[morzh]

As Rich said, the loop antenna is the front tuned circuit.

You could try to make a ferrite rod one, but then you need to experiment.

Or you could simply try to replicate the one that is missing. I am sure number of turns could be found somehow.

For example, here on our forum there was this thread.

https://philcoradio.com/phorum/showthread.php?tid=7816

Loop antenna for 46-420 Hippo

It has this link.

https://www.wa2ise.com/radios/12ba7.html#loop

See if this helps at all.