[AMRadio] Cable splitters for receivers


james.liles at comcast.net james.liles at comcast.net
Sun Jan 12 09:40:26 EST 2014


Good morning Bernie,

The input impedance of a receiver can accurately be measured by simply 
attaching your antenna impedance bridge to the antenna input.  doesn't 
matter if it's balanced or not for HF.

The Hallicrafters SR-150, SR-400, and SR-2000 are indeed almost right on 50 
ohm receivers.  Haven't measured the SX series but would expect them to be 
as defined in specs.  Would expect other radios to be close to specs as 
well.

Kindest regards Jim K9AXN

-----Original Message----- 
From: Bernie Doran
Sent: Sunday, January 12, 2014 8:07 AM
Cc: amradio at mailman.qth.net
Subject: Re: [AMRadio] Cable splitters for receivers

This discussion has come up before, the R390/ R390A people keep worrying
about having balanced input. My question is has anyone really performed a
lab study? I have just plain connected two and three receivers together and
at least on the lower bands have noticed no effects. I realize that it would
be easy for garbage from one receiver to get into another by doing that and
yes, for VHF probably not the way to do things.  The other question is, just
what is the input Z of a receiver? I do not care or believe what the
manufacture says. I would wager that it would be difficult to find any that
are close to 50 Ohms.  I would guess there is a range from about 10 Ohms to
a few hundred Ohms.  Hey, It has an SO239 on it, it must be 50 Ohms.
someday I will hook up the antenna analyzer to a RX input and see what it
says.   Bernie W8RPW


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