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How to demo P3/K3?

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Randy Moore

How to demo P3/K3?

Looks like we may have someone bring a P3 to demo at the Huntsville (AL) Hamfest. Is there a way to demo it, connected to a K3, without an antenna? We'll be deep in the Civic Center.

73,
Randy, KS4L
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Bill W4ZV

Re: How to demo P3/K3?

Randy Moore wrote

Looks like we may have someone bring a P3 to demo at the Huntsville (AL) Hamfest. Is there a way to demo it, connected to a K3, without an antenna? We'll be deep in the Civic Center.

I'd be surprised if you couldn't see something with a piece of wire connected to the K3, if not, any kind of signal source should work (e.g. XG2). You might want to add an attenuator if you have one to be able to show weak signal detection. Also remember to turn PRE on in the K3.

73, Bill

KK7P

Re: How to demo P3/K3?

>> Looks like we may have someone bring a P3 to demo at the Huntsville (AL)
>> Hamfest. Is there a way to demo it, connected to a K3, without an antenna?
>> We'll be deep in the Civic Center.

I've tried two demos of the P3 inside a building.

The first was in a restaurant in Tucson, AZ. We were able to pick up
WWV and look at its sidebands, but it wasn't easy!

The second was in a restaurant north of Seattle. We finally found one
weak AM broadcast station.

In both cases we had to connect up a fairly lengthy piece of wire: about
20' in one case and 60' in the other as I recall.

In your case, I'd probably bring along a KX1 or some other QRP rig, and
a couple of dummy loads, and then observe the signal from your QRP rig.
All you can be certain of at the convention center is that you'll pick
up plenty of noise from lighting fixtures and who knows what else, and
you wont; find signals to demonstrate with :-(

At hamfests, Elecraft uses a device that can record and playback a
significant chunk of RF spectrum to create a usable RF demonstration
environment.

73,

Lyle KK7P
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Steve Ellington

Re: How to demo P3/K3?

I've seen this device used at several hamfest for demonstrating ICOM rigs
such as the 7600 and Flex Radio. It's called the Time Machine.
http://www.expandedspectrumsystems.com/prod2.html
It's hard to tell the difference in a recording and the real thing.
A few years ago at the Dayton fest I stumbled across a booth with this setup
and found myself tuning through a huge CW contest. It totally fooled me!
Every receiver function worked just like it was the real thing.
Steve
N4LQ
----- Original Message -----
From: "Lyle Johnson" <[hidden email]>
Cc: <[hidden email]>
Sent: Monday, August 09, 2010 10:28 AM
Subject: Re: [Elecraft] How to demo P3/K3?

>
>>> Looks like we may have someone bring a P3 to demo at the Huntsville (AL)
>>> Hamfest. Is there a way to demo it, connected to a K3, without an
>>> antenna?
>>> We'll be deep in the Civic Center.
>
> I've tried two demos of the P3 inside a building.
>
> The first was in a restaurant in Tucson, AZ. We were able to pick up
> WWV and look at its sidebands, but it wasn't easy!
>
> The second was in a restaurant north of Seattle. We finally found one
> weak AM broadcast station.
>
> In both cases we had to connect up a fairly lengthy piece of wire: about
> 20' in one case and 60' in the other as I recall.
>
> In your case, I'd probably bring along a KX1 or some other QRP rig, and
> a couple of dummy loads, and then observe the signal from your QRP rig.
> All you can be certain of at the convention center is that you'll pick
> up plenty of noise from lighting fixtures and who knows what else, and
> you wont; find signals to demonstrate with :-(
>
> At hamfests, Elecraft uses a device that can record and playback a
> significant chunk of RF spectrum to create a usable RF demonstration
> environment.
>
> 73,
>
> Lyle KK7P
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
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> Post: mailto:[hidden email]
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Dick Dievendorff

Re: How to demo P3/K3?

Elecraft has used the Time Machine at its booths for some time.

Dick, K6KR

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Steve Ellington
Sent: Monday, August 09, 2010 7:52 AM
To: Lyle Johnson
Cc: [hidden email]
Subject: Re: [Elecraft] How to demo P3/K3?

