Can I run this harmonic filter backwards?

Hello all

This question deals with whether or not this RF harmonic filter is symetrical input to output.

I have a ten-year-old Silicon Valley 450B RF amp being used as the IPA for a 25 kw FM transmitter. It is conservatively opperated at about 350w forward. I don't have reliable figures for reflected, but I have been told that these units were designed to operate into fairly high reflected values in this kind of situation. In any case, the unit has operated reliably for the last ten years or so with the exception of power supply failures (blown fuses) two times in that period.

The unit failed (registering excessive reflected on the lcd) last September. When I opened it up, I discovered that the pin inside the N type input connector to the harmonic filter had burned up.

I also discovered that the RF power from the amplifier module was routed (through that connector) to the OUTPUT of the filter whereas the INPUT connector of the filter assembly was routed to the external RF output of the unit--where the RG 213 cable connects to carry the power to the transmitter PA cavity. It obviously came from the factory this way.

The filter itself appears to be a straight forward design of four sections with five ceramic capacitors shunt and four open air coils of about three turns of perhaps 8 guage solid wire in series between them. The capacitors appear to be all the same however I cannot verify that without complete dissassembly and I hesitate to do that because I bet this thing was tuned by adjusting the spacing of the turns in the coils and I don't have equipment to sweep it and return it to spec after reassembly.

I intend to put the filter back in place as it was unless I get really good info otherwise. The manufacturing company has been notably less than helpful. Bottom line--does your experience tell you that filters of this type are symetrical, that is, they don't care which way you send the signal through? Or are they stagger tuned in some fashion to broad band across the 88MHz to 108MHz band--and would that make any difference? The amplifier itself is designated as a broadband amplifier and requires no tuning or configuration to operate across this bandwidth.

Looking forward to your input.

Lonnie