Great wisdom this list brings.
Yoda
73
Arie PA3A
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Hm, I wonder if the KPA500 has or can have provision for this. That
amp can be driven to full output by 30 watts or so, IIRC. With the K3
(or K2), power control could be done automatically by having the amp
tell the radio that it's active over the serial interface, but it's
clear the KPA500 has
T0-220 style power film resistors are fairly cheap and can easily be mounted
on heat-sinking surfaces.
David
G3UNA
Hm, I wonder if the KPA500 has or can have provision for this. That
amp can be driven to full output by 30 watts or so, IIRC. With the K3
(or K2), power control could be done
The KPA500 has in internal 3 dB attenuator in the drive path that will
be switched in automatically by the amp in cases of overdrive.
73, Eric WA6HHQ
===
On 4/21/2010 10:44 AM, Doug Faunt N6TQS +1-510-655-8604 wrote:
Hm, I wonder if the KPA500 has or can have provision for this. That
amp
Probably the biggest issue is getting rid of the 70 watts of added
heat. If there's someplace in the exiting airstream to put these
resistors
73, doug
From: David Cutter d.cut...@ntlworld.com
Date: Wed, 21 Apr 2010 18:54:21 +0100
T0-220 style power film resistors are fairly cheap
When the K3 came out there was a big deal about the default ALC polarity that
resulted in a mod. Will the default connections of the KPA500 work with an
un-moded radio or will we need the mod?
David Wilburn
NM4M
Sent from my Verizon Wireless BlackBerry
-Original Message-
From: Doug
Dear OMs,
I can not understand why one would want to run the K3 at 100 W rather
than 20/30/50 Watts. Why drive the K3 harder when driving it more lightly
should improve reliability and possibly improve linearity. The waste of
energy is also undesirable; the fifty watts out that is
You will need the mod.
This change was included on All K3s shipped on Dec 10, 2008 and later.
(Rev B KIO3 Digital board)
See: http://www.elecraft.com/K3/k3_app_notes.htm
and scroll down to:
K3 Negative ALC and Ext Band Data Pull-up Mods, Rev B: REMIOUPGD
73, Eric WA6HHQ
(Approx s/n
I agree with Doug but from another prospective. Look at the energy budget for
portable work. Less total consumed power is good.
Mel, K6KBE
--- On Wed, 4/21/10, Doug Turnbull turnb...@net1.ie wrote:
From: Doug Turnbull turnb...@net1.ie
Subject: Re: [Elecraft] attenuator in amp was Re: K3 and
think of it as insurance to protect against a short circuit between the
headphones
Lew K6LMP
On Apr 21, 2010, at 2:31 PM, Mel Farrer wrote:
I agree with Doug but from another prospective.
[I assume you meant perspective]
Look at the energy budget for portable work. Less
I can not understand why one would want to run the K3
at 100 W rather
than 20/30/50 Watts. Why drive the K3 harder when driving
it more lightly
should improve reliability and possibly improve linearity.
The waste of
energy is also undesirable; the fifty watts out that is
discarded
On Wed, Apr 21, 2010 at 3:14 PM, Eric Swartz - WA6HHQ, Elecraft
e...@elecraft.com wrote:
You will need the mod.
Ah. Will the ALC connection be prescribed as mandatory for the K3/KPA500 system?
Bob NW8L
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I can not understand why one would want to run the K3 at 100 W rather
than 20/30/50 Watts. Why drive the K3 harder when driving it more
lightly
should improve reliability and possibly improve linearity. The waste of
energy is also undesirable; the fifty watts out that is discarded
30-watts dissipating as heat in the front end of the amp.
The 3dB pad does
improve return loss into the amp input by the same amount.
But, the
effective gain factor of the amp is then reduced by 3dB.
A 3dB pad gives 6 dB return loss. For example if load SWR is
2:1 (5.5dB RL) and we add a 3 dB
Yes, that's right, 3 dB per trip to and from the load. Not 3 dB in total as
I indicated.
Paul, W9AC
- Original Message -
From: Tom W8JI w...@w8ji.com
To: Paul Christensen w...@arrl.net; elecraft@mailman.qth.net
Sent: Wednesday, April 21, 2010 7:05 PM
Subject: Re: [Elecraft] attenuator
A 3dB pad gives 6 dB return loss. For example if load SWR is 2:1 (5.5dB
RL) and we add a 3 dB pad, return loss is 9.5 dB (1.4:1 SWR).
Tom,
The 6 dB R/L from the 3 dB pad is definitely correct but you lost me on the
2:1 SWR and corresponding R/L figure above. I calculate a 2:1 VSWR as a 9.3
The actual return loss improvement is twice the attenuation, but I know Paul
knows that.
--- On Wed, 4/21/10, Paul Christensen w...@arrl.net wrote:
For the same concerns, I think an auto-switched pad engaged
during an input
fault is a good idea. In the case of the SPE amp, I
would not
This thread started off with a K3 owner driving an Expert 1K-FA with
the power control set to 100 watts. That K3 owner can just set the
power knob to 30 watts and move on. Based upon the performance of the
current firmware in a K3, can't any K3 owner driving any amp can just
set the power control
- Original Message -
From: Paul Christensen w...@arrl.net
To: elecraft@mailman.qth.net
Sent: Wednesday, April 21, 2010 7:43 PM
Subject: Re: [Elecraft] attenuator in amp was Re: K3 and
Expert 1K-FA
A 3dB pad gives 6 dB return loss. For example if load SWR
is 2:1 (5.5dB
RL) and we
set the power control to the proper drive, and forget the ALC? ALC
doesn't fix leading spikes anyway, so what's it good for?
Arguably, ALC helps to function as a time-averaging RF level control that
can protect against ongoing over-drive but not necessarily peak power busts.
What I don't
Since the input Z of most solid-state amps is
well-controlled at 50-ohms,
that the input Z should not appreciably change as output Z
changes, then
can't we simply use a feed-forward ALC system instead of
feedback ALC? A
fast RF voltage peak detector can be bridged across the
amp's input Z.
I get that in general given all the various TRX out there.
But for the K3, the digital functions in firmware do a far better job
of signal management before the signal is ever analog, much less RF,
which can include pre-compensating for issues in the analog circuits.
Much of the talk seems to
Couldn't agree more. Especially the split-band processing part :-)
http://k6mhe.com/n7ws/S_PROC.pdf
BTW, arguably one of the best sounding SSB rigs around, the TS870 does use
split-band speech clipping done in DSP. I bought mine new in 1998 and it's a
late S/N.
Wes N7WS
--- On Wed,
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