Re: [Elecraft] KPA100W amp and KAT100 Tuner for the K2 in an EC2 Enclosure

[Michael Carter via Elecraft]

Hi Ray,

I don't have a copy of Lyle's original document.
One alternative description of the integration
of the KPA100 with the KAT100 in an EC2
enclosure is here:

https://ke4rg.blogspot.com/2015/03/assembling-and-using-kpa100kat100-ec2.html

I did this integration in 2018 with a KPA100
I built and a KAT100-2 I purchased already
built in the EC2 enclosure.  It was not difficult
and no separate manual
was needed to effect it.  If your amp/ATU
combo was working properly at time of
sale, I would connect it to your K2/10
as shown in Alan's (W3DVX) photos:

https://wilcoxengineering.com/kpa100-in-ec2/

The internal connections between the
KPA100 and KAT100 boards are shown
in one of the photos at Alan's web page.
Presuming the prior owner of the KPA100/KAT100
did the internal connections properly, the
most important external cable is the K2/10
to KAT100 cable.  DO NOT use any standard
RS-232 cables - this cable must be constructed
as described in the manual for the K2.

Configuring the K2 to use the KPA100 amp
is the same as described in the K2 manual.
One must enable the KPA100 in the menu.
The ATU must also be enabled in the K2's
menu system.  Once these steps are performed
the entire system operates as a seamless
100 watt transceiver with ATU.  If you set the
K2 power control to less than 12 watts, the
KPA100 is automatically bypassed but
the KAT100 remains available as the ATU.

73,
Mike, K8CN





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Re: [Elecraft] K3S PART ID

[Michael Carter via Elecraft]

I checked the interior of my K3 with the
new KPA3A 100 watt PA module installed.
There is an L-shaped hold-down bracket on the rear
edge of the KPA3A board, which is secured
to the rear fan panel with a single screw
(not visible from the top opening of the case).
It matches the dimensions of the bracket
you found.

I believe its function is to keep the two
connecting pin headers fully inserted,
especially after shipping/travel.
However, I can't find mention of it in the
KPA3A installation manual, nor is there
an errata sheet for that manual on the
Elecraft web site.  I can't recall if the
installation manual that came with my
KPA3A module also had a paper note
regarding that bracket.

If the bracket was free-floating inside
the case, it may also be that the nut/lockwasher
used to hold the rear panel screw in place may
be jammed elsewhere in the chassis - check
carefully!

73,
Mike, K8CN
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Re: [Elecraft] K3S PART ID

[Michael Carter via Elecraft]

Hi Mike (K4PI),

I recall a bracket like the one you described
from my recent addition of the KPA3A 100
watt PA module to my much older K3/10.
I don't find mention of it in the KPA3A manual,
but my recollection is that it was installed
on the rear panel of the K3 to stabilize/hold
down the KPA3A module PCB.  If I get time
later today I'll open up my K3 and see if it
is visible.

73,
Mike, K8CN
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Re: [Elecraft] Band-specific low output

[Michael Carter via Elecraft]

Hi Roger,

The fact that the low output corrected itself
after a band change suggests a relay problem
in either the lowpass or bandpass filter
sections.

Have you tried to run a TX Gain Cal routine
lately?  If not, that would be a worthwhile
first step before opening the case and
poking at relays.

73,
Mike, K8CN
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Re: [Elecraft] k2 q6 no 12v on q6 collector,

[Michael Carter via Elecraft]

Hi Carlos,

Since there is zero voltage measured
on either terminal 1 or 2 of transformer
T2, I would look at RFC4 and test continuity
there.  It could be that RFC4 is now open.
Keep tracing the voltage along that +12V
rail back to the point where it supplies
the Q7 and Q8 collectors via the transformer
T3.

73,
Mike, K8CN


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Re: [Elecraft] k2 driver q6

[Michael Carter via Elecraft]

Hi Carlos,

When you say 'no voltage'  measured
on Q6, can you be more precise?

The collector of Q6 should measure
about 12 V DC whether in TX or RX.
The base and emitter voltages will
be zero until the transmitter is
keyed on.  The base voltage depends
on the selected mode (CW or SSB),
and I recommend measuring in CW
mode.  The emitter voltage will be
roughly 0.6 V below the base voltage
once the transmitter is keyed.

73,
Mike, K8CN
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Re: [Elecraft] (ot) noise reduction resources

[Michael Carter via Elecraft]

Hi Robert,

You've used the term 'receiver noise', but specifically
mentioned heterodynes and harmonics as being of
concern.  All receivers, Elecraft not excluded, have
internal spurious signals generated in the VFO and
BFO circuits as well as clocks for digital circuits in the
radio.  The best way to identify internal spurious signals
is to remove the antenna(s) from the radio, terminate
the antenna ports in 50 ohm dummy loads, and then
carefully sweep the bands of concern to see if anything
is audible.  Internal spurs will typically be insensitive
to front-end gain/attenuation settings, but may vary
in strength with IF gain controls (e.g., the K2 has IF
gain control even though labeled as RF gain).  If
you have a second, different radio, try the same experiment
and see if the spurious carriers are replicated on it.

Switch-mode power converters are ubiquitous these
days and generate buzzy, drifting harmonics of the
switching frequency.  Turn off power to your entire
house, power your radio from a battery source, and
see if you still hear such signals.  Finding these sources
is easy, if a bit time consuming, once you've determined
they're on your local AC circuits.

