K3 Beta firmware rev. 2.80: Improvements to AFSK-A, DATA-A, SSB, AM, FM, DVR

[Richard Ferch]

It seems as if part of the problem with the power control in DATA A mode may
be that the power calibration appears to be done at an audio frequency which
is sub-optimal for this mode. Ideally, the power calibration would be done
at the point in the filter bandpass where the transmit filter's attenuation
is least. If this were the case, the delivered power would be equal to the
requested power at the optimal frequency, and equal or less at other points
in the filter bandpass. Delivered powers exceeding the requested power would
not happen. Lower output powers would be possible, especially towards the
edges of the bandpass, but this is normal and happens with every radio, not
just the K3.

Performing power calibration at the transmit filter's optimal frequency
might be sub-optimal for CW, though, because of the way the filter bandpass
is adjusted during CW. If this is the case, perhaps there should be separate
power calibrations for CW and for data modes.

As it happens, there is another anomaly in DATA A which has some
similarities to the above, although this may be coincidental. The SPOT
button in other digital modes produces an audio tone at an optimal frequency
(the selected mark tone in AFSK A and FSK D and the transmitted tone in PSK
D), but in DATA A the SPOT button produces a tone at the CW sidetone pitch.
The CW sidetone has nothing to do with DATA A mode, and it is far from the
optimal point in the filter bandpass in DATA A. Just as it would be better
to do power calibration at an optimal audio frequency, it would be better if
the SPOT button produced an optimal tone. Good candidates for an optimal
tone in DATA A would be either the current filter Fc or the default ("NORM")
Fc for DATA A (1500 Hz).

73,
Rich VE3KI
K3 #1595

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[Guy, K2AV]

Taking the DATA A readings below at face value, the more than 2 db bump
around 1000 Hz is rather startling. I'm not sure what could cause that, but
at least to me that seems to be screaming for an explanation.  There's an
old fireman's adage "never go past fire" to keep from being trapped by fire
closing around behind.

Is there any point at discussing any more subtle issues until we know why
there's a 2 db bump in the middle of an expected flat DATA A bandpass?
Everything from test equipment to meters would be in play until ruled out.

73, Guy.

----- Original Message -----
From: "Joe Planisky" <[hidden email]>
To: <[hidden email]>
Cc: "elecraft list" <[hidden email]>
Sent: Saturday, February 14, 2009 7:45 PM
Subject: Re: [Elecraft] K3 Beta firmware rev. 2.82

