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

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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 
click links or open attachments unless you recognize the sender and know the 
content is safe.


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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Re: [Elecraft] Main Ant Port Degraded

[Michael Carter]

Hi Mike,

I would first reduce the TX power control
for a setting less than 10 watts.  That will
bypass the KPA3 100 watt PA module via
the relay K1 on the KPAIO3 board.

If that restores your RX background signal
level to be comparable to that observed
when you put the same antenna on the
RX Antenna input port, then it's likely that
one or more of the PIN diodes in the T/R
switch on the KPA3 board has been damaged,
OR it's possible that one of the RF chokes
that supplies the DC switching voltage to the
PIN diodes has opened up.

If that test doesn't restore your RX background
signal level, then check that the KAT3 ATU is
still enabled in the CONFIG menu.  If it is enabled,
then set the KAT3 to 'bypass' by holding the
ATU button until BYPASS is shown on the screen.
If that doesn't restore RX background signal
level, then you may have bad relay in the KAT3
ATU.

Please keep us posted.

73,
Mike, K8CN
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Re: [Elecraft] AT1 Attenuator

[Michael Carter]

Hi Steve,

Each attenuator section is designed
to present a 50 ohm input impedance
when terminated in 50 ohms.  Of
course that will change as frequency
is increased and inductive effects
take greater prominence.

At what frequency(ies) did you
make your measurements?
What were the actual SWR readings
in the various attenuator section
combinations?  Is your
signal generator a 50 ohm output
impedance unit, and do you have
a known good 50 ohm termination
for the attenuator output port?

If the resistors measure within
a few percent of their nominal
values, I would suspect the
slide switches and/or solder
joints along the path.

I would also use an impedance
bridge/analyzer as a check on
your SWR meter.

73,
Mike, K8CN
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Re: [Elecraft] K2 Band Data

[Michael Carter]

Hi Jerry,

I had forgotten about the KRC2, Elecraft's
universal band decoder/relay driver unit,
so thanks to Jack, W6FB for reminding us.

The K2 uses five separate filter sections
(both for bandpass and lowpass selection),
and these do double duty for adjacent
ham bands.  From my brief inspection
of the W6PQL Low Pass Filter design, it
should be possible to decode the K2 filter
relay driver signals and design an appropriate
converter to create the Yaesu 4-bit band
encoding.  A microcontroller may be overkill,
but certainly more forgiving than a pure
hardware encoder if you don't get it right
the first time.

One clarification on the AUXBUS signal: the
'auxbus' is Elecraft's proprietary 1-wire
signaling scheme by which the main MCU
on the K2 Control board talks to all of the
other controller ICs on the various option
modules and the I/O controller (relay driver,
among other functions) on the K2 RF board.
The 'auxbus' signal is made available via the
KIO2 interface, if installed, for use with
external Elecraft modules (e.g. the KAT100
ATU, KPA100 PA, and the transverter modules).

The KIO2 module does provide RS-232
serial bidirectional communication for
rig control/status monitoring, and it
is possible to write your own monitoring
application that infers band data from
the KIO2 data stream.  If you go this
route, be sure NOT to use a standard
RS-232 cable, but DO wire the special cable
spelled out in the KIO2 manual.  The
KIO2 programmers' reference manual is
available on the Elecraft support pages.

The pin labeled 'AuxBus' on the Aux. I/O
port of the KIO2 is indeed the proprietary
signaling scheme used by Elecraft, and
would require more in-circuit data capture
while exercising the various option controls
to enable reverse engineering of the protocol.
It is not publicly documented to my knowledge,
so the KIO2 RS-232 data channel is probably
the preferred way to accomplish your objective.

73,
Mike, K8CN
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Re: [Elecraft] K2 Band Data

[Michael Carter]

Hi Jerry,

There is no simple access to band data in
the K2 unless you want to reverse engineer
the AUXBUS protocol.  Depending on how
your homebrew amp selects its lowpass
filter options, you may be able to pick up
the relay control signals for the K2's bandpass
and lowpass filter banks and use those
to encode a band data word in the format
used by Yaesu.  There is no isolated connector
on the K2 Front Panel, Control, or RF boards
that makes available those relay control lines,
so you would have to tap the traces where
those control signals are exposed.

Perhaps you can comment more on the
homebrew amp design with regard to
lowpass filter selection?

73,
Mike, K8CN
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Re: [Elecraft] K3 subreceiver works on CW only

[Michael Carter]

Hi Erik,

Did you check the filter selection for
the sub-receiver to be sure you don't
have a blank slot selected for SSB?

73,
Mike, K8CN
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Re: [Elecraft] KPA100 Power Surge Advice

[Michael Carter]

Thanks, Geert Jan, for recounting the 'origin story'
of the K2 'twins', the outboard combination of the
KPA100 and KAT100.  I had not previously heard
of the origin and Lyle's (KK7P) role in that process.

I hope Larry can provide more detail about
the actual configuration of his outboard
KPA100.

73,
Mike, K8CN
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Re: [Elecraft] KPA100 Power Surge Advice

[Michael Carter]

Hi Larry,

You mention in the title '...Power Surge Advice.'
I presume your KPA100 was working properly
prior to not powering up?

You also describe the connection from your power supply to
the KPA100 and then to the K2 - does this
imply a Y-connection from the power supply
to both the K2 and KPA100 since the units
use different power connectors?

