1Ж42А. As a mixer/Frequency changer????

[Mike Watterson]

Note unlike ALL regular valve contemporary to Rod Tubes, there is NO internal screen. Absolutely EVERY radio used a shield to clip the Rod Tube to the chassis, alumina Thick film circuit or PCB.
Coffee tin or other tinned steel is best as you need magnetic screen as well as electrical. Compare bringing a strong magnet near a Rod Tube and a DF91 / DF96.