> -----Original Message-----
> Subject: Re: Topband: 1820 spur
>
> It can be heard in Japan and Canada?! Where could it be coming from?
>
> 73, Mike
> www.w0btu.
We can be sure it is not a harmonic of an IF. :-)
1820 is a particularly bad frequency because it involves 2nd harmonics of a
popular channel (910) and also is a mixing product for many orders of
multiple channels.
I think most of it comes down to harmonics of 910.
The actual law is the BC station has a certain maximum allowed spurious
level, AND cannot cause harmful interference from any defect no matter what
the level. My bet is a significant number of stations today don't even meet
the allowed maximum harmonic level.
This is because AM stations are going broke, and deregulation and budget
cuts. The FCC dropped the 1st class FCC back in the 80's, so anyone can work
on radio stations.
I found a strong signal on 2.5 MHz from a station in north GA. A local CB
shop worked on it, tuned the transmitter 4-400A PA to 2.5 MHz with the wrong
dip, and adjusted the antenna tuning unit for a low SWR.
It ran that way, with a kilowatt daytime on 2.5 MHz to a matched antenna,
for months.
I can hear radio Disney and some other thing every day below the AM band. It
is a mixing of two stations.
There are a multitude of things like this, plus illegal level switching
supplies. One popular satellite TV company has gear that can be heard for
miles on 160.
73 Tom
_______________________________________________
Topband reflector - topband@contesting.com
|