|[AMRadio] Cable splitters for receivers|
k4kyv at charter.net
Sun Jan 12 14:04:18 EST 2014
> From: Bill Guyger <bguyger at yahoo.com>
> We'll, the most obvious point is that the splitters are 75 Ohm. If you
> can take the impedance bump and not not mind the mis-match you still
> have to take into account Mr. Kirchoff saying you loose part of the
> original signal every time you add another branch off the feed line.
> Bill AD5OL
The bump in impedance from 50 to 75 ohms is not going to make a
discernable difference in receiving. Impedance matching is not critical
with a receiver like it is with a transmitter. The worse thing that
would happen would be a fraction of a dB of signal loss. Besides, very
few receivers present a perfect 50-ohm non-reactive load to the incoming
transmission line. As I recall, the 75A-4 manual says its input
impedance is something like 150 ohms. Not sure of the exact figure, but
far from 50 ohms. I use an attenuator on mine, because my transmitting
antenna delivers too much signal and I could use a little attenuation
to avoid cross modulation.
The splitter will reduce signal levels at both receivers. Theoretically
it should be at least 3 dB, if the signal is divided equally between the
two receivers. If it is a resistive network, the attenuation will be
much more. The greatest likelihood will be extreme attenuation on 160m
if the gadget is rated down to only 5 mc/s.
I once used two receivers, a 75A-4 and a R-390, just by connecting the
same transmission line to both receivers using a T-connector. It didn't
seem to attenuate either receiver's signal level noticeably. The
greatest danger in doing that is that spurious products from one
receiver will show up in the other.
More information about the AMRadio mailing list
This page last updated 24 Nov 2017.