On Wed, 15 Sep 2004 11:08:21 +0200, Toni
wrote:

I have a Sony radio for SWL and I have seen that if I parallel a
300 ohm resistor to the antenna input the received signal drops
considerably

Hi Toni,

This is something you could test yourself:
- Having a 50 ohm feedline, would I benefit by using a 4:1 balun
in reverse at the rcvr input?
with a before/after 300 ohm resistor application. Sure it isn't a 330
Ohm resistor? 300 is not a standard value. Also, is there any chance
this resistor is wire wound? Makes an important difference!

Alternatively, the same phenomenon should occur if you put the
resistor in series. Be careful to maintain ground in all tests.

Finally, what are you using as an input reference? The signal from
this same 50 Ohm feedline?

73's
Richard Clark, KB7QHC