1986 Tassie Devil QRP CW transceiver kit
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WIA Tas Southern Branch Activities Centre
Tassie Devil QRP CW transceiver kit
1.2 watt transmitter and direct conversion receiver.
The original owner of this circuit boarc is unknown.
The kit was released in 1986. The accompanying information
shows that the kit construction was nct for the inexperienced.
The completed circuit board required a number of additional wires.
External components required were the normal controls.
The resulting transceiver had a number of problems, most of which
were found and corrected by the constructors. The problem | found
most annoying was that it produced horrendous key clicks. The clicks
were caused by the oscillator switching from receive frequency to
transmit frequency and back at the start and end of each dot and dash.
I did a modification to the one | built to improve the clicks which resulted
in only one click at the start of each transmission.
Richard Rogers VK7RO February 2018
Co-EE L
NEWS
- BULLETIN
PUBLISHED QUATERLY
“WE DO MORE WITH LESS”
RAI TAYLOR 25 TWELFTH AVE WEST MOONAH TASMANIA 7009
THe "TAS-DEVIL" 80N
Cw (RF TRANSCRIVEX Probably the most surprising circuit is the d.c, switching . Semi-breakin was considered
Baving had the pleasure of working "QRP" for nearly 12 months using the best compromise and in order not to reduce receiver
a Drew Diamond sensitivity a relay, rather than
design DSB/CW Tx I decided to build diodes was used to switch the aerial from Rx to Tx.
the SCD CVW transceiver . However , whilst SCD in VRS adjusts the release delay time of
concept, I did incorporate a RLA to allow for different keying speeds. The idea
standard Colpitts VFO and a home brew transmit section! being to prevent the relay releasing
The performance of the receiver was between characters, As ones speed increase s, the
very impressive andgood reports gained from the delay can be reduced.
transmitter. The VFO was made to tune over a frequency range of 3.50 to PB1 allows the VFO to be set to zero- beat without
3.80 MAz so I having to turn the RIT control to zero
had the additional pleasure of listening to the DX window. RIT and the position,
audio filter
were considered to be a must on this rig,
Circuits were constructed entirely on "strip board". Three were made - VFO, I.Smith VK7KAN
TX and
RX/filter/audio amplifier, Each part was "proved" and the lot put together.Th e VFO and
battery holder were placed in one aluminium box 100X100X50 and the Rx/Tx
in another, the
idea being to go portable on camping holidays etc.
Good news traveis fast, even with low power, and before L had time to oil
the key, requests
were being received for a single p.c,b, design suitable for easy home
construction.
Using the experience gained, it was decided to incorporate all the perceived desirable
features, This, of course, is very much an individual thing! The circuits are
fairly
conventional and mainly borrowed, However, the p.c.b, was designed from scratch and is
the end result of much midnight oil. I don't think I can look tram tracks in the face
again! The layout is such that sections can be removed and Jjoined up to make a separate
receiver, transmitter, VFO etc.
The following is an attempt to highlight the few unique aspects of the
circuits.
The VFO is supplied from a 5 volt voltage regulator as it is félt that
the regulation
is superior to a simple zener. The aim being to improve stability., A 1N4001 power diode
is used as a varicap as it was found to give both a greater capacitance
variation and
better linearity than a BA102, RS and R6 set the d.c. voltage across D1 and hence, the
transmit frequency. &3 switches on during key-down. Q4 switches on during receive
and
a variable voltage from VR3 gives receive-incremental-tuning, VR1 and VR2 set the (+)
and (=) RIT limits.
w
@©
Circuit design for the receiver is straight out of the SCD manual. However, the audio- o~
amplifier is a little different, This incorporate s a 4007 digital
z
i,c. biased to linear <
x
working conditions. Many of these amps have been built and they ~
give highgain, low noise x
>
amplification. The output power is about 150 mW which is more than adequate. Also, being
in three stages, it was convenient to provide mute and side-tone
functions.
The transmitter uses a PNP driver and this appears to improve both sensitivity and
stability, L2 and L5 are wound on a readily obtainable T.V. balun
former type 1050/2/¥14,
RFC3 comprisgs 3 turns on a Phillips 6 hole ferrite bead.,
This section is subject of a
separate article. (see the "upside-down" QRP P,A,)
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TAS DEVIL
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R43 C4I .