Ethernet signaling is long understood to generate
clock/data signals that are audible in the ham bands.
These signals can be identified once found on the
receiver by turning off (including any UPS-powered)
routers/switches that use Ethernet cabling.

Dave, NK7Z, has a nice tutorial on methods to
identify RFI sources generally:
https://www.nk7z.net/category/info/rfi-mitigation/i-have-rfi-series/

It sounds like you've done the good work of
grounding and bonding, which can help with
self-induced RFI (ask me how I know!), but it
won't address RFI sources such as internal
spurs in the radio or the other predominant
sources cited above.

73,
Mike, K8CN



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Re: [Elecraft] K2/100 down power on 20M

[Michael Carter via Elecraft]

Hi Jerry,

I agree that the relatively low TX power output on 20M
originates in the KPA100 module.  Did you build that
module and install it yourself?  The LPA circuit in the
base K2 seems to operating normally, and your
peaking of the BPF confirms that.

If you have capability to sweep the 20M/30M LPF
section on the KPA100 for insertion loss, that would
provide more insight.  However, those LPF sections
are also inline when the KPA100 is nominally
bypassed - it's only the amplifier circuit that is
bypassed.  If there was a significant problem in the
LPF on the KPA100, it would have been evident in
your tests on the 10 watt TX power setting.

I would check the ALC indication on each band, but
set the Power control for 100 watts rather than full
clockwise rotation.  You could also monitor the
ALC voltage on the Control board as you change
bands to see if for some reason the ALC control
is reducing TX power on 20 meters.  There is no
band-dependent circuitry in the ALC system,
but the SWR forward/reverse power detection
circuit on the KPA100 does have a trimmer cap
to balance the bridge.  It would be unlikely for
a resonance condition in the bridge to cause
an elevated VRFDET voltage on one band alone,
but I am curious if the ALC system is doing something
odd on 20 meters only.

73,
Mike, K8CN
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Re: [Elecraft] Considering purchase of K4D

[Michael Carter via Elecraft]

Hi Allen,

If you're not already aware of it, there is a dedicated K4
forum on groups.io that is likely a richer source of
answers to your question.  The posts here regarding the
K4 are infrequent.  Be prepared for a fire hose of response
when you pose your questions over there - elecraft...@groups.io.

73,
Mike, K8CN
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Re: [Elecraft] K2/100 refurbishment

[Michael Carter via Elecraft]

Hi Steve,

No answer for your question #2 - Elecraft sells
packs of 25 screws for modest price, but shipping
to U.K. and VAT (if applicable) may dictate
otherwise.  Maybe pose that question to John,
G3PQA - he's done a lot of work on Elecraft
radios for fellow hams in the U.K.

Before doing any tests on the PA module
itself, go into the K2 secondary menu
(tap Menu, then tap Display) and find
the PA entry - it should be 'on' - you can
also check the PA fan control for proper
functioning.

If the 100 watt PA is enabled and the
problem persists,  then the
detective work ensues.

On question #1: carefully remove the KPA100
100 watt PA module from the base K2/10.
There is an internal RF feed from the base K2
to the KPA100, a speaker cable, a 12 V DC power
cable, and a ribbon cable to the Control panel.
The small plugs are 2-pin plastic with non-locking tabs, and
are easy to remove.  Be careful to label the two
identical plugs for RF and 12 VDC feed - you
don't want to swap these upon reassembly.
You can lay the KPA100 alongside the K2 and keep it connected
for powered troubleshooting - use a couple
of books to raise the KPA100 up to the level
of the K2 side panel.

I would first check (with power supply off and
disconnected) the resistance between
the PowerPole terminals on the KPA100.
If it's low, then you could have a shorted
PA transistor (Q1 or Q2).  There are additional
resistance checks described in a table
on p. 45 of the KPA100 manual - see the
Support menu on the Elecraft web page
for access to manuals - the KPA100 manual
appears under the Classic Line link for
K2-related manuals.  Those checks require
removal of the KPA100 module, hence my
recommendation to pull it.  You could do
the PowerPole resistance check before
removing the PA module, of course.

If there's no PA transistor short, then
there may be a problem in the diode
T/R switch.  This would take a bit more
effort to test, so I would hold off until
you've done the other resistance checks.
Some radios have been damaged by
lightning-induced overvoltages
on the cables, and the T/R switch
diodes have been mentioned in older
posts.

Given what you observed about
case screws being corroded, I would
unplug and plug those internal cables
and inspect for corrosion when plugs
are separated from their mates.

73,
Mike, K8CN



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Re: [Elecraft] K2 Number

[Michael Carter via Elecraft]

Hi Harold,

The K2 serial number is on an adhesive tag to
be placed on the lower rear panel of the radio.
It was in a very small manila envelope in
my K2 kit. I don't believe there is any internal
coding of the MCU that contains the rig's
serial number as there is in the K3.

73,
Mike, K8CN
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Re: [Elecraft] Configure to send CW in SSB mode?

[Michael Carter via Elecraft]

Hi Mike,

>From K3 Owner's Manual in the section describing
menu entries, p.55:

CW WGHT 1.15 Adjusts element/space timing ratio (weight) for the internal keyer.
Additional functions of this menu entry, via numeric keypad (Advanced):
Tap 1 to select SSB -CW (default) or SSB +CW (allows CW in SSB modes).

