[AMRadio] RE: Kitset HF Linear amp.


Jim candela jcandela at prodigy.net
Thu Oct 27 22:07:45 EDT 2005


Andy Said at alt.binaries.schematic :

hi again all.
I have a kitset HF linear amp available, send an email to
pushpullamps at yahoo.co.nz for information and payment options.
Disclaimer: These amps cover 3-30mhz, it is illegal in most countries to use
such equipment on the citizen bands.Proper use of this equipment lays
entirely with the user.

Heres what you get:

Etched PCB ready to load.
ALL components.
Heatsink.
Full Schematic.
Parts Layout.
FEATURES:
· Broadbanded (3-30 MHz) push-pull design. No tuning required after a simple
one-time setup procedure.
· Power levels: 100Watts AM, 180Watts PEP.
· Now includes trimmer adjustable input and output tuned circuits for
perfect SWR matching. Just set it and forget it.
· All mode operation: AM, FM, CW, SSB.
· Internal SWR protection with rugged transistors.
· Bias switching lets you choose the most efficient method for Class C
(AM/FM/CW) or Class AB (SSB) operation.
· Carrier operated T/R relay with separate drop-out timing delays to
automatically match AM/FM or SSB operation.
· Switchable ON/OFF operation with LED indicator.
· Jumper adjustable input network matches 4-10W RF drive levels for most
popular HF transceivers.
· Transient spike protection in mobile use.
· Double-sided PCB design for excellent RF stability and voltage regulation.

Kindest regards andy jackson (RF Radio Engineer)



Reply by Jim Candela, WD5JKO:

Andy,

    You need to provide test data including schematic, and waveforms while
running at 100 watts carrier output, and then show the modulated envelope at
100% peak + (upward) AM modulation (w/o severe distortion). Do this to the
alt.binaries.schematic group, not just me. If you do, I'm sure you will make
more sales of your kit, and if the thing really does that, I'll endorse your
kit for any use other than CB. To a CB trucker, a real 100 watt (carrier)
amp that modulates to at least 90% peak + is a treasure.

    Now please understand that with a sine wave audio drive, at 100 %
modulation the amplifier must peak at 400 watts PEP, and a watt meter
(average responding) will read 150 watts. For AM at 100% modulation, each
side band is 6 db below the carrier power. As you know 6 db in power terms
is 1/4th (or 4), so for a 100 watts carrier power, you get 25 watts (avg) in
each side band. So the carrier stays at 100, and you get 100+25+25=150 watts
average.

    Now the crux where your amp will fall short, is that 400 watts PEP is
unobtainable. I'm sure you will agree with that statement. The problem with
AM linear amps is that they need the headroom to peak to 4X the carrier
power when modulated. This means that the amplifier output voltage doubles
from carrier level, and since E^2/R=W, if the voltage doubles, the power
quadruples.

Following are the formulas for finding AM Modulation depth:

PEAK + method: m = 100 * ((Emax - Eavg) / Eavg )

PEAK - method: m = 100 *((Eavg-Emin)/Eavg)

The above information is not something I made up.

Most amateur transceivers are rated at 100 watts PEP output for SSB. Most of
the ones that include AM state that the maximum output is 25 watts carrier.
This is limited to 25 watts AM because the ALC is designed to kick in at 100
watts PEP. Some other transceivers change the ALC from peak responding to
average responding for AM, and this allows them to rate AM at 40 watts
carrier. At 40 watts 100% modulated, you get 160 watts PEP. Your kit-amp
should do that fine, but not 100 watts. Don't you see, or understand what
I'm talking about? These transceivers all have a power amplifier board
similar to yours.

Most CB transceivers will easily modulate to at least 85%. Using the above
formulas, does the output of your amplifier do the same at the power level
you claim?

The Motorola application notes I referred to at the hyperlink in my last
post did show an amplifier running off 13.8 volts, and ran 100 watts AM. In
fact this amplifier is very similar to yours. The problem with this though,
is that when tone modulating, the upward modulation was limited to 20-25%. I
don't call this AM since IT IS OVERLOADED, COMPRESSED, AND DISTORTED.

http://pages.prodigy.net/jcandela/AM_Linear/AM%20Linear%20Operation.pdf


So how can you continue to stand by your specifications? They don't compute.
I think you mean 100 watts PEP AM, and 180 watts PEP SSB. If so, then the
only problem here is that AM is normally rated in carrier power assuming the
designer did the rating while allowing for 4X that power at modulation
peaks. So when you say 100 watts AM to you refer to PEP power, or
unmodulated carrier power with 100% peak + modulation capability?

Do you also stand by running the amplifier bias set to class C on AM? Yes
you can get away with this because it's really class B, however the
crossover distortion from NO bias is there, and does cause visible (scope),
and audible (receiver) distortion. Running SSB in class B with crossover
distortion sounds far worse.

Yes I may be an arse at times, that is true. That however isn't the issue.
The issue is what you market, and what you say it does is not possible. I
know that, and I think you do too. If your half the engineer that you say
you are, then you understand what I am talking about. Then again maybe you
knew all of this from the beginning, and your marketing strategy is to make
false claims, and sell kits to the uninformed.