TASSIE DEVIL
"THE SAGA OF A TaSSIE DEVIL"
Firstly I must appologise to the many members that I had to dissapoint because I
just oould not supply them with kits for the 80M QRP CW transciever. When Ian
VK7IJ first built the prototype it was obvious that at last here was a project
idealy suited to the home brewer. Not to complex, technically very interesting,
and inovative in some areas.
I was genuinely surprised how well it performed and naturally only to pleased
to make up @& kit. The Southern Branch of the W.I.A. do have an activity centre
and it was decided to investigate the componant availability and price ect.
This I did and from information that I received from local supply houses,
together with componants already on hand offeradthe kits to anyone interested
for a total cost of $35.00. The original target of I2 kits was decided on.
Thinking that it would be a sufficient amount we becan to order the PC boards
and componants ect. In the first week the orders came flooding in at about the
same time some of the componants began to arrive and further price lists ect.
It became obvious th:t the original prices quoted were no where near the current
prices and it was decided to make a target of 30 kits,to do this we had to
increase the price to $45.00 per kit. I personally wrote or oentacted the first
I2 people whose orders had been accepted,explaining the increase price. Fort-
unately no one objected, in fact quite a few did not know how on earth we could
of provided the kit for such a low price in the first place. Of course the
componants that I had on hand that hzd been bought years ago, help to off set
the cost.
The poirt is that in excess of 70 people showed their interest in the kit. This
response is very encouraging, it does prove that a lot of people still want to
home brew their own equipment, it is & pity thzt most of the major componant
suppliers have, or are reducing the quantity, and limiting the range of ham
radio componanis, true, computer buffs are being catered for very well, but I
do fear for the future, of ithe humble ham radio home brewer, eventuzlly even my
imense junk box will run .dry.
I must get off my soap box (full of junk) and get on with the question in hand.
- To cater for those unfortunates who missed out, we are making availsble a printed
circuit board, parts list and information so that you can build your own "Tas Devil"
and chase up yourown perts, the only real difficult componants.are good- Qquality
air spaced variuble capacitors, and slow motion dials. Buying new parts today
the estemated cost would be around $75.00.
So again I repeat if you would like & P.C.B. board and construction informationm,
write to me VKTVV, as soon as possible. This will make the ideal project during
the coming winter months. The cost which includes “postage within Australia and
Newzealand is $I6.00. Cheques made payable to"Tasmanian W.I.A. Southern Branch.
USING A-MULTIMETER TO FIND PNP or NPN-:
ettt
1. Clip meter -ve lead onto centre lead
of transistor.
Z. Set multimeter to high ohms (x1k range)
3. Positive lead to outer pins reads:
HIGH-HIGH 1T's PNP
*LOW-LOW IT's NPN
—
PARTS LIST.
~RI,R3,R5 IOOK QI VNBBAF RS COMPOKENTS 295135
k2 I0K PRESET FCT Q2 BC478 " 293612
k4
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3300hm
Q3 .2N3053
1C.I. 40495
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293561
306667
TAS DEVIL UPDATE
R7 82okm Heatsink-Q3 :: 4?%548 A cortinuing story
R8 10K Heat sink-QI by Ian VK7IJ
CI,c3 33PF NPO CERAMIC PgaB:ard doutle sided 3"X3" (75X75)mm I guess I now unders
c2 0.0Iuf ceramic rfcl 4.7uhy RS CONPONENT 228135 tand the meaning
right to improve the of the statemernt " We res
C4,C6,CI2,CI4,Ci6 O.Tuf ceramic ) desiga", Wishin g to
erve the
to add a few improveme fin ali se the design I decided
e ’ iOuf I5v electrolytic nts and in S0 doing
of worms, having rec unearthed an unexpecte
5?3015 4.Tuf tantatlum < overd fro m my d barrel
Cc7 Two features were
390PF polystyrene destine d for improv
ement: To run IC2
c8,C9 overcome the low from I2V to
I500PF polystyrene
Cc10 E80PF polystyrene
CII 68PF polystyrene iruit, the nodificat
_v_f——~._/~‘--;--’f-’-"-\_“’# ions procce ded thu sly
The lead supplying -
5volts to IC2 was
solder to ground plane é ted to the JT2volts
supply.
disco nnected from ICI
and r@connec
The wipers of VRI
on top of board CI7, PC tracks need to be
and VE2 were connec
ted to the
ds of
cut )o The 5vo lte weg
tra ck en VR3 ( the
VRI and VR2 and the applied to th e track of
other track end of VR2 both
This arrangerert all was taken to earth.
ovs s variable rreset voltage to be
endofVR3thus allowi applied to each
ngafar greater accura
range of the RIT, So cy in the setting of
enter the red face the
The mods to I1C2 which, :-.
