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K3 and Expert 1K-FA

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Franco Cazzaniga

K3 and Expert 1K-FA

Hello
I use the Expert 1K-FA with K3 full power and ALC , but i think i have two issue.
When i use K3 full power ( with Expert full power ) the rig output is not stable but fluctuates around 15 watt and more or less of 5 watt , and of course the output of Expert varies consequently .
When i use Expert half power i have not issue , the input and output power are stable.
Another issue is that when i put the Expert in STBY , the K3 output power does not return instantly at 100 w , but slowly in 3 - 4 seconds.
When i not use the ALC i have not issue.
Thank you
Franco I6QFZ
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Arie Kleingeld PA3A-2

Re: K3 and Expert 1K-FA

Franco,

Forget about the ALC.
Up till now I have never used the ALC between my TRX and PA. No need to.
Just gently set the power of the trx yourself to drive the PA to the
right powerlevel and go.

73
Arie PA3A

-----Oorspronkelijk bericht-----

Hello
I use the Expert 1K-FA with K3 full power and ALC , but i think i have
two issue.
When i use K3 full power ( with Expert full power ) the rig output is
not stable but fluctuates around 15 watt and more or less of 5 watt ,
and of course the output of Expert varies consequently .
When i use Expert half power i have not issue , the input and output
power are stable.
Another issue is that when i put the Expert in STBY , the K3 output
power does not return instantly at 100 w , but slowly in 3 - 4 seconds.
When i not use the ALC i have not issue.
Thank you
Franco I6QFZ

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Philippe Trottet

Re: K3 and Expert 1K-FA

Hi Franco,
Fully agree Arie's comments, I'm not using an auto Amp. only a manual
one with a Russian tetrode, and only checked on the K3 that the time
delay corresponds to the amp specs and that's all.
With my K3-100, most of the time I'm driving it with 12W and the output
with my amp is ±350W thats cover most of my applications. At 13W it
engage the KPA100 for higher power needs.
Just set the K3 to the power level you want to use without going over
the specs of your equipment.

Bst 73's
Philippe A65BI

>>> "Arie Kleingeld PA3A" <[hidden email]> 21-04-2010 11:25 >>>
Franco,

Forget about the ALC.
Up till now I have never used the ALC between my TRX and PA. No need
to.
Just gently set the power of the trx yourself to drive the PA to the
right powerlevel and go.

73
Arie PA3A

-----Oorspronkelijk bericht-----

Hello
I use the Expert 1K-FA with K3 full power and ALC , but i think i
have
two issue.
When i use K3 full power ( with Expert full power ) the rig output is
not stable but fluctuates around 15 watt and more or less of 5 watt ,
and of course the output of Expert varies consequently .
When i use Expert half power i have not issue , the input and output
power are stable.
Another issue is that when i put the Expert in STBY , the K3 output
power does not return instantly at 100 w , but slowly in 3 - 4
seconds.
When i not use the ALC i have not issue.
Thank you
Franco I6QFZ

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Bob Naumann W5OV

Re: K3 and Expert 1K-FA

Before this faulty opinion proliferates any further; what applies to tube amps does not follow with solid state amps.

ALC is required by most manufacturers of solid state amps to prevent overdriving and the resulting damage to the amplifier. ALC is the mechanism used to achieve this protection.

We were the original USA importer of the Expert 1KFA and it requires ALC. Tokyo Hy-Power does as well.

Can you manually limit your output from your radio and avoid damage? Yes. Even so, why take the risk? Hook up the ALC and adjust it according to the amplifier manufacturer's instruction.

If it is not working correctly, refer the problem to the amplifier manufacturer or dealer.

So, please do not advise someone with a solid state amp to disconnect their ALC- unless you want to assume the cost of repairs.

73,

Bob W5OV
Array Solutions
(Tokyo Hy-Power Dealer)

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of Philippe Trottet
Sent: Wednesday, April 21, 2010 2:52 AM
To: Franco Cazzaniga; Arie Kleingeld PA3A
Cc: [hidden email]
Subject: Re: [Elecraft] K3 and Expert 1K-FA

Hi Franco,
Fully agree Arie's comments, I'm not using an auto Amp. only a manual
one with a Russian tetrode, and only checked on the K3 that the time
delay corresponds to the amp specs and that's all.
With my K3-100, most of the time I'm driving it with 12W and the output
with my amp is ±350W thats cover most of my applications. At 13W it
engage the KPA100 for higher power needs.
Just set the K3 to the power level you want to use without going over
the specs of your equipment.