> Hi Joe,
>
>> Further, single tone power calibration is only accurate for
>> the specific frequency within the IF filter on which the
>> calibration is performed.  If I calibrate power in CW mode
>> that calibration point is approximately 300 Hz from one
>> "corner" of the 2.8 KHz filter thanks to the way the K3
>> offsets the filters.
>
> If I understand you correctly, you're essentially saying that in DATA-
> A (where, according to Elecraft, ALC action is intentionally minimized
> to minimize distortion), we're seeing more of the true shape of the
> filter passband.  Whereas in a voice mode (USB or LSB, where ALC
> action is more pronounced,) the ALC action will tend to make the
> filter passband appear flat if the input is a single tone.
>
> To test this, I used an audio signal generator to input single tones
> of various frequencies into my K3 in both LSB and DATA-A modes.  I set
> the power control for 30W.  Here are my measurements:
>
> AF input freq. Po-DATA-A    Po-LSB
> TUNE            25.7         25.2
>  200             4.6          6.1
>  400            27.0         24.8
>  600            34.5         24.8
>  800            45.6         24.8
> 1000            53.1         24.8
> 1200            47.5         24.8
> 1400            37.8         24.8
> 1600            32.3         24.8
> 1800            30.9         24.8
> 2000            31.9         24.8
> 2200            34.3         24.8
> 2400            37.9         24.8
> 2600            34.9         24.8
> 2800            13.9         24.8
> 3000             nil          nil
>
> So, neglecting the ~25 W vs 30 W error, it's clear that something is
> keeping a tight rein on things in LSB, but is not doing so in DATA-A.
> Presumably, this is the ALC action, which we are told is minimized in
> DATA-A mode.  The data also seem to corroborate your statement that
> the calibration point is 300 Hz from the filter corner.
>
> If I'm really wrong about something, please correct me.  If I'm NOT
> wrong, I think I might finally understand why power output in DATA-A
> doesn't seem to track the requested power closely.
>
> 73
> --
> Joe KB8AP
>
> On Feb 14, 2009, at 11:36 AM, Joe Subich, W4TV wrote:
>
>>
>> You CAN NOT make those tests at 50 Watts!  The power calibration
>> circuitry will be constantly changing the internal gain.  If
>> the ATU is enabled and/or your dummy load is not flat the changes
>> invalidate the measurements.
>>
>> Further, single tone power calibration is only accurate for
>> the specific frequency within the IF filter on which the
>> calibration is performed.  If I calibrate power in CW mode
>> that calibration point is approximately 300 Hz from one
>> "corner" of the 2.8 KHz filter thanks to the way the K3
>> offsets the filters.  When I switch to DATA A, and try to
>> test the power level with a 1500 Hz tone, I can see 2 dB more
>> power simply because my 2.8 KHz filter has a 4 dB slope across
>> the passband and the K3 gain calculation includes compensation
>> for the loss at the calibration frequency.  If I check the
>> power with a 1 KHz tone, the difference may be 3 dB (DATA A
>> is USB, CW calibration is LSB so the slope changes direction
>> with tone).  If I switch to AFSK A (REV to stay with USB)
>> and check power with a 2295 Hz (USB Mark) tone, the difference
>> may be down to one dB or so.
>>
>> There are too many uncompensated variables to expect the K3
>> to maintain absolute control over the power output with
>> changing antennas, power levels, modes, (relative) frequency
>> within the IF passband and possibly even different filters.
>> ALC controls the audio level into, and the RF level out of
>> the DSP (modulator) process - it is an ALC (automatic LEVEL
>> control) NOT an APC (automatic POWER control).
>>
>> The ALC is an open loop system - the loop gain is calibrated
>> once at the 5 watt level and once at the 50 watt level for
>> one specific frequency in the IF passband.  Once that is
>> done, ALC simply controls the DSP gain.  If you change the
>> system gain following the DSP, the output power level WILL
>> CHANGE.  I'm sure it would be theoretically possible to
>> calibrate the system gain from 100 Hz to 2900 Hz offsets
>> from the carrier (for both the USB and LSB cases) and apply
>> that mask to the modulation process but does the DSP system
>> have enough horsepower to do so and is it worthwhile simply
>> so the operator can avoid the need to check his power level
>> when changing mode or modulating frequency?
>>
>> 73,
>>
>>   ... Joe, W4TV
>>
>
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[Julian, G4ILO]

Richard Ferch wrote

It seems as if part of the problem with the power control in DATA A mode may
be that the power calibration appears to be done at an audio frequency which
is sub-optimal for this mode. Ideally, the power calibration would be done
at the point in the filter bandpass where the transmit filter's attenuation
is least.

I agree, this would be an improvement.

As it happens, there is another anomaly in DATA A which has some
similarities to the above, although this may be coincidental. The SPOT
button in other digital modes produces an audio tone at an optimal frequency
(the selected mark tone in AFSK A and FSK D and the transmitted tone in PSK
D), but in DATA A the SPOT button produces a tone at the CW sidetone pitch.
The CW sidetone has nothing to do with DATA A mode, and it is far from the
optimal point in the filter bandpass in DATA A. Just as it would be better
to do power calibration at an optimal audio frequency, it would be better if
the SPOT button produced an optimal tone. Good candidates for an optimal
tone in DATA A would be either the current filter Fc or the default ("NORM")
Fc for DATA A (1500 Hz).

I suspect this might actually be a bug. The trouble with DATA A is that the K3 doesn't know what center frequency the user is using (though it could possibly guess from the filter SHIFT setting.) Personally I prefer 1KHz because I like to hear what is going on and I find higher pitched tones irritating.

[Julian, G4ILO]

Guy, K2AV wrote

Taking the DATA A readings below at face value, the more than 2 db bump
around 1000 Hz is rather startling. I'm not sure what could cause that, but
at least to me that seems to be screaming for an explanation.  There's an
old fireman's adage "never go past fire" to keep from being trapped by fire
closing around behind.

Is there any point at discussing any more subtle issues until we know why
there's a 2 db bump in the middle of an expected flat DATA A bandpass?
Everything from test equipment to meters would be in play until ruled out.

I'm glad you asked that because I've been thinking about the same question. I have the 5-pole 2.7KHz filter and I observed the same peaks at 1000Hz and 2400Hz as Joe, who made those measurements. I guess he has the 5-pole filter too. It would be extremely interesting if someone with an 8-pole filter could run the same test and post the results to see whether there is less variation across the passband.

