Topband: 160m Condx

[Lee STRAHAN]

Just as a reminder to all that these BCI problems can also occur at 2nd and 3rd order IMD mixing.
Example 3rd order,  one station on 1220 where 2X equals 2440 and a second station at 620 subtracted puts a 3rd order product right on 1820 .
Another example 3rd order, is 2 stations at 600 where 2X equals 1200 added to a second station at 610 for a 3rd order product at 1810.
Second order is 1190 +620 is  1810 KHz   or 860 + 970 KHz is 1830 KHz
 These type of IMD products can be as a result from any amplifiers inline with the antenna and radio or even the radio itself mixing in nonlinear devices like BJT or FET transistors, even passive devices like transformers and crystal filters.
   This is directly related to the 3rd and 2nd order IMD specs on any particular piece of equipment.
  Sometimes these spurs are not just BC station harmonics.
Lee  K7TJR  OR

-----Original Message-----
From: Topband <topband-bounces at contesting.com> On Behalf Of Lee. KX4TT via Topband
Sent: Monday, November 12, 2018 10:58 AM
To: 'Mike Waters' <mikewate at gmail.com>; ve6wz at shaw.ca
Cc: 'topband' <topband at contesting.com>; 'Filipe Lopes' <ct1ilt at gmail.com>
Subject: Re: Topband: 160m Condx

Concur ..... if a frequency either ends with a zero, or if you add the digits up and get a number divisible by 9, it will likely have a greater change for BC interference. 

Example in Tampa (Florida, US) is 1860, which is the 3rd harmonic for WDAE 620, which is a 50kW stn.  An example for our UK friends is 1818, which is the 2nd harmonic for 909khz (BBC Radio 5)....................

Great discussion!

73 de Lee KX4TT



-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Mike Waters
Sent: Monday, 12 November, 2018 13:27
To: ve6wz at shaw.ca
Cc: topband <topband at contesting.com>; Filipe Lopes <ct1ilt at gmail.com>
Subject: Re: Topband: 160m Condx

Perfect! Thanks for sharing.

73, Mike
www.w0btu.com

On Mon, Nov 12, 2018 at 12:13 PM VE6WZ_Steve <ve6wz at shaw.ca> wrote:

> Know bad frequencies- great resource here:
> http://www.k8nd.com/TopbandBadFreqs.pdf
>
> However…a “best practice” on 160m is NEVER call CQ on an exact frequency.
> Why is it ever necessary to call on 1830, 1820, 1822 etc. exactly? 
> Call CQ on 1820.3, or 1820.4 or 1822.6 or 1827.8.
> Perhaps its human nature to want to use a nice “round” number, but 
> this accomplishs nothing except increase the chances of being on a harmonic QRG.
> Its surprising how many DX-peds will do this too.  We don't need a 
> nice frequency with no decimal points! You will be found just fine 
> with all the skimmers and spotters out there.
>
> de steve ve6wz.
>
>
>
> On Nov 12, 2018, at 9:31 AM, Filipe Lopes <ct1ilt at gmail.com> wrote:
>
> Hi
>
> Is there a listing of such frequencies? Want to avoid those in the 
> coming contests
>
> 73's Filipe
> CT1ILT CR5E CR6K
>
> Sent from my Huawei Mate 8
>
> Na(o) Seg, 12 de nov de 2018, 17:28, Mike Waters <mikewate at gmail.com>
> escreveu:
>
> I wish we could get the word out to avoid frequencies like that: 1810, 
> 1820, 1830, etc. There are almost always AM BC harmonics on those freqs.
>
> 73, Mike
> www.w0btu.com
>
> On Sun, Nov 11, 2018 at 4:24 PM k1zm--- via Topband < 
> topband at contesting.com>
> wrote:
>
>
> Band still down a bit from last week but 4k6fo good sigs now on 1830.0 
> from Alim.
> 73 JEFF
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