Elecraft

K3 and preamp

Classic

List

Threaded

25 messages Options

Guy Olinger K2AV

Re: K3 and Preamp

It has been established that there is a possible +27 dB total of various
between-the-ears enhancements, or conversely an absence of between-the-ears
enhancement.

This is of particular significance during contests and working DX pileups,
zero enhancement to DX spots clearly observed in entirely mechanical
responses having no relationship to the DX station's TX/RX rhythm.

73, Guy.

On Sat, Sep 6, 2014 at 5:48 PM, Don Wilhelm <[hidden email]> wrote:

> Bud,
>
> I think a lot has to do with the 'material between the ears'. Some have
> developed the ability to hear signals that to my ears are buried in the
> noise. Those chasing Low Band DX are examples of folks with that ability.
> Some report using a wide bandwidth while others report good results with a
> narrow bandwidth. I believe it all depends on the "brain training". The
> human brain can provide a wonderful filter if you know what to pay
> attention to (and ignore things that can distract). Some have it while
> others do not. It may be something that can be learned, but I have not
> accomplished that feat.
>
> 73,
> Don W3FPR
>
> On 9/6/2014 5:28 PM, W2RU - Bud Hippisley wrote:
>
>> On Sep 6, 2014, at 2:34 17PM, Dauer, Edward <[hidden email]> wrote:
>>
>> I received a couple of off-list comments that might be of interest to
>>> those who are following this thread. One was that narrowing the BW also
>>> improves the S/N.
>>>
>> Maybe. Maybe not. Or, maybe up to a point.
>>
>> I believe that whether one observes monotonic improvement in ability to
>> decipher the intelligence carried in a very weak signal as one reduces
>> receiver BW will be a function of _how_ the BW is narrowed in the various
>> electronic circuits and/or digital algorithms, as well as a function of our
>> own individual hearing characteristics.
>>
>> Perhaps I am not on the main part of the normalcy distribution curve (my
>> close friends will assure me I’m _not_!) but I know for a fact that many,
>> many times I have been best able to pull intelligible information out of a
>> very weak CW signal on the low bands by using a receiver BW somewhat
>> _wider_ than that provided by my narrowest filtering options. I have used
>> primarily Kenwoods and (more recently) the K3 for most of my serious
>> low-band DXing efforts, but I can’t tell you if this effect is more or less
>> apparent in one model vs. any other.
>>
>> I am also a strong believer in what I have been told is “stochastic
>> resonance” as an aid to hearing and copying the intelligence carried in
>> weak signals. I have found repeatedly, for instance, that I am more apt
>> to hear certain “unusual” vehicle sounds from the engine compartment or
>> underbody when I have the car radio playing music within a certain range of
>> amplitudes. Of course, that might also depend on my choice of music genre
>> … :-)
>>
>>
>>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

______________________________________________________________
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
Message delivered to [hidden email]

k6dgw

Re: K3 and Preamp

In reply to this post by Guy Olinger K2AV

I'm not sure anything in the menus would help for me ... the ability to
adjust both the width and the center frequency from the front panel was
what I was dreaming of. Since all the "turn-ies" [i.e. knobs] seem to
have multiple functions, I don't know how they could do it. Possibly
some external gizmo, similar to a PigKnob maybe? A little hands-on
training with someone who finds it useful would probably help too. :-)

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org

On 9/7/2014 7:20 AM, Guy Olinger K2AV wrote:

>
> On Sat, Sep 6, 2014 at 6:24 PM, Fred Jensen <[hidden email]
> <mailto:[hidden email]>> wrote:
>
> I've never had much luck with the K3 APF, I know others do and its
> probably pilot error for me, but I wonder what it would take to make
> it adjustable both in BW and frequency? DSP Q-Multiplier? :-)
>
>
> There is something I remember from the old radios and some really "bad"
> headsets that were peaky in their response, and that was a moderate
> rolloff above and below that allowed one to hear up there and down there
> but did not allow it to dominate. I've asked for a config menu
> adjustment on the APF but that never had enough support from others to
> move it up on the K3 do list.
>
> The audio shaping could do that, but I can't put in a menu selection of
> favorite settings, there is only the one. It would need to be easily
> accessible for switching in/out on a QSO by QSO basis.

Edward R Cole

Re: K3 and Preamp

In reply to this post by alsopb

Ted,

Observes that his K3 noise level drops on 10m if he disconnects the
antenna. That indicates that sky noise (plus any man-made noise in
his locale) is the dominant source of noise. But then he states that
the PR6 improves weak-signal copy. That is not exactly
contradictory. Noise power, Pn:
Pn = Psky + Prx + Plocal

So all these sources add up. The PR6 lowers the internal receiver
generated noise so Prx get smaller and that helps lower the N part of
S+N/N (or SNR as some write it). If Psky were many times larger than
Prx+Plocal then adding a preamp to lower Prx will have little effect
(probably not noticeable)...typically what exists on lower HF bands.

Also, it you live in a noisy urban electronic environment the Plocal
noise factor may rule what you can hear and the preamp will not be
much help. Noise level of your locale will certainly have an effect.

