Elecraft

RE: Power too high in PSK31 / S

Classic

List

Threaded

14 messages Options

Richard Ferch

RE: Power too high in PSK31 / S

Well, I'll be doggoned!

Thanks, Joe - I seem to recall reading that somewhere, but I hadn't really
taken it in, and I was still using the procedure that worked with my
previous radio.

If I set the K3's requested power to 100 watts, then with 0 bars ALC I get
IMD well below -30 dB, but with even 1 bar it rises to -26 dB, and gets
worse with more bars. At the same time, the average transmitted power rises
above 50 watts - clearly the peaks are getting into compression.

However, if I set the requested power to 50 watts, I can push the ALC right
up to 4 or 5 bars while the average transmitted power stays at 50 watts on a
two-tone signal and the IMD stays below -30 dB. That's a safer and easier
way to operate.

So now to remember: in modes like CW and RTTY set the requested power to
100w, but in PSK and other similar modes cut it back to 50w. I can probably
figure out a way for my digital-mode software to remember this for me and do
it by software control.

Actually, I think I'll set it to some other number, such as 40w, to lessen
the risk of inadvertently recalibrating TX gain by hitting the TUNE button.

Thanks again, Joe.

73,
Rich VE3KI / VE3IAY
K3 #1595

> > So, no bars equals more noise and IMD or even one bar causes
> > more IMD?
>
> My information comes directly from Lyle - I don't remember if
> it was on the reflector or in a direct e-mail during testing
> of some beta ALC code.
>
> > FWIW, I leave my K3's power control set at 100 watts, but I
> > adjust the mic gain control to a setting which ensures I get
> > zero ALC reading (even one bar causes a noticeable increase
> > in IMD as measured on a PSKmeter)."
>
> Setting the power out to 100 watts in PSK will guarantee that
> the final is being driven into compression on peaks if you see
> ALC (enough drive to reach 100 watts).
>
> I measure no difference in IMD with no ALC (just below the
> point at which the first bar shows) vs. five solid bars if
> the power level is kept below about 60 watts. Put another
> way, if the peak (CW equivalent) power level is kept below
> about 60 watts to prevent compression (and the onset of IMD
> generation) in the K3's finals, there is no difference with
> ALC just below the level of the first bar and five solid bars.
> If the mic/line gain is open just enough to get power output
> the PSK has more noise, has about 1 dB more IMD, and power
> output is less stable than with five bars of ALC.
>
> What Rich's procedure does accomplish is assure that the power
> output does not exceed the 50/60 watt level.

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Don Wilhelm-4

Re: Power too high in PSK31 / S

Richard and all,

If you look back to Lyle Johnson's reflector posting of April 6, you
will find the following: (plus other good information about setting up
data modes.

"In this case, the ALC meter display is acting as a "VU Meter" and is
being used to help you set the Tx audio path gain correctly. It is not
showing you how much you are over-driving the PA. This is why you can
set it up in Tx test mode, when you are not transmitting any RF at all. "

Additional information can be found in Rev D of the K3 user's manual on
page 32.

73,
Don W3FPR

Richard Ferch wrote:

> Well, I'll be doggoned!
>
> Thanks, Joe - I seem to recall reading that somewhere, but I hadn't really
> taken it in, and I was still using the procedure that worked with my
> previous radio.
>
> If I set the K3's requested power to 100 watts, then with 0 bars ALC I get
> IMD well below -30 dB, but with even 1 bar it rises to -26 dB, and gets
> worse with more bars. At the same time, the average transmitted power rises
> above 50 watts - clearly the peaks are getting into compression.
>
> However, if I set the requested power to 50 watts, I can push the ALC right
> up to 4 or 5 bars while the average transmitted power stays at 50 watts on a
> two-tone signal and the IMD stays below -30 dB. That's a safer and easier
> way to operate.
>
> So now to remember: in modes like CW and RTTY set the requested power to
> 100w, but in PSK and other similar modes cut it back to 50w. I can probably
> figure out a way for my digital-mode software to remember this for me and do
> it by software control.
>
> Actually, I think I'll set it to some other number, such as 40w, to lessen
> the risk of inadvertently recalibrating TX gain by hitting the TUNE button.
>
> Thanks again, Joe.
>
> 73,
> Rich VE3KI / VE3IAY
> K3 #1595
>
>
>

Simon (HB9DRV)

Re: Power too high in PSK31 / S

So when I'm in DATA mode how do I ensure that I am not using any ALC?

