SA612AN input output impedance?

Hi, I design an HF oscillator (2-30MHz) by mixing a switched crystal oscillator (max 32MHz) with a 4MHz ceramic resonator VXO, into an SA612AN. This oscillator, will be followed by a second SA612AN, operating as a DSB modulator.

I am taking the signal out of pin 4 and I would like to design a LPF for each band in HF following pin 4 of the first chip and feeding pin 6 of the second chip.

But what is the impedance in pin 4 so I can design the input of the filter correctly?
Also, what is the impedance on pin 6 so I can design the output of the filter correctly?

Pin 6 seems oscillator PIN, how you would use it as an input ?

If you drive this PIN for an external oscillator, the input impedance is too high.
BetaX25*10E3..
Don't worry about the matching because even you have a small signal level the buffer included in the OC will drive the Mixer core hard.

I have already designed my filters for 50R impedance, but the simulation shows a much different response on say 1K and even on 300R. I could include resistive impedance matching pi networks at inputs and outputs of the filter to 50R, but I need to have an estimation of the impedance of the sa612an to be able to match correctly. Attenuation of these networks wouldn't matter too much as the whole thing is used as a local oscillator and balanced modulator, so the signal levels are higher.

If your filter needs an impedance around 50 Ohm, insert a simple BJT Emitter Follower with a small RE resistance ( Common Collector config) between filter and PIN6 to make the filter sees always 50 Ohm.

I tend to avoid active matching, because the non-linearities of the transistor amplifier will introduce harmonics in the already harmonic-rich mixer circuit... It is not pbvious if these are in frequencies that can be filtered by the post filter.

You said that the input impedance in pin 6 is very high, do you have an estimation?
Also, is the impedance at pin 4 near 1.5K? (collector resistor)