I would not be overjoyed to have to splash $125 to solve the problem, but it might be better than the alternatives.

[Kok Chen]

On Feb 15, 2009, at 2/15    8:58 AM, Guy Olinger, K2AV wrote:

> Taking the DATA A readings below at face value, the more than 2 db  
> bump
> around 1000 Hz is rather startling. I'm not sure what could cause  
> that, but
> at least to me that seems to be screaming for an explanation.  
> There's an
> old fireman's adage "never go past fire" to keep from being trapped  
> by fire
> closing around behind.

While I agree that a 2 dB bump is really, really bad for us guys who  
use frequency-agile digital transmission, this phenomenon is not  
restricted to just the K3.

The FT-1000MP has a similar 3 dB peak when you select PKT (i.e.,  
AFSK); and, like the K3, the rig is flat when using voice SSB  
modes.   In the case of the FT-1000MP, it appears to be a  
deliberately designed peaking -- the peak is "centered" near the AFSK  
tone pair that you have selected to use.

To see the FT-1000MP's variability, you can look at the following URL

http://homepage.mac.com/chen/w7ay/cocoaModem/UsersManual/ 
UsersManual.html#equalizer

Scroll below the two control panels and you will see the graphical  
display of the variability.  (In this program, you enter the measured  
power in that second column on the left, and the program splines the  
"curve" to produce the power correction that is applied to the  
transmitted signal when you "click on the waterfall.")

73
Chen, W7AY

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[Bob Cunnings NW8L]

I'm not looking for another radio, as I've been doing what seems
obvious (to me) - using USB mode for sound card digital operation, not
DATA A. Yes, I forgo the benefit of the management of compression
setting and mic selection that comes with using DATA A - but as things
stand now one must change TX EQ manually when switching back and forth
between SSB and data modes anyway, right? The compromise would be
greater if TX EQ settings become available on a per mode basis. Yes,
as you state the difference in quality of signal doesn't seem to be
significant, my PSK31 signal is uniformly reported as good when in USB
mode, just as in DATA A. I set input level for 4-5 bars ALC.

Yes, DATA A is a work in progress. Prior to firmware version 2.23 DATA
A power control seemed much like that of LSB/USB, but after that
version (which introduced the "LSB/USB TRANSMIT EQUALIZATION" change)
the behavior of DATA A and LSB/USB diverged. I've observed the DATA A
changes that have taken place since, and corresponded with K3 support
on this topic a couple of times as the firmware evolved. However, at
the moment I simply run with current firmware and use USB for data
modes. Yes, I have an external peak reading watt meter in line at all
times so I could use DATA A and tweak the power setting as I move
around in the waterfall, but it's convenient to be able to set (and
confirm) power once and forget it, as I can in CW.

Bob NW8L

On Sun, Feb 15, 2009 at 4:14 AM, Julian, G4ILO <[hidden email]> wrote:
<snip>
> If the majority of other data mode users are happy with the K3 the way it is
> and Elecraft can't or won't change it, then it's probably time for me to
> look for another radio.
</snip>
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[Joe Subich, W4TV-4]

> So, neglecting the ~25 W vs 30 W error, it's clear that
> something is keeping a tight rein on things in LSB, but
> is not doing so in DATA-A.  
> Presumably, this is the ALC action, which we are told is
> minimized in DATA-A mode.  

It looks like the ALC uses the wattmeter as an input in
SSB but not in data mode.  I tried the same set of tests
and found that the SSB power would increase (or decrease)
over the course of 10 seconds or so to bring the power to
the set point.  That same effect was not present in DATA.

This would explain the differences between SSB and DATA
and would - depending on the time constants in the ALC
circuit - explain some of the IMD effects in SSB (and the
recommendation against the use of amplifier ALC).  

Here are my power measurements in DATA and DATA-R modes.
I have the 8-pole filters in both of my K3s but I have
not checked the other one to see if there s any difference
in "flatness" ...

