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K4HD question

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Gary Smith-2

K4HD question

At this time there are no nearby hams to
disrupt my K3s. There are no local AM
broadcasters that come in as overload. I
do have issues with a few 2nd harmonic
stations from the BC band, one for example
from S. America on 1.8400. I won't likely
be using my K4 at a contest site and I am
the only ham in the house.

With that, is there anything the K4HD
offers me Rx-wise, or otherwise, that the
K4D does not?

Thanks,

Gary
KA1J
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Grant Youngman-2

Re: K4HD question

Any of these things you mentioned might not bother you now BECAUSE you are using a K3.

The K4D adds a second A/D chain with dedicated front end filters for whatever band the second receiver is tuned to. Plus diversity reception.

I seem to recall some reference to a “wide-band” mode, which may come in to play if the two receivers in the K4 are tuned to widely disparate frequencies (e.g., one on 80M, one on 20M). This could exacerbate the A/D overload issue with wide-band direct sampled SDRs. Wouldn’t be an issue with the K4D. Although you might need a K4HD to get to the heat-proof front end you currently have with the K3.

Grant NQ5T
K3 #2091 KX3 #8342

> On May 29, 2019, at 3:52 PM, Gary Smith <[hidden email]> wrote:
>
> At this time there are no nearby hams to
> disrupt my K3s. There are no local AM
> broadcasters that come in as overload. I
> do have issues with a few 2nd harmonic
> stations from the BC band, one for example
> from S. America on 1.8400. I won't likely
> be using my K4 at a contest site and I am
> the only ham in the house.
>
> With that, is there anything the K4HD
> offers me Rx-wise, or otherwise, that the
> K4D does not?
>

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Gary Smith-2

Re: K4HD question

Thanks for the reply,

As I require diversity , the K4D is
necessary, as I also require an autotuner,
I need that as well. The costs are adding
up.

I certainly don't want a new rig that has
in any way, less capability than the fully
loaded K3s I have now. If a K4HD with
autotuner is functionally excess to my
having a K4D with autotuner, that helps me
budget.

73,
Gary
KA1J

> Any of these things you mentioned might not bother you now BECAUSE
> you are using a K3.
>
> The K4D adds a second A/D chain with dedicated front end filters for
> whatever band the second receiver is tuned to. Plus diversity
> reception.
>
> I seem to recall some reference to a "wide-band" mode, which may
> come in to play if the two receivers in the K4 are tuned to widely
> disparate frequencies (e.g., one on 80M, one on 20M). This could
> exacerbate the A/D overload issue with wide-band direct sampled SDRs.
> Wouldn´t be an issue with the K4D. Although you might need a K4HD
> to get to the heat-proof front end you currently have with the K3.
>
> Grant NQ5T
> K3 #2091 KX3 #8342
>
> > On May 29, 2019, at 3:52 PM, Gary Smith <[hidden email]> wrote:
> >
> > At this time there are no nearby hams to
> > disrupt my K3s. There are no local AM
> > broadcasters that come in as overload. I
> > do have issues with a few 2nd harmonic
> > stations from the BC band, one for example
> > from S. America on 1.8400. I won't likely
> > be using my K4 at a contest site and I am
> > the only ham in the house.
> >
> > With that, is there anything the K4HD
> > offers me Rx-wise, or otherwise, that the
> > K4D does not?
> >
>
>

wayne burdick

Re: K4HD question

Administrator

In reply to this post by Gary Smith-2

> Gary Smith <[hidden email]> wrote:
>
> At this time there are no nearby hams to
> disrupt my K3s. There are no local AM
> broadcasters that come in as overload. I
> do have issues with a few 2nd harmonic
> stations from the BC band, one for example
> from S. America on 1.8400. I won't likely
> be using my K4 at a contest site and I am
> the only ham in the house.
>
> With that, is there anything the K4HD
> offers me Rx-wise, or otherwise, that the
> K4D does not?

There are some subtleties in noise blanking that may distinguish the two modes (direct sampling or superhet). The blanking used in direct-sampling should have an advantage on complex, high-duty-cycle noise sources, while the hardware blanking modules used in the superhet may have an advantage with extremely short pulse sources. We'll be extensively testing and comparing them.