[highlighting is mine]

73,
Mike, K8CN
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Re: [Elecraft] K3/100 TX problem on 20m

[Michael Carter via Elecraft]

Hi Paul,

I'd say that our respective KPA3A TX Gain calibration
values are similar enough.  Having not had the
bipolar PA model KPA3, I don't have a point of
reference for whether your TX gain parameter
values are reasonable or not.

I would contact Elecraft Support and copy
Keith, WE6R  with
a request for their troubleshooting document
dealing with 'low TX output power.'  I don't
have a copy and only learned of its existence
by Keith mentioning it in another post.  I don't
think it's posted on the Elecraft public pages.

73,
Mike, K8CN
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Re: [Elecraft] K3/100 TX problem on 20m

[Michael Carter via Elecraft]

Hi Paul,

For comparison, here are the 50 watt TX gain values from the
calibration I did last November when I installed
the KPA3A 100 watt PA in my K3 (s/n 67xx):

1900 kHz TXGain HP  10
3750 kHz TXGain HP  06
5336 kHz TXGain HP  08
7150 kHz TXGain HP  08
10125 kHz TXGain HP  08
14200 kHz TXGain HP  05
18110 kHz TXGain HP  05
21200 kHz TXGain HP  03
24930 kHz TXGain HP  03
29000 kHz TXGain HP  05
52000 kHz TXGain HP  04

Do you know if your 100 watt PA module
uses RF bipolar transistors or MOSFETs
(the KPA3A uses MOSFETs; the original KPA3
uses bipolars)?
I don't know if the MOSFET version has higher gain
than the bipolars, but I suspect not.

I've been in a separate conversation
with Hal, W7YNC, who is an LDMOS RF amplifier
designer professionally.  There is some
uncertainty about whether the higher TX gain
parameters mean higher TX drive signal
amplitude or the converse.

In any event, your TX gain values don't
have wild swings from band to band,
although the difference between 20
meter and 30 meter gains is substantial.

Perhaps some others who have done
TX gain calibrations recently (or could
repeat them) on K3 units with the
bipolar PA transistors could post
their results?

73,
Mike, K8CN

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Re: [Elecraft] K3/100 TX problem on 20m

[Michael Carter via Elecraft]

Hi Hal,

The numbers themselves have meaning to the
DACs inside the K3, but in terms of actual
units I don't know.  The key thing is that as
those values are increased, the drive levels
from the TX DACs are increased, though I
don't know if the relationship is a linear one.

The gains of the LPA and PA stage transistors
fall off at higher frequencies, so one might
expect TX Gain parameters on those bands
to be somewhat higher than on the low bands.
However, if two immediately adjacent bands
have very different TX gain parameter values,
the likelihood is that something is amiss
in one of the filters (either BPF or LPF) and
the associated relays that select the filters.

73,
Mike, K8CN

From: dyno lab 
Sent: Tuesday, March 5, 2024 11:19 AM
To: Michael Carter ; Michael Carter via Elecraft 

Subject: Re: [Elecraft] K3/100 TX problem on 20m

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Do the TX gain parameter numbers have meaning such as dB or are they just 
relative numbers ?

73,
Hal
W7YNC


> On 03/05/2024 6:35 AM PST Michael Carter via Elecraft 
>  wrote:
>
>
> Hi Paul,
>
> Could you please post the TX gain parameters
> recorded by the K3 Utility at the 50 watt level
> for all bands?
>
> If there is a significant difference in those gain
> parameter values between adjacent bands (say
> 30 and 17 meters) and the value on the 20
> meter band, that may be an additional clue.
>
> The bandpass filter bank may be at issue here
> since you've checked the appropriate LPF.
> If there's a problem with the relay contacts
> on the relevant BPF or LPF section, that may
> also reduce the TX signal level and force
> an elevated TX Gain parameter value for that
> band.
>
> Keith, WE6R has a checklist of steps to
> try when diagnosing low TX output power.
> I recall he said to contact supp...@elecraft.com
> for that document.
>
> 73,
> Mike, K8CN
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Re: [Elecraft] K3/100 TX problem on 20m

[Michael Carter via Elecraft]

Hi Paul,

Could you please post the TX gain parameters
recorded by the K3 Utility at the 50 watt level
for all bands?

If there is a significant difference in those gain
parameter values between adjacent bands (say
30 and 17 meters) and the value on the 20
meter band, that may be an additional clue.

The bandpass filter bank may be at issue here
since you've checked the appropriate LPF.
If there's a problem with the relay contacts
on the relevant BPF or LPF section, that may
also reduce the TX signal level and force
an elevated TX Gain parameter value for that
band.

Keith, WE6R has a checklist of steps to
try when diagnosing low TX output power.
I recall he said to contact supp...@elecraft.com
for that document.

73,
Mike, K8CN
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Re: [Elecraft] PCB Cleaning - followup

[Michael Carter via Elecraft]

Hi Harold,

It's certainly true that cold solder joints
can arise from dirty/corroded PCB solder
lands.  The Elecraft boards in my K2/10 (now
17 years old, built by me) are very good
quality with plated-through holes and
durable solder mask.  I had occasion
to open my K2 to install the SSB and noise
blanker modules last week, and the boards
look as new as they did 17 years ago.  I
had more trepidation about the rework
and removal of some components than
I ever did at the initial construction.

If you've not had much soldering practice
recently, I suggest doing some practice
soldering of wires and trimmed component
leads to re-acquire your skill.  It will come
back..