A good data mode operator monitors ALC all the time as using ALC can often
result in a wide signal.

Simon Brown, HB9DRV
www.ham-radio-deluxe.com

----- Original Message -----
From: "Don Wilhelm" <[hidden email]>
>
> "In this case, the ALC meter display is acting as a "VU Meter" and is
> being used to help you set the Tx audio path gain correctly. It is not
> showing you how much you are over-driving the PA. This is why you can set
> it up in Tx test mode, when you are not transmitting any RF at all. "
>
> Additional information can be found in Rev D of the K3 user's manual on
> page 32.
>
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Julian, G4ILO

Re: Power too high in PSK31 / S

Simon (HB9DRV) wrote

So when I'm in DATA mode how do I ensure that I am not using any ALC?

A good data mode operator monitors ALC all the time as using ALC can often
result in a wide signal.

I think the K3 firmware is supposed to be clever enough not to use ALC if you set it up as directed. So you don't need to worry about it. To be honest there are so many other ways to screw up a data mode signal - overdriving the mic input, RF feedback etc. - that anyone who thinks their signal is clean just because no ALC is showing is relying on luck to a certain extent. Everyone should use an IMD meter or something like it.

Julian, G4ILO. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

Julian, G4ILO

RE: Power too high in PSK31 / S

In reply to this post by Richard Ferch

Richard Ferch wrote

Well, I'll be doggoned!

Thanks, Joe - I seem to recall reading that somewhere, but I hadn't really
taken it in, and I was still using the procedure that worked with my
previous radio.

If I set the K3's requested power to 100 watts, then with 0 bars ALC I get
IMD well below -30 dB, but with even 1 bar it rises to -26 dB, and gets
worse with more bars. At the same time, the average transmitted power rises
above 50 watts - clearly the peaks are getting into compression.

However, if I set the requested power to 50 watts, I can push the ALC right
up to 4 or 5 bars while the average transmitted power stays at 50 watts on a
two-tone signal and the IMD stays below -30 dB. That's a safer and easier
way to operate.

So now to remember: in modes like CW and RTTY set the requested power to
100w, but in PSK and other similar modes cut it back to 50w. I can probably
figure out a way for my digital-mode software to remember this for me and do
it by software control.

Actually, I think I'll set it to some other number, such as 40w, to lessen
the risk of inadvertently recalibrating TX gain by hitting the TUNE button.

Thanks again, Joe.

I operated for years with a QRP K2 and used 5W on PSK31 and there were surprisingly few contacts that I couldn't make it. Now I have the K3/100 but it simply never occurred to me to wind the power up to 100W. I don't see the point in getting the PA so hot so quickly. I never set it to more than 40W, and at 25W it runs noticeably cooler and doesn't seem to make much difference to the signal report.

Julian, G4ILO. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

Simon (HB9DRV)

Re: Power too high in PSK31 / S

In reply to this post by Julian, G4ILO

What would you do with modes other than PSK?

Simon Brown, HB9DRV
www.ham-radio-deluxe.com

----- Original Message -----
From: "Julian, G4ILO" <[hidden email]>

>
> I think the K3 firmware is supposed to be clever enough not to use ALC if
> you set it up as directed. So you don't need to worry about it. To be
> honest
> there are so many other ways to screw up a data mode signal - overdriving
> the mic input, RF feedback etc. - that anyone who thinks their signal is
> clean just because no ALC is showing is relying on luck to a certain
> extent.
> Everyone should use an IMD meter or something like it.
>

Joe Planisky

Re: Power too high in PSK31 / S

In reply to this post by Don Wilhelm-4

Now I don't know what to believe. In Lyle's April 6 post, he says:

> We recommend setting the Mic (or LINE IN) Gain so you get 5 bars of
> ALC,
> with possibly the 6th bar occasionally flickering...

Yet, on the "K3 Operating Tips" page of the Elecraft web site, in the
section about "Setting up your K3 for PSK" it says:

> Use the MIC control to set the drive level so that your output is
> equal or just below what you dialed in ... You should not see any
> ALC bars on the K3 display (when set to CMP/ALC).

