[Heathkit] DX100 & B.

[Glen Zook]

Here is the text from the message that I sent a few
days ago about the modification kits and the
differences between the DX-100 and DX-100B:

There were several Heath modifications to the DX-100. 
Those included the addition of a spotting switch which
was added under the Heathkit logo on the right hand
side of the panel.  This was part of the kit to
"improve keying characteristics" including grid block
keying.  That modification added capacitors to "shape"
the keying as well as allowing the VFO to run
constantly whenever the plate switch was placed in the
"transmit" position. Unfortunately, this did not allow
the signal to be monitored on a local receiver since
the VFO signal was usually strong enough to "block"
the receiver.  This kit was available for either the
DX-100 or the DX-100B.

The next modification was to replace the 50 pf
variable and fixed loading capacitors in the antenna
loading circuit.  Transmitters thus modified were
known as DX-100A units.  That is why the next version
of the DX-100 was known as the DX-100B and not the
DX-100A.  Again, a Heath modification kit was
available.

The final modification kit available from Heath was
the kit to add the SB-10 capabilities to the DX-100
and DX-100B.  The DX-100B chassis was "punched" for
the additional SO-239 connectors to install this kit. 
However, neither front panel was drilled for the
switch.  You had to drill (or punch) the DX-100
chassis to install the SO-239 connectors. 
Unfortunately, the stability of the VFO made SSB
operation a bit of a challenge.

The principal differences between the DX-100 and the
DX-100B are as follows:  The most "obvious" one is the
different cabinets.  The DX-100B had the continuous
tuning antenna loading which the "A" modification kit
added to the DX-100.  The DX-100B has only 1 crystal
position the switch for this was accessed through the
door in the top of the cabinet.  On the DX-100 there
are 4 crystals available but you have to remove the
entire transmitter from the cabinet to change the
crystals.

There was a very minor circuitry change in the 12BY7
driver circuit (a resistor and capacitor if I remember
correctly).  This increased the drive to the 6146
tubes on 10 meters.

The changes to the DX-100B actually reduced the cost
slightly in terms of manufacturing cost.  However, the
price remained the same, $189.95.

Glen, K9STH


--- Bill M Jenkins <bmjar.1 at juno.com> wrote:

Could some one of our Heathkit experts give the
difference(s) between the DX-100 and the 100-B. The
only difference I am aware of is the cabinet.
Enlighten us please.


Glen, K9STH

Web sites

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

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