Do you have an external fuse inline from the
the power supply to the KPA100 and separately
the K2?

The KPA100 has no visual indication of
power-up status unless you added some
indicator in its external enclosure - how
do you know it is not powering up?

I would disconnect the power supply from
both units, measure the open-circuit terminal
voltage, then connect only the K2 to the power
supply and your antenna (bypass the KPA100).
Verify that the base K2/10 works as before.

Check your cables from the power supply
to the KPA100 and K2 for low resistance - and
be sure that the Anderson PowerPoles are
fully seated in the KPA100 connector.

I would measure the resistance at the
KPA100 power connector - in the normal
polarity it should read a high resistance,
in the other polarity it should read a
low resistance due to the reverse polarity
protection diode.

Please let us know your findings.

73,
Mike, K8CN
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Re: [Elecraft] K3 Options Last Time Buy Update and other products status:

[Michael Carter]

Thanks very much, Eric, for the comprehensive
update!

73,
Mike, K8CN
(especially glad to know about the KPA3A
being close to shipping)
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Re: [Elecraft] K1 Low power output on one band

[Michael Carter]

Hi Paul,

It does sound as though the slug-tuned inductors
on the 20 meter and 15 meter sections of the
Filter board need tweaking.  As you noted, one
must remove the KAT1 ATU board from the
Filter board to access those coils.  It is necessary
to jumper pins 2 and 10 of J2 on the Filter board
to route RF to the antenna connector.  Once you've
done that you can proceed with the alignment
as described in the manual.

73,
Mike, K8CN
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Re: [Elecraft] K3 Receive gone

[Michael Carter]

Hi Jim,

Does your K3 have the KXV3 interface
or KRX3 subreceiver options installed?
If so, I would check the menu settings
to be sure that the rig doesn't have
the RX antenna port selected as its
antenna source and that the subreceiver
isn't the primary receiver.

If it's not a menu setting issue, I would
remove the ATU and re-install the original
KANT3 antenna board, then test again with
actual antenna or your signal generator.

You mentioned that the K3 sat on a shelf
for several months - was it connected to
anything or were all cables disconnected?

Was it stored in an environment where
corrosion on internal connectors/circuit
board headers might have occurred during
its 'vacation' from active use?

73,
Mike, K8CN

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Re: [Elecraft] K2/10

[Michael Carter]

Hi Allan,

In your original post you said your
K2 seemed somewhat 'deaf.'

Does that mean you hear no signals at
all on any band, no signals on one or
two bands, or just weak audio with
antenna or signal generator input?

Since your K2 has the K160RX option,
I would check that the RX antenna
is not inadvertently selected in the
menu, especially if there is nothing
connected to that antenna port.

In your most recent post you indicated
that the sudden deafness occurred
after the transceiver was working fine.
When you wrote that 'the power cut
out and left the K2 in this state' after
starting to recalibrate the ATU, can
you clarify what you mean by that
statement?  Is there any TX power
output or just not what the Power
control indicates?

I would recommend ceasing effort
to realign the radio from scratch
until the cause(s) of the abrupt
loss of some functionality is (are)
identified.  The issue with the
VFO realignment is a separate matter
unless the VFO has ceased to oscillate
at all.

73,
Mike, K8CN
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Re: [Elecraft] When/where was recent officialupdate (from WA6HHQ?) on K3 option last time buy ship status?

[Michael Carter]

Eric posted to this forum in early March 2023.
I believe his estimates of availability for various
modules are reflected in the current Shipping Status
information on the Elecraft web page.  Suffice to
say that only a few module types have shipped
at this juncture.  Some of his estimates were
in retrospect optimistic (no criticism implied or
intended).

73,
Mike, K8CN
(awaiting KPA3A 100 watt module myself)


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Re: [Elecraft] KPA3 Rev B not output

[Michael Carter]

Hi George,

Congratulations on your excellent sleuthing!
Regardless of which solder joints were
reflowed to solve the problem, you found
the troublesome one(s).

Thanks, too, for reporting back to the
reflector - it helps to spread the knowledge
base.

73,
Mike, K8CN
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Re: [Elecraft] Starting to Ship K3 & K3S Option Last Time Buy Orders (3/1/23)

[Michael Carter]

Just curious if there is a new update coming out this week
since it has been 3 months since the last update (presuming
I didn't miss an update and understanding that Elecraft has
been traveling to various ham conventions)?

73,
Mike, K8CN
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Re: [Elecraft] Power spike early K3

[Michael Carter]

Hi Mike,

I saw that you had posted a similar question
in January 2023 and had some suggestions
including running the TX Gain calibration, which
you did, but apparently without effect on the
spiking.

There have been numerous reports of
TX power spikes on first dit or first voice sound.
Some found that part of the issue was
inadvertent changes in the TX GAIN settings
when the TX POWER control was set to
precisely 5.0 W or 50 W and the TUNE
button was pressed. One respondent
to the reflector commented on this issue
and how the TX power spiking was eliminated:

https://www.mail-archive.com/elecraft@mailman.qth.net/msg252489.html

One question: does the power spiking upon changing
bands occur when only a 50 ohm dummy load is
attached instead of antenna or an amplifier?  Don't
put anything else in the line between the K3 and
the dummy load, and be sure the internal ATU in
the K3 (if installed) is set to BYPASS.

