Amps
[Top] [All Lists]

[AMPS] TS-2000

To: <amps@contesting.com>
Subject: [AMPS] TS-2000
From: W8JI@contesting.com (Tom Rauch)
Date: Fri, 3 Aug 2001 10:17:54 -0400
Hi Peter,

> >Look at the TS-2000 as an example. It is almost class C quality, yet
> >reviews all ignore that fact. 
> 
> Not quite Class C - it would be about 7 or 8 dB worse in that case! Tom is
> correct though - it is really unacceptably poor.

I've measured solid state zero-bias transistor amps at about the 
same IMD level as the TS-2000. I wonder what they did wrong? It 
would be interesting to look at one on a three-tone test, and to see 
how IMD varies with power.
 
> >Keyclicks are designed in by manufacturers using excessively fast rise
> >and fall times 
> 
> I believe there are two parts to this:
> 
> 1. A demand (or a belief that there's a demand) for rigs to be regularly
> operated at 50 or 60wpm.

I can operate 60 WPM and have bandwidth below a few hundred Hz.
 
> 2. A failure to look on a spectrum analyser at the design stage with the
> transmitter keyed with a square wave at 30wpm or so.

Keying speed is relatively unimportant as to bandwidth, and every 
key is a square wave output. Sideband bandwidth is controlled by 
the shape of the waveform, and level is a function of delta voltage at 
the slope. 

The problem is everyone, including the ARRL, has this fixation 
about a single-pole R/C filter (or the shape produced by such a 
poor filter) being adequate for waveshaping. The waveform in the 
ARRL Handbook is a pathetic single-pole filter slope (3dB per 
octave). 

The ideal shape is a raised sine wave shape, not the "perfect" 
shape they show. 

If you filter the keying signal in a multi-section filter and apply it to 
a linear modulator scheme you can cut off the sidebands at 150 Hz 
and have very good sounding CW at more than 60 WPM with 
sidebands suppressed 50 dB or more.

A single LM358 op-amp and a single PIN diode modulator would 
make a virtually clickless AM modulator for CW. It would cost less 
than $1 to make click-free radios. In some cases it is adding only a 
few resistors and capacitors!





> 
> This latter may well be because there aren't that many designers of
> transceivers who actually are operators, especially CW operators.
> 
> If transmitters met the old marine specs, it would be an improvement.
> Incidentally, in my recently built 'classic' 807 tx, I found that it was
> impossible to get down to 99% power bandwidth of 250Hz (as per ITU
> recommendations) at 30 wpm dots without excessive rounding of the
> characters. I could get it within 400Hz, though. The 'break' seems usually
> to be the problem, but not in this case.
> 
> And I still don't go a bundle on ALC!
> 
> 73
> 
> Peter G3RZP
> 
> 
> --
> FAQ on WWW:               http://www.contesting.com/FAQ/amps
> Submissions:              amps@contesting.com
> Administrative requests:  amps-REQUEST@contesting.com
> Problems:                 owner-amps@contesting.com
> 


73, Tom W8JI
W8JI@contesting.com 

--
FAQ on WWW:               http://www.contesting.com/FAQ/amps
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com


<Prev in Thread] Current Thread [Next in Thread>