Jim,
I was thinking of back in the 1950's when class-C was used with
amplifiers for CW. I guess the finals were direct-keyed and not
driven by a keyed stage. Its been awhile. My DX-35 used grid-block
keying and ran screen-grid AM on the 6146. But then you youngsters
probably don't go that
interdiction to conduction and vice versa.
I had to work a lot but at the end I got a very clean TX.
73, Fausto IK4NMF
- Original Message -
From: Alan n...@sonic.net
To: Fausto Coletti faustocole...@alice.it
Sent: Monday, July 27, 2015 5:21 PM
Subject: Re: [Elecraft] K3: 630m amplifiers
To catch up on the comments I address all that I have so far:
Re: linear vs class-C is really a moot point as its easy enough to
build a linear at 500-KHz. CW, JT65, FSK all do fine with class-C,
of course. And its true that any modulation of a continuous carrier
will impart some bandwidth.
On Mon,7/27/2015 10:43 AM, Edward R Cole wrote:
CW, JT65, FSK all do fine with class-C, of course.
Ed,
I suggest that you drive a Class C amp with a K3 transmitting CW and
look at the spectra with a P3 both at the output of the rig and at the
output of the amp. Set the P3 display for 5 kHz.
Phil,
That is correct, and the keying of that output stage was shaped in many
cases.
Grid-block keying was all the rage for help in shaping the keying envelope.
Cathode keying was used too, but usually not with keying. You had to be
careful the key did not bite from the voltage on it.
73,
The need for linear amplifiers with CW has been known for many years.
Quoting from the 1964 ARRL Handbook:
When key clicks introduced by the addition of an amplifier stage
are found only near the transmitter frequency, amplifier clipping
is indicated. It is quite common when fixed
I'd have to dig out my old circuit diagrams, but
it seems like when we used Class C amps back in
the day (1950's and 60s) we keyed the output
stage, not only the driver as with linear amps --
and we modulated the output stage in the AM days, too.
73, Phil W7OX
On 7/27/15 11:42 AM, Jim Brown
Interesting discussion, but I'm now confused.
In all the old handbooks the discussion of amplifier design says ( page
76, 1941) In amateur transmitters, and r.f. amplifier is invariably
operated Class C ( see Chaptr 3). I though the final tuned circuit was
simply pulsed at the RF freq and
In the good old tube days, typically the transmitter's final amplifier
was the keyed stage, or at least one of them. So the key shaping was
not degraded by a subsequent amplifier. It's OK if the PA is a class C
amplifier as long as the key shaping circuit takes that into account.
One way to
Those first point contact transistors such as the CK722 were rather
'finicky'. Not much margin for error, and they were expensive.
Now we can buy 2NAs for pennies.
73,
Don W3FPR
On 7/27/2015 8:49 PM, Alan wrote:
You could abuse a spark transmitter, but the tubes would die if you
Hi Jim,
I do have much more modern handbooks. Current in fact. :) Just
remembered more Class C referenced in the older ones.
Will have to go read articles back then on key clicks and distortion.
And continue to look at what amplifiers I could use on the two soon to
be lowest bands.
73,
On Mon,7/27/2015 4:57 PM, Tom Azlin W7SUA wrote:
In all the old handbooks the discussion of amplifier design says (
page 76, 1941) In amateur transmitters, and r.f. amplifier is
invariably operated Class C ( see Chaptr 3). I though the final tuned
circuit was simply pulsed at the RF freq and
Don,
You are making feel old. I remember the CK722. I had one as an
audio amp behind a crystal set I built using a 1N34, not sure it was
even an A version. I had a 210 foot piece of wire strung from the radio,
through my bedroom window to a post in the back of our yard. I could
hear,
OK on all the thread.
Ed, Yes, I am interested in following your linear amplifier project.
73, tom w7sua
On 7/27/2015 10:43 AM, Edward R Cole wrote:
To catch up on the comments I address all that I have so far:
Re: linear vs class-C is really a moot point as its easy enough to build
a linear
Clearly you are not among those who reminisce
about the rotary spark gap, Alan :-)
73, Phil W7OX
On 7/27/15 1:53 PM, Alan wrote:
The need for linear amplifiers with CW has been
known for many years. Quoting from the 1964 ARRL
Handbook:
When key clicks introduced by the addition of
an
On 07/27/2015 05:32 PM, Phil Wheeler wrote:
Clearly you are not among those who reminisce about the rotary spark
gap, Alan :-)
By crackey them vacuum tubes are just too durn delicate for serious ham
radio work. Old reliable spark is much more rugged.
