[R-390] HSR-2 vs 390a

[Jim Brannigan]

Hiss or internal receiver noise is generated by the mixers and amplifiers in
the receiver.  This is quite normal.  The first test of a receiver is to
connect an antenna to the input terminal.  The ambient noise level should be
louder than the internal noise of the receiver.  If it is not, than the
first RF stage is not amplifying properly (usually).

Jim

> So... the matter of hiss ,  as we call it,  came up.  This is the noise
that
> occurs when the r.f gain is turned up all the way with the antenna
> disconnected.  On my receiver (and the author's 390a which he no longer
> owns),  with the rf gain up all the way with the antenna disconnected,
> there is a noticeable hiss,  or background noise. The hiss is greater with
> the bfo on and increases in magnitude as the bandwith is switched to wider
> settings.  The hiss doen't move the S meter.  I took this as normal and
> typical of most radios.