73,
Mike, K8CN
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[Elecraft] K2 troubleshooting (was: K2 AGC)

[Michael Carter via Elecraft]

Hi Iran,

I changed the subject line to reflect that this
thread is continuing as a general troubleshooting
exercise with your K2.

The NE602 product detector has a balanced
output circuit and unless you use a differential
scope probe (or do the CH1 - CH2 trick with
your single-ended probes) you will mainly
see bleed-through of the BFO on either output
pin.

Your subsequent post indicated that you
ran the BFO test and it passed?

What do you hear at the audio output,
either speaker or phones?  Can you
hear the tone from your signal generator
as it's down-converted and amplified?

73,
Mike, K8CN

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Re: [Elecraft] K2 'CAL TPA' setting maxed out

[Michael Carter via Elecraft]

Hi Jim,

I don't have an answer to your question, but
will note that you are the 2nd person in the last
month to report this issue. Thomas, WA8UNS
also experienced repeated random resettings
of the CAL TPA parameter to large values, often
in excess of 200.  He reset the parameter to
the actual room temperature (in Celsius), things
worked for a bit, then the PA Hot message reappeared.
It's not clear yet if this random resetting occurs
if the KPA100 module is bypassed by setting the
POWER control to less than 10 watts.

If you can replicate the issue on a dummy load,
that would be of much interest.  RFI in the shack
is always problematic and can lead to weird issues.

73,
Mike, K8CN
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Re: [Elecraft] My K3S Has Issues- Ideas?

[Michael Carter via Elecraft]

And one more thought, with thanks to Bill, K9HZ who
reminded me that relay K1 on the KPAIO3A riser board
can produce the same symptoms if it fails to engage
the 100 watt PA module when the Transmit Power control
is set above 12 watts.

73,
Mike, K8CN
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Re: [Elecraft] My K3S Has Issues- Ideas?

[Michael Carter via Elecraft]

Hi Dick,

Does your K3S receive OK if the TX Power control
is set to less than 12 watts?

Do you have transmitter output if the TX Power
control is set to less than 12 watts?

If the answer to both of those questions is 'Yes,'
then you're looking at one or more of the following
issues in the KPA3A 100 watt PA module T/R switch:

- failure (shorted) of PIN diodes D5 or D8,
OR
- loss of DC bias to those diodes, which can
arise from a lead break in one of the red toroid
RF chokes (L1, L3, L4, L5)
OR
- failure of bias switch Q6 on the KPA3A board
which turns on the bias to D5 and D8 in transmit mode.

Even if one or both of the final PA MOSFETs
failed shorted, those are isolated from the
receive signal path by PIN diodes D5 and D8
being turned 'OFF'.  The PIN diodes D2 and D3
are biased 'ON' in receive mode to provide
the thru path around the 100 watt PA module.
Signal attenuation on receive can be due
to problems in the D2/D3 path OR to loading
of that path by an unintended connection
to the PA module input or output via D5 or
D8.

I suggest you remove the KPA3A PA module
and inspect the red toroids comprising the
RF chokes in the T/R switch section. If those
are intact and you're comfortable testing
the PIN diodes, that will give useful information.

Alan, W3DVX has offered repair services on
the K3/K3S radios for some years now.  You
can find him at https://wilcoxengineering.com/.

73,
Mike, K8CN


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Re: [Elecraft] K3 Sub-RX Deaf on One Band

[Michael Carter via Elecraft]

I'm glad that one was relatively easy to resolve, Pete.
No hardware intervention required - sigh of relief.
Joe is a wealth of knowledge!

73,
Mike, K8CN
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Re: [Elecraft] K3 Sub-RX Deaf on One Band

[Michael Carter via Elecraft]

Hi Pete,

If you've confirmed that the RX ANT is NOT selected
on the 80 meter band for the sub-RX,  I would
check the CONFIG entry for the KRX3 to be sure
that it's not selecting the AUX RF input.  It might
have been selected inadvertently if you used
BSET to change the sub-RX settings.

73,
Mike, K8CN


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Re: [Elecraft] K2 TUNE power reduction without ATU installed .

[Michael Carter via Elecraft]

My apologies to Steve and Dave W8FGU!

I re-read the KPA100 manual and learned
that the K2/100 DOES reduce TX power
to 20 watts when the TUNE button is pressed
and the POWER control setting is above
that level.

I have my KPA100 integrated with a KAT100
in an outboard case rather than being installed
in the K2 case.  That might explain why I
didn't realize (or remember) that the TUNE
function doesn't require the outboard ATU
to reduce the TUNE power - doh!

Slinking back into my cave..

73,
Mike, K8CN
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Re: [Elecraft] K2 TUNE power reduction without ATU installed .

[Michael Carter via Elecraft]

Hi Steve,

There is no documented method to set a lower
TUNE power when a non-Elecraft external ATU
is used or when no external matching unit is
present.  The TUNE button on the K2 keys
the transmitter at the requested TX power
set by the POWER control, e.g. 100 watts,
in the absence of a connected Elecraft
ATU.

To fool the K2 into using a lower TUNE
power setting than the POWER control
displays, one would need to reverse engineer
the AUXBUS protocol to make the K2 think
an Elecraft ATU is connected.  The K2's
MCU would have to communicate with the
spoofing unit in such a way as to make it appear
that the spoofing unit is an Elecraft ATU.
The AUXBUS protocol has not been made
publicly available to the best of my knowledge.

