K3: course wanted: Panadaptor 101

[DOUGLAS ZWIEBEL]

Hi all:

Just as lots of folks needed a tutorial on what a roofing is (and
isn't), I'm sure there are at least an equal number (now including me)
that need an introductory course on Pan displays (specifically, what
we forecast Elecraft might do versus what Softrock can already do -
and not do).

It is hard for me to (currently) understand how there is something out
there already for US$11.00 that apparently provides "what is wanted."
Or maybe it doesn't?

I gather that we need a PC to run Softrock and if you're like me (with
kids), you have lots of computers around the house that are "old" or
minimally used, or currently in use in the shack but with lots of
untapped horsepower still available.  Or maybe you just need an excuse
to upgrade.

I have noted the article in a recent QST on soundcards and I wonder if
we need "the best" sound card to simply get a Pan display (not running
an SDR radio).

What sort of additional functionality might Elecraft include on
"theirs" that would not be available in the Softrock (looking for
conjecture)?

And if you can bascially "do this" for $11.00 (assuming we already
have a PC we can use/share for this app), why would Elecraft even
bother to start to design their own Pan display?

And my final request for the gurus here...please keep it simple and
take an operational approach.  I don't care "how" it does it, I want
to know how the user can USE it, and to compare/contrast Softrock and
whatever E might come out with.

Thanks,
de Doug KR2Q
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[Jack Smith-6]

I'll give my views as the designer of the Z90/91 panadapters. Others may
well have different views.

First, I have a definite bias to stand-alone equipment that works
without a computer. And, I have more computers around here than I can
keep track of, going back to a 386 monochrome laptop residing at the
back of a closet someplace. Hence things like the Softrock don't meet my
stand-alone requirement. I have enough trouble finding space on my
operating desk for radios. And, the more computers running, the greater
the likelihood of noise being generated.

How one uses a panadapter depends on the mode of operation used. If you
are a VHF/UHF operator, for example, a panadapter, particularly operated
in waterfall mode, can quickly let you know whether there is any
operation on the band. On HF, a panadapter can show you a pile up
quickly, or in general give you a good idea where the activity is at any
given instant.

For these uses, in my view, a panadapter requires a span of at least 100
KHz, and preferably more. The Z90 has a maximum default span of 200 KHz,
and maximum user-defined span of 250 KHz. In retrospect, I wish that I
had made it 500 KHz, with perhaps 3 KHz resolution bandwidth, as it
would provide a greater overview of most of an HF band (excluding 10
meters, of course).

Another use of a panadapter with frequency flexibility is as a piece of
test gear, suitable for measuring and adjusting carrier and unwanted
sideband suppression and transmitted intermodulation via a two-tone
test. For this, the panadapter must have a minimum resolution bandwidth
of 200 Hz or less.

In my personal opinion, a panadapter with a maximum span of 48 KHz is
less useful than one with a wider span. Others may disagree, as it
depends on how one operates.

My web site has many examples of modulation analysis, transmitter
measurements and the like made with the Z90 panadapter, but these are
generic and are applicable to any panadapter with similar performance.
They can be found linked at the main site www.cliftonlaboratories.com.


Jack K8ZOA


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[N8LP]

I don't have a SDR, but have been pursuing this idea on my LP-100
reflector with some sharp guys who do. What I have been able to gleen is
that with the best sound card currently available (which requires a
Firewire interface), you can get 192 kHz bandwidth to sample. After
filtering to avoid aliasing, I assume this would be maybe 180 kHz of
clean display. With the best board tested by QST, the bandwidth would be
about half that.

The dynamic range would be in the 100-110 dB range... adequate for a
panadapter in a normal RF environment. The ADC will overload in the
presence of strong signals, however, unless you pad the signal from the
IF. I assume this would result in a flat line on the display at the top.
There is the chance that signals outside the display width could cause
interference as well, since the only filtering would be the bandpass
filters in the K3, and a 3-pole filter on the input of the softrock, but
they would have to be very strong.

