Using the SB-301 on CW

[W6CUX]

Hi Allen,
Moving the CW-BFO crystal frequency is just a matter of putting a 
parallel trimmer capacitor across it. However, a problem comes about 
because that same crystal (3396.4KHz) is used as the USB-BFO and should 
not be changed.

A solution I've used is to install a second 3396.4KHz crystal in place 
of the RTTY crystal. At the wafer switch MS4R, clip the jumper between 4 
and 3 and install jumper between 1 and 4. Now when the switch is in the 
CW position, the new 3396.4 crystal becomes the BFO.

The new crystal should be moved DOWN in frequency** to be within 600-700 
Hz (I like 600 Hz) of the center of the CW filter of 3395.4KHz.  This 
can be done with a 3-30pf trimmer capacitor, installed in parallel 
across the RTTY crystal socket. You will need about 20 pf.  A good 
source of these caps is your neighbor's junk-box or  
http://www.surplussales.com/Variables/Ceramic/CerCap1.html  

All this presupposes that you don't work RTTY. There is another solution 
where a cap is diode-switched across the existing USB crystal in the CW 
mode. I made this mod in the 70's on a SB-101 and a SB-303 but it's all 
been lost to history. W0QNI still has the SB-101 so maybe he can 
reverse- engineer it.

Now we need an easy way to change the side-town oscilator to 600 Hz.

73, Stu W6CUX

**[3395 .4 + 0.6 = 3396.0 KHz]


Allen Jones wrote:

>The 1000 Hz note you get when you center a CW station
>using the Heath CW filter is much too high in
>frequency for me.  I prefer something lower, 700-750
>Hz which seems to be the norm for most of the stuff
>built today.  Anyone aware of a mod to change the peak
>frequency?  I assume it would require shifting the
>BFO.
>
>Thanks
>
>Allen, W9DZ
>
>
>  
>

-----------------------------------------------------------
Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/HEATH.html