73,
Mike, K8CN

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Re: [Elecraft] K3S audio issue?

[Michael Carter via Elecraft]

Hi Dave,

By 'full output' do you mean on transmit or receive or both?
The SSB filters are physically the same for USB or LSB on
a given filter slot.What differs is the frequency offset
programmed into the TX DSP.

Check the procedure on p. 49 of the K3S Owner's Manual
to see what you have stored for the Transmit Crystal Filter
Selection, which is done on a per-Mode basis.  It may
be possible the stored offset value has become corrupted
in flash memory.

73,
Mike, K8CN
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Re: [Elecraft] [Elecraft-K3] K3S TX calibration failure

[Michael Carter via Elecraft]

Hi Ron,

Did you use the K3 Utility to run the TX Gain Cal
automatically or did you perform the calibration
manually?

If you used the K3 Utility, it should display
the status of the TX Gain on each band
and at each of the 3 power levels.  Does
the TX Gain Cal report indicate that the
transverter output test fails on every band
or just on some bands/

Did you use the Configuration menu to enable
the KXV3B module?

73,
Mike, K8C



From: elecraft...@groups.io  on behalf of Ron na2o 

Sent: Wednesday, December 20, 2023 8:09 PM
To: elecraft...@groups.io 
Subject: [Elecraft-K3] K3S TX calibration failure

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Not entirely - the 5W and 50W calibration went fine.  But the XVTR output 
failed.  Message indicated that there was not enough output for a “pass”.
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Re: [Elecraft] K2 SSB Power Overshoot on First Syllable

[Michael Carter via Elecraft]

Hi Karin,

You've resurrected a topic that was once very
active on this same Elecraft reflector:

https://www.mail-archive.com/elecraft@mailman.qth.net/msg27397.html

It's a long thread.  I recommend skipping down if you're
in a hurry to read the post by David, M0DHO:

https://www.mail-archive.com/elecraft@mailman.qth.net/msg27499.html

While David's post is not conclusive, it reveals some
information that numerous other posts do not.

Suffice it to say, you're not the first to make this
observation.  The presence of TX power overshoot
on SSB and not CW may also be correlated to
which version of MCU firmware and KSB2 firmware
one is running. It's not clear if the SSB power overshoot
issue was ever fully addressed by K2/KSB2 hardware modifications
or firmware upgrades.

You might contact Dave, W8FGU, who is now the
legacy K2 repair guy after Don's (W3FPR) long stint
in that role.  Dave's web page is 
https://w8fgu.com/index.html .
Dave may know if there was any resolution of this issue.

73,
Mike, K8CN
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Re: [Elecraft] K3 circuit breaker

[Michael Carter via Elecraft]

Hi Mark,

The high current condition on the KPA3 (or KPA3A, if newer K3) PA module may 
arise from a problem in one of the lowpass filter sections if it's not purely 
an external fault condition.

If you have the internal KAT3 ATU, you could try putting a dummy load on the 
2nd antenna port and occasionally loading up into that load on the bands on 
which you have observed the overcurrent condition.  If that pops the DC 
breaker, that's a sure sign a problem exists in one or more of the lowpass 
filters.

I would also check for connector intermittents outside of the K3 antenna 
connector(s).
If you have a transient fault in one of the coax connectors downstream of the 
rig, you could draw too much current for a short time, sufficient to pop the 
breaker.  I'm leaning toward this possible cause as a first line of 
investigation - the possible fault in one or more lowpass filters is a less 
probable cause.

73,
Mike, K8CN
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Re: [Elecraft] Correction, pricing info for k3s/p3

[Michael Carter via Elecraft]

Hi Jerry,

When I'm searching for pricing information
on used ham gear, I search three sites

https://www.eham.net/classifieds

https://forums.qrz.com/index.php?forums/ham-radio-gear-for-sale.7/

https://swap.qth.com/index.php

Each of these sites enables search for specific keywords.
It may take a bit of time to parse the hits that come
back if you use 'K3s' or 'P3' as keywords, but you can
refine the search and also limit the time interval of
the search.

You could also consult Larry, K6RO, who has a large
inventory of K3/K3s/P3 units for sale.  His email
is k6r...@gmail.com.

Prices on the big auction site are often well in
excess of what you'll find on any of the aforementioned
sites.  On the other hand, one can get an approximate
idea of actual selling price by restricting the search
to 'sold' or 'completed' auctions only.

73,
Mike, K8CN

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Re: [Elecraft] K3 displayed power out is incorrect

[Michael Carter via Elecraft]

Hi Gary,

The K3 computes forward and reflected power
from samples taken in the SWR bridge circuit.
A Tif X Gain calibration could fail because the
forward power reading is incorrect due to
a failure in that portion of the SWR bridge
circuit.

Do you have the KAT3 ATU in your K3?
If so, be sure that you select BYPASS
using the ATU TUNE button on the
front panel.  The K3 Utility will do this
automatically on each band if
you run a TX Gain Calibration via the
Utility.

Unfortunately, with the exception of two
51 ohm bridge termination resistors on the top side of the RF board,
the remaining bridge components are on the underside
of that board.  You can access them by removing
the rear bottom cover, but DO NOT key the transmitter
while the cover is off because it will kill the driver
transistors in the Low Power Amp assembly.

