By T. W. Dresser

Figure 1

It is customary for newcomers to  amateur  radio to think in terms of
Hammerlund,  Hallicrafter and  similar  receivers and tramsmitters of
100 watts upwards, complete with lines of meters. V.F.O.s and a whole
load  of  other  gear;  a laudable  aim,  but  not  one  particularly
realisable in these days of short pockets and long prices. As regards
the fellow  living in  the country,  even if he  is in a  position to
spend a fair amount of cash on his hobby, all too often he is without
electrical  power and the cost of operating  a normal amateur station
from batteries is completely prohibitive-for any ordinary individual,
anyway. For the city fellow with little cash,  the countryman with no
mains,  or either of  them with little  room for a full-sized  den of
their own,  the cigar box transmitter, then is really the answer to a
prayer.  It will provide a lot of fun at small cost and when the user
has finished his "ragchew" on the band,  he can close the lid and put
the transmitter away in a bureau drawer until the next time!      The
power,  of course,  is in relation to  the size of the rig;  in other
words, it is very low, 1 watt to be precise.  But if you imagine that
1 watt  will not get you  anywhere at  all,  just  give  this  little
transmitter a try and you will find that it is quite possible to work
DX, even with 1 watt.  Given a decent aerial, of course, and having a
little regard for the times when the bands are less congested than in
the evening or Saturday afternoon.

The  arrangement  is  conventional,   crystal  oscillator  and  power
amplifier both valves being standard 1S4 types. Switching is provided
for the crystals, the rig operating on fundamental frequencies on the
1.7, 3.5 and 7 Mc/s bands, while doubling is used for 14 Mc/s.  It is
felt that there is not much point in making the transmitter available
for 28 Mc/s,  but this can  be done if the user wishes,  and the coil
data for this band will be furnished on request.   In addition to the
crystals, provision for VFO operation is made by a further contact on
the  selector  switch,  enabling the  VFO to be switched  in at will.
Metering,  too  is very simple,  a 100mA meter,  which can be plugged
into  sockets  on  the  front  of the box,  permitting all  necessary
circuits  to  be  checked  and  tuned  for  resonance. Al components,
wherever  possible,  are  miniature  types  and so  indicated  in the
component  list.  Obviously the  components should be obtained first,
and the cabinet made or obtained to suit.

Figure 2

The  station is solely  intended for code  work as it stands,  keying
being carried out in the negative HT circuit of the oscillator valve.
The theoretical diagram is given in Fig. 1  andthe layout in Fig. 2. 
The batteries, naturally are  not included  in the cigar  box case;  
that would be  asking too much. 
However, as originally planned and constructed, a simple three-
valve TRF receiver, using miniature valves,  occupied one half of the
case  and the transmitter  the other half.   It is  felt that readers
would not  be greatly  interested in  the receiver and would probably
prefer  to  use  one  they  already  own or to build one to their own
design  rather  than  attempt to build both receiver  and transmitter
into such a small case.  Nevertheless, if readers express interest in
the  receiver  too,  all pertinent  details will  be given at a later
The coil data is given on below for all bands in common use. When these coils have been wound and the little transmitter assembled and its wiring checked it should be attached to a half-wave end-fed aerial of 66ft. in length, and the 7 Mc/s crystalswitched into circuit. The meter should be plugged into the sockets in the anode circuit of the oscillator valve, and the circuit tuned to resonance by means of the variable condenser in the circuit. This will be indicated by a "dip" in the anode current as shown on the meter, in other words a reduction in the anode current. The meter should then be removed and the socket shorted together with a "U" link, two plugs joined by a sturdy piece of wire. The same procedure should then be gone through with the power amplifier, then the transmitter is ready to go on 7 Mc/s. Naturally it will be necessary to tune in this way whenever the frequency is changed, but the procedure takes only a minute or two at most.

Provided the components are bought judiciously - and many of them can
be obtained at surplus dealers - the cost of this transmitter will be
very small and  the subsequent enjoyment  out of all proprtion to the
time and cost involved in the construction.   One can hardly say more
of any transmitter, however powerful and expensive it may be.

      Components list
==============================               Winding
Xtals for 1.7, 3.5 & 7 Mc/s      Range turns Length       L2*
1 - Single pole 4-way switch     ===== ===== ======= ================
1 - 3-pole 2-way switch           1.7   50   1-3/4   As L1, tap = 18t
2 - 2 valve holders               3.5   28   1-1/2   As L1, tap =  8t
2 - 1S4 valves                     7    14   1-1/4   As L1, tap =  5t
1 - 100mA moving coil meter       14     8   1-1/2   As L1, tap =  3t
3 - 0.01uf fixed condensers      ====================================
1 - 0.05uf fixed condenser        All coils are would with 20 S.W.G.
1 - 150pf fixed condenser         enamelled wire. Winding length is
1 - 3 Henry R.F. choke            given in inches. All formers are
1 - 100pf variable condensers     1-1/2 inches in diameter.
6 - Banana sockets
4 - Banana plugs                  * = Tap may have to be adjusted to
Resistors as as in Fig. 1             ensure good loading.

I am very grateful to Harry, SM0VPO for giving me permission to use his circuits and ideas. He can be reached by Email at harold.lythall@era.ericsson.se

Frank, G3YCC

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