[Heathkit] DX-100 vs DX-100B

[Larry Knapp]

Glen - Great job and very accurate on describing the differences.  Nice job as
always.

My suggestion to Tim, wb8owx, is to not care about modifications (which can be
found to change nearly every component in the transmitter) at this time.  Make
sure the transmitter works as designed.  It sounds and works very well as the
Heath engineer designed it.  After using it awhile, then if your disappointed,
look then.  Stock is not bad at all.  Best to you Tim.

73, Larry KC8JX
Owner of a DX-100B for many years.

--- Glen Zook <gzook at yahoo.com> wrote:
The DX-100B uses the 3-section variable capacitor in the antenna loading
whereas the DX-100 uses fixed capacitors and a 50 pf variable for the antenna
loading.  Heath did have a field modification kit to change the loading
capacitor arrangement on the DX-100 units to a 3-section variable. 
Transmitters thus modified were called DX-100A.  That is why the 2nd model of
the DX-100 was called the "B" model and not the "A" model.
 
The DX-100B has two capacitor values changed in, I believe, the driver
circuitry, to improve the drive especially on 10 meters.  This change is very
minor and I have seen the details of making the modification to the DX-100.
 
The DX-100B only has one crystal position instead of four as in the original
DX-100.  However, the single position can be accessed through the door in the
top of the cabinet whereas in the DX-100 you had to remove the transmitter from
the cabinet to access the crystal sockets.
 
The DX-100B uses the "Apache" style cabinet instead of the larger version of
the DX-100.
 
The DX-100B came with the holes for adding the SB-10 SSB adapter already
drilled whereas to use the SB-10 with the DX-100 you had to drill these holes.
 
Now, there is an approved Heath modification to add a spotting switch to both
the DX-100 and the DX-100B.  There was a field modification kit available for
this.  The kit also has provision for changing the keying of the DX-100 and
DX-100B to help with chirping.  However, if you make this modification the VFO
runs continuously when the transmit switch in "on".  If you happen to use your
receiver to monitor your keying this can be annoying!  You can download these
sheets from BAMA at http://bama.sbc.edu and do the modification yourself.
 
The kit came with four-page instructions including a template for drilling the
hole for mounting the spotting switch.  You can duplicate this modification
fairly easily.
 
There was a modification kit available from Heath to add the SB-10 SSB adapter
to both units.  This added a switch on the front panel and two SO-239 UHF
connectors on the rear panel.  Basically you diverted the driver from
connecting directly to the final amplifier tubes and added circuitry to change
the final from Class C to AB-1 when the transmitter was switched to SSB.
 
Frankly, the DX-100B and the DX-100 are basically the same transmitter.  The
changes made to the DX-100B actually resulted in a slightly lower price to
manufacture (elimination of two switches - the antenna loading and the crystal
selection, 3 crystal sockets, etc.).  Also, the Apache style cabinet was
cheaper than the older style cabinet (which I personally prefer - but my 2nd
primary transmitter back in 1960 was a DX-100!).
 
I have a DX-100 in my AM shack.  If you are interested, there are photos on the
K9STH website the URL of which is listed at the end of this message.
 
Glen, K9STH
http://home.comcast.net/~k9sth
http://home.comcast.net/~zcomco
 
> 
> --- wb8owx at fuse.net wrote:
> 
> First...what is the difference between the DX-100 and the DX-100B 
> 




	
		
__________________________________
Do you Yahoo!?
New and Improved Yahoo! Mail - 100MB free storage!
http://promotions.yahoo.com/new_mail