Quoting from The World of Ham Radio,
Don wrote:
Those first point contact transistors such as the CK722 were rather
'finicky'.
Point-contact transistors could be variable in terms of electrical
characteristics, but mechanically they were a lot better than mythology
presents. Regardless, the famous 1953 Raytheon CK722 was *not*
CW also requires a highly stable ALC system, without unwanted dynamics, to
preserve ideal envelope shaping. This is lacking on some all-mode rigs that pay
little attention to CW.
Wayne
N6KR
On Jul 26, 2015, at 9:32 PM, Alan n...@sonic.net wrote:
CW would be another mode that would not
It depends on how you made the amplifier.
I produce some models of amplifiers, of different powers, all in switching
operation.
Here an image of the DK7FC grabber, you can see at 472.1 KHz the
spectrogram of
a German station that use a class D amplifier, at 472.5 an Italian station
that use a
A CW amplifier can be designed to run class-C but to be keyed in such a
way as to pass through the linear portion of the amplifying device's
curve when a CW element is starting or ending, in order to preserve the
shaping.
A simple example is the tube-type amplifier that has just enough fixed
On 07/26/2015 05:32 PM, Don Wilhelm wrote:
Soundcard sourced digital modes are really SSB signals and need a linear
amplifier.
The one exception might be FSK. It is constant-amplitude so a class C
amplifier should be fine.
FSK modes include RTTY and I believe WSPR and WSJT.
Alan N1AL
Do we run into the FCC external amplifier 15 dB gain limit here?
73 de dave
ab9ca/4
On 7/26/15 7:51 PM, Joe Subich, W4TV wrote:
Don,
WSPR, JT65 and JT9 are (1 of N tone) FSK modes. They are no
different than conventional AFSK (1 of 2) in that the tones
are continuous phase, constant
Hi Don and Alan,
I was thinking one of the slow multi tone FSK modes that are a single
tone at a time. WSQ is in the same class.
http://www.qsl.net/zl1bpu/SOFT/WSQ.htm
CW would be another mode that would not need a linear amp I think.
On the other hand PSK31 would require a linear amp.
73,
CW would be another mode that would not need a linear amp I think.
No, CW requires a linear amplifier. CW is not constant-amplitude - the
amplitude changes every time you open or close the key. A class-C
amplifier would mess up the key shaping, causing key clicks.
Any true FSK or MSK
Hi Tom,
It's convenient to think that, but it's wrong. The problem is that
neither of those signals are continuous -- both are changed to convey
information. Mother nature recognizes a keyed CW waveform as a square
wave modulating a carrier. Any waveform more complicated than a
continuous
Tom,
Soundcard sourced digital modes are really SSB signals and need a linear
amplifier.
73,
Don W3FPR
On 7/26/2015 8:25 PM, Tom Azlin W7SUA wrote:
Hi Ed.
I am more interested in a non-linear class C or higher amp for those
bands as was not thinking to run modes that need a linear amp.
Don,
WSPR, JT65 and JT9 are (1 of N tone) FSK modes. They are no
different than conventional AFSK (1 of 2) in that the tones
are continuous phase, constant amplitude and can be amplified
by a class C amplifier without generating undue IMD or clicks.
I haven't seen the details of WSQ yet - if
Not if you build your own is my understanding!
73, tom w7sua
On 7/26/2015 5:56 PM, dave wrote:
Do we run into the FCC external amplifier 15 dB gain limit here?
73 de dave
ab9ca/4
On 7/26/15 7:51 PM, Joe Subich, W4TV wrote:
Don,
WSPR, JT65 and JT9 are (1 of N tone) FSK modes. They are
Hi Ed.
I am more interested in a non-linear class C or higher amp for those
bands as was not thinking to run modes that need a linear amp. WSPR, a
WSJT mode, WSQ, and the like.
73, tom w7sua
Chino Valley AZ
On 7/26/2015 1:23 PM, Edward R Cole wrote:
With the recent expansion of use to 630m
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