Topband: 1820 spur

[Robin]

ALL of the 10 KHz frequencies are bad somewhere in NA, and the same issues apply to the 9 
KHz spaced MW stations in other parts of the world.

Second harmonic, and regular ordered products abound.  Example 980+840=1820

These products/harmonics are generated in lots and lots of things, from our own receiver 
front ends to the nearby rusty chain link fence, and our own guywires

The stations need not be near by. Consider just how loud any 50KW Omni station is after 
just ONE hop.  Easily many tens of millivolts will appear in every topband TRANSMIT 
vertical within 1000 miles - from each station.  Just look at how hard the S meter pins at 
60 dB over 50 microvolts when tuned to one of the powerhouse stations

http://en.wikipedia.org/wiki/List_of_50_kW_AM_radio_stations_in_the_United_States
This is JUST the 50KW stations, there are thousands more in the 1 to 10 KW class

Run your own ordered mix calculator, and you will be surprised at the results.  Its 
amazing we are not plagued much more than we are by products and harmonics.  It takes a 
LOT of harmonic suppression to reduce 50KW to a power we can not hear with a beverage 
pointed at the station, FAR more than required by the rules.

Bottom line, stay away from any exact KHz, especially any exact 10 KHz in North America. 
The worst possible freqs in NA are 1820, 1840, 1860, etc. as these can be both harmonic 
and product frequencies.  Never use these (or any) exact frequencies.  An offset if 150 Hz 
is often enough to make your signal easily readable where it would be obliterated by a 
weak carrier on the exact frequency

Robin Critchell, WA6CDR


----- Original Message ----- 
From: "Tim Duffy K3LR" <k3lr at k3lr.com>
To: "'Mike Waters'" <mikewate at gmail.com>; "'topband'" <topband at contesting.com>
Sent: Friday, November 02, 2012 19:59
Subject: Re: Topband: 1820 spur


> Hello Mike:
>
> I believe that the 1820 spurs are created from multiple sources. That is why
> you can hear it at many QTHs around the world (although the spur content is
> technically different with respect to the origin).
>
> There are 57 different licensed AM broadcast stations in the USA and Canada
> that operate on 910 KHz. Most all of them are operating within licensed
> parameters with respect to second harmonic radiation limits.
>
> Topband stations are best to avoid operating directly on 1810, 1820, 1830,
> etc. for this reason.
>
> 73,
> Tim K3LR
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Mike
> Waters
> Sent: Friday, November 02, 2012 9:17 PM
> To: topband
> Subject: Re: Topband: 1820 spur
>
> It can be heard in Japan and Canada?! Where could it be coming from?
>
> 73, Mike
> www.w0btu.com
> _______________________________________________
> Topband reflector - topband at contesting.com
>
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