73,
Mike, K8CN




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Re: [Elecraft] K3 RX Issue?

[Michael Carter]

Hi Lee,

Do you also have a reduced RX signal level
on 30 meters as well as 20 meters, at least
by comparison with your KX3?

Since the TX output is OK, I will hazard a
guess that one of the relays in the
20/30M bandpass filter is not making
good contact or has developed a weak
solder joint on the RF board.  While that
should also reduce the TX output, the
TX Power control loop may compensate
enough to make the added loss through
the relay less noticeable.

I would carefully inspect all solder joints
in the 20/30M bandpass filter circuit,
maybe do the same for the lowpass
filter.  I would try gently pressing on the
relay casings while listening to a good
strong signal on 20 meters and 30 meters
to see if there is an audible change in RX signal
level.

73,
Mike, K8CN
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Re: [Elecraft] K3S dead.

[Michael Carter]

Hi OM,

I would first disconnect anything connected to the
rear panel ACC connector - pin 8 may inhibit
the PWR_ON signal.  If nothing is connected
to the ACC jack, I would try temporarily grounding
the end of R77 (the other end attaches to pin 4
of Q2), which is the /PWR_ON signal.  If that
fails to power up the rig, you likely have a bad Q2
MOSFET.  There is a possibility that a problem
downstream of Q2 is preventing its drain terminal
from coming up at PWR_ON, but I would
see if you can force /PWR_ON to ground to
open Q2's channel.

If a forced /PWR_ON does turn on the radio,
then you'll need to look at the KIO3B module
and the Front Panel board.  I traced this circuit
out just recently, but I can't recall the precise
path from the front panel POWER switch to
the active circuitry..will look back at another
email on this issue.

73,
Mike, K8CN


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Re: [Elecraft] K3s problem

[Michael Carter]

Hi Jerry,

First, a couple of questions:

-- does the abrupt loss of power occur if you operate
with the TX PWR set to less than 12 watts on
15 meters?  This engages only the low power
driver amplifier and takes the 100 watt PA module
out of the picture.

-- if you're operating on 15 meters at the
75-85 watt TX PWR level and the power
drop-out occurs, is full power restored
if you switch bands, then go back to 15 meters?

My suspicion is one of the relays on the
15 meter lowpass filter section has a contact problem.

73,
Mike, K8CN

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Re: [Elecraft] K3 Won't Turn On all of a sudden!

[Michael Carter]

Hi Rick,

I've not experienced the problem you described,
but I've also not used my K3 as a remote front panel
for another K3.

Have you checked pin 8 of the ACC connector to
be sure that it is not held 'high' by some chance
(not likely since you pulled all the cables)?

If there isn't a problem with that ACC pin and
accompanying circuit in the KIO3 digital interface,
I would investigate Q2, the 2N7002K MOSFET
on the front panel board.

Once the POWER switch is depressed, that pulls
up the gate voltage of Q3, thus pulling down
the /PWRON signal, which is required to be
held low to keep the series-connected P-MOSFET
in the 12 VDC input line conducting for the switched
power supplied to the rest of the radio.  That /PWRON
line is held low if Q2 receives the POWERHOLDON
signal from the front panel MCU even after the
front panel POWER switch is released.

The LCD display backlight is powered from
the 8V regulator when a signal VLCDBKLT
from the MCU is asserted.  The LCD segment drives come
from a separate controller chip rather than
the MCU directly.  I'll hazard a guess that your
MCU is operating properly, but something in the
POWERHOLDON path is not allowing Q2's gate to
be held high, thus turning off the K3 when the
POWER switch is released.

Mike, K8CN
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Re: [Elecraft] K3 KPA100 not putting out in high power

[Michael Carter]

Hi Jim,

Since the bypass relay actuates, can you check the
KPA3 (or KPA3A, depending on which generation
of K3 you have) input side of the relay to verify
that the relay is doing its job, i.e. that RF is making
it onto the KPA3 input?  A scope is best,
but a simple RF probe and DMM would also suffice.
The principal difficulty is accessing the KPAIO3
board on which the bypass relay is mounted.

If the relay is switching the TX drive into the KPA3,
but you're not seeing any output power from the
KPA3, there are several places where the KPA3
module can fail and produce that effect.  Keith,
WE6R, the Elecraft K3/K4 tech par excellence,
may advise how best to test the KPA3 module
since the component side is not accessible when
it's mounted in the K3.

73,
Mike, K8CN
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Re: [Elecraft] Keying the K3s

[Michael Carter]

My previous post under this thread elicited
a private response from Kent, K9ZTV who
noted the same concern expressed by others
publicly about using the TUNE button
with the PWR control set ** exactly **
at 5.0 W or 50 W.  I thank Kent for piquing
my curiosity about this issue because I
had not experienced any inadvertent
resetting of TX GAIN parameters as a
result of a decade of QRP operation with
the PWR control set at exactly 5.0 W.  Other
posters also alluded to not having any
apparent triggering of the TX GAIN
calibration, which made me even more
curious and sent me back to the K3s manual.

For context, I have a K3/10 with the internal
KAT3 ATU rather than the K3s.  My K3 has the
last issued firmware updates for that model.
I use one, sometimes two, wire antennas on
multiple bands via the internal ATU.  While
I frequently use the ATU TUNE button to
adjust the ATU for changes in apparent
feedpoint impedance (I use window line,
which is subject to rain and snow-induced
changes in its characteristic impedance),
I never use the TUNE button, which
may in part explain why I've not inadvertently
launched the TX GAIN calibration routine.

