[Elecraft] K3 NB

[Mike Scott]

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: elecraft at mailman.qth.net
>From: VR2BrettGraham <vr2bg at harts.org.hk>
>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.