I would check diodes D36 and D37 on the RF
board first, which form the RF detectors for the
forward and reverse power metering circuits, respectively.
Those diodes are DC forward biased and should show a
forward voltage drop of perhaps 0.3-0.4 V when
sitting idle (transmitter NOT keyed).

If those diodes are OK, then it gets more tricky to
troubleshoot the SWR bridge without access to
the bottom side of the RF board (DO put the rear
bottom cover back in place before any further
testing proceeds!).  This is where Keith, WE6R,
the K3/K4 super-tech at Elecraft, should be
consulted about other possible failures in the
SWR bridge circuit.  There may be vias accessible
on the top side of the RF board that would enable
you to measure the VFWD and VREFL voltages
from U16 (op amp unity gain buffers), but I don't
know that level of detail without opening up
my K3 for careful inspection.

73,
Mike, K8CN


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Re: [Elecraft] Noise from KAT500?

[Michael Carter via Elecraft]

One more thing to check, Eugene:

Are the other two antenna ports
on the KAT500 connected to
anything?  If so, disconnect
those ports other than the one
you used in your video demonstration.

73,
Mike,
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Re: [Elecraft] Noise from KAT500?

[Michael Carter via Elecraft]

Hi Eugene,

Are you using a switch-mode power supply
to feed the KAT500?  If so, try a linear regulator
supply or a battery instead.

Is your KAT500 bonded to your other station
equipment and AC ground with a short, wide
conductor? (not just the coax shields)

Since you're not the original constructor of
the KAT500, I would check inside the case
to be sure that the case sections have the
powder coat removed where circuit board
standoffs and case section screws are placed.

What kind of cable do you use to connect
the KAT500 to your shack computer?  One
should NOT use a standard VGA cable as
the manual makes clear.

73,
Mike, K8CN
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Re: [Elecraft] K3 - Erratic receive

[Michael Carter via Elecraft]

+1 for what Brian, K0DTJ suggested!

The front panel buttons use a similar
voltage divider with a multiplexed
A/D converter to determine which button
has been depressed.

73,
Mike, K8CN
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Re: [Elecraft] K3 KAT3 usage

[Michael Carter via Elecraft]

Hi Paul,

Glad the TX Gain calibration fixed the ATU issue.
Always thankful for the 'no soldering/de-soldering
fixes required!'

73,
Mike, K8CN
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Re: [Elecraft] K3 KAT3 usage

[Michael Carter via Elecraft]

Hi Paul,

I would first check that the KAT3 is still enabled.
Use the CONFIG menu to scroll through until
you see the KAT3 status.

I find sometimes that if my finger lingers too
long on the ATU TUNE button, it causes the
ATU to go into BYPASS mode, i.e. the ATU is
not inline.  It should show BYPASS briefly
if you attempt ATU TUNE and the ATU
is bypassed.

As frequent prior threads on this and
other Elecraft forums have emphasized,
do NOT press the XMIT button with
the transmit power control set at ** exactly **
5 watts or 50 watts - this will initiate a
TX Gain calibration that you probably don't
intend to launch.

73,
Mike, K8CN


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Re: [Elecraft] K3 low temperature VFO tuning oddity - clicking relay

[Michael Carter via Elecraft]

Email copied below is from a post I made
in response to Jim, K9YC on the elecraft...@groups.io
forum.  This email has some additional observations
made early this morning.  The shack temperature
was a New Hampshire-balmy 54F/12C.

73,
Mike, K8CN

-- begin copied email ---
Thanks, Jim.  Your suggestions had come
to mind earlier from my recollection of your
wise counsel to the various forums I read
daily.

Alas, the odd behavior I reported originally
occurs without any transmission at all - just
powered up the K3 in a cold room, started
tuning the band (any band) and heard the
relay clicking irregularly when either VFO A
or VFO B knobs are rotated across a few kHz to
tens of kHz.  Anomalous behavior is independent
of tuning rate.

To see if I could isolate which relay(s) is (are)
being activated by the VFO tuning, I went into
the CONFIG menu, disabled both the PA module
(KPA3A) and the ATU (KAT3),  powered down and
then powered back up.  If the Front Panel temperature
is at or below ~ 16C, then the relay clicking while tuning
either VFO A or VFO B persists until the Front Panel
temperature rises enough, then the clicking no longer
occurs.  The PA Temperature was fixed at about 13C,
its cold start-up temperature, because I did not transmit
or enable the ATU auto-tune.

It appears that the relay clicking may be emanating
from the LPF section on the RF board.  I listened carefully
with one ear in the open top of the K3 over the BPF section,
and those relays are not changing while tuning across a
single band.   With the LPF section of
the board now largely covered by the KPA3A PA module,
I can't put a finger on individual relays to see if one
particular relay is the source of the clicking.  I may
pull the PA module and replace the jumper block
to test whether this behavior is innate to the K3/10
configuration, but I'm loathe to do that until necessary.

One more observation: I've noticed on my P3 display
that when the relay clicks while tuning either VFO A
or VFO B, there is a narrow (in time) flat green line displayed
on the waterfall.  However, when I use the band switch to
change bands, the P3 waterfall shows a much wider dark
band until the IF signal is restored.

Operationally, the clicking is only annoying for the 15 minutes
or so it takes the Front Panel to warm up even if the room
temperature remains frosty (54F/12C) while I'm doing these
experiments.  Once the Front Panel is above 17C, I can't get
the relay clicking to occur while tuning either VFO A or VFO B.

