SB-303 impressions....

[Glen Zook]

Having owned both the SB-301 and SB-303 the SB-301, in
my opinion, is definitely the better receiver!

The noise generated in the SB-303 is internal and not
due to "better sensitivity".  The SB-303 was
Heathkit's first attempt at making an amateur band
fully solid-state receiver and it shows!

I have serviced a "fair" number of SB-303 and SB-301
receivers over the years and without exception the
minimum detectable signal on the SB-301 is MUCH better
than the SB-303.  The MDS is the minimum signal that
can be detected when running a signal generator,
matched to 50 ohms, and with an accurate attenuator
into the receiver.  Virtually all SB-301 receivers can
detect a signal well under 0.1 microvolts (even on 10
meters).  The SB-303 has to really strain to make even
0.1 microvolts.  In general, the SB-301 receivers are
at least 6 dB more sensitive than the SB-303.

Of course the MDS doesn't apply in the real world with
all the noise that is generated on the bands.  In
virtually all locations the noise level is quite a few
dB above the MDS.  But, as a measure of the actual
performance of a receiver, the MDS gives a very good
comparison.

I did not like the high level of noise coming from the
SB-303 when not actually receiving a signal.  The
constant "rush" is very annoying to me!  The SB-301 is
noticeably quieter.  This is due to the inherent
higher noise factor of the transistors that were used
in the design of the SB-303 and has nothing to do with
the basic sensitivity of the receiver.

The attenuator on the SB-303 is there because the
receiver does overload very badly.  Basically, it is
nothing more than a potentiometer across the input
circuit.  The SB-301 does not need this!  However, it
does have an r.f. gain control  A tube type front-end
is MUCH less likely to suffer overload than a
transistor front end.

You do have to wait about a minute for the SB-301 to
"warm up" whereas the SB-303 is "instant on".  Other
than that, the SB-301 outperforms the SB-303 99.9
times out of 100 (if not more!).

In an urban or suburban area where there are several
amateur radio stations close by, the SB-303 will go
"belly up" unless you really "crank in" a lot of
attenuation.  But, this then cuts down on the
effective sensitivity and you cannot receive many
stations that well, if at all.  The SB-301, on the
other hand, with the tube type front end, generally
will not overload, cross talk, intermod, etc., unless
the other station is located next door and is running
the full legal limit!  The SB-303 will do all of these
things if the other station is within 2 or 3 miles
from you unless you really crank in the attenuation!

Thus, I traded off my SB-303 for an excellent
Hammarlund HQ-140X about 3 years ago and haven't
looked back!  The HQ-140X was to recreate my station
when I was a senior in college.

Glen, K9STH


--- "Guy G. Giacopuzzi" <gggdds at JS-NET.COM> wrote:

Having used both a 303 and 301 side by side for
several years, I have to side with the 303.  The 301
might seem a bit "quieter" relative to extraneous
noise, but this might be the greater sensitivity of
the 303....with them both side by side, i find myself
going to the 303' more often....Never experienced the
infamous overload problem, but I do use the RF ATTEN
control; the 301' doesn't have one....


=====
Glen, K9STH

Web sites

http://home.comcast.net/~k9sth
http://home.comcast.net/~zcomco



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