On Mar 17, 1:51*pm, Bob wrote:
Hello,

I'm mainly a sw listener, Sr. Citizen now, and frankly not very
knowledgeable about radio theory.

Have a new WinRadio receiver that I'm enjoying very much.

But I realize there are several optional settings that I really don't
understand, and don't have a handle on.

I do listening from about 1 MHz up thru the vhf/uhf scanner freq's,
including MIL and Maritime stuff on SSB.

Regarding the IF Bandwidth options:

Might someone please give me a short discourse on what this does, and
what it effects.

And, some suggested (Default) settings that I could get started with for:

AM
NFM
LSB
USB

Also the effect of slow, medium and fast for what I think is
the the AF Filter

Thank you very much; appreciate the help,
Bob

Hi, Bob -

In terms of IF, Bandwidth describes the width of the slice of the
frequency spectrum that gets through to your final RF stage, and also
affects the width of the audio slice that reaches your speaker. It
serves to determine both the audio quality (how much the of high freqs
get cut off) and the amount of adjacent channel information is allowed
to get through.

As an example - For SWL on AM, most stations are spaced about 5 kHz
apart. That means one on 9,555, one on 9,560, one on 9,565 and so
forth. If you want to listen to a station on 9,560 and you don't want
adjacent interference from those other freqs, the slice you take
should be narrow enough to reject those adjacent signals but wide
enough to provide a pleasing audio regime. In this case, a 6 kHz IF
filter width (typical for a wide AM with good midrange tones) would be
adequate, cutting off everything more than 3 kHz away on either side
and leaving you with a clear channel. You would hear everything from
0 to 3,000 Hz audio, an adequate range for comfortable hearing and
understanding.

If you run across a station closer than 5 kHz, you may want to narrow
your filter a bit. If an offending station is on 9,558, you would
have to take a narrower slice, and maybe use a filter that cuts off at
4 kHz width. You again get a clean signal, but the trade-off is that
you lose some high audio frequencies. The desired signal gets a
*little* bit harder to understand.

Lots of things can affect this, of course. If your filter has steep
"skirts", meaning a good solid cutoff at each end, then they should
work very well. If your filter has gentle skirts, they may not work
as well as their bandwidth rating would suggest, allowing in some
adjacent interference. I am not sure about the WinRadios, but if they
have continuously variable bandwidths, you should be able to adjust
the filter width so that the skirt quality will be slightly less
important. Also, if the adjacent signal is very strong and your
desired signal is weaker, even a decent filter may have a harder time
rejecting the adjacent interference. In this case, a passband / IF
shift adjustment can be handy - it can take the whole desired signal
and essentially shove it away from the offending adjavcent
interference. Again, I don't know if the WinRadios have this feature.

For AM SWL, good bandwidths are something nice and wide for strong
signals on clear channels (6 kHz or more), a 6 kHz filter for general
listening on a modestly crowded band, and a 3 - 4.5 KHz bandwidth for
the modest signal next to the stornger station. If you get much
narrower, you may lose a lot of audio and the sound becomes very
muddy.

This is where SSB - USB - LSB can help. If you get interference from
a station a few kHz away and the AM filter won't cut if out, a switch
to the sideband farther away from the offending signal can make a big
difference. In fact, using sideband for AM listening can help with a
number of problems ranging from noise to fading. For USB / LSB, you
can have narrower bandwidths, say 1.5 - 3 kHz, and still enjoy decent
audio, because the slice you take is only half the incoming signal,
and it can include everything from 0 up to the desired higher
frequency.

The passband / IF shift can also help on USB / LSB, sliding your
signal away from the interference. You will probably hear some
variation in the sound of the SB signal, though, so it must be used
judiciously.

Finally, if you have a REALLY close signal but you can use SSB, you
can switch to that sideband farther from the offending signal and
switch in a narrow filter. Howeve, you may still get a whistling
heterodyne from the nearby station - in that case, switch in a Notch
filter to cut it out, and adjust it is possible to achieve the desired
level of whistle removal.

Does that help?

73,
Bruce