I like to think of ALC as receiver AGC in reverse. Done properly, it
results in minimal distortion while keeping the signal level nearly
constant. As far as I can tell, commercial transceivers have all been
doing this pretty well for a long time.
What I've never been able to figure out is
The original concept of ALC was devised by Collins engineers as part of
their development program for speech processing. Speech clipping
flattens the peak amplitude, but also introduces some splatter which
then has to be filtered out - but the filtering re-introduces a small
amount of level
__
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Elecraft@mailman.qth.net
This list hosted by: http://www.qsl.net
Please help support this email list:
The compression modulates the signal. That will have a fourier transform of
its own. If we think of it as a simple amplitude modulation then, as for AM
signals, the spectrum of the original signal will be combined (convolved)
with upper and lower sidebands representing the spectrum of the
Wes:
Yes but I assume you have have used or use other xcvrs as well. As a general
comment, that doesn’t change the idea that using ALC to control a xcvr’s power
to one’s linear isn’t the purpose of ALC and would seem to not be a very
healthy practice. If one were to choose that path, then
You do know that the K3(S) uses a slow ALC system for power control don't you?
Wes N7WS
On 7/12/2019 8:53 PM, Brian Denley wrote:
Nothing when that’s what you want. But using ALC to control xcvr power is
uncontrolled compression that may or may not be desired.
Brian
KB1VBF
Sent from my
Nothing when that’s what you want. But using ALC to control xcvr power is
uncontrolled compression that may or may not be desired.
Brian
KB1VBF
Sent from my iPad
> On Jul 12, 2019, at 4:09 PM, Wes wrote:
>
> And what exactly is the problem with compression? It's used all over the
>
A common cause of incidental AM is ripple in the crystal filter(s) in
use. One reason I went to the 2.8 kHz filter was that it had less
ripple, and the difference was obvious on RTTY.
73, Jim K9YC
On 7/12/2019 3:45 PM, Conrad PA5Y wrote:
It should be mentioned that FT8 and JT65 are constant
Actually, gain compression reduces "gain" not dynamic range. All signals are
reduced in amplitude by the same number of dB. This is the only way it doesn't
introduce distortion.
This reminds me of the endless discussions about RX AGC where everyone has their
favorite combination of rf-gain,
@mailman.qth.net
Subject: Re: [Elecraft] ALC implementation
Well ... I think it depends on your definition of distortion. One can argue
that, if the RF envelope does not exactly equal the original AF envelope, the
signal has been distorted and that is certainly the case when the dynamic range
has
Well ... I think it depends on your definition of distortion. One can
argue that, if the RF envelope does not exactly equal the original AF
envelope, the signal has been distorted and that is certainly the case
when the dynamic range has been reduced with compression. It doesn't
increase the
Don't confuse compression and clipping. Compression reduces dynamic range
while clipping sets a hard ceiling and does generate distortion. Compression
used correctly does not generate distortion.
73
Bob, K4TAX
Sent from my iPhone
> On Jul 12, 2019, at 4:00 PM, Wes wrote:
>
> What
What distortion?
On 7/12/2019 1:15 PM, Jim Rhodes wrote:
Nothing when it is done correctly on a mode that can stand the distortion. I
personally won't use it on digital modes as my rigs tend to turn it off by
default.
Jim Rhodes
K0XU
On Fri, Jul 12, 2019, 15:10 Wes
Nothing when it is done correctly on a mode that can stand the distortion.
I personally won't use it on digital modes as my rigs tend to turn it off
by default.
Jim Rhodes
K0XU
On Fri, Jul 12, 2019, 15:10 Wes wrote:
> And what exactly is the problem with compression? It's used all over the
>
And what exactly is the problem with compression? It's used all over the place.
Wes N7WS
On 6/28/2019 11:38 AM, Brian Denley wrote:
I have always thought that ALC is not appropriate for power control. It’s a
protection system. Over use of ALC acts like compression. No?
Brian
KB1VBF
Sent
Greg,
The Elecraft power control is done in the RF stages and not the audio.
After a band change or a change in the POWER knob, the power control
loop is reset.
The response time is quick enough that you do not notice it in normal
operation, although it does take a dot or two in CW or a couple
Don Wilhelm writes:
> The above method works fine for many transceivers, but NOT for
> Elecraft which measures the actual power output, compares it with the
> set power and adjusts the RF drive accordingly. This is a fully
> closed loop system. As far as I know, Elecraft is the only amateur
>
Right. Almost ten years ago, I used an audio FFT to measure the
harmonics in a Thinkpad's line level (also used for headphones) output.