Re-reading of the K3s manual led to this
summary:

-- the ATU TUNE button activates the
ATU adjustment process at a fixed TX
PWR level, either 5 or 10 watts depending
on whether the 100 watt PA module is
installed.  The current PWR control setting is
ignored by the ATU TUNE button.

-- the TUNE button activates a CW
transmission at the current setting
of the PWR control ** unless ** the
per-band TX power control parameter
has been configured for that option.
If the TUN PWR has been set to NOR
(Normal) in the CONFIG parameter menu,
the present setting of the PWR control
is the value used.  As others have
commented and Elecraft personnel
have confirmed, activating TUNE with
PWR set ** exactly ** at 5.0 W or
50 W launches the TX GAIN calibration
process, and doing so into an antenna
rather than a good dummy load will
result in erroneous resetting of TX GAIN
parameters.

Since I have yet to use an external
power amplifier, I have not had occasion
to use the TUNE button, and I've
confirmed that my K3 has set the
TUN PWR parameter to NOR(mal),
so it would be subject to inadvertent
launching of the TX GAIN calibration
if I hit the TUNE button and the PWR
control was left at its customary 5.0 W
setting.

This thread has made clear that different
station configurations (e.g. whether the
internal ATU is used, whether an external
power amplifier is used) may or may not
result in the inadvertent triggering of the
TX GAIN calibration process.  The advice
that others have given and Elecraft has
confirmed about not pressing the TUNE
button when PWR is set ** exactly **
at 5.0 W or 50 W is germane ** IF ** one
has left the TUN PWR parameter set to
NOR(mal) in the CONFIG menu.  It does
not mean that one cannot send CW
(or SSB) at exactly 5.0 W or 50 W
in routine operation for fear of triggering
the TX GAIN calibration.

73,
Mike, K8CN
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Re: [Elecraft] K3S-KPA3 100 Watt Amplifier not working

[Michael Carter]

Hi Dick,

By 'not working' I presume you mean that advancing
the TX Power control above 12 watts does not yield
increasing TX power output?

Does advancing the TX Power control above 12 watts
produce any increased TX output power or none at all?  Here
I presume you have an external wattmeter with which to
measure TX output power.

The K3s uses the KPA3A power amplifier, which is a
RF MOSFET-based amplifier.  The 100 watt amplifier
is either bypassed or inserted inline after the KLPA3A low
power amplifier using PIN diode switches and depending
on the setting of the TX Power control.  That you're still
able to measure 12 watts TX output from the KLP3A
suggests the 'bypass' path through the PIN diode switches
is operating correctly.

Keith, WE6R, the Elecraft tech guru, had posted some
common failures on the KPA3A board - you can search
them on this forum or the K3 groups.io forum.  He may
chime in here before I can locate his very helpful posts.

73,
Mike, K8CN
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Re: [Elecraft] Keying the K3s

[Michael Carter]

Hi Dave,

The K3s (and K3) bypasses the 100 watt PA module
when you set the Power control to less than 11
watts and relies on the KLPA3A 10 watt PA driver module.
No harm will come to the K3s when operating
at 5 watts presuming you have an SWR within
spec for the K3s.

I used a simple optocoupler interface
to key my K3 from N1MM+ function keys
in CW contests, but replaced it with a Mortty,
which emulates the WinKey protocol from
a USB port on the computer.   There are
a variety of single transistor keying interfaces
described on the web if you search a bit.

Others may recall if one can share the K3s serial port
for both rig control and CW keying without
a separate interface circuit - I remember seeing
various discussions on this issue years ago,
but can't retrieve them now.

73,
Mike, K8CN
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Re: [Elecraft] K2

[Michael Carter]

Hi Mark,

It sounds like self-induced RFI, but occurrence at a very low
nominal TX power is suspicious.  Can you say more about:
-- antenna(s) in use
-- any external or internal ATU in use
-- connections to your K2 other than antenna, DC power, and key/paddle?

73,
Mike, K8CN
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Re: [Elecraft] K3 - 100 watt amp dead?

[Michael Carter]

Thanks for the update on your visual inspections, George.

Best wishes for the holidays!

73,
Mike, K8CN
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Re: [Elecraft] 12 v power source for Elecraft Transceivers

[Michael Carter]

"Clearly case of stimulation of overactive ham hormone resisting disposal of
anything looking potentially useful."

Ed, your characterization of this personality quirk is the
best explanation I've seen yet - I'll share it with my XYL,
although I doubt it will temper her (un)enthusiasm for
my collection of castoffs and electronic rescues!

73,
Mike, K8CN

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Re: [Elecraft] K3 - 100 watt amp dead?

[Michael Carter]

Hi George,

Your test confirmed that the low-power amp (K3 LPA) survives.
To clarify, do you have the K3 or K3s?

The original 100 watt PA (KPA3) used RF BJTs as the finals,
whereas the KPA3A used RF MOSFETs (LDMOS).

