[600MRG] Amp

Mon Aug 3 10:58:29 CDT 2015

What I find particularly interesting about THIS discussion is that these issues 
were discussed, and solutions found and implemented beginning in the 
1920s...

Ken W7EKB

On 3 Aug 2015 at 10:54, John Langridge wrote:

> >CW is a square wave modulation that is full of harmonic
> energy which will cause horrible clicks out many KHz if not properly
> conditioned.
> 
> I think the key here is "properly conditioned" and specifically related to
> the RF source.  If the rise and fall times of the *source* CW signal is
> purely square, then yeah, you are going to have a clicky, harmonic-filled
> signal.  If, however, the source signal rounds that waveform off at the
> transitions like it should be, you are not going to generate additional
> trash (assuming the PS has capacity and is not AMing, for example).  This
> was the topic of discussion for years on the topband reflector WRT various
> radio manufacturers and their click problems.  If you are using an HF rig
> as an exciter, the quality of that signal source is largely
> going to determine the quality of what comes out of the amp.
> 
> One of the amps that I built uses a fixed signal source where the amp's
> drain is keyed directly and, in fact, through RC networks, the rise and
> fall times are modified accordingly.  The CW waveform is clean, there are
> no
> clicks and there is no broadening of the signal because the shape of that
> input square wave from the driver is rounded appropriately.
> Neither of the techniques that I use for making a CW signal is clicky or
> wide because the source signal is "clean" coming into the amp.
> 
> I think you are correct about linear if we assume that the driver signal is
> poor.  But it does not have to be and many guys who have been running topband
> for a long time have either switched to clean radios or modified their existing
> radios, as I have done.
> 
> 73,
> John XIQ
> 
> On Mon, Aug 3, 2015 at 10:28 AM, Edward R Cole <kl7uw at acsalaska.net> wrote:
> 
> > John,
> >
> > Unfortunately too many hams believe this.  An unswitched carrier is fine
> > with non-linear modes.
> >
> > This was topic was just thoroughly discussed recently on the Elecraft
> > Reflector.  CW is a square wave modulation that is full of harmonic energy
> > which will cause horrible clicks out many KHz if not properly conditioned. A
> > carrier with harmonic energy will have the harmonics amplified greatly by a
> > non-linear amp;  that is why they are used for triplers and multipliers. If
> > you want harmonics just overdrive an amp into non-linear operation.
> >
> > You will not find any class-C amps offered for hams since CW is now
> > generated by an exciter and not by direct keying of the amplifier as was
> > done years ago (of course these amps also are used for SSB, but no mfr
> > offers a bias adj to place the amp into class-C for CW).  Also, CW
> > modulation is not zero bandwidth; only a carrier with zero phase modulation is
> > zero bw.  Even back in pre-SSB years when one used grid-block keying the CW
> > voltage still had to be shaped to avoid clicks; something that modern
> > transceiver mfr's seem of have forgotten (except a few wise one's).
> >
> > If you run CW thru a non-linear amp the result will be broadening of the
> > bandwidth and co-channel interference.  FM and some FSK modes are OK.
> >
> > Therefore, my amplifiers will be linear; its not that hard to do!  Output
> > filtering is a must to reduce harmonic output even with linear amps.
> >
> > 73, Ed - KL7UW
> >
> > At 03:33 AM 8/3/2015, John Langridge wrote:
> >
> >> >Linear is needed for CW
> >>
> >> Linear is NOT required for CW.. only when amplitude and/phase varies is
> >> linear required.  It would be needed for PSK, which has been rarely used in
> >> the last few years.
> >>
> >> 73!
> >>
> >> John XIQ
> >>
> >> On Sun, Aug 2, 2015 at 11:25 PM, Edward R Cole <kl7uw at acsalaska.net>
> >> wrote:
> >>
> >> > Jim, and all:
> >> >
> >> > The K3 can be upgraded to operate down as low as 100-KHz by upgrading
> >> the
> >> > Synth board for $219.95.  Reception is improved by a minor change in the
> >> > General Coverage band filter and one component on the main board.
> >> >
> >> > So it is capable at this time by incorporating those changes.  Elecraft has
> >> > just rolled out a new model called the K3S which comes standard with these.
> >> >
> >> > 100w seems a good target for 5w ERP (depends on your antenna
> >> efficiency).
> >> >
> >> > I think one should just figure on using a linear amp.  Linear is needed for
> >> > CW and psk modes and gain is not difficult to achieve at 500-KHz.  I would
> >> > guess 60-65% efficiency in the high power stage so you need dissipation of
> >> > say 50% of RF output as a minimum to have a safe margin. 100w dissipation
> >> > would ensure almost bullet proof running of any mode.
> >> >
> >> > Not sure you saw my recent post on the Elecraft reflector regarding 630m
> >> > amplifiers?  I will be looking at making up a 100w linear amp that runs
> >> > with 1mw drive sometime this winter when outdoor stuff is not as nice to
> >> > do.  I am giving thought to offering it as a kit or partial-kit for
> >> sale.
> >> > I was once considering transverters but others have beat me to that and
> >> > with the K3 and TS590S both able to run 630m an amplifier is the needed
> >> > item (probably a preamp too).
> >> >
> >> > Don't ask for particulars at this point - just an idea that needs some
> >> > research and building a proof of concept.  No idea of cost.  Most likely
> >> > will use FETs and run with 13.6v for simplicity, though 28v and 50v
> >> > transistor specs are better.  Driving with 1mw makes such an amp usable
> >> > with simple mixer schemes, as well.
> >> >
> >> > I discussed this with Wayne-N6KR of Elecraft and the market is too small
> >> > for them to consider making an amp.
> >> >
> >> > 73, Ed - KL7UW
> >> > http://www.kl7uw.com/kits.htm
> >> >
> >> > At 05:10 PM 8/2/2015, Jim Miller wrote:
> >> >
> >> >> Now that the K3 is getting closer to being a 630 capable machine and
> >> the
> >> >> FCC is lumbering toward a band decision I'm thinking more about an amp.
> >> >> I'm assuming the market is too small for an Elecraft offering.
> >> >>
> >> >> The K3 puts out 1mW on the transverter output. I'm assuming that I'll
> >> need
> >> >> 50-100w to get to 5w ERP.
> >> >>
> >> >> Assuming 100w for a minute and assuming 10-15db for the final amp stage
> >> >> then you only need 5-10w before then. That should mean that even with
> >> poor
> >> >> efficiency not a lot of power will be dissipated until the finals. That
> >> >> means that I could keep the chain to that point linear and make the
> >> output
> >> >> stage decision based on what modes are most prevalent.
> >> >>
> >> >> I assume CW for historical reasons and JTXX for practical reasons,
> >> WSPR as
> >> >> well. Not sure about PSK or other modes which would require a more
> >> linear
> >> >> final.
> >> >>
> >> >> So I could build a 1mW to 10W linear then wait and see about the
> >> finals.
> >> >>
> >> >> Thoughts?
> >> >>
> >> >> 73
> >> >>
> >> >> jim ab3cv
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> >> >>
> >> >
> >> > 73, Ed - KL7UW
> >> > http://www.kl7uw.com
> >> >     "Kits made by KL7UW"
> >> > Dubus Mag business:
> >> >     dubususa at gmail.com
> >> >
> >> >
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> >> >
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> >>
> >
> > 73, Ed - KL7UW
> > http://www.kl7uw.com
> >     "Kits made by KL7UW"
> > Dubus Mag business:
> >     dubususa at gmail.com
> >
> >
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Kenneth G. Gordon W7EKB

"Courage is being scared to death but saddling up anyway."--- John   Wayne