DSW-II series documentation:

Early Production:

The DSW-II-20 was released first, and two versions of printed circuit board have been produced. The early version is marked '7/15/02' and was used only for the 20M version.

The manual for the early DSW-II-20 version is at:

http://smallwonderlabs.com/old_DSW20_Manual

Several component-value changes were incorporated early in production based on user comments:

Issue: 1) rough or 'hashy' sidetone, erratic SWR

The original impedance-transformation network from PA collector to low-pass filter used a series-inductance input. This inductance and circuit stray capacitance may yield VHF oscillation. (Wes Hayward, W7ZOI discussed this topic in QST many years ago- a case of 'reinventing the wheel'. Current component values are as follows:

C32- 330 pF
C33- 470 pF
L8- 10 turns on T37-2 (red) core

• If your DSW-II-20 component values do not match the ones above, ask for mod. pack A'

Issue: 2) 'thumpy' keying

The Audio muting FET (Q1) was not consistently turning off on key-down. The original 5V regulator (U9) has been replaced with a 6V regulator

• If you have a 78L05 at U9 and keying thump is objectionable, ask for mod. pack 'B'

The manual above was changed to reflect the changes for 1) and 2)

3) 'Tunable' digital noise

During the DSW-to-DSW-II development, L1 was relocated quite close to the microcontroller, U7. Some users reported tunable tones, which may have been noticeable based on local external noise conditions. Measurements revealed that the coupled digital energy had increased by 8 dB due to L1's closer proximity. Replacing that (solenoidal) RF choke with a toroid reduced magnetic pickup by 21 dB.

• If L1 is a 4.7 uH RF choke, request mod. pack 'C'. This consists of a T44-2 toroid and #26 magnet wire- wind 30 turns.

If you want to update your early-production DSW-II, contact me, dave@smallwonderlabs.com , to request the applicable mod packs. Please include your mailing address in printable format (i.e., please don't make me cut and paste!)

Current DSW-II Production:

The current version of the printed circuit board (marked 11/24/03) cleaned up several reversed silkscreen legends and replaced the L1 (RF choke) pads with a toroidal inductor 'footprint'. IF YOU HAVE THE '11/24/03' BOARD VERSION, ALL THE ABOVE CHANGES HAVE BEEN INCORPORATED. The URLs below document the current configurations:

http://smallwonderlabs.com/DSW20_Manual

The 30M, 40M and 80M versions use the newer board and have all the above changes incorporated .

http://smallwonderlabs.com/DSW30_Manual

http://smallwonderlabs.com/DSW40_Manual

http://smallwonderlabs.com/DSW80_Manual

/ (if in doubt, the last page of each of these documents has a revision history.)

Dave Benson, K1SWL 2/12/04