Apart from failure of one of the PA final transistors,
the loss of TX output power when the 100 watt
amp is switched in can be due to failure in the
PIN diode T/R switch around the 100 watt PA.
The fact that you can generate 12 watts indicates
that the '100 watt module bypass' path through
the PIN diode switch is OK.  Failure of the PIN
diode switches connecting the LPA to the 100 watt PA
can arise from failure not only in the PIN diodes
themselves, but also from the bias circuitry that
switches the diode states.  A recent post with a
similar problem revealed the fault to be in one
of the RF chokes (the red toroids on the 100 watt
PA board) that feed DC to the PIN diode switches.
The problem was a broken wire on one RF choke.

I suggest opening the top cover, do a visual
inspection of the top of the 100 watt PA module,
then remove the 100 watt PA module to inspect
the underside.  Barring any obvious sign of
burned components or board traces, the next
step would be to check the PA transistors, but
the actual test depends on whether your K3
has the older BJT finals or the more recent
MOSFET finals.

 Let us know what you find., and 73,

Mike, K8CN
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Re: [Elecraft] K3 #8862 unwanted sidebands

[Michael Carter]

Thanks, Wes!

 As a 99.9% CW operator,
I never looked into the Tech Mode options
for SSB testing in my K3.  That's a really useful
feature!  It's good to be reminded of the
built-in troubleshooting utilities in the K3.

73,
Mike, K8CN
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Re: [Elecraft] K3 #8862 unwanted sidebands

[Michael Carter]

Hi Martin,

Do you observe (or hear) sidebands outside
the nominal transmitted bandwidth with
CW transmissions or only SSB transmissions?

Can you perform a 2-tone test with an
audio source other than speech?

The fact that the unwanted sidebands
are not observed when the KPA3 100
watt amplifier is bypassed suggests
a possible change in the bias point of
the PA transistors.  If you have the original
BJT version of the KPA3, not the LDMOS
version of the KPA3A, perhaps you can measure
the base or collector bias current when the
KPA3 is engaged (PWR control set at 12 watts
or above) with no audio modulation applied.
That may be difficult to do without temporarily
lifting a component lead.

Perhaps Keith, WE6R from Elecraft can
suggest a way of confirming proper bias
point setting for the KPA3 without too
much intrusion?

73,
Mike, K8CN
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Re: [Elecraft] [K3] Strange Selective Hearing in My K3

[Michael Carter]

Hi Eric,

I'm voting with my friend Dave, K1WHS,
for looking first at the voltage regulators.

The 8 volt regulator supplies the TC4427
gate driver IC, which in turn provides 7R/7T voltages
separately to the Transmit and Receive switching circuits.
The loss of the 7R/7T voltages would disable the
PIN diode T/R switches and render the radio deaf
and unable to transmit.

If the 8 volt regulator doesn't collapse after some
time observing its output voltage, I would check
the TC4427 (U11 on the RF Board) to be sure its
outputs are correct (the 7R/7T voltages).  The
regulator is likely the first culprit - its '8A' output
pin provides power to a large number of circuits
in the radio.

73,
Mike, K8CN
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Re: [Elecraft] K2 Question: RF Gain Pot

[Michael Carter]

Hi Dave,

You'll need to replace that pot.  I've got the same problem
in my K2/10, and it's getting progressively worse.  The
issue is not solvable with contact cleaner - I recall older
posts on this same problem, and the advice was the
same: replace the pot.  Some commenters suggested
ordering replacements for all four pots to the left of
the VFO knob, but I've only had issues with the RF Gain
pot.  If you're like me, I turn off the AGC most of the
time and ride the RF Gain pot a lot, especially when
contesting.  That no doubt contributed to my problem.

73,
Mike, K8CN
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Re: [Elecraft] K2 Menu Button

[Michael Carter]

Hi Aaron,

The symptoms you describe indicate to me a mechanical
flexure problem.  I would pull the Front Panel board out
of the RF board socket (first removing the Control board)
and carefully inspect all pins for corrosion.  I would also
inspect the solder joints on the Menu/Edit button switch.

The failure of the Menu/Edit button switch to produce any
response on some occasions while causing display blanking
and loss of receive function on others is odd, but the fact
that cycling the Power switch restores function suggests
that mechanical forcing on the RF board is sufficient to
reconnect an intermittent power feed to the Control and
Front Panel boards.  I'm betting the J1/P1 connector junction
between the Front Panel board and the RF board
is the source of this behavior.

73,
Mike, K8CN

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Re: [Elecraft] problem with K2, KAT100 and K2100PA combo

[Michael Carter]

Occam's Razor comes to mind - forget all that
diagnostic stuff I pumped out earlier!

Glad you found the true cause, the simple true
cause, Brian.

73,
Mike, K8CN
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Re: [Elecraft] problem with K2, KAT100 and K2100PA combo

[Michael Carter]

Hi Brian,

Could you give a bit more detail?

You said the 'power went off on the K2' after
attempting to auto-tune the KAT100.  Do you
mean the DC power went dark on the K2 and
the screen display went blank, or something
else?

Have you tried to auto-tune the KAT100
at the low power level (set K2 Power control
less than 10 watts to yield 2 watt for
KAT100 tune)?

Have you tried connecting the KAT100  to
a good 50 ohm dummy load and doing
auto-tune at low and high power?

Does the K2 still 'talk' to the KPA100,
i.e. can you access the KPA100 menus?
If so, are there any Error/Status codes
displayed in the PA menu?  Can you
set the KAT100 to 'bypass' mode
and still get low power to a dummy load
on the KAT100?

