Topband: S9LA on topband - filters for 160m for next time Dx-peditions !!!

[Ulli Grunow]

Hi topbanders and DX-pedition teams !
Whatever Dx-pedition plans lowband activities, they should prepare the
filters designed and published by Frank Donovan, W3LPL
check his webside (info at www.qrz.com)

I build 2 filters based on his design for G4VGO in the direct neighborhood
of BBC-World service super power AM-station !
Even when running a 50m vertical (raised by a balloon during contests !)
G4VGO can now use operate topband without ANY problems as he mentioned to me
by e-mail

By the way, BBC is running 1.5MW to the antenna - the strongest AM
transmitter on medimwave in Europe... and they have 7dB gain antenna also
pointing to Eu-continent...just bombing on the QTH of G4VGO !!!

The filter is extremly small because I used to NP0-ceramics (10% of the
price of silver mica and I measured the same Q of >200 on topband) and
Amidon t50-2 cores... (about 6cm x 4cm x4cm for single band)
If you build it for both 80m and 160m you can simultanious use two rx's at
one rx-antenna - this is useful for large multi tx-dxpeditions... the size
of the filters is of coarse double...hi

I modified the W3LPL filter for 160m to just cover EU topband spectrum
(1810....1870kHz) - tuning the filter to minimum bandwidth, only 40kHz/-3dB
was possible...but more important is the excellent rejection of AM
broadcasters...... >90 rejection at 1000kHz is possible....

The problem of interference would have been completely gone with such
filters....

Thanks to nice design by W3LPL....

Ulli, PA5AT