Rev D1 of the operating manual seems to agree with Lyle in that it says:

> You can use the same procedure outlined for voice modes (pg. 28)
> except that speech compression should not be used. [Pg. 28]: adjust
> MIC for a peak ALC meter indication of about 5-7 bars.

If the operating tip on the web site is wrong, it ought to be
corrected or removed.

73
--
Joe KB8AP

On Oct 4, 2008, at 1:54 PM, Don Wilhelm wrote:

> Richard and all,
>
> If you look back to Lyle Johnson's reflector posting of April 6, you
> will find the following: (plus other good information about setting
> up data modes.
>
> "In this case, the ALC meter display is acting as a "VU Meter" and
> is being used to help you set the Tx audio path gain correctly. It
> is not showing you how much you are over-driving the PA. This is
> why you can set it up in Tx test mode, when you are not transmitting
> any RF at all. "
>
> Additional information can be found in Rev D of the K3 user's manual
> on page 32.
>
> 73,
> Don W3FPR
>
>>

Don Wilhelm-4

Re: Power too high in PSK31 / S

In reply to this post by Simon (HB9DRV)

Simon,

My guess is that you are driving too hard if the ALC bars indicate more
than 5 or 6 bars on a regular basis.
Since Lyle is the designer of those parts, I would tend to believe what
he is saying.

73,
Don W3FPR

Simon (HB9DRV) wrote:

> So when I'm in DATA mode how do I ensure that I am not using any ALC?
>
> A good data mode operator monitors ALC all the time as using ALC can
> often result in a wide signal.
>
> Simon Brown, HB9DRV
> www.ham-radio-deluxe.com
>
> ----- Original Message ----- From: "Don Wilhelm" <[hidden email]>
>>
>> "In this case, the ALC meter display is acting as a "VU Meter" and is
>> being used to help you set the Tx audio path gain correctly. It is
>> not showing you how much you are over-driving the PA. This is why
>> you can set it up in Tx test mode, when you are not transmitting any
>> RF at all. "
>>
>> Additional information can be found in Rev D of the K3 user's manual
>> on page 32.
>>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - http://www.avg.com
> Version: 8.0.173 / Virus Database: 270.7.5/1706 - Release Date: 10/3/2008 6:17 PM
>
>

Don Wilhelm-4

Re: Power too high in PSK31 / S

In reply to this post by Joe Planisky

Joe,

There have been a few changes over the course of this part of the
firmware development. I do not know the date of that particular PSK
Operating Tip on the Elecraft website.
I would tend to believe the latest information from Lyle since he is
designing that part, but Wayne's answers should be definitive too. If
he is reading the reflector this weekend, we may get a good answer from him.
In general, the Rev D manual contains up-to-date information.

73,
Don W3FPR

Joe Planisky wrote:

> Now I don't know what to believe. In Lyle's April 6 post, he says:
>
>> We recommend setting the Mic (or LINE IN) Gain so you get 5 bars of ALC,
>> with possibly the 6th bar occasionally flickering...
>
> Yet, on the "K3 Operating Tips" page of the Elecraft web site, in the
> section about "Setting up your K3 for PSK" it says:
>
>> Use the MIC control to set the drive level so that your output is
>> equal or just below what you dialed in ... You should not see any ALC
>> bars on the K3 display (when set to CMP/ALC).
>
> Rev D1 of the operating manual seems to agree with Lyle in that it says:
>
>> You can use the same procedure outlined for voice modes (pg. 28)
>> except that speech compression should not be used. [Pg. 28]: adjust
>> MIC for a peak ALC meter indication of about 5-7 bars.
>
> If the operating tip on the web site is wrong, it ought to be
> corrected or removed.
>
> 73
> --
> Joe KB8AP
>
>
> On Oct 4, 2008, at 1:54 PM, Don Wilhelm wrote:
>
>> Richard and all,
>>
>> If you look back to Lyle Johnson's reflector posting of April 6, you
>> will find the following: (plus other good information about setting
>> up data modes.
>>
>> "In this case, the ALC meter display is acting as a "VU Meter" and is
>> being used to help you set the Tx audio path gain correctly. It is
>> not showing you how much you are over-driving the PA. This is why
>> you can set it up in Tx test mode, when you are not transmitting any
>> RF at all. "
>>
>> Additional information can be found in Rev D of the K3 user's manual
>> on page 32.
>>
>> 73,
>> Don W3FPR
>>
>>>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG - http://www.avg.com
> Version: 8.0.173 / Virus Database: 270.7.5/1706 - Release Date: 10/3/2008 6:17 PM
>
>