I may try reloading the firmware when the rig is warm - my
prior MCU firmware version in the K3/10 was only one step
removed from the most current version (5.67), and the
DSP and FPF codes were already at the most recent versions.
I am wondering if there is a communication issue on the
serial control line from the MCU to the LPF relay controllers
that goes away as the MCU gets warm?

Thanks for the ideas, and 73,

Mike, K8CN

-- end copied email ---
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Re: [Elecraft] K3 low temperature VFO tuning oddity - clicking relay

[Michael Carter via Elecraft]

Hi Pete,

I originally posted my observations to both
the official Elecraft reflector and the elecraft...@groups.io
forum.  Until your response on the official reflector
there had been only two responses on the other forum.
I posted additional observations this morning on the
groups.io forum - if you're not monitoring that forum,
I will copy them here.

73,
Mike, K8CN
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[Elecraft] K3 low temperature VFO tuning oddity - clicking relay

[Michael Carter via Elecraft]

I've been getting reacquainted with my K3 (S/N 67XX)
since adding the 100 watt PA module (KPA3A) last
weekend.  I also updated the firmware to the latest
versions and ran the TX Gain Calibration successfully
at all three power levels.  The K3/10 had been sitting
disconnected from everything since maybe 2019 when
I used it to test the XV432 transverter I built.

In operating in the early mornings this past week
I observed an odd clicking of a relay as I tuned
VFO A.  Additional experimentation revealed that
VFO B would also produce the sporadic relay
clicking while tuning that control. There was no
apparent pattern to the clicking, i.e. no regular
frequency interval at which clicks occurred.

In both instances the relay clicking disappeared after
a brief warm-up period.  I confirmed this behavior
again by leaving the shack heat off and the rig off
for a couple hours.  The Front Panel temperature and
PA Temperature both registered 12C on a cold start
(yes, it is New Hampshire on a fall day), and the
anomalous relay clicking on tuning either VFO A
or VFO B ceased once the Front Panel temperature
rose above 17C.  This behavior was never observed
in many years of operating the K3/10 in contests
and general DXing, and the shack was plenty cold
through those fall and winter mornings until the
heat kicked up.

I'll open the top cover and determine which relay
is being activated during the cold start-up.  Both VFO
encoders go directly to the Front Panel MCU
with no intervening circuitry save for connectors
and printed wiring.

At first I thought the relay clicking might be from
the internal KAT3 ATU, but this behavior occurs in
RX mode with no effort to transmit or activate
ATU TUNE.  It occurs with the ATU bypassed as
well as in-circuit.  I'm now wondering if the
MCU developed a low temperature sensitivity
during its long hiatus from daily use?

Has anyone seen this kind of low temperature
relay clicking when tuning the receiver right after
a cold start?

Thanks in advance, and 73,
Mike, K8CN
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Re: [Elecraft] KPA3A and 6 meter TX Gain Calibration

[Michael Carter via Elecraft]

Thanks very much, Dick!

73,
Mike, K8CN

From: Dick Dievendorff 
Sent: Thursday, November 9, 2023 9:20 PM
To: Michael Carter 
Cc: Elecraft Reflector Reflector 
Subject: Re: [Elecraft] KPA3A and 6 meter TX Gain Calibration

CAUTION: This email originated from outside of the University System. Do not 
click links or open attachments unless you recognize the sender and know the 
content is safe.


2. The K3Utility displays the results of the most recent calibration it 
performed.

73 de Dick, K6KR



> On Nov 9, 2023, at 18:13, Michael Carter via Elecraft 
>  wrote:
>
> Last weekend I installed the 100 watt PA module (KPA3A)
> in my K3/10 (S/N 67xx).  I used the K3 Utility to perform the TX Gain
> Calibration at the 5 watt, 50 watt, and 1 mW levels - all
> completed successfully.  However, when I read the
> firmware update page I found that one should perform
> the 6 meter TX Gain Calibration after adding attenuation
> in the transmit signal chain.  I followed the instructions
> on the firmware page and found a new value of the TX Gain
> parameter on 6 meters (28 vs.  the 05 value obtained after
> the automatic calibration routine finished).
>
> Question 1: was the originally determined TX Gain value
> on 6 meters adequate or was it actually necessary to
> insert attenuation and then calibrate the TX gain on that
> band?
>
> After performing the manual TX Gain Calibration on
> 6 meters only (with attenuation in place), I tried to
> check the gain value using the K3 Utility.  However,
> it seemed to retain the previously found value of 05.
>
> Question 2:
> Does the K3 Utility peek into the TX Gain table and
> give the present values, or does it retain the table
> found at the previous TX Gain Calibration?
>
> 73,
> Mike, K8CN
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[Elecraft] KPA3A and 6 meter TX Gain Calibration

[Michael Carter via Elecraft]

Last weekend I installed the 100 watt PA module (KPA3A)
in my K3/10 (S/N 67xx).  I used the K3 Utility to perform the TX Gain
Calibration at the 5 watt, 50 watt, and 1 mW levels - all
completed successfully.  However, when I read the
firmware update page I found that one should perform
the 6 meter TX Gain Calibration after adding attenuation
in the transmit signal chain.  I followed the instructions
on the firmware page and found a new value of the TX Gain
parameter on 6 meters (28 vs.  the 05 value obtained after
the automatic calibration routine finished).