The distortion decreased by 10 dB when the output was first set just
below clip and then reduced by 6 dB (half the output voltage). Just
below clip, the
Among other issues, this article is incorrect when calling for the
"Device" (Master) volume level in Windows to be set to 100%. Nearly
every sound card for which I've seen test results has increased
distortion above the 70 - 80% level (-1 to -2 dB or -3 to -6 dB
depending on the driver
Analog ALC is a fully closed loop too. And Elecraft measuring the output and
generating feedback isn't without flaw either. There is an ADC in that output
measurement system that introduces low-level power jitter easily observed on a
spectrum analyzer.
Wes N7WS
On 6/28/2019 12:04 PM, Don
Richard,
When you put the KX3 into DATA A mode, the mic gain is reduced to
something resembling Line level.
Depending on your soundcard output, you may still need an attenuator.
Strive for each audio control in the computer and application to be at
30 to 50%, and then if you have too much
-boun...@mailman.qth.net
[mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Brian Denley
Sent: Friday, June 28, 2019 1:38 PM
To: Jim Rhodes
Cc: elecraft@mailman.qth.net; Andy Durbin
Subject: Re: [Elecraft] ALC implementation
I have always thought that ALC is not appropriate for power control
" which measures the actual power output, compares it with the set power
and adjusts the RF drive accordingly. This is a fully closed loop
system. As far as I know, Elecraft is the only amateur transceiver
using that type of system."
I think you will find that is exactly how TS-590 power
Brian,
ALC should never be used for power control doing so usually causes RF
compression and distortion.
Many of the digital application instructions tell you to set for NO ALC
as a *maximum* audio level, set the power control for the maximum
desired and then reduce the audio level to
That's interesting thanks. It means that by aiming for no ALC indication
I've been under modulating.
I assume the input stage in the KX3 can take higher levels?
On Fri, 28 Jun 2019, 16:35 Bob McGraw K4TAX, wrote:
> Well written generic paper for operation of FT-8 and other digital
> signals of
: Friday, June 28, 2019 1:38 PM
To: Jim Rhodes
Cc: elecraft@mailman.qth.net; Andy Durbin
Subject: Re: [Elecraft] ALC implementation
I have always thought that ALC is not appropriate for power control. It’s a
protection system. Over use of ALC acts like compression. No?
Brian
KB1VBF
Sent from
On 6/28/2019 11:38 AM, Brian Denley wrote:
I have always thought that ALC is not appropriate for power control. It’s a
protection system. Over use of ALC acts like compression.
You are absolutely right. ALC should never be used between a transceiver
and an amplifier for power control.
I have always thought that ALC is not appropriate for power control. It’s a
protection system. Over use of ALC acts like compression. No?
Brian
KB1VBF
Sent from my iPad
> On Jun 28, 2019, at 1:11 PM, Jim Rhodes wrote:
>
> Yes Andy, I used a TS590 at field day. But this is the Elecraft
Yes Andy, I used a TS590 at field day. But this is the Elecraft reflector.
These rigs work differently. Use my K3 for FT8 often. I built an interface
for my Kenwood rig too. But you treat them differently.
Jim Rhodes
K0XU
On Fri, Jun 28, 2019, 11:21 Andy Durbin wrote:
> I strongly disagree
I strongly disagree that ALC should be zero for FT8 but that is based only on
my experience with the TS-590S.
My draft paper on FT8 harmonics can be found here -
https://www.dropbox.com/s/85aoc937kz235iq/FT8%20audio%20harmonics%20draft%20d%20k3wyc.pdf?dl=0
ALC must be in the control range for
Well written generic paper for operation of FT-8 and other digital
signals of like mode. It does not totally nor correctly apply to
Elecraft radios as power management is handled by a totally different
means. And those means and methods suggested in this paper are not
applicable to
Does anyone know of any rig that uses "compression" rather than linear gain
control to implement ALC?
ref - https://www.dropbox.com/s/f4uaop5tqwzaweu/FT8Noise6.docx?dl=1
73,
Andy, k3wyc
__
Elecraft mailing list
Home:
32 matches
Mail list logo