I shoud adg s included
to pin 14, worked rer strapping pins I2 and 13
fectly, however the RIT
PEI Svolts was bresen did not work. On pushing
t across DI inst ead
ion of R29R2I. Mpe dis of the 2vol ts as at the Juncti
covery -Q7 and Q8 are
wired as eritter follower
s
rosetosomenominal
of RI&,FI9 and the bas value determined by
e currents of Q7 the value
° ‘pg‘ -5 There is a happy end and Q8.
to the story- Q7 and
2N3905 devices, RI8 Q8 were replaced wit
was connected h PNP
to the tase of Q7. Thi to the bas e of Q8 and RI9 connected
s modification has
frequercy stability, improved out~of-sight
the rea son for the
being determined by thi s is that the tias on DI was
the tase-emitter cha
the voltage across racter ist ics of Q7 and not by
R20 as was the int ention of the design.
cteristics are very tem These chara—
perature deperdent hen
The mod to VRI,VR2,VE3 ce the dritt,.
was very wor th vhi le
set the ran ge,neg as it is noy Possible to
ative lim it ang positive limii
and still allow a nul of the RIT independentl
l at the migs meckanica y
The mod to the unuced l positi cn of VR3.
gate of IC2 is recommend
ing to recommended ed asy apa rt fro m corform—
corvention for CMUS
ible random switching devices it prevents
due to the gat any poss-—
or high. As far as IC3 e not kno win g if its
goes the inpul is low
increased by about 20d des ire d res ult was acheived, the gai
b wit h the sup ply n
necessary however to rep of I2V instead of 5V. It is
rge area of vacant copper lace R22 with a short
ad justmert of the switch circuit to allow prorer
fzetiabglt on a piece of alumin ing action vig VR5e A mod
vided and I must leave ified circuit is pro-
ium heat sink sheet. I gsed a the implementati
They are well worth whi on of the cha nge s up to you.
piece of 20x20mm aluminium right le,as has been verifi
during QSO's after com ed by the comments rec
angle,bolted to the top of the pleting the eived
I do appoligise for the m on my own rig,
board QI is then bent over and "bl und er" but ask you
the self—teaching aspects to tear with me on thi
bolted to it with a mica washer of our hobby, I guess that s
and associated standard hardware tetween the amateur and s the difference
the professional .HI.
QI is in a TO202 case and the
tab must be insulated from'earth
The vertical part of the right
angle heatsink can be used to
bolt the unit to the case. 15
[
< "TAS DEVIL RIG"
MODIFIED CIRCUIT
Q5'over heating No heateink fitted Fit heatsink (this is
! essential)
;
Output appears to be L3/base Q5 incorrectly Remove R14 and replace
frequency goubled terminated
SIDE-TONE GEN.
with a link . Bonnect
o1
2 resistor with value of
| ]iczdpn
47 to 100.a between link ond’
VRIS
earth (i.e, across 13)
R2?
This mod. is recommended!
/3
<
2
VFO not oscillating Q1 high thus reducing Reduce R2 to 100+
/
(no other faults) supply volyage via R2
. L
Mute circuit ineffective Q6 =.emitter follower, Replace Q6 with PNP type 8 §
due tc¢ low voltage output = 5-0.6=4.4v transistor, emitter to 12v. w -~
on IC3-1 Disconnect B15 from IC2
and reconnect to wiper of
VRS. (this leaves IC2 o/p
floating).
Side tone generator Q12 faulty Check.
not working
NOTE: SOME MAY TRY TO ACHIEVE GREATER OUTPUT POWEK = HOWEVER THIS IS NOT PRACTICAL =
WITBOUT A yAJOR REDESIGN Viz, with a 12v supply and 50 a filter -
output =V' = 144 = 1.44 Watts so save those output transistors! :‘
. 22 -10Q Ly
o
@ .
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» P
1 wish to express my appreciation to all who have helped compile this list and for % }
all the encouraging reports about the design received so far, E
Tap Smith z b
VK713 : W ~-
6~-5-86
VK5ZF Q Y
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