Topband: Bad Frequencies and Loop Pre-amps

John Farrer farrerj at
Tue Nov 13 09:44:32 EST 2018

As Lee KX4TT stated, a harmonic on 1818kHz is a problem for us in southeast England in the vicinity of the Brookmans Park transmitter for Radio 5 on 909kHz.
John G3XHZ

Sent from my iPhone

> On 13 Nov 2018, at 13:24, Roger Kennedy <roger at> wrote:
> I have never received ANY harmonics or intermod products from any of our
> British Medium Wave (AM) broadcast stations.  That's at several different
> QTHs, some of which were quite near the transmitters. (and never heard of
> anyone else having issues)
> They have to meet VERY high specs . . . but also, most are less than 1kW !
> (one of the stations I worked for had such a good Tx site - a salt marsh -
> they had to turn the power down to 150 watts!) Even the very big ones are
> usually only 10kW.
> So no need to avoid the 9kHz harmonics as far as us Brits are concerned!
> What IS a problem is all the Russian Navigation Beacons in the Baltic that
> pretty much wipe out everything between 1810 and 1820 kHz, so please try and
> avoid that part of the band if you want to work any EU !  (they sometimes
> turn them all off . . . but they are on most of the time.)
> The pre-amp I use on my 6ft 160m receiving loop is actually the design MFJ
> use in their 1026 noise canceller (I have a 1025 but copied their preamp
> design, as it uses the same pcb) . . . I get no intermod during contests,
> even though many EU stations are 45dB over S9 !
> Roger G3YRO
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