I've seen this device used at several hamfest for demonstrating ICOM rigs
such as the 7600 and Flex Radio. It's called the Time Machine.
http://www.expandedspectrumsystems.com/prod2.html
It's hard to tell the difference in a recording and the real thing.
A few years ago at the Dayton fest I stumbled across a booth with this setup

and found myself tuning through a huge CW contest. It totally fooled me!
Every receiver function worked just like it was the real thing.
Steve
N4LQ
----- Original Message -----
From: "Lyle Johnson" <[hidden email]>
Cc: <[hidden email]>
Sent: Monday, August 09, 2010 10:28 AM
Subject: Re: [Elecraft] How to demo P3/K3?

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David Gilbert

Re: How to demo P3/K3?

In reply to this post by Randy Moore

Baseband TV video is somewhere around 4 MHz, so I wonder if it would be
possible to record some 80m activity using the video (yellow) input of a
VCR or DVR, and then feed the recorded signal into the K3 at the
hamfest. You'd have to pay attention to signal levels ... it probably
would require an RF preamp for the 80m feed to the VCR/DVR, and you'd
probably need a bunch of attenuation between the VCR/DVR and the K3, but
it might work. I suspect you'd also get a lot of added noise ...

I've never tried any of that, but it popped into my mind as a
possibility. Maybe somebody here smarter than I can comment on its
feasibility.

73,
Dave AB7E

On 8/9/2010 6:11 AM, Randy Moore wrote:

> Looks like we may have someone bring a P3 to demo at the Huntsville (AL) Hamfest. Is there a way to demo it, connected to a K3, without an antenna? We'll be deep in the Civic Center.
>
> 73,
> Randy, KS4L
> ______________________________________________________________
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>

George & Jan

Re: How to demo P3/K3?

The machine will expect synchronizing pulses to lock up the head and capstan
motors. Without sync some machines will not even go into the record mode, if
it does noise will really confuse the motor servos.

The pass band of a video recorder for NTSC (analog) is not necessarily flat
to 4 MHz. depending on the specific machine. The color subcarrier (double
sideband centered at 3.58 MHz with about 1.5 MHz band pass) is processed
differently in the various formats. In most semi-pro & consumer NTSC units
the color subcarrier is converted to "Color Under" centered at about 0.5 MHz
(Yep creates negative sidebands!).

Don't even think about digital video recorders without converting to a
compatible digital format!

George
AI4VZ
* * * * * * * * *
Baseband TV video is somewhere around 4 MHz, so I wonder if it would be
possible to record some 80m activity using the video (yellow) input of a
VCR or DVR ...

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David Gilbert

Re: How to demo P3/K3?

In reply to this post by Randy Moore

Ray, K2ULR, mentioned to me that VCR's probably use the sync pulses of a
normal baseband video signal to sync the rotating heads, which would
make them unusable for recording simple RF. A DVR might not have that
problem, although noise and signal levels could still be an issue. It
might also be the case that any standard video recorder (or at least the
software associated with it) might try to insert sync pulses on playback.

I've seen USB video capture devices for $20 or less, but none seem to
have a port for playback. I'm pretty certain that many of the PCI card
versions do, though.

Of course, it would always be possible to build a simple mixer that
shifted a ham band down to lower than 200 Khz and record that with a
decent computer sound card, and then mix it back up to feed it into the K3.

73,
Dave AB7E

On 8/9/2010 6:11 AM, Randy Moore wrote:

Don Wilhelm-4

Re: How to demo P3/K3?

Dave,

You don't have to build that mixer to shift the ham band down to the
audio range, a Softrock receiver will do that.
For that matter, you don't need the I and Q channels, so any DC receiver
without audio filtering after the mixer will do that job too.
Turning it back into RF is the bigger problem. You need an SSB
generator followed by a wide band filter for that unless you want to
tolerate the carrier and the opposite sideband as well.

73,
Don W3FPR

David Gilbert wrote:
> Of course, it would always be possible to build a simple mixer that
> shifted a ham band down to lower than 200 Khz and record that with a
> decent computer sound card, and then mix it back up to feed it into the K3.
>
>
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David Gilbert

Re: How to demo P3/K3?

True, but I figured more people would be able to build a simple mixer
than happen to own a DC receiver, especially if time was a consideration
prior to the hamfest (per the original query). And I didn't think the
carrier or opposite sidebands from the up conversion would be an issue
for a simple demo.

