[Hallicrafters] S-40A Sensativity

[Glen Zook]

Try a single wire or else connect the braid to the center conductor of the coaxial cable and then connect to the terminal that is the farthest from the ground.  Connect the 2nd antenna terminal to the ground terminal.  A lost of the receivers from before at least the mid 1950s do not like a low impedance from coaxial cable.  They have considerably better sensitivity with feedline impedance between 300 ohms and 600 ohms or with a single wire.

If that improves the sensitivity then you can use a TV balun connected to the two antenna terminals (with the ground removed) and then use coax.  The article that appeared in Electric Radio a while back can be found at

http://k9sth.com/uploads/TV_baluns.pdf

Even if you find other problems connecting the antenna as described above will help considerably.

Glen, K9STH

Website:  http://k9sth.com


--- On Sun, 1/25/09, James R Carr <n7fcf at hctc.com> wrote:

I re-capped and re-tubed a 1947 S40a, and exchanged the 6SA7 mixer for a 6SB7-Y  but sensativity is still zilch. Even with a 135 ft. dipole. What do I look for next?