Sunday, May 9, 2010

FT-817 Tip - Spectrum Scope

The Spectrum Scope Monitor (SSM) is a very handy feature of the FT-817 allowing you to monitor a quiet band and see when signals pop up outside the receiver passband. There are a couple of things not explained in the manual that make SSM more valuable as an operating aid.

If you look at the region of the display just under the frequency you'll see  11 segments. Each segment can rise and fall according to the received signal strength on that frequency. The center segment represents the frequency on the display and there are 5 segments below and five segments above. The value of each segment is controlled by Menu Item 47 "SSB Step", when set to 1 kHz each spectrum display segment represents 1 kHz so you are monitoring 10 kHz of spectrum. At a 2.5 kHz you can see a 25 kHz slice of the band (12.5 each side of the center frequency) and when Menu 47 is set to 5.0 kHz you'll see a 50 kHz chunk of RF.

SSM can run in either a continuous sweep or in check mode that performs a sweep every 10 seconds, this is controlled by Menu Item 43 "Scope". While SSM is running if s signal pops up just turn the main tuning knob to bring that signal to the center of the display then turn off SSM by pushing in the Select knob. You should now hear the signal. This procedure is a little more difficult in check mode since it must be accomplished in 10 second iterations. I find that when monitoring CW signals with 1 kHz steps, if the narrow filter is installed, turning it on improves the operation greatly. If you're listening to a 25 or 50 kHz section of band, turn the narrow filters off so there is a little bit of overlap between scan steps.

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