Adding some attenuation between the K3 and softrock (beyond what would
be needed for proper interfacing to the K3 IF output), would help
protect the ADC in the soundcard, but you would lose some sensitivity.
The amount would depend on the strength of the ADC. Depending on
soundcard, 10 dB would give you a range of  about -10dBm to -110 /
-120dBm between MDS and 1dB compression point... a bit less if the upper
limit is more stringent. This should be fine for most
locations/situations, although I can think of a couple very specific
exceptions.

To sum up, I would expect that you would spend about $250-400 for this
setup, assuming you already have the PC, and depending on the level of
sound card you use, with the high end required for a BW > ~90 kHz. You
would not have the ability to point and click to jump to a signal like
the Z90/91 offers... although it's possible that some enterprising soul
could add this feature to one of the open source SDR apps I suppose. And
you don't have much portability.

73,
Larry N8LP



Jack Smith wrote:

> I'll give my views as the designer of the Z90/91 panadapters. Others
> may well have different views.
>
> First, I have a definite bias to stand-alone equipment that works
> without a computer. And, I have more computers around here than I can
> keep track of, going back to a 386 monochrome laptop residing at the
> back of a closet someplace. Hence things like the Softrock don't meet
> my stand-alone requirement. I have enough trouble finding space on my
> operating desk for radios. And, the more computers running, the
> greater the likelihood of noise being generated.
>
> How one uses a panadapter depends on the mode of operation used. If
> you are a VHF/UHF operator, for example, a panadapter, particularly
> operated in waterfall mode, can quickly let you know whether there is
> any operation on the band. On HF, a panadapter can show you a pile up
> quickly, or in general give you a good idea where the activity is at
> any given instant.
>
> For these uses, in my view, a panadapter requires a span of at least
> 100 KHz, and preferably more. The Z90 has a maximum default span of
> 200 KHz, and maximum user-defined span of 250 KHz. In retrospect, I
> wish that I had made it 500 KHz, with perhaps 3 KHz resolution
> bandwidth, as it would provide a greater overview of most of an HF
> band (excluding 10 meters, of course).
>
> Another use of a panadapter with frequency flexibility is as a piece
> of test gear, suitable for measuring and adjusting carrier and
> unwanted sideband suppression and transmitted intermodulation via a
> two-tone test. For this, the panadapter must have a minimum resolution
> bandwidth of 200 Hz or less.
>
> In my personal opinion, a panadapter with a maximum span of 48 KHz is
> less useful than one with a wider span. Others may disagree, as it
> depends on how one operates.
>
> My web site has many examples of modulation analysis, transmitter
> measurements and the like made with the Z90 panadapter, but these are
> generic and are applicable to any panadapter with similar performance.
> They can be found linked at the main site www.cliftonlaboratories.com.
>
>
> Jack K8ZOA
>
>
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>

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[Brett gazdzinski-2]

I don't want and wont have a computer in the shack.

I wonder why they can not down convert the IF to something
a cheap sound card could handle easy, or maybe they do?

Down convert, product detector, audio to sound card?

I personally would love a simple bandscope, with maybe a mouse
or some way to click on a signal to set the k3 to move the vfo
there, but just a band scope would be enough, without using
a hash generating, space hogging, expensive PC.

Brett
N2DTS

>
> Hi all:
>
> Just as lots of folks needed a tutorial on what a roofing is (and
> isn't), I'm sure there are at least an equal number (now including me)
> that need an introductory course on Pan displays (specifically, what
> we forecast Elecraft might do versus what Softrock can already do -
> and not do).
>
> It is hard for me to (currently) understand how there is something out
> there already for US$11.00 that apparently provides "what is wanted."
> Or maybe it doesn't?
>
> I gather that we need a PC to run Softrock and if you're like me (with
> kids), you have lots of computers around the house that are "old" or
> minimally used, or currently in use in the shack but with lots of
> untapped horsepower still available.  Or maybe you just need an excuse
> to upgrade.
>
> I have noted the article in a recent QST on soundcards and I wonder if
> we need "the best" sound card to simply get a Pan display (not running
> an SDR radio).
>
> What sort of additional functionality might Elecraft include on
> "theirs" that would not be available in the Softrock (looking for
> conjecture)?
>
> And if you can bascially "do this" for $11.00 (assuming we already
> have a PC we can use/share for this app), why would Elecraft even
> bother to start to design their own Pan display?
>
> And my final request for the gurus here...please keep it simple and
> take an operational approach.  I don't care "how" it does it, I want
> to know how the user can USE it, and to compare/contrast Softrock and
> whatever E might come out with.
>
> Thanks,
> de Doug KR2Q
> _______________________________________________
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> Post to: [hidden email]
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>
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> Elecraft web page: http://www.elecraft.com
>

