I have a question about "best practice" in regards to how the 2nd mixer IF port is coupled to (in my case) a 20m double tuned filter on transmit.
I'm currently building out the transmit chain for a 20m single band SSB transceiver and I've got as far as the second mixer. It's a standard and simple single conversion superhet design. The mixer is a double-balanced ADE-1, with the 9MHz IF arriving on the RF port (as the output of the final IF amp) and the VFO feeding the LO port (si5351 ~ 5MHz). The 14MHz signal component from the IF port is currently around -30dBM, with the other mixer product (~4MHz) having the same power.
I'm going to follow this with a double tuned 14MHz BPF to eliminate any unnecessary mixing products. The BPF has a loss of around 8dB. From there, it's on to the amplifier chain.
My question is in relation to the 2nd mixer IF port on transmit. Best practice would say that you should terminate this port in 50 ohms at all frequencies. In the receive path for the same mixer, I terminated the IF port in a 9MHz (the IF freq) diplexer to ensure this happened. But, I'm not sure what to do for the transmit path and I don't see a definitive answer in my reference material. I'm tempted to just use a 6bB attenuator pad on the basis that I'm heading into a large amplifier. So, even though my signal budget isn't great, I can make up the loss in the following stage. But, I'm just not sure. Any advice would be greatly appreciated!