The fact that the 12 VDC via the
PowerPoles doesn't reach the
base K2 suggests that diode D9
has opened.  It is also possible
that a collector-base short in
one of the PA transistors is
pulling down the 12V line.  This
begs the question: what are
you using for the DC power supply?

Although I have my KPA100 and KAT100
outboard of my K2, I have observed
situations where the KAT100 fails
to continue searching for a match
if the impedance seen at its output
is a very bad mismatch (high SWR).
In virtually all of those instances I can get the
KAT100 to properly auto-tune by
reducing the K2's Power control
to less than 10 watts (but more than
2 watts).

If you have an ohmmeter/multimeter,
you can check the resistance between
the PowerPoles with the 12 V power
supply disconnected at the PowerPoles
AND at the coaxial DC input.   That
resistance should be high - if not, one
of the PA transistors may have shorted
through.

Don't forget that the KPA100 manual
has troubleshooting procedures
and much more detail than I've
given here - see page 66 of the manual.

73,
Mike, K8CN
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Re: [Elecraft] k3 no power out over 12 watts

[Michael Carter]

Hi Scott,

Check the KPA3 settings in the CONFIG menu
to be sure the 100 watt PA is not bypassed.

If the KPA3 is set to PA NOR in the CONFIG
menu, then you may have a diode failure
in the PIN diode T/R switch or the PA bypass
PIN diode switch.

Mike, K8CN


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Re: [Elecraft] Indefinite support for K3s

[Michael Carter]

Wayne, N6KR, posted on 23 April that Eric (WA6HHQ) will
have an update on K3 modules 'next week.'

My recollection is that Elecraft set a cutoff date in spring 2021
for ordering of K3/K3s modules to gauge interest and allow
ordering of long-lead-time parts.

I can't find another recent post in which it was said that
there may be a few 'spares' of select K3/K3s modules
available for those who did not order them in spring 2021.

73,
Mike, K8CN

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Re: [Elecraft] K2 SN 25xx has very low sensitivity in 20 and 80m bands

[Michael Carter]

Hi Chris,

Does your K2 transmit OK on those bands, i.e. at full power output?

The fact that other bands have normal sensitivity indicates
that the main receiver functional blocks are OK.  The bandpass
filters for 20 and 80 meters have only one component in
common, relay K3, but that relay selects 80/160 meters or separately
20/30 meters by adding additional shunt capacitors for the
lower frequency band in the proper filter section.

I would check your per-band settings to be sure that you
haven't inadvertently selected an antenna port
that isn't connected to the proper antenna for one of those
bands OR that a separate RX ANT is selected when you
have no antenna on that port (presuming you have the
160 meter/RX ANT module installed).

73,
Mike, K8CN
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Re: [Elecraft] question order date of recently received K4D

[Michael Carter]

Hi Darrell,

Join this group to get a good handle on delivery rates
of K4/K4D radios:

creativek4shippingsta...@groups.io

It's a lot of fun to watch the delivery reports and
serial numbers roll in!

73,
Mike, K8CN
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Re: [Elecraft] Interference on 17M

[Michael Carter]

William, I suspect you had an attachment
stripped by the reflector.  Was it a sound
file or spectrum view?

Ron, does the RFI occur only on 17M?
I presume you've checked other bands?

The switch-mode power conversion
in PV inverters can generate RFI
across a broad spectrum, but it would
be unusual to have an isolated spectral
peak, even line-broadened, at one
discrete frequency in the 18 MHz
range.  The switching frequencies
in power converters are typically
much lower.  The harmonics of the
switching frequency could appear
in the 17M band, but those would
be weak relative to the fundamental
in the few hundred kHz to perhaps
2 MHz range.

Ron, do you have HF portable RX
capability, even if only temporarily
in your car?  Some phone calls or
emails to other hams in your
community would help with local
RFI checks.

Keep us posted!

73,
Mike, K8CN
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Re: [Elecraft] KPA500 Mosfet SD2933 vs VRF2933

[Michael Carter]

Hi Ziv,

The SD2933 is an older part - Mouser lists it as 'obsolete'
and otherwise unavailable.  A review of the datasheets
for the two devices (VRF2933, SD2933) reveals that the
VRF2933 has a higher drain-source breakdown voltage
than the SD2933, and it is tolerant of SWR values up
to 70:1.  The SD2933 tolerates at least SWR of 3:1, possibly
greater, but that is the only spec in its datasheet.  The
VRF2933 has a somewhat lower gate capacitance than the
SD2933.  In other respects, the two MOSFETs are very similar.

I suspect the SD2933 will work in place of the VRF2933, but
you may need to watch the SWR on your antennas a bit more
carefully to avoid exceeding the maximum drain-source
breakdown voltage.  You will also need to carefully check
and adjust the gate bias voltage pots to ensure the proper
quiescent drain currents in each MOSFET.

73,
Mike, K8CN
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[Elecraft] Failed K3

[Michael Carter]

Rick,

Can you provide more detail about how your K3 failed?

My impression from reading not only this reflector,
but also the K3 and K4 groups.io fora, is that Elecraft
is fully occupied with K4 support and firmware evolution.
Others note longer than historically observed service
times for units of any kind sent back for repair - not
unique to you.  I don't believe this backlog will persist
indefinitely.  Moreover, ordering a K4 now won't
shorten the delay in getting a radio - it seems the
last of the Group 2 orders for the K4, which were
mostly made in 2020, are just being fulfilled now.
Orders in Group 3 already made are looking at June/July 2022 for
shipment.