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[Jack Smith-6]

A 192 kb/s sample rate gives you a usable bandwidth (Nyquist = sample
rate/2) of 96 KHz, assuming a brick-wall anti-alias filter. More likely,
the usable bandwidth will be about 80 KHz with a practical anti-alias
filter.

Jack


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[Simon (HB9DRV)]

----- Original Message -----
From: "Brett gazdzinski" <[hidden email]>
>
> I personally would love a simple bandscope, with maybe a mouse
> or some way to click on a signal to set the k3 to move the vfo
> there, but just a band scope would be enough, without using
> a hash generating, space hogging, expensive PC.
>

A decent laptop and a ferrite ring or two and you will not have any RF
problems, especially with well-engineered Elecraft hardware.

I also await a bandscope with its own display and a computer interface so
that I can click on a signal using the computer. An advantage of a computer
is automatic signal detection, for example 6m is quiet most of the day, the
computer can wake you up when it hears a beacon.

I prefer to work 15m, 10m and 6m. Using a software monitor I ended up
working Z21FO (Zimbabwe) on 15m PSK31. I would never have seen his signal
otherwise as I was concentrating on writing some dodgy software :-) Zimbabwe
may not be all that rare, but for me on 15m and PSK31 it's not that common.

<g>You do realise that there's a computer in the K3? </g>

Simon HB9DRV

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[N8LP]

DOH! I knew I should have proofread that post before sending it ;-) Too
early in the AM for me. Yes, divide all my BW numbers by 2.

Larry N8LP


Jack Smith wrote:

> A 192 kb/s sample rate gives you a usable bandwidth (Nyquist = sample
> rate/2) of 96 KHz, assuming a brick-wall anti-alias filter. More
> likely, the usable bandwidth will be about 80 KHz with a practical
> anti-alias filter.
>
> Jack
>
>
>
> .
>

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[N8LP]

Corrected text...

I don't have a SDR, but have been pursuing this idea on my LP-100
reflector with some sharp guys who do. What I have been able to gleen is
that with the best sound card currently available (which requires a
Firewire interface), you can get 192 kHz sampling. *After filtering to
avoid aliasing, I assume this would provide maybe 90 kHz of clean
display. *With the best board tested by QST, the bandwidth would be
about half that.

The dynamic range would be in the 100-110 dB range... adequate for a
panadapter in a normal RF environment. The ADC will overload in the
presence of strong signals, however, unless you pad the signal from the
IF. I assume this would result in a flat line on the display at the top.
There is the chance that signals outside the display width could cause
interference as well, since the only filtering would be the bandpass
filters in the K3, and a 3-pole filter on the input of the softrock, but
they would have to be very strong.

Adding some attenuation between the K3 and softrock (beyond what would
be needed for proper interfacing to the K3 IF output), would help
protect the ADC in the soundcard, but you would lose some sensitivity.
The amount would depend on the strength of the ADC. Depending on
soundcard, 10 dB would give you a range of  about -10dBm to -110 /
-120dBm between MDS and 1dB compression point... a bit less if the upper
limit is more stringent. This should be fine for most
locations/situations, although I can think of a couple very specific
exceptions.

To sum up, I would expect that you would spend about $250-400 for this
setup, assuming you already have the PC, and depending on the level of
sound card you use, with the high end required for a BW > ~45 kHz. You
would not have the ability to point and click to jump to a signal like
the Z90/91 offers... although it's possible that some enterprising soul
could add this feature to one of the open source SDR apps I suppose. And
you don't have much portability.