Bst 73's
Philippe A65BI

>>> "Arie Kleingeld PA3A" <[hidden email]> 21-04-2010 11:25 >>>
Franco,

Forget about the ALC.
Up till now I have never used the ALC between my TRX and PA. No need
to.
Just gently set the power of the trx yourself to drive the PA to the
right powerlevel and go.

73
Arie PA3A

-----Oorspronkelijk bericht-----

Hello
I use the Expert 1K-FA with K3 full power and ALC , but i think i
have
two issue.
When i use K3 full power ( with Expert full power ) the rig output is
not stable but fluctuates around 15 watt and more or less of 5 watt ,
and of course the output of Expert varies consequently .
When i use Expert half power i have not issue , the input and output
power are stable.
Another issue is that when i put the Expert in STBY , the K3 output
power does not return instantly at 100 w , but slowly in 3 - 4
seconds.
When i not use the ALC i have not issue.
Thank you
Franco I6QFZ

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Philippe Trottet

Re: K3 and Expert 1K-FA

Hi Bob,
I will apologize because I responded to quickly thinking all Hams are
like me...by bad habit.
I will not listed here problems faced with not properly designed ALC's
during the past and as Hams we are suppose to go a bit further to keep
the maximum of our equipment...within the limits.
As the original importer it is your duty to write it and I fully agee
with your comments.
ALC is useful for full auto Amps, specially the solid states one.
During my all career in Telecoms started 1972, I never burned any Amp
(Ham & Broadcast), solid state or valves by overdriving.
But I read carefully the specs before testing any new equipment and
have costly equipment in my pro lab to monitor it, that is not the case
of most of Hams.
So again mea culpa.

Bst 73's
Philippe A65BI
K3#3616
"By Hams, for Hams...What else ?"

Philippe TROTTET
Head of Field Telecom Unit - DUBAI

United Nations High Commissioner for Refugees
International Humanitarian City
Office Building Nº3 - Room 2, 1st Floor
Doha Street
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DUBAI - U.A.E.

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Website: www.unhcr.org ( http://www.unhcr.org/ )

>>> "Bob Naumann" <[hidden email]> 21-04-2010 16:36 >>>
Before this faulty opinion proliferates any further; what applies to
tube amps does not follow with solid state amps.

ALC is required by most manufacturers of solid state amps to prevent
overdriving and the resulting damage to the amplifier. ALC is the
mechanism used to achieve this protection.

We were the original USA importer of the Expert 1KFA and it requires
ALC. Tokyo Hy-Power does as well.

Can you manually limit your output from your radio and avoid damage?
Yes. Even so, why take the risk? Hook up the ALC and adjust it according
to the amplifier manufacturer's instruction.

If it is not working correctly, refer the problem to the amplifier
manufacturer or dealer.

So, please do not advise someone with a solid state amp to disconnect
their ALC- unless you want to assume the cost of repairs.

73,

Bob W5OV
Array Solutions
(Tokyo Hy-Power Dealer)

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Philippe
Trottet
Sent: Wednesday, April 21, 2010 2:52 AM
To: Franco Cazzaniga; Arie Kleingeld PA3A
Cc: [hidden email]
Subject: Re: [Elecraft] K3 and Expert 1K-FA

Hi Franco,
Fully agree Arie's comments, I'm not using an auto Amp. only a manual
one with a Russian tetrode, and only checked on the K3 that the time
delay corresponds to the amp specs and that's all.
With my K3-100, most of the time I'm driving it with 12W and the
output
with my amp is ±350W thats cover most of my applications. At 13W it
engage the KPA100 for higher power needs.
Just set the K3 to the power level you want to use without going over
the specs of your equipment.

Bst 73's
Philippe A65BI

>>> "Arie Kleingeld PA3A" <[hidden email]> 21-04-2010 11:25 >>>
Franco,

Forget about the ALC.
Up till now I have never used the ALC between my TRX and PA. No need
to.
Just gently set the power of the trx yourself to drive the PA to the
right powerlevel and go.

73
Arie PA3A

-----Oorspronkelijk bericht-----

Hello
I use the Expert 1K-FA with K3 full power and ALC , but i think i
have
two issue.
When i use K3 full power ( with Expert full power ) the rig output is
not stable but fluctuates around 15 watt and more or less of 5 watt ,
and of course the output of Expert varies consequently .
When i use Expert half power i have not issue , the input and output
power are stable.
Another issue is that when i put the Expert in STBY , the K3 output
power does not return instantly at 100 w , but slowly in 3 - 4
seconds.
When i not use the ALC i have not issue.
Thank you
Franco I6QFZ

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P.B. Christensen

Re: K3 and Expert 1K-FA

In reply to this post by Bob Naumann W5OV

> So, please do not advise someone with a solid state amp to disconnect
> their ALC- unless you want to assume the cost of repairs.

