A small Filter tunable to anywhere within the 23 cm Amateur band is described that can be used in front of the ATV preamplifier to get rid of 13 cm spure from the ATV transmitter and limit QRM from radar signals. Tree serial L-C circuits are used. Inductance is made from brass rods. Tuning Capacitors are 4 mm brass screws which are fixed with lock nuts after tuning.
http://df2ck.de/tech/23cmfilter