73,
Larry N8LP



Jack Smith wrote:

> A 192 kb/s sample rate gives you a usable bandwidth (Nyquist = sample
> rate/2) of 96 KHz, assuming a brick-wall anti-alias filter. More
> likely, the usable bandwidth will be about 80 KHz with a practical
> anti-alias filter.
>
> Jack
>
>
>
> .
>

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[dj7mgq]

> A 192 kb/s sample rate gives you a usable bandwidth (Nyquist = sample
> rate/2) of 96 KHz, assuming a brick-wall anti-alias filter. More likely,
> the usable bandwidth will be about 80 KHz with a practical anti-alias
> filter.

Make that 80 or so kHz lower side band and 80 or so kHz upper side band, and
then you have 160 or so kHz total, without breaking Nyquist. This assumes that
you have I & Q signals.

This is what Flex-Radio does.

See:

http://www.flex-radio.com/Data/Doc/qex1.pdf
http://www.flex-radio.com/Data/Doc/qex2.pdf
http://www.flex-radio.com/Data/Doc/qex3.pdf
http://www.flex-radio.com/Data/Doc/qex4.pdf 

vy 73 de toby
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[Geoffrey Mackenzie-Kennedy-2]

Jack Smith <[hidden email]> wrote:

> First, I have a definite bias to stand-alone equipment that works without
> a computer.

I'll second that!

>.On HF, a panadapter can show you a pile up quickly, or in general give you
>a good idea where the activity is at any given instant.

In a pile up situation I have found it very useful to be able to turn on a
line marker which shows where my transmitter frequency is positioned with
respect to the other callers, before transmitting, and using a span which
covers the DX station's frequency and his listening frequencies. If the DX
is working SSB 'wide split' e.g. transmitting on 7205  kHz and listening
7060 kHz, I would monitor 7060 kHz +- with the panadapter (and audio) while
listening to the DX's audio on 7205 kHz.

> For these uses, in my view, a panadapter requires a span of at least 100
> KHz, and preferably more. The Z90 has a maximum default span of 200 KHz,
> and maximum user-defined span of 250 KHz. In retrospect, I wish that I had
> made it 500 KHz, with perhaps 3 KHz resolution bandwidth, as it would
> provide a greater overview of most of an HF band (excluding 10 meters, of
> course).

With respect my personal view is that a span of 200 - 250 kHz is ample for
routine monitoring purposes at HF and VHF. For greater spans the receiver
can be put into SCAN  mode while using the panadapter as long as the
receiver's scan rate is not too high. My K2 scans too rapidly for my
purposes at VHF.

73,
Geoff
GM4ESD



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[Jack Smith-6]

Yes, of course. I had forgotten it was an I/Q demodulator.

Jack K8ZOA


[hidden email] wrote:

>> A 192 kb/s sample rate gives you a usable bandwidth (Nyquist = sample
>> rate/2) of 96 KHz, assuming a brick-wall anti-alias filter. More likely,
>> the usable bandwidth will be about 80 KHz with a practical anti-alias
>> filter.
>>    
>
> Make that 80 or so kHz lower side band and 80 or so kHz upper side band, and
> then you have 160 or so kHz total, without breaking Nyquist. This assumes that
> you have I & Q signals.
>
> This is what Flex-Radio does.
>
> See:
>
> http://www.flex-radio.com/Data/Doc/qex1.pdf
> http://www.flex-radio.com/Data/Doc/qex2.pdf
> http://www.flex-radio.com/Data/Doc/qex3.pdf
> http://www.flex-radio.com/Data/Doc/qex4.pdf 
>
> vy 73 de toby
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>  

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[N8LP]

I didn't... and then I did... all in the course of a few minutes ;-)  It
pays to put all your reasoning in your posts, so that you can convince
yourself all over again that what you're saying makes sense. I forgot
that and paid the price. Please refer to my original post and ignore the
revision.

Bottom line is that if you don't mind being tied to a PC, and being
limited to BW in the 80-90 kHz range (or 160-180 kHz range, depending on
the sampling and filtering quality in the sound card), then a softrock
approach can be a reasonable alternative... although far from cheap if
you want top performance.

One advantage is that for casual listening, you have a second (or third)
receiver.

