On Mar 6, 12:56Â am, Dave Heil wrote:
wrote:
On Mar 5, 3:09�pm, Dave Heil wrote:
wrote:
On Mar 3, 8:23pm, Dave Heil wrote:

A few years ago, a small company began manufacturing
a reduction knob
for the 75A-4, machined out of solid brass. Functional and
attractive.

I noted them when I saw the ads in Electric Radio. Â
The price was very dear.

$125 IIRC.

How did it provide PBT?

I'm going to have to dig out the paperwork
on the Universal Service unit
(which I got copies of just a year or two back) and let you know.

Will be good to know.

The CW filter I have is the 800 Hz unit. Â One of these days I may
replace it with an Inrad unit. Â I'll have to juggle things a bit to
match the modern Collins mechanical filter to the radio.

I think the same company that made the reduction knob made exact plug-
in filters. Dunno if they made a CW one.

At the University ham shack we had two 75S-3s. One had the
200 Hz filter, aka "the ringmaster". But boy could they hear!

IIRC the 1-A predated the S-line and KWM-2.

I think you'll find that all of them hit the market in '57.

The KWM-2 came after the original S-line (75S-1/32S-1) Check your old
QSTs, you'll see the 1-A advertised well before the KWM-2.

It was a revolutionary
design; small, light and compact at a time when even
inexpensive
receivers were big and heavy. Note the tiny, taller-than-it-is-wide
front panel and the very deep chassis.

Unfortunately it was built as an SSB-only receiver. Â There
were no provisions for a narrow filter for CW or a wider one for
AM. Â In
fact, the BFO could not be turned off at all. Â I sold a number of rig
s
after coming back stateside and the Drake 1-A was one of them.

1-A was Drake's entry into the ham receiver market; previously
they had only made things like lowpass filters. Their idea was to
cut the cost of SSB to the bone by making a receiver specific to
the mode and leaving out anything not needed for SSB. Hence no
diode detector, no BFO-off, no narrow filter, etc. But it had PBT,
which also gave sideband selection, an S-meter and AGC that
worked on SSB, and was very stable.

That mode-specific thing inspired many of the Southgate receivers.

The 2-A and 2-B are excellent receivers for their price and
complexity, and are prized today. But they were a dead end
in one way:
there was no matching transmitter that could transceive with
them.

In the time when they were introduced, many folks were still using
separates. Â I've kept my 2-B because it really is a classic and
performs
well today. Â The matching 2-BQ adds a lot to the receiver.

About 15 years ago I walked away from a hamfest table that
had a 2-B/2-BQ combo for $75. "To think about it". Oh fer dumb.....

What the KWM-2 and S-line did was to make
"transceiving" popular.

Well, they made it popular for those with lots of money.

Not just those folks. The idea got wide publicity and led to lots
more rigs at a lot lower prices.

If I recall correctly, there were identical-looking models with two
different power output levels.

Cosmophone 35 and Cosmophone 1000.

Indeed, a homebrew 40 meter *CW* transceiver built
around a surplus
BC-453 was described in a 1954 QST, probably the
first published use
of the idea in amateur radio. It even had full QSK.
But it was ahead
of its time.

You've aroused my curiosity. Â
I'll have to dig through the back issues
and check it out. Â There's a '453 lying about here somewhere.

IIRC the author's last name was Deane. I do not know of any earlier
HF amateur transceiver being described in QST or any other
publication.

The KWM-2 and S-line took transceiving to another level. Not only were
they smaller and lighter than their predecessors, they had relatively
few controls. They made SSB more popular with hams by reducing the
cost and size and eliminating the job of zerobeating the transmitter.
Tune an SSB station correctly and the transmitter was automatically on
the right frequency.

I have to disagree with the reduction of cost. Â
When the KWM-2 was
introduced, my dad made a little less than
$6,000 per year gross pay as
a Miami Herald reporter. Â That transceiver would have cost about a
quarter of a year's pay.

And $6000/yr gross income was solid middle class. A family of four
could live very well on $6K, 50 years ago.

What I meant was that a KWM-2 and power supply/speaker cost less than
top-of-the-line separates like a 75A-4 and HT-32B.

Or compare the price of an S-line and a KWM-2.

To get an idea of the influence of the KWM-2, google "LWM-3"...


 Fast forward a bit.  When I bought a Ten-Tec
Omni VI, the new cost was a small fraction of a year's pay
and that rig
offered features only dreamed about at the time of the
introduction of
the Collins rig. Â The KWM-2 was smaller and lighter but an HT-
32B and an
HQ-170 would have been cheaper by hundreds of dollars.

Agreed. But the KWM-2 put the idea of the one-box station out
there in a big way. A lot of less-expensive transceivers with
minimal controls followed. People saw the success of the KWM-2
and designed less-expensive alternatives based on the idea.

Add to this the grounded-grid linear amplifier and things really
changed. High power 'phone became not only less expensive
but a lot
smaller and lighter. Transceivers and matched-pair separates
became
the new paradigm in HF ham gear; AM wasn't part of that.

There are a couple of "duh" factors buried in there for us to mull
over.
It would have been possible for radio amateurs to have built and
used
grounded-grid linear amps for use with AM rigs much earlier. Â A
rig such
as the Johnson Ranger would have driven one to a KW AM input
with ease.

Some hams did that but the big problem was the low efficiency of AM
linear without the use of special circuits like the Doherty, which
isn't the fastest QSY circuit.

With AM linear you only get 30-35% carrier efficiency. Which
means 300-350 watts carrier at the old 1 kW legal limit. Plus
your final tubes have to be able to dissipate 650-700 watts!
The same results could be had from a 450-watt class plate-modulated AM
rig - say, a pair of 812As modulated by a pair of 811As.

AM also required power supplies that could stand the 100% duty cycle
of the mode. The low duty cycle of early unprocessed SSB rigs meant a
lot of liberty could be taken in PSU design.

The end result was rigs like the NCX-3 and the SB-100, which cost as
much as a good receiver but were complete 100-watt SSB stations that
you could indeed set up on a card table.

When Heath introduced the SB-200 in 1954, it cost $200. Legal limit on
CW, 1200 watts PEP on SSB (input). That was a lot cheaper than the
equivalent AM, and would fit on the card table.

IOW, high power AM cost a lot of dough and a lot of space/weight. The
SSB transceiver/GG linear paradigm drastically reduced those
requirements.

Fun fact: AFAIK only two 1 kW-input-legal-limit plate-modulated AM
rigs were ever made for the amateur market: the Collins KW-1 and the
Johnson Desk Kilowatt. Total production was very limited - maybe 2000
units combined.

I can't begin to recall the number of models of legal-limit GG
amplifiers made. EFJ Thunderbolt, SB-220, Heath KL-1...

More to come...

73 de Jim, N2EY