26. Protecting the filter from aging.
When the filter needs no more adjustment or changing, it is time to conserve the good
properties. Use CRC 2-26 or 3-36 or 5-56 as an oxide-remover and re-oxidation-preventer.
I have used CRC2-26 over the years, and experenced, that it dissolves surface oxidation etc. exactly like said on the can. You will find the dissolved material as green "drab" at the bottom of the sprayed apparatus. Remaining CRC evaparates slowly, and within a few moths most of the liquid is evaporated. After that, a moleculair thin, oil-like layer shuts all surfaces off from the air, preventing new oxidation.
But during the first time, while it is evaporating slowly, it can act like an extra diŽlectric in L's and C's. The properties of C's and L's then keep changing. Also is a sertain pressiure nessacery to penetrate it and make contact possible. Motorbrushes can have trouble, spark, and burn the CRC and collector.
Warning: Do NOT apply CRC to variable condensers, close-wound coils and motor-brushes.
It works very well in plugs/connectors, potentiometers, switches, and as a light lubrication for very light running bearings etc. It drives moist out of the way, cleans the surface, and protects it from further corrosion, enhancing electrical contacts.
27 Applying the anti-oxidant:
27.1 Drill small holes (just big enough to pass the spray-tube) in the middle of each sidelid and cavity-bottom for spraying.
27.2 Drill a 3mm hole right in one lower corner of each cavity-sidelid for draining. Drill them close to the bottom-plate "G", all on the same side of the cavities (f.i. the "Ant"-side).
27.3 Spray generously on the central conductor, coupling links, and all internal walls.
27.4 Spray the inside of each central conductor through the hole in the top-compartment of each cavity.
27.5 Turn the filter around in all positions to roll the fluid around onto all surfaces.
27.6 Place the filter on absorbing paper, and let it drain for a few days. Tilt the filter in different directions to drain easier.
27.7 After a few days, you could apply and drain CRC2-26 for a second time if you want.
27.8 Then check the filter-performance. It should not be changed.
As you see, it is a lot of work to build and adjust the filter, but it is interesting and fullfilling. After all, the technics are not used much in the amateur-world. I could not find much theory about it. I hope, to have at least given good info, about which mechanical and RF-properties are important with respect to good performance, also after years of service, and what is important for correct adjustment an measurement of the filter.
If you find better info, or have other suggestions, please inform me via Email.
73's from Nico, pa0nhc.