"Dave" wrote
The second and third baluns are to allow me to plug it into my external
antenna connector. The first (attached to he coax) makes it possible to
carry the received signal to the second (with the mini-plug on it.) I am
using this with a small portable radio.

Dave, 300 ohm to 75 ohm RG-59 will work just fine for receiving, you should
be unable to tell the difference between that and 50 ohm coax. There is a
problem with adding multiple baluns, especially the cheap kind that previous
posters have warned you about. You could never need more than one balun, and
where receive-only is concerned, in most cases this simply allows easy
connection of coax to antenna - and little more. Well made current-type
baluns do provide both electrical isolation, a small amount of lightning
protection, and of course keep RF off the feedline when transmitting. I
don't understand why once you convert from antenna to coax - you ever
thought you needed another balun. Recommend eliminating the other two
upstream from the antenna-coax interface.

Jack