Set:      60   W
Measured: 58.2 W (Tune)

           NOR  (USB)     REV  (LSB)
-----------------------------------
 200       0.3 (-22.9)    0.1 (-27.6)
 400      22.0  (-4.2)   15.2  (-5.8)
 600      46.4  (-1.0)   39.2  (-1.7)
 800      55.8  (-0.2)   50.5  (-0.6)
1000      57.0  (-0.1)   55.8  (-0.2)
1200      45.9  (-1.0)   49.0  (-0.7)
1400      43.8  (-1.2)   46.5  (-1.0)
1600      52.9  (-0.4)   50.8  (-0.6)
1800      64.5  ( 1.1)   61.5  ( 0.2)
2000      69.0  ( 1.2)   72.0  ( 0.9)
2200      59.0  ( 0.6)   68.2  ( 0.7)
2400      50.0  (-0.7)   63.0  ( 0.3)
2600      48.5  (-0.8)   64.9  ( 0.5)
2800      15.4  (-5.8)   26.5  (-3.4)
3000       0.0            0.0

A sweep of the filter using K3FilterTools in the receive
mode shows very close correlation with the USB power
measurements including the broad peak at 1800-2000 Hz,
the roughly 7 dB decline from peak to 2800 Hz and the
2 dB slope between 500 and 2000 Hz.  The greater than
expected roll off below 600 Hz is apparently due to the
audio input response.

> -----Original Message-----
> From: Joe Planisky [mailto:[hidden email]]
> Sent: Saturday, February 14, 2009 7:46 PM
> To: [hidden email]
> Cc: elecraft list
> Subject: Re: [Elecraft] K3 Beta firmware rev. 2.82
>
>
> Hi Joe,
>
> > Further, single tone power calibration is only accurate for the
> > specific frequency within the IF filter on which the calibration is
> > performed.  If I calibrate power in CW mode that
> calibration point is
> > approximately 300 Hz from one "corner" of the 2.8 KHz
> filter thanks to
> > the way the K3 offsets the filters.
>
> If I understand you correctly, you're essentially saying that
> in DATA-
> A (where, according to Elecraft, ALC action is intentionally
> minimized  
> to minimize distortion), we're seeing more of the true shape of the  
> filter passband.  Whereas in a voice mode (USB or LSB, where ALC  
> action is more pronounced,) the ALC action will tend to make the  
> filter passband appear flat if the input is a single tone.
>
> To test this, I used an audio signal generator to input single tones  
> of various frequencies into my K3 in both LSB and DATA-A
> modes.  I set  
> the power control for 30W.  Here are my measurements:
>
> AF input freq. Po-DATA-A    Po-LSB
> TUNE            25.7         25.2
>  200             4.6          6.1
>  400            27.0         24.8
>  600            34.5         24.8
>  800            45.6         24.8
> 1000            53.1         24.8
> 1200            47.5         24.8
> 1400            37.8         24.8
> 1600            32.3         24.8
> 1800            30.9         24.8
> 2000            31.9         24.8
> 2200            34.3         24.8
> 2400            37.9         24.8
> 2600            34.9         24.8
> 2800            13.9         24.8
> 3000             nil          nil
>
> So, neglecting the ~25 W vs 30 W error, it's clear that something is  
> keeping a tight rein on things in LSB, but is not doing so in
> DATA-A.  
> Presumably, this is the ALC action, which we are told is
> minimized in  
> DATA-A mode.  The data also seem to corroborate your statement that  
> the calibration point is 300 Hz from the filter corner.
>
> If I'm really wrong about something, please correct me.  If I'm NOT  
> wrong, I think I might finally understand why power output in DATA-A  
> doesn't seem to track the requested power closely.
>
> 73
> --
> Joe KB8AP
>
> On Feb 14, 2009, at 11:36 AM, Joe Subich, W4TV wrote:
>
> >
> > You CAN NOT make those tests at 50 Watts!  The power calibration
> > circuitry will be constantly changing the internal gain.  
> If the ATU
> > is enabled and/or your dummy load is not flat the changes
> invalidate
> > the measurements.
> >
> > Further, single tone power calibration is only accurate for the
> > specific frequency within the IF filter on which the calibration is
> > performed.  If I calibrate power in CW mode that
> calibration point is
> > approximately 300 Hz from one "corner" of the 2.8 KHz
> filter thanks to
> > the way the K3 offsets the filters.  When I switch to DATA
> A, and try
> > to test the power level with a 1500 Hz tone, I can see 2 dB more
> > power simply because my 2.8 KHz filter has a 4 dB slope across
> > the passband and the K3 gain calculation includes compensation
> > for the loss at the calibration frequency.  If I check the
> > power with a 1 KHz tone, the difference may be 3 dB (DATA A
> > is USB, CW calibration is LSB so the slope changes direction
> > with tone).  If I switch to AFSK A (REV to stay with USB)
> > and check power with a 2295 Hz (USB Mark) tone, the difference
> > may be down to one dB or so.
> >
> > There are too many uncompensated variables to expect the K3 to
> > maintain absolute control over the power output with changing
> > antennas, power levels, modes, (relative) frequency within the IF
> > passband and possibly even different filters. ALC controls
> the audio
> > level into, and the RF level out of the DSP (modulator)
> process - it
> > is an ALC (automatic LEVEL
> > control) NOT an APC (automatic POWER control).
> >
> > The ALC is an open loop system - the loop gain is
> calibrated once at
> > the 5 watt level and once at the 50 watt level for one specific
> > frequency in the IF passband.  Once that is done, ALC
> simply controls
> > the DSP gain.  If you change the system gain following the DSP, the
> > output power level WILL CHANGE.  I'm sure it would be theoretically
> > possible to calibrate the system gain from 100 Hz to 2900 Hz offsets
> > from the carrier (for both the USB and LSB cases) and apply
> > that mask to the modulation process but does the DSP system
> > have enough horsepower to do so and is it worthwhile simply
> > so the operator can avoid the need to check his power level
> > when changing mode or modulating frequency?
> >
> > 73,
> >
> >   ... Joe, W4TV
> >
>

