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w7aqk

P3 Questions

I may need some assistance on how my P3 should act. My P3
arrived while I was away on an extended trip to the
Northwest. I now have it up and running, but I have some
questions. I've perused the manual, including the newer
version on the website. It seems that my levels may be
wrong, but not sure.

Here's what I have done--I updated my K3 firmware to the
latest version on the website. I also updated the P3
firmware. I also had to make the mod to my K3 (#96) for the
I.F. output gain. Prior to making that modification, the
noise level seemed to be around -110 dbm, but that was also
before I updated my K3 firmware also.

Now, I seem to have a reference level way down to
around -140 dbm. I do see signal spikes, but it seems to
take an S8 or S9 signal to really show on my screen (to
differentiate them from just noise), which I assume is
indicative of my noise floor. None of the illustrations in
the manual show something starting that low. It makes me
wonder if I did the K3 mod properly. I did replace the SMT
part with the supplied SMT device (or think I did!).
Hopefully I didn't screw that up.

All of this scaling varies from band to band somewhat, but
it's always -120 dbm or lower. I see nice spikes from
stronger signals, but some that are quite copiable on the K3
don't seem to make much of a spike at all. The waterfall
does seem to show the signal better in those cases. I'm
assuming it's just because those signals are right at the
noise level, but I was primarily concerned about the fact
that my setting has to be so much lower (higher numberical
value of "minus" dbm) than anything shown in the manual.

Dave W7AQK

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Alan Bloom

Re: P3 Questions

A noise level of -140 dBm is reasonable with no antenna connected or a
quiet band. It also depends on the span and how you have the K3 set up.
On mine, the noise level is around -160 dBm with no antenna connected to
the K3, the K3 preamp turned on, and the span set to 2 kHz. If I turn
off the preamp, turn on the attenuator, and set the span to 200 kHz, the
noise level is a little below -120 dBm. With an antenna connected it is
higher than that.

You can get an idea if everything is working right by comparing the K3
S-meter reading of a signal within the receive passband. S9 should show
as roughly -73 dBm on the P3 display and change by 6 dB per S-unit below
that. There's a table of dBm levels versus S-units in the latest P3
manual.

Alan N1AL

On Fri, 2010-10-29 at 11:38 -0700, David Yarnes wrote:

> I may need some assistance on how my P3 should act. My P3
> arrived while I was away on an extended trip to the
> Northwest. I now have it up and running, but I have some
> questions. I've perused the manual, including the newer
> version on the website. It seems that my levels may be
> wrong, but not sure.
>
> Here's what I have done--I updated my K3 firmware to the
> latest version on the website. I also updated the P3
> firmware. I also had to make the mod to my K3 (#96) for the
> I.F. output gain. Prior to making that modification, the
> noise level seemed to be around -110 dbm, but that was also
> before I updated my K3 firmware also.
>
> Now, I seem to have a reference level way down to
> around -140 dbm. I do see signal spikes, but it seems to
> take an S8 or S9 signal to really show on my screen (to
> differentiate them from just noise), which I assume is
> indicative of my noise floor. None of the illustrations in
> the manual show something starting that low. It makes me
> wonder if I did the K3 mod properly. I did replace the SMT
> part with the supplied SMT device (or think I did!).
> Hopefully I didn't screw that up.
>
> All of this scaling varies from band to band somewhat, but
> it's always -120 dbm or lower. I see nice spikes from
> stronger signals, but some that are quite copiable on the K3
> don't seem to make much of a spike at all. The waterfall
> does seem to show the signal better in those cases. I'm
> assuming it's just because those signals are right at the
> noise level, but I was primarily concerned about the fact
> that my setting has to be so much lower (higher numberical
> value of "minus" dbm) than anything shown in the manual.
>
> Dave W7AQK
>
>
>
> ______________________________________________________________
> 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

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Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

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Please help support this email list: http://www.qsl.net/donate.html

Rick Prather-2

Re: P3 Questions

Alan,

My S9 appears to be off by about 10db. How are you coming on a level calibration routine?

TIA,
Rick
K6LE

On 10/29/2010, at 3:23 , Alan Bloom wrote:

> A noise level of -140 dBm is reasonable with no antenna connected or a
> quiet band. It also depends on the span and how you have the K3 set up.
> On mine, the noise level is around -160 dBm with no antenna connected to
> the K3, the K3 preamp turned on, and the span set to 2 kHz. If I turn
> off the preamp, turn on the attenuator, and set the span to 200 kHz, the
> noise level is a little below -120 dBm. With an antenna connected it is
> higher than that.
>
> You can get an idea if everything is working right by comparing the K3
> S-meter reading of a signal within the receive passband. S9 should show
> as roughly -73 dBm on the P3 display and change by 6 dB per S-unit below
> that. There's a table of dBm levels versus S-units in the latest P3
> manual.
>
> Alan N1AL

Alan Bloom-2

Re: P3 Questions

Rick,

That's what I'm working on right now.

73,

Alan N1AL

On Fri, 2010-10-29 at 17:20 -0700, Rick Prather wrote:

> Alan,
>
> My S9 appears to be off by about 10db. How are you coming on a level calibration routine?
>
> TIA,
> Rick
> K6LE
>
>
>
> On 10/29/2010, at 3:23 , Alan Bloom wrote:
>
> > A noise level of -140 dBm is reasonable with no antenna connected or a
> > quiet band. It also depends on the span and how you have the K3 set up.
> > On mine, the noise level is around -160 dBm with no antenna connected to
> > the K3, the K3 preamp turned on, and the span set to 2 kHz. If I turn
> > off the preamp, turn on the attenuator, and set the span to 200 kHz, the
> > noise level is a little below -120 dBm. With an antenna connected it is
> > higher than that.
> >
> > You can get an idea if everything is working right by comparing the K3
> > S-meter reading of a signal within the receive passband. S9 should show
> > as roughly -73 dBm on the P3 display and change by 6 dB per S-unit below
> > that. There's a table of dBm levels versus S-units in the latest P3
> > manual.
> >
> > Alan N1AL