Greg - AB7R

Re: Power too high in PSK31 / S

In reply to this post by Joe Planisky

Joe,

I have to change the operating tips page. It was done prior to a major ALC
change. I was waiting for another update as Lyle is changing the ALC meter
feedback. It will change to 1-bar as the desired setting. For now, you can
adjust it for 4 bars. If you cannot get 4 bars 3 is still OK.

73
Greg

----- Original Message -----
From: "Joe Planisky" <[hidden email]>
To: <[hidden email]>
Cc: "Elecraft Reflector" <[hidden email]>
Sent: Saturday, October 04, 2008 4:15 PM
Subject: Re: [Elecraft] Power too high in PSK31 / S

> Now I don't know what to believe. In Lyle's April 6 post, he says:
>
>> We recommend setting the Mic (or LINE IN) Gain so you get 5 bars of
>> ALC,
>> with possibly the 6th bar occasionally flickering...
>
> Yet, on the "K3 Operating Tips" page of the Elecraft web site, in the
> section about "Setting up your K3 for PSK" it says:
>
>> Use the MIC control to set the drive level so that your output is
>> equal or just below what you dialed in ... You should not see any
>> ALC bars on the K3 display (when set to CMP/ALC).
>
> Rev D1 of the operating manual seems to agree with Lyle in that it says:
>
>> You can use the same procedure outlined for voice modes (pg. 28)
>> except that speech compression should not be used. [Pg. 28]: adjust
>> MIC for a peak ALC meter indication of about 5-7 bars.
>
> If the operating tip on the web site is wrong, it ought to be
> corrected or removed.
>
> 73
> --
> Joe KB8AP
>
>
> On Oct 4, 2008, at 1:54 PM, Don Wilhelm wrote:
>
>> Richard and all,
>>
>> If you look back to Lyle Johnson's reflector posting of April 6, you
>> will find the following: (plus other good information about setting
>> up data modes.
>>
>> "In this case, the ALC meter display is acting as a "VU Meter" and
>> is being used to help you set the Tx audio path gain correctly. It
>> is not showing you how much you are over-driving the PA. This is
>> why you can set it up in Tx test mode, when you are not transmitting
>> any RF at all. "
>>
>> Additional information can be found in Rev D of the K3 user's manual
>> on page 32.
>>
>> 73,
>> Don W3FPR
>>
>>>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

--------------------------------------------------------------------------------

No virus found in this incoming message.
Checked by AVG - http://www.avg.com
Version: 8.0.173 / Virus Database: 270.7.5/1708 - Release Date: 10/4/2008
11:35 AM

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Joe Subich, W4TV-3

RE: Power too high in PSK31 / S

Greg,

> It will change to 1-bar as the desired setting. For now, you
> can adjust it for 4 bars. If you cannot get 4 bars 3 is still
> OK.

If Lyle specifically said, "We recommend setting the Mic (or
LINE IN) Gain so you get 5 bars of ALC, with possibly the 6th
bar occasionally flickering..." why would you recommend 1 bar?

