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P3 auto REF LVL adjust?

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Mike Markowski-2

P3 auto REF LVL adjust?

Since the PA temp is available as well as the filter bandwidth in use, I
wonder if the P3 could have an auto-adjust of REF LVL? It would only
work within a given band and only after the op has adjusted the REF LVL
to begin with. But after that it seems that the good ol' N = kTB would
be a simple enough calc that P3 REF LVL could be auto-adjusted as SPAN
or filter bw is changed.

I know, talk about being lazy... :-) Happy 2012!

Mike ab3ap
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Mike Markowski-2

Re: P3 auto REF LVL adjust?

Gary VE1RGB is traveling and asked that I forward to the list his note that
was accidentally sent only to me. He describes a table lookup rather than
the noise temp calc in my note. Maybe there are still more ideas?

73,
Mike ab3ap

On Sun, Jan 1, 2012 at 5:10 PM, Gary Bartlett <[hidden email]>wrote:

> Hi, Mike:
>
> As a field tester for the P3, I pestered Elecraft about this very thing
> and I was told that it had made the list of enhancements to do to the P3 at
> some point. I use wire antennas matched by the K3 and verticals which are
> externally tuned and two different listening antennas, and the noise levels
> of those antennas show great variance at any given point in time. As a
> mostly S&P CW contester, I am continually changing antenna selections and
> that means that I have my fingers on the REF LVL controls constantly. I
> was not the only field tester who wanted something a little more
> sophisticated w.r.t. the way REF LVL works.
>
> My idea was that REF LVL would have memories, so to speak, that would
> recall its setting for each combinations of ANT 1/ANT 2 and RX ANT
> selections, Tuner ON/BYPASS settings by band (maybe some other control
> settings too) such that once set up at the start of a contest, I would not
> need to touch REF LVL again except to make minor adjustments in response to
> changes in local noise level and daily propagation changes during a
> contest. It is something of a nuisance as currently configured, and I
> don't see this as laziness on my part :)
>
> Alan N1AL can probably tell us where that sits on the priority list.
>
> 73,
> Gary VE1RGB P3 #007
>
>

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Mike Markowski-2

Example - Re: P3 auto REF LVL adjust?

In reply to this post by Mike Markowski-2

I'll follow up on my own note because there's nothing as helpful as an
example:

1) I move to 17m band with P3 set for +/-100 kHz span
2) P3 REF LVL knob used to set -122 dBm to match noise level at my QTH

3) -122 dBm = 6.30957 x 10^-13 mW
4) Since noise power N = kTB, (k is Boltzman's constant),
T = N / (kB) = 6.30957 x 10^-13 / (k x 200 kHz)
k = 228500 K <--- recalc when REF LVL knob is twiddled again!

Now I want to change P3 span to +/-5 kHz, or B = 10 kHz:

5) N = kTB = (1.380648813 x 10^-23) x 228500 x 10x10^3
= 3.15479 x 10^-14 mW
= -135 dBm <--- new REF LVL setting, send to P3

Easy to add to firmware? If not, it is easy to add to external
software. The only thing not automatic is that the initial manual REF
LVL setting is required to take into account antenna system noise
presented to the P3.

I hope other REF LVL twiddlers find this useful. 73,

Mike ab3ap

On 01/01/2012 03:26 PM, Mike Markowski wrote:

> Since the PA temp is available as well as the filter bandwidth in use, I
> wonder if the P3 could have an auto-adjust of REF LVL? It would only
> work within a given band and only after the op has adjusted the REF LVL
> to begin with. But after that it seems that the good ol' N = kTB would
> be a simple enough calc that P3 REF LVL could be auto-adjusted as SPAN
> or filter bw is changed.
>
> I know, talk about being lazy... :-) Happy 2012!
>
> Mike ab3ap

Alan Bloom

Re: Example - Re: P3 auto REF LVL adjust?

The P3 already does this if you have MENU:SpanScale set to anything
other than "OFF".

Alan N1AL

On Tue, 2012-01-03 at 19:52 -0500, Mike Markowski wrote:

> I'll follow up on my own note because there's nothing as helpful as an
> example:
>
> 1) I move to 17m band with P3 set for +/-100 kHz span
> 2) P3 REF LVL knob used to set -122 dBm to match noise level at my QTH
>
> 3) -122 dBm = 6.30957 x 10^-13 mW
> 4) Since noise power N = kTB, (k is Boltzman's constant),
> T = N / (kB) = 6.30957 x 10^-13 / (k x 200 kHz)
> k = 228500 K <--- recalc when REF LVL knob is twiddled again!
>
> Now I want to change P3 span to +/-5 kHz, or B = 10 kHz:
>
> 5) N = kTB = (1.380648813 x 10^-23) x 228500 x 10x10^3
> = 3.15479 x 10^-14 mW
> = -135 dBm <--- new REF LVL setting, send to P3
>
> Easy to add to firmware? If not, it is easy to add to external
> software. The only thing not automatic is that the initial manual REF
> LVL setting is required to take into account antenna system noise
> presented to the P3.
>
> I hope other REF LVL twiddlers find this useful. 73,
>
> Mike ab3ap
>
> On 01/01/2012 03:26 PM, Mike Markowski wrote:
> > Since the PA temp is available as well as the filter bandwidth in use, I
> > wonder if the P3 could have an auto-adjust of REF LVL? It would only
> > work within a given band and only after the op has adjusted the REF LVL
> > to begin with. But after that it seems that the good ol' N = kTB would
> > be a simple enough calc that P3 REF LVL could be auto-adjusted as SPAN
> > or filter bw is changed.
> >
> > I know, talk about being lazy... :-) Happy 2012!
> >
> > Mike ab3ap
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

Mike Markowski-2

Re: Example - Re: P3 auto REF LVL adjust?

So it does! And to think of all my unnecessary REF LVL adjusting. One of these days I'm going to have to spend more time with that thing called a manual.

Thanks and 73,
Mike ab3ap, who -thought- he read it through.

On Jan 3, 2012, at 11:39 PM, Alan Bloom wrote:

> The P3 already does this if you have MENU:SpanScale set to anything
> other than "OFF".
>
> Alan N1AL
>
>
> On Tue, 2012-01-03 at 19:52 -0500, Mike Markowski wrote:
>> I'll follow up on my own note because there's nothing as helpful as an
>> example:
>>
>> 1) I move to 17m band with P3 set for +/-100 kHz span
>> 2) P3 REF LVL knob used to set -122 dBm to match noise level at my QTH
>>
>> 3) -122 dBm = 6.30957 x 10^-13 mW
>> 4) Since noise power N = kTB, (k is Boltzman's constant),
>> T = N / (kB) = 6.30957 x 10^-13 / (k x 200 kHz)
>> k = 228500 K <--- recalc when REF LVL knob is twiddled again!
>>
>> Now I want to change P3 span to +/-5 kHz, or B = 10 kHz:
>>
>> 5) N = kTB = (1.380648813 x 10^-23) x 228500 x 10x10^3
>> = 3.15479 x 10^-14 mW
>> = -135 dBm <--- new REF LVL setting, send to P3
>>
>> Easy to add to firmware? If not, it is easy to add to external
>> software. The only thing not automatic is that the initial manual REF
>> LVL setting is required to take into account antenna system noise
>> presented to the P3.
>>
>> I hope other REF LVL twiddlers find this useful. 73,
>>
>> Mike ab3ap