Topband: New use for Noise Canceling box
art at nk8x.net
Sat Dec 3 11:08:52 EST 2016
A similar method has been in use here for a couple years. It let me snag
VP8STI among others underneath a big noise last winter.
This year, I made a wire flag for 80/160 as a noise pickup antenna, and
pointed the null 180 degrees away from the noise source(s). The flag is
routed to a variable gain preamp before the phasing unit.
It appears that adding the noise pickup antenna, can add lobes or skew the
pattern of my 4 square rx antenna. That doesn't mean that the desired
signal's SNR won't be improved. Often it is.
Prior to the flag, bogs were being used here as the pickup antenna. I still
use them when the signal can be improved from polarity diversity.
de Art NK8X
On Sat, Dec 3, 2016 at 9:01 AM, Tree <tree at kkn.net> wrote:
> Last night - around 8 PM or so - this HUGE noise signal showed up on 160 -
> sweeping up the band slowly. Probably a DC power supply with signals every
> 80 kHz or something. But - it has some energy all over the ban - thus
> rasing my noise floor. Sorry if I was an alligator last night.
> I put a Beverage up to the East just before the contest started - so I had
> two RX antennas - the other being a Hi-Z 4 square. The Hi-Z said the noise
> signal was East - perhaps a bit stronger in the South direction than North
> - so call it just South of East. The Beverage picked it up very well - so
> it agreed. A feeble attempt at DFing last night was unsuccessful - but
> will be tried again if it stays on during the daytime. It is still on this
> morning before Sunrise.
> The nasty part of the noise is about the same signal strength as most good
> signals coming in that are not local (looking at the band scope). It has a
> 10 kHz or so wide peak.
> I was able to put the two RX antennas into a MFJ-1026 - with the output
> going to the RX input of my K3 - and adjusted the controls to null out the
> noise. With a local signal - I have been able to obtain deep nulls and
> this proved to be true with this noise. I was actually running guys on the
> East coast right in the middle of the worst part of the noise after doing
> This technique would likely be useful for those who have a similar noise
> situation - so I wanted to share. You obviously don't need a beverage for
> the "noise" antenna - just something that is good at picking up the noise
> and perhaps nothing much else. If you have a neighbor that has a noisy
> device - just put something that is close to their house.
> It's a battle out there to keep your noise sources under control. I'll
> report back if I am successful in finding this one.
> 73 Tree N6TR / K7RAT
> Topband Reflector Archives - http://www.contesting.com/_topband
More information about the Topband