Larry N8LP



Jack Smith wrote:

> Yes, of course. I had forgotten it was an I/Q demodulator.
>
> Jack K8ZOA
>
>
> [hidden email] wrote:
>>> A 192 kb/s sample rate gives you a usable bandwidth (Nyquist =
>>> sample rate/2) of 96 KHz, assuming a brick-wall anti-alias filter.
>>> More likely, the usable bandwidth will be about 80 KHz with a
>>> practical anti-alias filter.
>>>    
>>
>> Make that 80 or so kHz lower side band and 80 or so kHz upper side
>> band, and then you have 160 or so kHz total, without breaking
>> Nyquist. This assumes that you have I & Q signals.
>>
>> This is what Flex-Radio does.
>>
>> See:
>> http://www.flex-radio.com/Data/Doc/qex1.pdf
>> http://www.flex-radio.com/Data/Doc/qex2.pdf
>> http://www.flex-radio.com/Data/Doc/qex3.pdf
>> http://www.flex-radio.com/Data/Doc/qex4.pdf
>> vy 73 de toby
>> _______________________________________________
>> Elecraft mailing list
>> Post to: [hidden email]
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>> Elecraft web page: http://www.elecraft.com
>>
>>  
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>

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[Ron D'Eau Claire-2]

Yeah, a "panadapter" is almost as good as turning the tuning dial <G>. The
panadapter lets one scan the band faster with a nice visual display, but it
may not show you all the signals.

There's a *huge* performance tradeoff involved in trying to "see" the a wide
frequency range on a 'scope and trying to hear *one* weak signal. In
receivers with a front end that is "broad as a barn" (including the first
I.F. in modern receivers), the panadapter can show you many signals within
that passband, but not all the signals.

As others have pointed out all of those signals coming through for display
compromise the dynamic range. They can't be filtered out or they won't show
up on the panadapter. The strongest among them defines the response to all
the signals, no matter how weak. If there's a really strong signal in the
passband it'll either overload the receiver, creating hash and spurs in the
passband or the gain has to be reduced, making weak signals even weaker.

An ideal receiver would filter out everything but the signal of interest at
the antenna terminal! Nothing would enter the first stage except that one
signal we want to hear. We'd do that on all receivers except no one has yet
devised a suitable tunable filter. That's why we have "superheterodyne"
receivers. They convert a tunable range of signals to a single intermediate
frequency (I.F.) where we can have a very effective fixed-frequency filter
that stops all but the desired signal.

The K3 offers a selection *narrow* roofing filters designed to provide the
minimum practicable bandwidth needed for various modes from a few hundred Hz
for CW to several KHz for ESSB or AM, etc.

Many receivers on the market today don't use such a filter. They have a very
broad first I.F. (roofing) filter that allows the desired signal and many
signals around it through. They are, frankly, a compromise design that the
K3 avoids. It's a compromise that one can usually get away with unless
conditions are tough (e.g. a contest or DX pileup). But isn't than when you
want the best performance?

So it's not practicable to pass a swath that incorporates most of a Ham
band, or even a CW or phone sub-band without seriously endangering the
receiver performance under the toughest conditions. And if you don't pass a
swath of frequencies through the first I.F. you can't show them on a
"bandscope" or "panadapter".

I think my interest in such a device would be to have it running on its own
receiver, not the one I'm trying to use to hear weak signals in a pileup.
Whether or not it's worth doing that is debatable except to show general
band activity or the presence of a group of quite strong signals. It may not
show some signals thanks to its performance being limited by the strongest
signal in the passband, but I'm sure it's a very useful tool if, like any
tool, one understands its limitations.

Ron AC7AC



-----Original Message-----

Jack Smith <[hidden email]> wrote:

> First, I have a definite bias to stand-alone equipment that works
> without a computer.

I'll second that!

>.On HF, a panadapter can show you a pile up quickly, or in general give
>you a good idea where the activity is at any given instant.

In a pile up situation I have found it very useful to be able to turn on a
line marker which shows where my transmitter frequency is positioned with
respect to the other callers, before transmitting, and using a span which
covers the DX station's frequency and his listening frequencies. If the DX
is working SSB 'wide split' e.g. transmitting on 7205  kHz and listening
7060 kHz, I would monitor 7060 kHz +- with the panadapter (and audio) while
listening to the DX's audio on 7205 kHz.

