[Boatanchors] difference bet. 75A3 and A4?

[Glen Zook]

The difference between the 75A3 and 75A4 is
substantial.  The 75A4 has a product detector from the
factory and the 75A3 does not.  The 75A4 was designed
to be an SSB receiver whereas the 75A3 is an AM/CW
receiver and works well on NBFM if the optional FM
adapter is in place.

The 75A4 came from the factory with a 3.1 KHz
mechanical filter and two additional sockets for more
filters.  The 75A3 came from the factory with a 3.1
KHz mechanical filter and space for one additional
filter.  Also, the 75A3 has a crystal filter that
works in conjunction with the mechanical filters
whereas the 75A4 does not.  The 75A4's AVC is designed
to work with SSB whereas the 75A3 turns off the AVC
when the BFO is turned on.  The "S" meter on the 75A4
works on SSB whereas the meter on the 75A3 does not.

I have both the 75A4 and 75A3 (along with a 75A2 which
is the same as the 75A3 except that it does not have
provision for mechanical filters).  Each receiver has
its pluses and minuses.  For SSB use the 75A4 is
definitely the better receiver.  For AM / CW I prefer
the 75A3 even though I have an 8 KHz wide mechanical
filter in the 75A4 for AM.  However, in the 75A3 I do
not use the 3.1 KHz filter for AM but have a resistive
network across the socket for the 2nd mechanical
filter.

There are too many minor differences between the two
receivers to try to list.  You really have to use both
to know which you are going to prefer to use.

Glen, K9STH

--- Eugene Hertz <ehertz at tcaf.org> wrote:

Can anyone give me a brief comparison of the collins
75A3 and A4 receivers?  I understand that the
mechanical filters in both allow some kind of ssb
reception (2.8k? 3.1k?) but I have also heard that a
product detector is even better and would be desirable
for either the 3 or 4.

Glen, K9STH

Web sites

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


		
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