73,
Wayne
N6KR

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K9MA

Re: K4HD question

I've never found the K3 noise blanker to be very effective on power line
noise, and I've tried all possible combinations of settings. If the K4
noise blanker were really effective on line noise, I might buy one.

73,
Scott K9MA

On 5/29/2019 20:39, Wayne Burdick wrote:
> There are some subtleties in noise blanking that may distinguish the two modes (direct sampling or superhet). The blanking used in direct-sampling should have an advantage on complex, high-duty-cycle noise sources, while the hardware blanking modules used in the superhet may have an advantage with extremely short pulse sources. We'll be extensively testing and comparing them.

--
Scott K9MA

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k6dgw

Re: K4HD question

Noise blankers were designed for repetitive impulse noise, the largest
former example of which was ignition noise from vehicles. They have not
ever been very effective against power line hash which tends to be
non-impulsive and highly random. These days, repetitive ignition noise
is not a problem for many, don't know why, there are still spark plugs
in there. Power line hash comes from a myriad of sources ... hardware
anchoring insulators, transformers, fuses, and the like, as well as
micro arcing across dust covered insulators. It's highly random, over
even small time intervals, and just not the enemy noise blankers were
designed to fight. If Wayne had graduated from Hogwarts, he might have
some magic to make them work on power line hash. Lacking that, not sure.

73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 5/29/2019 6:43 PM, K9MA wrote:

> I've never found the K3 noise blanker to be very effective on power
> line noise, and I've tried all possible combinations of settings. If
> the K4 noise blanker were really effective on line noise, I might buy
> one.
>
> 73,
> Scott K9MA
>
> On 5/29/2019 20:39, Wayne Burdick wrote:
>> There are some subtleties in noise blanking that may distinguish the
>> two modes (direct sampling or superhet). The blanking used in
>> direct-sampling should have an advantage on complex, high-duty-cycle
>> noise sources, while the hardware blanking modules used in the
>> superhet may have an advantage with extremely short pulse sources.
>> We'll be extensively testing and comparing them.
>
>

K9MA

Re: K4HD question

On 5/29/2019 20:57, Fred Jensen wrote:
> Noise blankers were designed for repetitive impulse noise, the largest
> former example of which was ignition noise from vehicles. They have
> not ever been very effective against power line hash which tends to be
> non-impulsive and highly random.

That has not been my experience. Most line noise IS impulsive, and some
noise blankers can be quite effective, but only if there are no strong
signals nearby. I'm hoping a direct sampling receiver could avoid that
problem. One method that has been used in the (distant) past was a
second receiver tuned to a nearby but clear frequency to control the
noise blanker. It seems that a direct sampling receiver ought to be able
to do something like that.

73,

Scott K9MA

--
Scott K9MA

[hidden email]

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Jim Brown-10

Re: K4HD question

In reply to this post by k6dgw

On 5/29/2019 6:57 PM, Fred Jensen wrote:
> Noise blankers were designed for repetitive impulse noise, the largest
> former example of which was ignition noise from vehicles. They have
> not ever been very effective against power line hash which tends to be
> non-impulsive and highly random.

Huh?

The ARRL book on power line noise specifically states that virtually all
power line noise is impulse noise, the result of arcing at positive and
negative peaks of the 60 Hz line voltage. It is NOT random noise. It IS
quite broadband. Arcing can also occur in big motors, or in any system
where an arc occurs.

BEFORE the days of microprocessors, switch-mode power supplies, and
other power control systems that use square waves, nearly all man-made
noise was impulse noise. NOW, most of the noise that surrounds us is
from those microprocessors, switch-mode supplies, and other power
control equipment. That noise is NOT impulse noise, and noise blankers
cannot act on it.

73, Jim K9YC

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K9MA

Re: K4HD question

On 5/29/2019 22:12, Jim Brown wrote:
> BEFORE the days of microprocessors, switch-mode power supplies, and
> other power control systems that use square waves, nearly all man-made
> noise was impulse noise. NOW, most of the noise that surrounds us is
> from those microprocessors, switch-mode supplies, and other power
> control equipment. That noise is NOT impulse noise, and noise blankers
> cannot act on it.

Alas, even in my urban neighborhood, I fear the day is coming when all
this electronics generated noise will drown out the line noise.

--
Scott K9MA

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