Could you approach a local ham friend who might
have a rig to loan?  It may not be plug-compatible
with the rest of your Elecraft gear, but it would
avoid need to purchase something at a time when
it seems like everything is back-ordered.

73,
Mike, K8CN


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Re: [Elecraft] K2 side tone loss on tx

[Michael Carter]

Bob,

You said it's "great on phones."  Is that to say
you experience the sidetone volume decay
only on the internal or external speaker?

What is your headphone impedance?

The sidetone volume is controlled by
MOSFET Q5 on the Control Board.

Are you able to manually vary the
sidetone volume STL and pitch STP
using the Menu?

If you alter the sidetone level STL, does
the sidetone level remain
constant over time at the new volume
setting?

The slow decay of sidetone volume
suggests drift in the Q5 gate voltage (which
controls the MOSFET channel resistance)
or a problem downstream of Q5, including
the op amp filter which smooths the DAC
sidetone waveform.

Mike, K8CN
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Re: [Elecraft] K3/K3S options and upgrades

[Michael Carter]

Rich,

I wrote to Elecraft in late October 2021 to inquire
about the status of options and upgrades.  I don't
think Madelyn reviews the many emails on the
official reflector, but she kindly answered my query
via direct email.

As of early November, the estimate is 4-6 months
for most K3/K3S options and upgrades, but Elecraft
intended to publish to the Shipping Status pages updated
delivery dates on individual items as their availability
becomes more certain.  Long lead time parts and
board vendor capacity is the bugaboo here
pretty much the bane of the entire electronics industry.

73,
Mike, K8CN
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Re: [Elecraft] K3/K3s protection diodes

[Michael Carter]

Mike,

I searched the Elecraft Support pages for mods
on the K3 and K3s, but found nothing about
"protection diodes" for the LPA (low power
amplifier module).  I did a search of the
archives on the official reflector and again
found only your mention of "protection
diodes" for the LPA.  I have not yet checked
the K3 groups.io forum - perhaps there is
discussion of the need for such diodes there?

73,
Mike, K8CN
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Re: [Elecraft] KAT3 ATU Problem

[Michael Carter]

Tom,

Glad that the MotherShip is helping out directly!

It wouldn't have occurred to me to look at
the LPA stage as a source of trouble, but if
the TX power is ramping up slowly, then I can
see where the ATU control algorithm is
confused by the change in power levels both
forward and reflected.  My ATU seems to
change relay settings very fast, and the control
algorithm is looking at change direction (maybe
change magnitude as well) in SWR to decide
which relays to flip next.  The relative adaptation
speed of the control algorithm and the TX power
ramp-up could certainly cause interactions that
might slow the ATU convergence, but I would
think that once the TX output power stabilized,
the ATU control algorithm would be receiving
valid SWR readings as it flips relays.

When you say it takes seconds to ramp up
to full (TUNE) output power, does this happen
on every TUNE button press?  Does it also occur
when you send CW from the paddle/key? Can
you watch the RF envelope on a scope to time
the power ramp-up?

73,
Mike, K8CN
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Re: [Elecraft] K3 Auto ATU Problem

[Michael Carter]

Tom,

I'm going to go out on a limb here, but hey,
it's only a virtual limb!

I am going to withdraw my previous statement
that the K3 SWR bridge is operating correctly.
Given what you've said, the ATU control algorithm
is receiving bad information from the SWR bridge.

Here's how to test this hypothesis:

-- use a different resistive load than 50 ohms, e.g. two
50 ohm loads in parallel using a tee-junction,
or build a higher resistance load using
several non-inductive power resistors, or
use a 4:1 balun reversed to present a 200 ohm
load to the ATU when balun terminated in 50 ohms.

-- put the KAT3 ATU in 'bypass' mode

-- measure SWR at low TX power (whatever
power the ATU uses automatically is fine
as long as your loads can tolerate the dissipation
briefly).

Schottky diodes D36 and D37 in the K3
SWR bridge detector circuit are known
to be sensitive to high voltage transients,
e.g. ESD or lightning-induced voltages.
Failure of either or both diodes produces
bad SWR estimates, which may not
be observed when using a good 50 ohm
termination.

If you have a good high impedance DC
voltmeter (DMM), you might check
the voltages VFWD and VREFL at the
outputs of the LM358 op amp unity
gain buffers (U16 on the K3 RF board)
to observe how each behaves with
different load resistances at the ANT
port(s).  If the VREFL voltage doesn't
change predictably with mismatched
loads, it could be that diode D37 has
failed.

A search of the old Elecraft reflector
and the separate K3 groups.io forum
reveals lots of discussion about anomalous
behavior of the ATU, frequently associated
with SWR bridge component failure.

73,
Mike, K8CN
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Re: [Elecraft] K3 Auto ATU Problem

[Michael Carter]

Aye, Tom - you've given us a good puzzle
to solve!

Back to looking at the schematics, possibly
opening up my K3 to do direct visual inspection.

What, if any, options do you have installed
in your K3 (including KPA3 100 watt PA)?

73,
Mike, K8CN
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Re: [Elecraft] K3 Auto ATU Problem

[Michael Carter]

Tom,

Does the problem you describe occur
on each of the ANT1 and ANT2 ports
on the KAT3 output when the ports
are terminated in a good 50 ohm power
load?

