[AMRadio] Matching A Crystal Filter To A Tube-Mixer

[Byron Tatum]

Hello-
    I am building a small tube type 80/40 meter receiver and am borrowing some 
of the front end/mixer circuitry from the "Mate To The Mighty Midget", a 3 tube 
(all 6U8 tubes) 80 / 40 meter set. This small set uses a half-lattice 455 KHz 
crystal filter that consists of two crystals spaced about 1 KHz apart and a 
tuned circuit at 455 KHz. My version is going to have a little more circuitry, 
with more IF gain and a product detector/AVC.
    I have a 2.8 KHz BW 455 Khz crystal filter from a later model Icom 
transceiver that I would like to use in place of the half lattice filter. I have 
looked at a few circuits where a tube mixer is feeding a conventional (6 or 8 
pole) crystal filter and some of them just feed the filter directly through 
coupling capacitors. 

    I believe most 8 pole crystal filters are around 500-800 ohms impedance. Is 
any form of matching needed between the tube mixer plate / crystal filter 
input or the tube IF amp grid/crystal filter output?
                    Thanks,
                            Byron WA5THJ