Overall, I agree with that assessment. However, I do no not make use of the
K3's ALC line with my SPE solid-state amp. In looking at the SPE's
protection circuitry, a fault buss is created that applies a high level of
bias to the power MOSFETs when any of about 6-7 different fault conditions
occur. The response time is exceptionally fast to the point where if I
deliberately blast the SPE with full power from the K3 without ALC connected
(don't try this at home - I'm a risk taker but did so only after reviewing
the circuit), the SPE detects the presence of high input power and applies
enough MOSFET bias to keep output power below about 1100 watts. How
instantaneous? I have not measured the response time but it does respond
well to the leading-edge power spike from another well-known transceiver.
Today, a solid-state amp should be smart enough to know when it's being
overdriven.

Also, an unknown with the SPE amp is what happens to amplifier linearity
when the bias protection circuitry begins to engage to keep power from
exceeding 1KW? But the same question must be asked of any transceiver that
interfaces to an amp while using an ALC line. I like to think that when an
amp and transceiver come from a common manufacturer, the ALC circuitry is
probably optimized since the designer knows exactly what's needed at the ALC
"meet me" point between the amp and transceiver.

Paul, W9AC

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Bob Naumann W5OV

Re: K3 and Expert 1K-FA

Paul,

What if you have one of the 200w or new 400w output rigs? What if you have
one of those radios that shoot out a spike of greater than 100w at the
beginning of every transmission?

Do people blast the inputs of their SS amps with 200w or 400w? You bet they
do. They fry the FETs immediately too. We see them on a fairly frequent
basis and we have gotten adept at swapping out FETs quickly - at significant
expense to the owner of the amp. In the vast majority of cases, they had ALC
disconnected and made a mistake when switching antenna outputs from these
high-power transceivers.

So, if you feel confident that you won't make a mistake, then go ahead and
take the risk of not having ALC connected and adjusted properly. But, keep
in mind the costly consequences that can result if you make a mistake. I do
not understand why one would not connect the ALC when its purpose is to
prevent damage. Not using ALC is not a "badge of courage"; instead, it is a
foolish tempting of fate - in my opinion.

Also, most amp manufacturers recommend that you only increase the output of
the radio high enough to achieve the desired output from the amp - they do
not recommend turning the radio output up "full-blast" and throttling the
output back down with ALC - which, as we all know can cause distortion and
all sorts of bad things. There is no downside to using ALC in the manner
that SS amp manufacturers recommend.

So, the bottom line is to follow the manufacturer's recommendation regarding
ALC and setting your radio to work properly in conjunction with it.

73,

Bob W5OV

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Paul Christensen
Sent: Wednesday, April 21, 2010 9:10 AM
To: [hidden email]
Subject: Re: [Elecraft] K3 and Expert 1K-FA

> So, please do not advise someone with a solid state amp to disconnect
> their ALC- unless you want to assume the cost of repairs.

Overall, I agree with that assessment. However, I do no not make use of the

K3's ALC line with my SPE solid-state amp. In looking at the SPE's
protection circuitry, a fault buss is created that applies a high level of
bias to the power MOSFETs when any of about 6-7 different fault conditions
occur. The response time is exceptionally fast to the point where if I
deliberately blast the SPE with full power from the K3 without ALC connected

(don't try this at home - I'm a risk taker but did so only after reviewing
the circuit), the SPE detects the presence of high input power and applies
enough MOSFET bias to keep output power below about 1100 watts. How
instantaneous? I have not measured the response time but it does respond
well to the leading-edge power spike from another well-known transceiver.
Today, a solid-state amp should be smart enough to know when it's being
overdriven.

Also, an unknown with the SPE amp is what happens to amplifier linearity
when the bias protection circuitry begins to engage to keep power from
exceeding 1KW? But the same question must be asked of any transceiver that
interfaces to an amp while using an ALC line. I like to think that when an
amp and transceiver come from a common manufacturer, the ALC circuitry is
probably optimized since the designer knows exactly what's needed at the ALC

"meet me" point between the amp and transceiver.