Question 1: was the originally determined TX Gain value
on 6 meters adequate or was it actually necessary to
insert attenuation and then calibrate the TX gain on that
band?

After performing the manual TX Gain Calibration on
6 meters only (with attenuation in place), I tried to
check the gain value using the K3 Utility.  However,
it seemed to retain the previously found value of 05.

Question 2:
Does the K3 Utility peek into the TX Gain table and
give the present values, or does it retain the table
found at the previous TX Gain Calibration?

73,
Mike, K8CN
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Re: [Elecraft] K3 Options Last Time Buy Update

[Michael Carter via Elecraft]

Hi Dave,

I can't speak to the module you ordered, but I
received on 28 October the KPA3A 100 watt upgrade I had
ordered back in spring 2021.  The effort to ship upgrades
is definitely a 'live effort,' and the Shipping Status updates
on the Elecraft web page accurately reflected the
status of the module I ordered.

73,
Mike, K8CN
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Re: [Elecraft] [RFI] HI CUR warning on K3

[Michael Carter via Elecraft]

Hi Pete,

I had a similar set of symptoms with my K3
several years back.  Turns out it was not the
K3 at all, but a failing filter capacitor in
my linear regulated power supply.  I
had sporadic audio dropouts after transmitting
in much the same way as you described,
always at QRP TX levels.

Try a different power supply of newer vintage.
I tested the ESR of the filter capacitors in
my supply and found it to be much too high.

73,
Mike, K8CN

From: RFI  on behalf of Pete 
Smith N4ZR 
Sent: Tuesday, November 7, 2023 10:31 AM
To: Elecraft List ; RFI List 
Subject: [RFI] HI CUR warning on K3

CAUTION: This email originated from outside of the University System. Do not 
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I send a few characters of CW into my Carolina Windom on 40M and after a
delay (1-5 seconds after I stop sending) the K3 flashes a HI CUR
warning, and the audio gain is reduced significantly.  Touch the AF gain
control and it instantly returns the gain to normal, but frequently the
HI CURR warning returns over and over, without any additional
transmissions.  This sequence does not happen, even with 1500 watts,
into my dummy load, nor does it happen on the same antenna on 80M, or on
20 meters on my tribander.

I've read the HI CUR warning discussion on page 65 of the manual, but it
doesn't seem relevant, because I don't have external speakers.  The fact
that it  only happens when feeding an actual antenna on one band
suggests RFI, but the fact that the HI CUR warning and gain reduction
recur again and again long after any RF has me puzzled.  Any suggestions
gratefully accepted!

--
73, Pete N4ZR
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Re: [Elecraft] K2 Sidetone help

[Michael Carter via Elecraft]

Thanks to Don, W3FPR for the reminder on how
to check the firmware version.

To Mike, WA5POK:  as point of reference, I
checked my K2 STL setting and it's quite
loud at 002 using headphones.  I recommend
trying a lower STL level setting than the 060
I originally suggested.  I only use headphones
and did not test the sidetone level with the internal
speaker.

73,
Mike, K8CN
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Re: [Elecraft] K2 Sidetone help

[Michael Carter via Elecraft]

Hi Mike,

You mentioned that you jumped through
all the menu hoops to no avail.  Do you
know which version of firmware 2.04 you
have installed? (there will be a letter after
the 2.04, e.g. 2.04P or 2.04R).

If you have set the sidetone level to, say,
060 and the sidetone pitch to a value
between 500 and 600 Hz, you should
hear the sidetone in your headphones.
If you haven't done it already, try the
test of sidetone generator and audio amp
described on p. 47 of the manual.  The
SPOT switch should also activate the sidetone.

If these tests don't work, it's time to
probe with a scope and voltmeter.

73,
Mike, K8CN
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Re: [Elecraft] K3 Randomly Changes Modes

[Michael Carter via Elecraft]

Hi Gary,

I bet you've never used that retort before now.

I don't need any servants, but I could use a
'memory' (not Memory) with same day service.

73,
Mike


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Re: [Elecraft] K3 Randomly Changes Modes

[Michael Carter via Elecraft]

Hi Randy,

If memory serves me correctly, others have reported
similar gremlins with seemingly random activation
of front panel controls that were not intended.  The
remedy was (1) check whether your radio has the
gold pin connectors on the front panel-to-RF board
interface, and (2) carefully clean the pins on the male header - not
by spraying, but by using contact cleaner on a cotton
swab.  Re-insert the front panel to the RF board.

73,
Mike, K8CN

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Re: [Elecraft] K3 Filters

[Michael Carter via Elecraft]

Hi Dave,

Without a saved CONFIG file, I don't think there
is a way to retrieve the filter settings directly from
the K3.  Have you tried examining the filter settings
for any information that is stored in a CONFIG file?
The K3 Utility permits viewing and editing stored
crystal filter settings.

You could try to visually inspect the filter bandwidths
using an audio spectrum analysis tool, but you would
have to turn off any DSP filtering to see the actual
IF crystal filter response at audio frequencies.  With
some effort you could distinguish 5-pole from 8-pole
filters using the transition band slopes, but estimating
-6 dB bandwidths should be more straightforward from
the displayed spectrum.  While a separate wideband
noise generator would be the best source, you might
have enough local wideband noise to obtain a reasonable
spectrum depiction over the crystal filter response width.

73,
Mike, K8CN


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