sense that the narrower bandwidth is recommended for ATS on the skywave.

There is a limit though to narrow filters. The sensitivity is higher with a narrow filter but if filter is too narrow then you may not be able to detect or recover the desired signal. For instance, trying to listen to a weak SSB transmission on a 500 kHz filter (designed for CW) will not work well because the bandwidth is too narrow for the bandwidth of a SSB transmission.