> For these uses, in my view, a panadapter requires a span of at least
> 100 KHz, and preferably more. The Z90 has a maximum default span of
> 200 KHz, and maximum user-defined span of 250 KHz. In retrospect, I
> wish that I had made it 500 KHz, with perhaps 3 KHz resolution
> bandwidth, as it would provide a greater overview of most of an HF
> band (excluding 10 meters, of course).

With respect my personal view is that a span of 200 - 250 kHz is ample for
routine monitoring purposes at HF and VHF. For greater spans the receiver
can be put into SCAN  mode while using the panadapter as long as the
receiver's scan rate is not too high. My K2 scans too rapidly for my
purposes at VHF.

73,
Geoff
GM4ESD



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[Geoffrey Mackenzie-Kennedy-2]

Ron D'Eau Claire <[hidden email]> wrote:

>There's a *huge* performance tradeoff involved in trying to "see" the a
>wide
>frequency range on a 'scope and trying to hear *one* weak signal. In
>receivers with a front end that is "broad as a barn" (including the first
>I.F. in modern receivers), the panadapter can show you many signals within
>that passband, but not all the signals.

That is true to a point which depends greatly on the design and signal
handling capability of both the receiver and of the panadapter. Also the
requirements placed on a panadapter for use in a pile up or for use in the
type of routine band monitoring that I had in mind ( "dead" VHF or HF
bands ) are quite different. In a pile up situation I would not attempt to
"copy" a weak DX signal with the panadapter but do use it in attempting to
find a clear spot among the callers, in which case the panadapter can be fed
via a wide filter branching from but otherwise separate from the main signal
path. A nominal bandwidth of 7kHz appears to cover most pile up situations.
But the true In Passband 3rd Order dynamic range of both receiver and
panadapter must be suitably large to avoid trash being displayed.

73,
Geoff
GM4ESD


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[Ron D'Eau Claire-2]

Yep! That's a huge advantage for the K3 in which one can open up the roofing
filter bandwidth for casual, non-critical operation and use a panadapter,
then close the bandwidth down by selecting a narrower roofing filter for
best dynamic range and weak-signal performance and give up the panoramic
display.

Like anything else, getting good results from a great tool requires that it
be used correctly.

Ron AC7AC

-----Original Message-----

Ron D'Eau Claire <[hidden email]> wrote:

>There's a *huge* performance tradeoff involved in trying to "see" the a
>wide
>frequency range on a 'scope and trying to hear *one* weak signal. In
>receivers with a front end that is "broad as a barn" (including the first
>I.F. in modern receivers), the panadapter can show you many signals within
>that passband, but not all the signals.

That is true to a point which depends greatly on the design and signal
handling capability of both the receiver and of the panadapter. Also the
requirements placed on a panadapter for use in a pile up or for use in the
type of routine band monitoring that I had in mind ( "dead" VHF or HF
bands ) are quite different. In a pile up situation I would not attempt to
"copy" a weak DX signal with the panadapter but do use it in attempting to
find a clear spot among the callers, in which case the panadapter can be fed

via a wide filter branching from but otherwise separate from the main signal

path. A nominal bandwidth of 7kHz appears to cover most pile up situations.
But the true In Passband 3rd Order dynamic range of both receiver and
panadapter must be suitably large to avoid trash being displayed.

73,
Geoff
GM4ESD



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[Brett gazdzinski-2]

I liked the band scope on the 756 pro, it did exactly
what I wanted it to do, which was to show any signals
close (+/- 12.5 KHz, or 25 KHz total) to where I was operating.

While working around the shack, I could see if anyone was
on without tuning anything.
They work real well on AM, not as good on ssb or cw where
signals are not steady/constant, but they work.

I don't remember how icom designed the band scope, but you
could expand it quite wide.
It DID have an odd glitch, as you centered a signal its amplitude
shrunk on the display, making signals out of the passband
seem stronger then they were, an agc thing no doubt.

The band scope was the only thing I found impressive on the icom,
it WAS very well done.

It even showed clearly when someone's signal was wider than it
should have been....

Brett
N2DTS


 

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