Bob wrote:


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

The IF bandwidth is how wide (in frequency) a signal you want to receive.
Filters have shapes, or more acurately, if you plotted the response of the
filter, it's going to be better at one frequency (the center) and as you go
away from it (up or down) the response curve will have a shape.

Narrow filters look like an upside down letter U, with a sharp cutoff,
wide filters have a long curve of the sides. Narrow filters are more expensive
and have other characteristics.

Then there is the bandwidth of the filter. Those terms only really work in
context, for example a wide filter for AM is 6khz "wide", for SSB 3kHz and
for CW 1kHz.

For example, if you were listening to an AM shortwave station with little
noise and no nearby stations, you would want a 6kHz filter with a wide
response. As the band gets more crowded, you would want one with a narrower
frequency response, though at around 3kHz it starts to become difficult to
understand them (like an old digital cell phone) and by 2 almost impossible.

The narrower a filter is, the more sounds become odd going through it,
a phenomenon known as "ringing". So if you have a choice or adjustment,
you want the widest filter bandwidth with the widest response curve that
blocks out enough interference and noise to understand the station.

Got that? Read it over a few times, it's difficult to understand, and
I'm not a great teacher.

The same principal applies to SSB (single side band), except that SSB
only has have of the wave, (top or bottom) and you can filter out the
side you don't want. So a 3kHz SSB filter is like a 6kHz AM filter.
Generally SSB filters start at 2.4kHz and become narrower.

CW is just a switched carrier, on and off, so a narrow filter (250Hz) is fine.
Since at that narrow a filter you get lots of ringing, and other effects,
it becomes difficult to listen to. To make listening easier, you want as wide
a filter as possible.

Hams and commerical radio operators before WWII were trained to copy with wide
filters and to be able to pick out the one signal in may nearby ones intended
for them. As good IF filtering became available during WWII it became less
of a technological requirement, but until the turn of the century when digital
signal processing at the IF became reasonably available, many hams did without
it.

Many hams still use relatively wide (2-3kHz) filtering for CW because
they are used to it, or it's cheap and simple.


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

AM

AM (amplitude modulation) is the traditional way of adding voice to a signal.
The AM broadcast band in the US is 530kHz to 1750kHz, and scattered through
out the shortwave broadcast bands are mostly AM stations. There are a handful
transmitting in USB or digital radio, but almost everything you will hear
is AM.

Sort range (air/ground to tower, etc) avation is on 108-130(?) mHz and is AM.

NFM

Narrow band FM. Wide band FM is used for broadcasts, such as the US
FM band (88-108 mHz) and analog TV (which is almost dead in the US).

NBFM is (aka NFM) is used for communications. You won't hear any below
26 mHz.

There you may hear remote to studio links for radio stations, illegal
"freebanders", CB operators (FM is illegal in the US on CB) and from
29.5 to 29.7 mHz FM is used by hams.

Over 30 mHz, there are commercial, millitary, government and hams using
FM. Ham bands to listen for are 50-54, 144-148, 223-225,430-450 mHz and so
on.

Short range boats use a band around 165 mHz, there are also weather
forecasts near there.

LSB
USB

Upper and lower sideband. This is used for longer range communications
than AM can provide. Everyone uses USB, ships, airplanes, hams, commercial,
millitary and government etc on HF. Hams and military aircraft use it
on VHF and UHF.

LSB (lower side band) is pretty much only used by hams and only below 10mHz.

Either when not tuned in properly gives you that quacking sound like the
attack scene in star wars.

Note that hams are not required to use either USB or LSB on an particular
band (except for the 5mHz band in the US). It's more convention than
anything else. Occasionaly you will hear a ham using a military or marine
(boat) radio that is only USB below 10mHz.




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

No, it's the AGC (automatic gain control) time. The AGC adjusts how loud
the signal sounds, although it usually works in the IF. In the IF it
adjusts how well it is received in relation to the internal noise of the
receiver. Stronger signals can be received with less gain, so the receiver
generates less internal noise. Weaker ones require more gain, which means
more noise.

Fast medium and slow determine how quickly it "resets". For voice you
don't need much of a delay, so a fast delay is desireable. Morse code has
lots of gaps in it, so a slow agc is prefered. Until you get used to it,
leaving it on medium is a good start.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation.
i.e possessing less facts or information than can be found in the Wikipedia.