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[Julian, G4ILO]

Bob Cunnings wrote

I'm not looking for another radio, as I've been doing what seems
obvious (to me) - using USB mode for sound card digital operation, not
DATA A. [snip]

Yes, I can see the logic in that, which is what I had to do with the K2 before the v2 firmware was released. But I ordered the K3 mainly because it promised to be a much superior radio than the K2 for data operation, so to resort to such a workaround would seem like a major step backwards.

[G3TCT]

Julian
Before you do anything drastic like looking for another radio, can I ask a
silly question or 2?
If the output power is flat across the AF spectrum when using ssb mode, why
doesn't everyone use it rather than DATA-A?
And since the output power is apparently so poorly controlled in DATA-A,
(with much higher power than called for) doesn't this actually give higher
rather than lower IMD?

Graham
----- Original Message -----
From: "Julian, G4ILO" <[hidden email]>
To: <[hidden email]>
Sent: Sunday, February 15, 2009 11:14 AM
Subject: Re: [Elecraft] K3 Beta firmware rev. 2.82


>
> I have just run a set of tests across a range of audio frequencies as did
> Joe, KB8AP. The results were almost identical, so I am not going to
tabulate
> them here. In SSB I adjusted the input level to give sufficient drive and
> just enough ALC action to result in a flat output from 600Hz to 2600Hz.
>
> At the same time I checked the PSK31 IMD level across the spectrum using
the
> KK7UQ IMD meter. I observed no degradation of IMD resulting from the use
of
> minimum ALC to control the power to a flat level, compared to using DATA A
> mode where there is apparently no ALC feedback at all. Therefore it seems
to
> me that the solution that has apparently been adopted in DATA A mode for
the
> purpose of minimizing IMD is in fact producing no useful benefit at all,
> while at the same time depriving data users of a meaningful power control.
>
> I would much prefer the K3 to work the way other radios work, where you
can
> increase the drive level until the ALC just starts, and then you know that
> you are producing the requested power and no more. This is how I believe
it
> used to work in early versions of the firmware. DATA was just USB with a
> different input source option and compression automatically disabled.
>
> I will concede that the approach adopted by Elecraft is more foolproof in
> regard to avoiding IMD, but this is achieved at the cost of a loss of
> confidence in knowing the output power. However for me it is just too
> unsettling to not know how much power the radio is putting out,
particularly
> as I wish to operate remotely via the network and can't see for myself the
> power output. I have had to give this up for the last few months after I
> found myself transmitting nearly 100W when I was intending to use 40W.
>
> If the majority of other data mode users are happy with the K3 the way it
is
> and Elecraft can't or won't change it, then it's probably time for me to
> look for another radio.
>
> -----
> Julian, G4ILO. K2 #392  K3 #222.
> http://www.g4ilo.com/ G4ILO's Shack   http://www.g4ilo.com/blog.html
G4ILO's
> Blog    http://www.g4ilo.com/kcomm.html KComm for Elecraft K2 and K3
> --
> View this message in context:
http://n2.nabble.com/K3-Beta-firmware-rev.-2.80%3A-Improvements-to-AFSK-A%2C
-DATA-A%2C-SSB%2C-AM%2C-FM%2C-DVR-tp2305650p2329434.html
> Sent from the Elecraft mailing list archive at Nabble.com.
>
>
>

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[Guy, K2AV]

My MP has those bumps also, and it's full of INRAD's.

