On Mar 30, 9:07*pm, SC Dxing wrote:
Operator Bob,

I guess the questions I am asking. Does having separate USB/LSB switch
make a difference when listening to sideband signals? Will having
separate USB/LSB along with synch detection make that much of a
difference trying to listen to weak AM signals both on AM and
shortwave?

The Sony 7600-SW also is coming to mind.

Anyone have any hands on with the 7600-SW?

Thanks a mil

Separate LSB and USB, if properly implemented, makes a big
difference. Instead of just providing a beat frequency oscillator
(BFO) to allow you to tune in one or another sideband, the separate
sideband provision is a more dedicated electronic approach. The
result, in my experience, is a much cleaner signal. It definitely
helps with weak signals. Does the G5 not do this for you?

The SD for the AM is a nice feature for smoothing out a fading
signal. The best of all worlds would allow for a double-sideband
Synch along with sideband-selectable synch. This would allow for the
greatest versatility when trying to get a good copy on a fading
signal. Judicious use of the ssb can get you about the same results,
but it isn't quite the same.

Bruce

Bruce,

My G5 can do SSB but it's via a fine tune knob. Not separate USB/LSB.
I can't really complain about the G5, I think I just want a new toy to
play with.

Now my G6, I can only get in USB signals, it just won't work with
anything on LSB. Weird.

On Wed, 31 Mar 2010, SC Dxing wrote:

Bruce,

My G5 can do SSB but it's via a fine tune knob. Not separate USB/LSB.
I can't really complain about the G5, I think I just want a new toy to
play with.

But that's not some different technique, it's just cheaper.

it's cheaper to have a variable oscillator as the BFO than two crystals to
allow for a fixed BFO that is properly placed for upper and lower
sideband. Crystals cost money, the tuneable BFO is cheaper and allows
for a level of fine tuning (though once you use it for fine tuning, you
lose the ability to place it right where it should be on the slopes of
the IF filter, but with a tuneable BFO you'd only be guessing anyway).

In both cases, there is a BFO. Some people seem confused by that, since
in the old days of a tuneable BFO, the knob was labelled BFO, but once
sideband receivers came along with crystal controlled BFOs, the knob
was labelled "mode" or "sideband".

With a sync detector, you need a tuneable BFO anyway to lock to the
incoming signal, so there's little sense in tossing that out for a
crystal controlled BFO for SSB reception.

Michael

Bob Dobbs wrote:

Wonder why neither the 2010 nor the SW77 had it,
or why it isn't on newer units like the G3?

The 2010 is an interesting story. The ICF-7600D aka ICF-2002 had already
came out, which was a much better (and smaller) radio than the ICF-2001.
The then obsolete ICF-2001 design was sold to Sangean, who was producing
them for Radio Shack and selling them under their own brand name ATS-803.

Meanwhile Sony found that AM stereo had bombed and they had a warehouse
full of AM stereo decoder chips with no one interesting in buying them.
There were four competing systems of AM stereo and in the US, the FCC
let the market decide. The market, as it were, decided that AM stereo
was not something they were interested in buying radios for.

A Sony engineer figured out that he could use the AM stereo decoder chip
as a selectable sideband synchronous detector chip. The sync detector
of the 2010 worked the way it did, because that's how it worked. No one
said "let's design a sync detector" and made it that way, it was
the other way around.

The 2010 was a combination of the 2002's design, the sync chip and the 2001's
ergonomics, put together to produce a new radio. It added some features
(such as air band) that were not available before in addition to the sync
detector.

Eventually, Sony sold many 2010's and still had more chips, so they
"improved" the 2010 and sold that as the SW-77. One of the noticable
improvments was 100 memory channels instead of 32. From what I
understand shortwave performance was not as good. :-(

Eventually Sony sold out of the chips and since they had been manufactured
in the early 1980's was unable to produce more. It would have required
a re-design to use manufacturing techniques 20 years newer, which would
have required a new radio design and there was not enough demand for it.

BTW, the 7600-GR, is a descendent of the 2002 with similar size and
ergonomics.

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.

Geoffrey S. Mendelson wrote:
Bob Dobbs wrote:

Wonder why neither the 2010 nor the SW77 had it,
or why it isn't on newer units like the G3?

The 2010 is an interesting story. The ICF-7600D aka ICF-2002 had already
came out, which was a much better (and smaller) radio than the ICF-2001.
The then obsolete ICF-2001 design was sold to Sangean, who was producing
them for Radio Shack and selling them under their own brand name ATS-803.

Meanwhile Sony found that AM stereo had bombed and they had a warehouse
full of AM stereo decoder chips with no one interesting in buying them.
There were four competing systems of AM stereo and in the US, the FCC
let the market decide. The market, as it were, decided that AM stereo
was not something they were interested in buying radios for.

A Sony engineer figured out that he could use the AM stereo decoder chip
as a selectable sideband synchronous detector chip. The sync detector
of the 2010 worked the way it did, because that's how it worked. No one
said "let's design a sync detector" and made it that way, it was
the other way around.

Considering that the Kahn system used independent sidebands there was
not much to figure out. Left was one sideband, right was the other.


The 2010 was a combination of the 2002's design, the sync chip and the 2001's
ergonomics, put together to produce a new radio. It added some features
(such as air band) that were not available before in addition to the sync
detector.

Eventually, Sony sold many 2010's and still had more chips, so they
"improved" the 2010 and sold that as the SW-77. One of the noticable
improvments was 100 memory channels instead of 32. From what I
understand shortwave performance was not as good. :-(

Eventually Sony sold out of the chips and since they had been manufactured
in the early 1980's was unable to produce more. It would have required
a re-design to use manufacturing techniques 20 years newer, which would
have required a new radio design and there was not enough demand for it.


But they had the chips for the 7600G/GR, so having a chip to make the
radio wasn't the issue. Demand for a $500 portable was much lower than
that for a $150 portable.

BTW, the 7600-GR, is a descendent of the 2002 with similar size and
ergonomics.

Geoff.