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[P3] Reference level; scale

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alorona

[P3] Reference level; scale

The thing that will take most getting used to will be that the P3 calls the
*bottom* of the scale the "reference level". On a typical spectrum analyzer the
reference level is usually the *topmost* line.

Additionally, a spectrum analyzer thinks in terms of reference level and a scale
(in dB per division), whereas the P3's "scale" is the total vertical distance of
its display, from top to bottom. In my mind, I'm going to be dividing this
"scale" by the number of divisions so that I can have an idea of the dB/div.

But these are artifacts of years of using HP and Agilent equipment. Time to
learn a new system, I guess. :^)

Al W6LX
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wayne burdick

Re: [P3] Reference level; scale

Administrator

Hi Al,

Note that the P3 was designed by a former H-P engineer :) Alan Bloom
(N1AL) is our newest staff engineer and an expert in RF test equipment
design. He's also a heavyweight technical contributor to the ARRL
Handbook.

Another of our engineers (Bob, N6CM), a real stickler for signal
processing performance, recently tested the P3's FFT and signal chain
accuracy. Using the best test gear available, he found that the P3
performs as well or better than most laboratory spectrum analyzers. To
quote Bob: "I'm beyond impressed." He doesn't say this lightly.

We believe that the P3 will set a new standard for stand-alone
panadapters.

73,
Wayne
N6KR

On Jul 30, 2010, at 10:38 AM, Al Lorona wrote:

> The thing that will take most getting used to will be that the P3
> calls the
> *bottom* of the scale the "reference level". On a typical spectrum
> analyzer the
> reference level is usually the *topmost* line.....

> But these are artifacts of years of using HP and Agilent equipment.
> Time to
> learn a new system, I guess. :^)
>
> Al W6LX

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Alan Bloom-2

Re: [P3] Reference level; scale

In reply to this post by alorona

As a former HP/Agilent engineer I agree. Originally the P3 defined REF
LVL as the reference level at the top of the screen and SCALE was in
dB/division. But I got talked out of it.

For a panadapter you generally want to set the noise to be near the
bottom of the display. As you change the scale you don't want that to
change. That's the reason for using the bottom of the display as the
reference level.

Also, it goes against my intuition that the reference level decreases
(becomes more negative) as you turn the knob clockwise. Again, the
thought was that for a panadapter, people expect the signal to get
bigger as you turn the knob to the right.

Basically a panadapter and a spectrum analyzer are used for different
purposes so it makes sense that the user interface is different.
Hopefully we got it right.

Alan N1AL

On Fri, 2010-07-30 at 10:38 -0700, Al Lorona wrote:

> The thing that will take most getting used to will be that the P3 calls the
> *bottom* of the scale the "reference level". On a typical spectrum analyzer the
> reference level is usually the *topmost* line.
>
> Additionally, a spectrum analyzer thinks in terms of reference level and a scale
> (in dB per division), whereas the P3's "scale" is the total vertical distance of
> its display, from top to bottom. In my mind, I'm going to be dividing this
> "scale" by the number of divisions so that I can have an idea of the dB/div.
>
> But these are artifacts of years of using HP and Agilent equipment. Time to
> learn a new system, I guess. :^)
>
> Al W6LX
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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Bill W4ZV

Re: [P3] Reference level; scale

Alan Bloom-2 wrote

Basically a panadapter and a spectrum analyzer are used for different
purposes so it makes sense that the user interface is different.
Hopefully we got it right.

Noise floor and dynamic range above that floor are how I like to think of the P3. First set the P3 REF LVL just above the noise floor and then adjust SCALE depending on how much dynamic range is needed in your area of interest (i.e. SPAN). If we could set our receivers as easily (instead of RF GAIN fully to the right), more guys would actually be utilizing the full dynamic range of their K3s.

