Al Klein wrote:
On Thu, 06 Oct 2005 20:37:32 -0700, matt weber
said in rec.radio.scanner:
On Wed, 05 Oct 2005 21:18:23 -0400, Al Klein
wrote:
On Tue, 04 Oct 2005 10:39:59 GMT, (Peter Newman)
said in rec.radio.scanner:
On 29 Sep 2005 21:18:12 -0700, wrote:
there has to be some other modes that normal scanners wouldn't decode.
any thoughts?
ISB, DSB ?
Any receiver that will receive SSB will also receive DSB, since both
sidebands are the same. ISB too, but only 1 at a time.
Only if the IF is narrow enough to keep the other sideband out,
otherwise you get both at once.....
A SSB receiver is one that has a bandwidth narrow enough to receive
only 1 sideband. If it's 6 KHz wide it's a DSB receiver. (Yes,
almost any ham receiver is either SSB or DSB, depending on the filter
you have running at the moment.)
Of course finding DSBSC signals on the air today is a bit difficult.
(They used to be much more prevalent, but ARC5s are expensive antiques
today, not cheap transmitters. And is there still 1 operational
DSB-100?)
You can't assume that any filter over 3kHz or so is symetrical about the
'carrier' frequency just because that is the normal configuation of consumer
equipment.
Just for fun I am currently listening to an LSB conversation on 3763 kHz with
a 7.5 kHz filter and I cannot hear any sign of the conversation on 3765 - but,
the noise is a bit higher due to the wider filter. I wouldn't normally do this
but just had to try it. Of course, if I select DSB or ISB I get both signals,
although the 3765 conversation is inverted and shifted in frequency.
I don't know how much DSB is still on the air but a quick google search for
"double side band' gets over 12 million hits. It may not be encountered in
normal voice communications on HF and scanner frequencies but it is hiding in
other places and frequencies from a quick look at some of the hits.
Dave