Paul, W9AC

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P.B. Christensen

Re: K3 and Expert 1K-FA

> Do people blast the inputs of their SS amps with 200w or 400w? You bet
> they
> do. They fry the FETs immediately too.

And that can occur whether or not an ALC line is used between the
transceiver and amp since ALC is a feedback function and the response time
back to the transceiver, and the response time of the transceiver, is not
instantaneous.

> We see them on a fairly frequent
> basis and we have gotten adept at swapping out FETs quickly - at
> significant
> expense to the owner of the amp. In the vast majority of cases, they had
> ALC
> disconnected and made a mistake when switching antenna outputs from these
> high-power transceivers.

When repairing the THP amps for failed MOSFETs, how do you know with
certainty the ALC line was disconnected by the customer? Also, what is the
typical ALC response time of the THP amplifiers?

I think it would be an interesting exercise to set up multiple transceivers
across vendors, together with multiple solid-state amps across vendors, and
measure the total ALC loop time period.

Paul, W9AC

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Guy, K2AV

Re: K3 and Expert 1K-FA

In reply to this post by Franco Cazzaniga

Franco, you should only use the ALC as amplifier protection.

ARRL's 1K-FA product review listed the 1K-FA drive requirements as
28-32 watts typical for full output. Driving it at 100 watts and
using dynamic ALC to reduce the level to 30 watts running SSB
definitely will produce varying results. This is not a K3 problem.
Since the ALC had been reducing your drive to 30 watts, the K3 is
operating with the idea that when you set the power to 100 what you
really need is 30. When you put the amp in standby, it takes a while
for the K3 to figure out, by lack of ALC coming from the Expert, that
now you really do want 100 watts with the power knob at 100 watts.

The K3 has a slow power recovery curve to keep from spiking amps in
similar situations where ALC is slow or non existent.

Reduce the K3 output power to 25 watts and only increase it until you
have full power from the Expert which DOES NOT engage the Expert ALC.
Use a peak power meter, or adjust it on CW to determine the drive. Do
NOT use ALC to accomplish speech compression, use the compression
control in the K3, which is a far more clever digital method without
the side effects.

Driving the ALC more than three times normal drive power WILL produce
splatter, no matter how good manufactures say their ALC is.

73, Guy

On Wed, Apr 21, 2010 at 3:03 AM, Franco Cazzaniga <[hidden email]> wrote:

> Hello
> I use the Expert 1K-FA with K3 full power and ALC , but i think i have two issue.
> When i use K3 full power ( with Expert full power ) the rig output is not stable but fluctuates around 15 watt and more or less of 5 watt , and of course the output of Expert varies consequently .
> When i use Expert half power i have not issue , the input and output power are stable.
> Another issue is that when i put the Expert in STBY , the K3 output power does not return instantly at 100 w , but slowly in 3 - 4 seconds.
> When i not use the ALC i have not issue.
> Thank you
> Franco I6QFZ
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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HarrytheHam

Re: K3 and Expert 1K-FA

In reply to this post by Bob Naumann W5OV

CONTENTS DELETED

The author has deleted this message.

W8JI

Re: K3 and Expert 1K-FA

In reply to this post by Bob Naumann W5OV

<<<What if you have one of the 200w or new 400w output rigs?
What if you have
one of those radios that shoot out a spike of greater than
100w at the
beginning of every transmission?

Do people blast the inputs of their SS amps with 200w or
400w? You bet they
do. They fry the FETs immediately too. We see them on a
fairly frequent
basis and we have gotten adept at swapping out FETs
quickly - at significant
expense to the owner of the amp. In the vast majority of
cases, they had ALC
disconnected and made a mistake when switching antenna
outputs from these
high-power transceivers.

So, if you feel confident that you won't make a mistake,
then go ahead and
take the risk of not having ALC connected and adjusted
properly. But, keep
in mind the costly consequences that can result if you make
a mistake. >>>

A word of additional caution....

While external ALC might force a long term power reduction,
the external ALC system generally does not correct overshoot
in radios. It almost never reduces power spikes on leading
edges.

The reason ALC does not normally affect the spikes, and why
typical external ALC systems cannot reduce the spike, is the
response delay in the ALC system inside the radio. There is
group delay in filter, and there is propagation delay
through the radio. There is also delay in the actual ALC
system. The gain control system is up front in the radio,
almost always ahead of filters and the delays. The ALC
sampling is after filters, and in the case of amplifier
derived ALC it is no better than the directional coupler
that samples power inside the radio. It is a serious mistake
to let the external ALC, derived after the filters and group
delay in the radio, do primary power control.

