K3 NB

[VR2BrettGraham]

Some time back, somebody asked about how the K3's NB
handles the Hainan woodpecker.  I don't think I saw any
response, though may have missed it.

Hainan is QRV 24/7 whenever there is something they want
to watch going on, such as the recent VK/W war games in
VK4.  Several pulse rates are used & either some of rates
and/or combination of propagation results in pulses that
none of the NBs in rigs here can put much of a dent in;
other times they can take a healthy bite out of it.

The rest of the time, it pops up intermittently & has pretty
much rendered 40m useless when I turn the radio on
nowadays (as well as 80 & sometimes 30 & even 20m).

With the British & now Chinese woodpeckers seemingly
here to stay with us, I wonder if it might be possible to do
some 'predictive' blanking with the hardware NB gate (does
anyone remember the AEA WB-1)?

On a good day, these things are only 20 over - but usually
stronger & 'detected' blanking with 100-or-more kc of
S-meter pegging OTHR is a bit of a challenge...

73, VR10BrettGraham/p.

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[Terry Conboy]

At 05:37 PM 2007-08-31, VR2BrettGraham wrote:
>With the British & now Chinese woodpeckers seemingly
>here to stay with us, I wonder if it might be possible to do
>some 'predictive' blanking with the hardware NB gate (does
>anyone remember the AEA WB-1)?

How about some simple countermeasures (for a future firmware release):
Blank, then transmit an equal length pulse (on a clear frequency, of
course), with optional automatic ID every N minutes.

I'm sure we have some real "spooks" on the list who could suggest a
much better protocol...

Keep clam,
Terry N6RY





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[Doug Smith-9]

On Fri, 2007-08-31 at 20:29 -0700, Terry Conboy wrote:
> How about some simple countermeasures (for a future firmware release):
> Blank, then transmit an equal length pulse (on a clear frequency, of
> course), with optional automatic ID every N minutes.

That is the best argument I've heard for remote control of a radio.  

There's nothing quite like making a big fat juicy target out of yourself
on someone's radar scope!   ;-)

OTOH, it would be fun to write the DSP code to make it appear as though
the planet Mars was on a collision course with the radar site.

Or, maybe not...

73 OM,
-Doug, W7KF


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[k6dgw]

Terry Conboy wrote:
>
> How about some simple countermeasures (for a future firmware release):
> Blank, then transmit an equal length pulse (on a clear frequency, of
> course), with optional automatic ID every N minutes.

If it's anything like the Russian woodpecker, it likely transmits a
string of bits using a psuedo-random code in each "pulse', and the radar
RX can separate it's own echoes from fake ones.

That's got to be very difficult noise for any NB.  My TS-850 has a NB
designed for the old Russian woodpecker, but I don't know how it works,
and that radar is gone now so I can't try it out.  Maybe there's some
way to tailor the K3 DSP NB to the characteristics of the radar?

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2007 CQP Oct 6-7
- www.cqp.org
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[Mike Scott-7]

Brett,

OTHR is a big problem in NA, at least on the west coast. On 40M in the early
AM it can prevent operation over the entire CW segment using my current
equipment (no noise blanker). This is a primary focus of my wanting NB
capability.

I have yet to hear a report of any tester on the efficacy of the K3 NB on
OTHR. Perhaps this is because the NB is late-arrival functionality and the
summer QRN has just about shut the band down here during the early dark
hours.  For example this morning; I can't hear one CW signal through the
noise at 5:00am local. During winter up through late July this was prime DX
time except when the OTHR was present. When it was I just turn the radio
off.


Mike Scott - AE6WA
Tarzana, CA (DM04 / near LA)
QRP-ARCI #12326/ KX1  #1311/ Swan 350C


Date: Mon, 03 Sep 2007 00:58:34 +0000

>To: [hidden email]
>From: VR2BrettGraham <[hidden email]>
>Subject: Re: [Elecraft] K3 NB
>
>K6DGW replied to N6RY's apparently somewhat-not-serious
>response:
>
>> > How about some simple countermeasures (for a future firmware release):
>> > Blank, then transmit an equal length pulse (on a clear frequency, of
>> > course), with optional automatic ID every N minutes.
>>
>>If it's anything like the Russian woodpecker, it likely transmits a
>>string of bits using a psuedo-random code in each "pulse', and the radar
>>RX can separate it's own echoes from fake ones.
>
>One suggestion we had from RAAF's 1RSU (VK air force's unit
>that runs their OTHR systems) early on was that the Hainan
>woodpecker might be a comms system.
>
>A constant pulse train on HF would be hard to use to convey
>any data with either amplitude or phase.  And no one has yet to
>see anything but the pulses that make the woodpecker sound.
>
>The reason why we could force the Russian woodpecker to
>move back in the late 70s/early 80s was because they
>apparently could not differentiate between echoes from their
>pulses & anything else that looked like them.
>
>Since then, technology has come a long way & it is easy to
>imagine the computing horsepower & DSP now available
>would make most active countermeasures useless.
>
>And in practice, that seems to be the case.
>
>I get the impression here that OTHR isn't a problem in NA.  You
>lot are very lucky then.  In ITU Regions 1 & 3, it is a _big_
>problem.
>
>73, VR10BrettGraham/p.

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[VR2BrettGraham]

AE6WA said:

>OTHR is a big problem in NA, at least on the west coast. On 40M in the early
>AM it can prevent operation over the entire CW segment using my current
>equipment (no noise blanker). This is a primary focus of my wanting NB
>capability.
>
>I have yet to hear a report of any tester on the efficacy of the K3 NB on
>OTHR. Perhaps this is because the NB is late-arrival functionality and the
>summer QRN has just about shut the band down here during the early dark
>hours.  For example this morning; I can't hear one CW signal through the
>noise at 5:00am local. During winter up through late July this was prime DX
>time except when the OTHR was present. When it was I just turn the radio
>off.

It's odd, depending on who you are talking to, on the east coast
of NA the ZC4 woodpecker is/isn't a problem; likewise on the west
coast BY7.  Maybe this is a sign of how active one is, as these
things are hard to miss (ZC4 can be 20-40 over S9 here by itself
on a band with no other signals; BY7 taking out the entirety [for
much of the rest of the world, at least] of 40m should also be hard
not to notice).

With the K3 hardware NB having just been finished, I guess we'll
have to wait a while to see how well it works, at least from NA.

With a synchronous string of pulses, it should be easy to
generate & synchronize same to drive an upstream noise gate &
not have to detect when to blank in the presence of numerous
signals pushing the better part of -10 dBm.  Otherwise, not much
use for that ID timer if we're switching the rig off & giving it all a
miss. ;^)

73, VR10BrettGraham/p.

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