Have you checked the K3 ANT selection
when the KAT3 is installed to be sure that
the port to which your 50 ohm load is
attached is the one selected on the front
panel?

The fact that the anomalous behavior
occurs with a substitute KAT3 board,
and that it doesn't occur with the KANT3
board installed, indicates that the K3's SWR bridge
circuit is operating properly.

The fact that putting the KAT3 in BYPASS
mode provides a correct SWR reading
indicates that the relays in parallel with
the series-connected inductors are
properly switched as are the relays
in series with the various shunt capacitors
of the L-network (the latter group of
relays all switched off their connections
to the associated capacitors).

You could try the KAT3 tests using
manual control mode (as described
on p. 56 of the K3 Owner's Manual,
rev. D10) to verify proper operation
of each of the relays in the L-network
individually. The manual control options allow one
to read out or clear the per-band memory of the
ATU L-C settings, which might also
be useful in diagnosis.

73,
Mike, K8CN
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Re: [Elecraft] P3 Issue

[Michael Carter]

Ken,

I have not experienced the difficulty
with my P3 that you encountered,
but the fact that both the P3 front
panel display and the external SVGA
display shut down indicates a problem
with data not being provided to either
display driver system OR there is a
thermal problem with one of the
onboard voltage regulators on the P3
Rear Panel I/O board.  The P3 has
both +5V and + 3.3V regulators with
crowbar over-voltage protection, and
both are fed from the +12V DC input
jack.  The P3 SVGA board has additional
voltage regulators supplying 1.2, 2.5, and
3.3V, and these are fed from the +5 V
regulated supply on the P3 Rear Panel I/O
board.

My suspicion is a thermal sensitivity
in the +5 V regulator or its crowbar
protection circuit.  However, I would
first check the +12V DC input connection
to the P3 and be sure that it is stable
at +12V over time.  If you supply that
voltage from the auxiliary +12V output
of a K3 or K3s, you should also check
that the problem doesn't stem from
a problem inside the transceiver.  My
recollection is that a modification
was required in the original K3 to
increase the available current at the
auxiliary +12V DC output to support
the SVGA option in the P3.

I am curious to know what you find...

73,
Mike, K8CN
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Re: [Elecraft] K3S RX ANT COR?

[Michael Carter]

Eric,

The schematic for the KXV3B-2 BNC Board
shows a COR and associated RF detector
circuitry for the RX ANT IN port.  There
is also a protective spark gap on that
input, presumably for lightning induced
voltages on the RX antenna.

I haven't checked the K3s manual,
but the RF detector circuit uses
a Schottky rectifier/peak detector
circuit to switch an NPN Darlington
pair that controls the COR coil.  I
estimate about 1.5 volts peak
RF on the RX ANT input would
trigger the COR and disconnect
the RX ANT input from the rest
of the RX signal processing chain.

73,
Mike, K8CN
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Re: [Elecraft] [K3} [K3s] Final round of module orders?

[Michael Carter]

Sorry about the October 1st mention - I thought I had
placed my order for the KPA3A 100 watt upgrade
module at the end of June 2021, but it was the
end of July.  I estimated 12 weeks from end of June,
and that is the source of the mistaken October 1st
date (the "shipping no earlier than" date).

I wrote to Elecraft and received a nice response
from Madelyn Gomez, which I won't reproduce
verbatim here.  I was told that long lead time
components are the source of extended delays
in filling orders for the K3/K3s "last call."  It
may be 4-6 months before those boards/modules
are received in-house at Elecraft.  I was told
that product-specific estimated availability dates
will be posted within the next several weeks.

Sorry for creating any false panic - looks like
we have plenty of time to work on other
projects before some of those upgrades arrive!

73,
Mike, K8CN
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[Elecraft] [K3} [K3s] Final round of module orders?

[Michael Carter]

Just curious if anyone who participated in
the "last call" for K3/K3s modules/upgrades
last summer has received the ordered
modules or even just an email of impending
shipment?

I checked the Shipping Status page
at Elecraft's web page and saw that
all of the available modules/upgrades
are listed as "Availability TBD."  At
one time there was an indication that
nothing would be available until after
1 October 2021, but I've not seen any
further status updates.

Mike, K8CN
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Re: [Elecraft] K2 K2 QSK?

[Michael Carter]

Jerry,

There has been a LOT of discussion on the K4
groups.io forum about the QSK performance
of the K4.  If not subscribed to that forum,
it's worth doing so if only to follow the chatter
about the K4's features and reported bugs.

Follow Don's advice, especially on any matter
involving the K2!

73,
Mike, K8CN
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[Elecraft] P3 Acting Wonky

[Michael Carter]

Jim,

At the risk of asking the obvious question, did you remember to
connect the coaxial cable from the K3 IF output to the P3 input?
The other data functions are handled by the RS-232 cabling,
but without RF there's nothing to display.

Mike, K8CN
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Re: [Elecraft] K4: "R" in display

[Michael Carter]

This question arose on the K4 groups.io list
recently.  The "R" is actually a "D" superposed
over "R" - the white portion is the "D" and
the entire character is the "R."  The indicator
shows that Dynamic Range optimization is ON.

Mike, K8CN
(hoping that Santa Claus may inadvertently
drop a K4D down my chimney this Christmas!)
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