More low-pass filters

Fri Jul 31 10:37:00 EDT 1992

I bought 2 of the 6 kW ICE low-pass filters, before they even appeared in   
their catalog.  They are ruggedly made and come with an attenuation curve
from an HP network analyzer.  I plugged them in (one for each amplifier) and
they worked fine on receive but one of them would short out on transmit.  It
turns out the cover alignment was very critical.  It was very close to one
of the components.  Realigning the cover solved the problem.  I brought it
to the attention to Mike W9SU at ICE.  The older design low-pass filters
(such as B&W) do not have as sharp of a roll-off above 30 MHz as the newer
designs.  I put several of them on a network analyzer, and the one that 
looked particularly good was the AEA.  I opted for the ICE because of its
ruggedness (if rated for 6 kW, it should be undestructable at 1500 watts!).
Look for high attenuation around 40-45 MHz, where TV IF's lie.  That also
happens to be where the TS-930 first IF lies, and I hoped that low-pass 
filter would also help in curing some IF interference between the two
TS-930's (it didn't...).
                                        -- Rich K1CC

More information about the CQ-Contest mailing list