With only a minor amount of Spectrogram investigation in my K3, I see a 2db
variation across the passband in the 2.7 filter.  It is easily seen on RX,
particularly if one lies about how wide it is to put the DSP out at 4.0
whilst being confined only by the 2.7 roofing filter.  Further the 2.7
filters on my 2 RX K3's have nearly identical response, and the order of the
bumps reverses perfectly when I go from DATA to DATA REV.  Whether that
would be more predictable with a 2.8 8 pole filter would depend.  I don't
own one so cannot comment. (The shape of the two 2.7's are closer than the
shapes on the two 1.8's.)

Therefore, without TX EQ set only for DATA mode, power will vary up and down
depending on the filter when using a fixed segment audio width of the band
and letting the PSK program pick the transmit audio tone.

I note that me ears cannot detect changes in the mid-passband.  What I hear
when shifting RX passband is the drop or addition of lows and highs as the
passband *skirts* move.  This is to enforce that for SSB, the passband
ripple cannot be heard.

The data mode transmit exposes what the ear cannot hear only because
operators apparently look for variability less than half a db.  Given the
characteristics of some amplifier tubes and the sudden onset of grid
saturation and high current, etc, the desire to control power is
understandable.

Given the circumstances, would seem to be an interesting idea to have a data
mode only TX eq that flattens out the filter *and properly flips* for data
rev mode.  It would remain to be seen, though whether introduction of the
equalization does anything negative to transmitted IMD.

Approaching it from the other direction, Wayne & Co seem reluctant to
embrace any automatic leveling of data mode transmitted power. It would seem
on the surface that data is far more predictable than SSB, that a quick
attack, slow release and clamped-across-RX-state auto gain adjustment would
work well. There may be a lot more to it than that, but this too seems a
good idea.

73, Guy.


----- Original Message -----
From: "Kok Chen" <[hidden email]>
To: "elecraft list" <[hidden email]>
Sent: Sunday, February 15, 2009 12:31 PM
Subject: Re: [Elecraft] K3 Beta firmware rev. 2.82

> On Feb 15, 2009, at 2/15    8:58 AM, Guy Olinger, K2AV wrote:
>
>> Taking the DATA A readings below at face value, the more than 2 db
>> bump
>> around 1000 Hz is rather startling. I'm not sure what could cause
>> that, but
>> at least to me that seems to be screaming for an explanation.
>> There's an
>> old fireman's adage "never go past fire" to keep from being trapped
>> by fire
>> closing around behind.
>
> While I agree that a 2 dB bump is really, really bad for us guys who
> use frequency-agile digital transmission, this phenomenon is not
> restricted to just the K3.
>
> The FT-1000MP has a similar 3 dB peak when you select PKT (i.e.,
> AFSK); and, like the K3, the rig is flat when using voice SSB
> modes.   In the case of the FT-1000MP, it appears to be a
> deliberately designed peaking -- the peak is "centered" near the AFSK
> tone pair that you have selected to use.
>
> To see the FT-1000MP's variability, you can look at the following URL
>
> http://homepage.mac.com/chen/w7ay/cocoaModem/UsersManual/
> UsersManual.html#equalizer
>
> Scroll below the two control panels and you will see the graphical
> display of the variability.  (In this program, you enter the measured
> power in that second column on the left, and the program splines the
> "curve" to produce the power correction that is applied to the
> transmitted signal when you "click on the waterfall.")
>
> 73
> Chen, W7AY
>
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[Julian, G4ILO]

Graham Kimbell (G3TCT) wrote

Julian
Before you do anything drastic like looking for another radio, can I ask a
silly question or 2?
If the output power is flat across the AF spectrum when using ssb mode, why
doesn't everyone use it rather than DATA-A?

Well the main reason as I said in my post that I sent about the same time you were writing yours is that it is a hassle changing all the EQ, switching the input from MIC to LINE IN and remembering to turn off the compression. Of course some people may work digi all the time and never use a mic, in which case it would be the most sensible option. But I don't want to go through all that when I hear someone on SSB that I would like to call. Plus, many programs know what mode the K3 is in and won't do data if SSB is selected.

And since the output power is apparently so poorly controlled in DATA-A,
(with much higher power than called for) doesn't this actually give higher
rather than lower IMD?

Yes, although as long as the power is below 100W the IMD should still be within acceptable limits.