73, Bill

P.S. Another ex-HP employee of ~30 years in Loveland, CO...where the 3585 HF and 3582 LF Spectrum Analyzers were developed before being transferred to Lake Stevens, WA. I once hauled a 3585 prototype home over a weekend to use as a Panadapter in a contest on 10m in the early 80s. It's a tribute to its rugged design that I didn't blow out the front end! The P3 is better as a Panadapter and costs a heck of a lot less!

http://www.testequipmentdepot.com/usedequipment/hewlettpackard/spectrumanalyzers/3585a.htm

n7ws

Re: [P3] Reference level; scale

In reply to this post by Alan Bloom-2

As a guy who had a hand in buying and/or specifying the purchase of millions of dollars worth of HP equipment (never bought any Agilent, couldn't figure out how to pronounce it) and who used a lot of it, I also think the reference belongs at the top.

But why not a spectrum analyzer mode and a panadapter mode?

--- On Fri, 7/30/10, Alan Bloom <[hidden email]> wrote:

> As a former HP/Agilent engineer I
> agree. Originally the P3 defined REF
> LVL as the reference level at the top of the screen and
> SCALE was in
> dB/division. But I got talked out of it.
>
> For a panadapter you generally want to set the noise to be
> near the
> bottom of the display. As you change the scale you
> don't want that to
> change. That's the reason for using the bottom of the
> display as the
> reference level.
>
> Also, it goes against my intuition that the reference level
> decreases
> (becomes more negative) as you turn the knob
> clockwise. Again, the
> thought was that for a panadapter, people expect the signal
> to get
> bigger as you turn the knob to the right.
>
> Basically a panadapter and a spectrum analyzer are used for
> different
> purposes so it makes sense that the user interface is
> different.
> Hopefully we got it right.
>
> Alan N1AL

alorona

Re: [P3] Reference level; scale

In reply to this post by Bill W4ZV

Bill, W4ZV wrote: "Noise floor and dynamic range above that floor are how I like
to think of
the P3."

And that's just the way I will start to think about it. Thanks, Bill.

A panadaptor ain't a spectrum analyzer, strictly speaking, and I knew I would
have to change my way of thinking.

Hey, we could have an ex-HP reunion with alls youse guys on here.

Good weekend,

Al W6LX
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Brett Howard

Re: [P3] Reference level; scale

In reply to this post by n7ws

I just got done spending a quarter million on two Agilent spectrum
analyzers and spend a good bit of time using them.... I find that for
the panadapter use case that having it at the bottom takes much less
getting used to that I'd thought it would.

~Brett (N7MG)

On Fri, 2010-07-30 at 18:43 -0700, Wes Stewart wrote:

> As a guy who had a hand in buying and/or specifying the purchase of millions of dollars worth of HP equipment (never bought any Agilent, couldn't figure out how to pronounce it) and who used a lot of it, I also think the reference belongs at the top.
>
> But why not a spectrum analyzer mode and a panadapter mode?
>
> --- On Fri, 7/30/10, Alan Bloom <[hidden email]> wrote:
>
> > As a former HP/Agilent engineer I
> > agree. Originally the P3 defined REF
> > LVL as the reference level at the top of the screen and
> > SCALE was in
> > dB/division. But I got talked out of it.
> >
> > For a panadapter you generally want to set the noise to be
> > near the
> > bottom of the display. As you change the scale you
> > don't want that to
> > change. That's the reason for using the bottom of the
> > display as the
> > reference level.
> >
> > Also, it goes against my intuition that the reference level
> > decreases
> > (becomes more negative) as you turn the knob
> > clockwise. Again, the
> > thought was that for a panadapter, people expect the signal
> > to get
> > bigger as you turn the knob to the right.
> >
> > Basically a panadapter and a spectrum analyzer are used for
> > different
> > purposes so it makes sense that the user interface is
> > different.
> > Hopefully we got it right.
> >
> > Alan N1AL
>
>
>
>
>
> ______________________________________________________________
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