With the current firmware, power output and "ALC" is very stable
at five bars. If the Line In level is significantly below the
five bar level, I see significant "hunting" or motorboating of
the ALC and some variability (above and beyond the content
related variation inherent in PSK31) of the output power.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Greg
> Sent: Saturday, October 04, 2008 7:41 PM
> To: [hidden email]; [hidden email]
> Cc: Elecraft Reflector
> Subject: Re: [Elecraft] Power too high in PSK31 / S
>
>
> Joe,
>
> I have to change the operating tips page. It was done prior
> to a major ALC
> change. I was waiting for another update as Lyle is changing
> the ALC meter
> feedback. It will change to 1-bar as the desired setting.
> For now, you can
> adjust it for 4 bars. If you cannot get 4 bars 3 is still OK.
>
> 73
> Greg
>
>
>
> ----- Original Message -----
> From: "Joe Planisky" <[hidden email]>
> To: <[hidden email]>
> Cc: "Elecraft Reflector" <[hidden email]>
> Sent: Saturday, October 04, 2008 4:15 PM
> Subject: Re: [Elecraft] Power too high in PSK31 / S
>
>
> > Now I don't know what to believe. In Lyle's April 6 post, he says:
> >
> >> We recommend setting the Mic (or LINE IN) Gain so you get
> 5 bars of
> >> ALC, with possibly the 6th bar occasionally flickering...
> >
> > Yet, on the "K3 Operating Tips" page of the Elecraft web
> site, in the
> > section about "Setting up your K3 for PSK" it says:
> >
> >> Use the MIC control to set the drive level so that your output is
> >> equal or just below what you dialed in ... You should not
> see any ALC
> >> bars on the K3 display (when set to CMP/ALC).
> >
> > Rev D1 of the operating manual seems to agree with Lyle in that it
> > says:
> >
> >> You can use the same procedure outlined for voice modes (pg. 28)
> >> except that speech compression should not be used. [Pg.
> 28]: adjust
> >> MIC for a peak ALC meter indication of about 5-7 bars.
> >
> > If the operating tip on the web site is wrong, it ought to be
> > corrected or removed.
> >
> > 73
> > --
> > Joe KB8AP
> >
> >
> > On Oct 4, 2008, at 1:54 PM, Don Wilhelm wrote:
> >
> >> Richard and all,
> >>
> >> If you look back to Lyle Johnson's reflector posting of
> April 6, you
> >> will find the following: (plus other good information
> about setting
> >> up data modes.
> >>
> >> "In this case, the ALC meter display is acting as a "VU
> Meter" and is
> >> being used to help you set the Tx audio path gain
> correctly. It is
> >> not showing you how much you are over-driving the PA. This is why
> >> you can set it up in Tx test mode, when you are not
> transmitting any
> >> RF at all. "
> >>
> >> Additional information can be found in Rev D of the K3
> user's manual
> >> on page 32.
> >>
> >> 73,
> >> Don W3FPR
> >>
> >>>

KK7P

Re: Power too high in PSK31 / S

The "change to 1 bar" is something we discussed, but decided to not do it.
Adjust for 4 or 5 bars. If you see the "hunting" then either decrease MIC
gain until it goes away (probably at 2 or 3 bars) , or increase it slightly
until it goes away (probably at 5 bars). Increasing will activate the ALC a
bit (its threshold is 5 bars) and you may see it in slightly degraded IMD.
Decreasing will not degrade IMD but may slightly affect affect power control
accuracy.

I'm digging into the hunting among other tasks.

73,

Lyle KK7P/7
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Mario Lorenz

Re: Power too high in PSK31 / S

In reply to this post by Simon (HB9DRV)

Am 04. Oct 2008, um 23:59:38 schrieb Simon (HB9DRV):
> What would you do with modes other than PSK?

Easy: You want a good, linear signal path. That involves
mainly setting the various levels. Once this is accomplished
for the mode where it is measured easily (ie., PSK, with the
imdmeter), that setup should be good for RTTY or any other
data mode too, no?

Mario

--
Mario Lorenz Internet: <[hidden email]>
Ham Radio: DL5MLO@DB0ERF.#THR.DEU.EU
* Newsflash: Microsoft announces Visual Edlin for Windows98!
_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com

Jim Brown-10

RE: Power too high in PSK31 / S

In reply to this post by Richard Ferch

On Sat, 4 Oct 2008 16:20:33 -0400, Richard Ferch wrote:

>If I set the K3's requested power to 100 watts, then with 0 bars ALC I get
>IMD well below -30 dB, but with even 1 bar it rises to -26 dB,

ALSO -- don't ignore the setting of the computer sound card when using
computer-generated PSK or AFSK. Tests on sound cards in my IBM Thinkpads show
that the percent distortion drops by 10 dB if I run the sound card level 6 dB
below clip rather than only a dB or so below clip. Obviously, all sound cards
are not created equal, so check your own sound card.

The "details" of what I'm suggesting here is nothing more than turning down
the sound card a bit and turning up the Line In gain of the K3 to get the
needed level to drive the K3.

73,

Jim Brown K9YC

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com