Regards,
Jim Candela
WD5JKO

-----Original Message-----
From: supersparks [mailto:pirateradiofm at xtra.co.nz]
Sent: Thursday, October 27, 2005 4:51 AM
To: Jim Candela
Subject: Re: Kitset HF Linear amp.


it works as i say it does, i dont need to validate my statements to you or
anyone else, stop being a know it all, no one likes smart asses, i garrentee
my product, that is all that matters here.


----- Original Message -----
From: "Jim Candela" <jcandela at prodigy.net>
To: "supersparks" <pirateradiofm at xtra.co.nz>
Sent: Tuesday, October 25, 2005 3:34 AM
Subject: Re: Kitset HF Linear amp.


>
> OK, I am listening. Please explain why I am incorrect.
> I think maybe we can both learn something.
>
> Jim
> --- supersparks <pirateradiofm at xtra.co.nz> wrote:
>
> > that is incorrect
> > ----- Original Message -----
> > From: "JC" <jcandela at prodigy.net>
> > Newsgroups: alt.binaries.schematics.electronic
> > Sent: Monday, October 24, 2005 2:41 PM
> > Subject: Re: Kitset HF Linear amp.
> >
> >
> > >
> > > Beware, this is another splatter making CB linear
> > amplifier. Here is why:
> > >
> > > >Power levels: 100Watts AM, 180Watts PEP
> > >
> > > ** If the power is really 180 watts PEP, then the
> > AM carrier power maximum
> > > is 25% of that or 45 watts ---NOT 100 watts. In
> > fact to be clean, and
> > linear
> > > I wouldn't run more than 25 watts output on AM
> > (100 watts PEP).
> > >
> > > >Bias switching lets you choose the most efficient
> > method for Class C
> > > >(AM/FM/CW) or Class AB (SSB) operation.
> > >
> > > ** For linear amplification of AM or SSB you need
> > class A, or AB ---NOT
> > > class C
> > >
> > > Most CB radios when exciting an amplifier such as
> > this will overdrive the
> > > amplifier, and result in significant distortion,
> > and splatter. A 3-6 db
> > pad
> > > between the exciter and amplifier is usually
> > needed to prevent this. Most
> > CB
> > > rigs have 15 - 20 watts PEP output (about 4 watts
> > carrier AM) -- too much
> > > for this amp. Very few Ham operators would buy
> > this kit. We all know the
> > end
> > > users are CB'ers who choose to operate illegally.
> > >
> > > > Now includes trimmer adjustable input and output
> > tuned circuits for
> > > perfect SWR matching. Just set it and forget it.
> > >
> > > ** Yea custom designed to work best between 27 and
> > 27.5 Mhz
> > >
> > > I have converted several of these boot-leg CB
> > linears to use on 10 meters
> > > AM, and they all required significant effort to
> > get the gain, and
> > linearity
> > > within accepted amateur radio standards. Of course
> > for CB, all that is out
> > > the window. Just connect and drop the hammer! "hey
> > good buddy, your S9+40
> > on
> > > channel 19, and S9 on channels 1, and 40 all at
> > the same time!"
> > >
> > > Jim
> > >
> > >
> > >
> > > "andy" <pirateradiofm at xtra.co.nz> wrote in message
> > > news:EAn6f.1915$S24.133359 at news.xtra.co.nz...
> > > > hi again all.
> > > > I have a kitset HF linear amp available, send an
> > email to
> > > > pushpullamps at yahoo.co.nz for information and
> > payment options.
> > > > Disclaimer: These amps cover 3-30mhz, it is
> > illegal in most countries to
> > > > use
> > > > such equipment on the citizen bands.Proper use
> > of this equipment lays
> > > > entirely with the user.
> > > >
> > > > Heres what you get:
> > > >
> > > > Etched PCB ready to load.
> > > > ALL components.
> > > > Heatsink.
> > > > Full Schematic.
> > > > Parts Layout.
> > > > FEATURES:
> > > > · Broadbanded (3-30 MHz) push-pull design. No
> > tuning required after a
> > > > simple
> > > > one-time setup procedure.
> > > > · Power levels: 100Watts AM, 180Watts PEP.
> > > > · Now includes trimmer adjustable input and
> > output tuned circuits for
> > > > perfect SWR matching. Just set it and forget it.
> > > > · All mode operation: AM, FM, CW, SSB.
> > > > · Internal SWR protection with rugged
> > transistors.
> > > > · Bias switching lets you choose the most
> > efficient method for Class C
> > > > (AM/FM/CW) or Class AB (SSB) operation.
> > > > · Carrier operated T/R relay with separate
> > drop-out timing delays to
> > > > automatically match AM/FM or SSB operation.
> > > > · Switchable ON/OFF operation with LED
> > indicator.
> > > > · Jumper adjustable input network matches 4-10W
> > RF drive levels for most
> > > > popular HF transceivers.
> > > > · Transient spike protection in mobile use.
> > > > · Double-sided PCB design for excellent RF
> > stability and voltage
> > > > regulation.
> > > >
> > > > Kindest regards andy jackson (RF Radio Engineer)
> > > >
> > > >
> > > >
> > >
> > >
> >
> >
>

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