What the ALC does buy people is gain control or power
limiting if the knob on the radio is adjusted wrong, but it
most certainly will not correct leading edge spikes.

It's my understanding the K3 uses a two stage system, and
handles the sampling before passing through filters. I'm
still trying to get my head around how it works and why I am
uncomfortable with how the meters act, but at least it
addresses the overshoot problem.
The amplifier ALC should be connected, if the manufacturer
requires it, but don't expect it to make something like an
IC 775 not pop FET's. The correct approach would be an
attenuator pad so the radio could run at near full power and
not have a chance of overdriving the amp, or better yet buy
a radio that does not spike to 250 watts at the leading
edge.

Now there is one exception to this. If the amplifier has a
memory on ALC, and holds the ALC at the highest value and
reduces ALC until power comes slowly up to the correct
value,, then there would be no overshoot. I'm not aware of
any amplifiers that do this, and I expect customers would
complain about the slow power response and lack of
compression or reduced average power with a system like
that.

Without an attenuator to "match levels", people are gambling
with or without the ALC connected.

73 Tom

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Alan Bloom

Re: K3 and Expert 1K-FA

On Wed, 2010-04-21 at 12:23 -0400, Tom W8JI wrote:

> The correct approach would be an
> attenuator pad so the radio could run at near full power and
> not have a chance of overdriving the amp, ...

I don't understand why more people don't do that. For example, a 3 dB
attenuator between the transceiver and amplifier ensures that a 100W
exciter won't overdrive an amplifier that requires 50W of drive. The 3
dB loss on receive is hardly ever an issue but if you're worried about
it, just put the attenuator inside the amplifier, after the T/R relay.

Seems like a simple, foolproof solution.

Al N1AL

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Doug Faunt N6TQS +1-510-655-8604

attenuator in amp was Re: K3 and Expert 1K-FA

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 much provision for being used with radios other
than the K3.

73, doug

From: Alan Bloom <[hidden email]>
Date: Wed, 21 Apr 2010 10:32:18 -0700

On Wed, 2010-04-21 at 12:23 -0400, Tom W8JI wrote:

> The correct approach would be an
> attenuator pad so the radio could run at near full power and
> not have a chance of overdriving the amp, ...

I don't understand why more people don't do that. For example, a 3 dB
attenuator between the transceiver and amplifier ensures that a 100W
exciter won't overdrive an amplifier that requires 50W of drive. The 3
dB loss on receive is hardly ever an issue but if you're worried about
it, just put the attenuator inside the amplifier, after the T/R relay.

Seems like a simple, foolproof solution.

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n7ws

Re: K3 and Expert 1K-FA

In reply to this post by Alan Bloom

Yes. In fact since with the except of a few newer radios 100W seems to be the "standard" it seems to me that amplifier suppliers should build amps to that standard.

If they have enough gain to deliver rated power with only 50 W in, then put a 3 dB pad inside. There are additional benefits to this, including a more uniform match for the exciter (possibly lowering IMD) and a better defined source match for the amplifier (possibly lowering IMD).

In fact, it can be argued that the ALC should be internal to the amplifier, rather than depending on some unknown loop characteristics in the exciter. Imagine a receiver designer trying to design an AGC loop when he doesn't know the characteristics of the gain-controlled stage(s).

Seems to me that some combination of fixed attenuation, some PIN diodes and active control of the device bias would solve a lot of operational issues.

Wes N7WS

--- On Wed, 4/21/10, Alan Bloom <[hidden email]> wrote:

> On Wed, 2010-04-21 at 12:23 -0400,
> Tom W8JI wrote:
>
> > The correct approach would be an
> > attenuator pad so the radio could run at near full
> power and
> > not have a chance of overdriving the amp, ...
>
> I don't understand why more people don't do that. For
> example, a 3 dB
> attenuator between the transceiver and amplifier ensures
> that a 100W
> exciter won't overdrive an amplifier that requires 50W of
> drive. The 3
> dB loss on receive is hardly ever an issue but if you're
> worried about
> it, just put the attenuator inside the amplifier, after the
> T/R relay.
>
> Seems like a simple, foolproof solution.
>
> Al N1AL

David Cutter

Re: attenuator in amp was Re: K3 and Expert 1K-FA

In reply to this post by Doug Faunt N6TQS +1-510-655-8604

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 automatically by having the amp
> tell the radio that it's active over the serial interface, but it's
> clear the KPA500 has much provision for being used with radios other
> than the K3.
>
> 73, doug
>
Tom W8JI wrote:

>
> > The correct approach would be an
> > attenuator pad so the radio could run at near full power and
> > not have a chance of overdriving the amp, ...
>
> I don't understand why more people don't do that. For example, a 3 dB
> attenuator between the transceiver and amplifier ensures that a 100W
> exciter won't overdrive an amplifier that requires 50W of drive. The 3
> dB loss on receive is hardly ever an issue but if you're worried about
> it, just put the attenuator inside the amplifier, after the T/R relay.
>
> Seems like a simple, foolproof solution.
>
>

Eric Swartz - WA6HHQ

Re: attenuator in amp was Re: K3 and Expert 1K-FA

Administrator

In reply to this post by Doug Faunt N6TQS +1-510-655-8604

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 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 much provision for being used with radios other
> than the K3.
>
> 73, doug
>
> From: Alan Bloom<[hidden email]>
> Date: Wed, 21 Apr 2010 10:32:18 -0700
>
> On Wed, 2010-04-21 at 12:23 -0400, Tom W8JI wrote:
>
> > The correct approach would be an
> > attenuator pad so the radio could run at near full power and
> > not have a chance of overdriving the amp, ...
>
> I don't understand why more people don't do that. For example, a 3 dB
> attenuator between the transceiver and amplifier ensures that a 100W
> exciter won't overdrive an amplifier that requires 50W of drive. The 3
> dB loss on receive is hardly ever an issue but if you're worried about
> it, just put the attenuator inside the amplifier, after the T/R relay.
>
> Seems like a simple, foolproof solution.
>
>

Doug Faunt N6TQS +1-510-655-8604

Re: attenuator in amp was Re: K3 and Expert 1K-FA

In reply to this post by David Cutter

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" <[hidden email]>
Date: Wed, 21 Apr 2010 18:54:21 +0100

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 automatically by having the amp
> tell the radio that it's active over the serial interface, but it's
> clear the KPA500 has much provision for being used with radios other
> than the K3.
>
> 73, doug
>
Tom W8JI wrote:
>
> > The correct approach would be an
> > attenuator pad so the radio could run at near full power and
> > not have a chance of overdriving the amp, ...
>
> I don't understand why more people don't do that. For example, a 3 dB
> attenuator between the transceiver and amplifier ensures that a 100W
> exciter won't overdrive an amplifier that requires 50W of drive. The 3
> dB loss on receive is hardly ever an issue but if you're worried about
> it, just put the attenuator inside the amplifier, after the T/R relay.
>
> Seems like a simple, foolproof solution.
>
>

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dave.wilburn-2

Re: attenuator in amp was Re: K3 and Expert 1K-FA

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 Faunt N6TQS +1-510-655-8604 <[hidden email]>
Date: Wed, 21 Apr 2010 14:00:02
To: <[hidden email]>
Cc: <[hidden email]>
Subject: Re: [Elecraft] attenuator in amp was Re: K3 and Expert 1K-FA

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" <[hidden email]>
Date: Wed, 21 Apr 2010 18:54:21 +0100

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 automatically by having the amp
> tell the radio that it's active over the serial interface, but it's
> clear the KPA500 has much provision for being used with radios other
> than the K3.
>
> 73, doug
>
Tom W8JI wrote:
>
> > The correct approach would be an
> > attenuator pad so the radio could run at near full power and
> > not have a chance of overdriving the amp, ...
>
> I don't understand why more people don't do that. For example, a 3 dB
> attenuator between the transceiver and amplifier ensures that a 100W
> exciter won't overdrive an amplifier that requires 50W of drive. The 3
> dB loss on receive is hardly ever an issue but if you're worried about
> it, just put the attenuator inside the amplifier, after the T/R relay.
>
> Seems like a simple, foolproof solution.
>
>

______________________________________________________________
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Doug Turnbull

Re: attenuator in amp was Re: K3 and Expert 1K-FA

In reply to this post by Doug Faunt N6TQS +1-510-655-8604

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 discarded probably
costs 100 Watts of energy. The idea of adding an attenuator for 50 Watts of
energy sounds mad to me and environmentally unfriendly as well.

73 Doug EI2CN

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Eric Swartz - WA6HHQ

Re: attenuator in amp was Re: K3 and Expert 1K-FA

Administrator

In reply to this post by dave.wilburn-2

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 2362+)

On 4/21/2010 12:24 PM, [hidden email] wrote:
> 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
>
>
>
______________________________________________________________
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123