73,
Dave AB7E

On 8/9/2010 12:19 PM, Don Wilhelm wrote:

> Dave,
>
> You don't have to build that mixer to shift the ham band down to the
> audio range, a Softrock receiver will do that.
> For that matter, you don't need the I and Q channels, so any DC
> receiver without audio filtering after the mixer will do that job too.
> Turning it back into RF is the bigger problem. You need an SSB
> generator followed by a wide band filter for that unless you want to
> tolerate the carrier and the opposite sideband as well.
>
> 73,
> Don W3FPR
>
> David Gilbert wrote:
>> Of course, it would always be possible to build a simple mixer that
>> shifted a ham band down to lower than 200 Khz and record that with a
>> decent computer sound card, and then mix it back up to feed it into
>> the K3.
>>
>

Geoffrey Mackenzie-Kennedy

Re: How to demo P3/K3?

In reply to this post by Don Wilhelm-4

Don,

The main difficulty I believe with down-converting a band to "audio", and
then up-converting back to RF to demonstrate the performance of the P3,
could be the spurious products generated during each conversion, which might
reflect badly on the true performance of the P3 if the products generated
during each conversion resulted in spurs within the chosen span of the P3.

If the P3 included a record - playback scheme similar to that provided by
the Perseus SDR, it would then be vey easy to demonstrate the performance of
the P3. So far I have not found any "alien" spurs when using this feature of
Perseus.

I have not yet investigated how this scheme is implemented in Perseus, but
on occasion when using my Perseus either as a panadapter or as a stand-alone
receiver I have recorded up to several hours worth of "band activity". Mind
you the total size of the resulting files is massive!! The record-playback
feature is also very useful when using Perseus as a spectrum analyzer during
the development of circuitry, in that it provides a record of the effect of
changes made.

FWIW

73,

Geoff
GM4ESD

Don Wilhelm wrote on Monday, August 09, 2010 8:19 PM

> You don't have to build that mixer to shift the ham band down to the
> audio range, a Softrock receiver will do that.
> For that matter, you don't need the I and Q channels, so any DC receiver
> without audio filtering after the mixer will do that job too.
> Turning it back into RF is the bigger problem. You need an SSB
> generator followed by a wide band filter for that unless you want to
> tolerate the carrier and the opposite sideband as well.

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David Woolley (E.L)

Re: How to demo P3/K3?

In reply to this post by David Gilbert

David Gilbert wrote:
> make them unusable for recording simple RF. A DVR might not have that
> problem, although noise and signal levels could still be an issue. It
> might also be the case that any standard video recorder (or at least the
> software associated with it) might try to insert sync pulses on playback.

The lossy compression strategies used in DVRs make them only suitable
for moving picture for direct human consumption. They do things like
only encoding the differences between frames, encoding the movement of
blocks, transmitting a rough update to a frame and then refining it over
successive frames if it doesn't change, and selective control of spacial
frequency response.

Because the compression is 3D (two in space and one in time), sync
pulses are even more important to them.
--
David Woolley
"we do not overly restrict the subject matter on the list, and we
encourage postings on a wide range of amateur radio related topics"
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David Gilbert

Re: How to demo P3/K3?

Makes sense.

I guess someone wanting a cheap and dirty solution would have to use a
down-converting mixer and record to a file via a sound card, and then
mix back to a ham band (assuming, as I suspect would be the case, that
for a demo they'd be willing to put up with the image and carrier).

73,
Dave AB7E

On 8/11/2010 11:10 PM, David Woolley (E.L) wrote:

> David Gilbert wrote:
>> make them unusable for recording simple RF. A DVR might not have
>> that problem, although noise and signal levels could still be an
>> issue. It might also be the case that any standard video recorder
>> (or at least the software associated with it) might try to insert
>> sync pulses on playback.
>
> The lossy compression strategies used in DVRs make them only suitable
> for moving picture for direct human consumption. They do things like
> only encoding the differences between frames, encoding the movement of
> blocks, transmitting a rough update to a frame and then refining it
> over successive frames if it doesn't change, and selective control of
> spacial frequency response.
>
> Because the compression is 3D (two in space and one in time), sync
> pulses are even more important to them.