The point raised about receiving weak-signals with adjacent high
level signals is also true. High IP3 devices should be used in a
preamp used under these conditions. Typical low-noise devices are
sensitive to any RF energy in their passband which usually pretty
wide. So in conditions often seen on HF, a preamp may not work
well. The dynamic range of the K3 may be more important in that
situation. Operating on 6m during a contest would even be an example
of that in many locations with high ham population.

If you live in a quiet neighborhood and have no local QRO stations,
then a low-noise preamp will usually help get those weak ones (on
10m+). This is much more apparent at 2m and above.

On 2m noise on the horizon is about one s-unit higher than looking up
into the sky. On 1296 I can only find about two birdies in the first
100 KHz of the band; my antenna noise is dictated by what I am
looking at with my dish. I see the noise rise as I lower it to the
horizon where I pick up thermal noise of the earth (rises about 6-dB
over cold sky. If I look at the sun my noise rises 16-dB!

73, Ed - KL7UW
-------------------
From: "Dauer, Edward" <[hidden email]>

No argument with the theory here, though my personal experience is not
consistent with the earlier observation that a preamp won?t do much if the
noise level drops perceptibly when the antenna is disconnected. On my K3
on 10M the noise level drops when no antenna is connected (by 10dB? Maybe
not); AND the PR6-10 preamp improves the readability of very weak signals
when it is in the circuit compared to when it is not. If that?s just a
placebo effect, I?ll take it.

I received a couple of off-list comments that might be of interest to
those who are following this thread. One was that narrowing the BW also
improves the S/N. That is quite true - indeed, BW narrowing in the K3 is
generally better, in my circumstances, than the K3?s on-board NB and NR
facilities are (though I confess I have much to learn about those.)
==snip

73, Ed - KL7UW
http://www.kl7uw.com
"Kits made by KL7UW"
Dubus Mag business:
[hidden email]

______________________________________________________________
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
Message delivered to [hidden email]

W7CS

Re: K3 and preamp

In reply to this post by alsopb

Dave, N7AIG,

Please define "stochastic resonance", a new term for me, which may
apparently aid in weak signal detection.

When I was very active on 2M CW EME, in order to better detect very
weak signals below the noise, I played all kinds of adjustment games
with the CW BW, tone and IF shaping of my TS-930S. For my needs
(type of noise) it had by far the best NB that I've ever used. In
addition, I also used an Autek QF-1 external audio filtering system,
centered at about 400 Hz and an estimated 25 Hz audio BW. It did not
ring when adjusted properly. By dumb luck and extensive
experimenting, I discovered that the least expensive (cheapest)
headphones that Radio Shack sold, had a strong mechanical (audio
peak ?) resonance, also at 400 Hz.

My hearing (unadmitted at the time) had also like Fred's, had been
exposed to many, many very, very loud noises, during one of my
careers, and suffered greatly from Tinitus and overall hearing
impairment. It happened that my preferred or best CW weak signal
copying frequency, was 400 Hz.

Anyway when the searched for very weak signal ( sometimes > -10 dB
below the noise) lined up with all the adjusted BWs, it just seemed
to "pop" out of noise and become detectable.

So Dave, is this at all related to, or similar to " stochastic resonance" ?

Chuck, W7CS

______________________________________________________________
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
Message delivered to [hidden email]

LA7NO

Re: K3 and preamp

Have a look here:

http://en.m.wikipedia.org/wiki/Stochastic_resonance

P-T
LA7NO

On 10 September 2014 01:24, Chuck Smallhouse <[hidden email]> wrote:

> Dave, N7AIG,
>
> Please define "stochastic resonance", a new term for me, which may
> apparently aid in weak signal detection.
>
> When I was very active on 2M CW EME, in order to better detect very weak
> signals below the noise, I played all kinds of adjustment games with the CW
> BW, tone and IF shaping of my TS-930S. For my needs (type of noise) it had
> by far the best NB that I've ever used. In addition, I also used an Autek
> QF-1 external audio filtering system, centered at about 400 Hz and an
> estimated 25 Hz audio BW. It did not ring when adjusted properly. By dumb
> luck and extensive experimenting, I discovered that the least expensive
> (cheapest) headphones that Radio Shack sold, had a strong mechanical
> (audio peak ?) resonance, also at 400 Hz.
>
> My hearing (unadmitted at the time) had also like Fred's, had been exposed
> to many, many very, very loud noises, during one of my careers, and
> suffered greatly from Tinitus and overall hearing impairment. It happened
> that my preferred or best CW weak signal copying frequency, was 400 Hz.
>
> Anyway when the searched for very weak signal ( sometimes > -10 dB below
> the noise) lined up with all the adjusted BWs, it just seemed to "pop" out
> of noise and become detectable.
>
> So Dave, is this at all related to, or similar to " stochastic
> resonance" ?
>
> Chuck, W7CS
>
> ______________________________________________________________
> 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
> Message delivered to [hidden email]
>

73,

Per-Tore / LA7NO