1. This will be a VFO for a QRP 80m TRX
following the idea of DL6CGC, Peter. The board is
simply cut with a long lever tin cutter and the pads
were punched at a local locksmiths.
Due to the punching machine they are not totally
equal but show a slight vault. You can easily press
8 pads in a small vise at once. The pads are ca 7mm . October 2009
The board is 100 x 50 mm
2. The circuit by DL6CGC. You can
see the 220 Ohm (not p ) in the plus
line. The board shows the gap where it
will be soldered later. The three pads
for the transistor are clearly to be seen.
On the very left the ring core will be put.
The design of the board is fairly easy:
follow the connections
in the schematic .
You see some pencil drawn lines to help to order the pads when you will glue them. It looks nicer.
Since this little rig was used by Peter during the Minimal Art Session - a well known QRP event -
he proudly called it MASter.
3. I put the schematic into SPICE and
Stephen, VE7NSD, run a simulation
showing that it will oscillate with an
inductance of 2.7uH.
DL7UWE designed the board for
conventional assembly and set up and
offered some improvements
So we have kind of an
International Project 2009.
4. DL7UWEs workbench : First tests
show a remarkable drift of the oscillator. So some extra experiments
have to be done surely. All is under construction, lets see what changes will
result in more stability
You see that the drift is ca 3kHz after switching on and it stops after ca 15 minutes.
T 2N2222, core T37 - 2 R emitter 2.2 kOhm
5. The drift was obviously caused by the temperature relation between ZDiode and T-core.
Separating the ZD and its R on a tiny extra board solved the problem immediately.
6. Assembling the Manhattan board is no
problem. A good preparation will save a lot of
Here I only took all the parts out of the little
plastic bags from my home store, checked
with a meter and then soldered.
Searching and finding the proper parts
needed more time than assembling and
soldering. No drift problems.
The next TX-RX stages will see all parts neatly
pinned into the schematic on a foam board,
then transferred to the board.
6. This method saves a lot of time: Find all parts first and put them onto the schematic. It is pinned to a
styro foam board.
The transistors, crystal and some other parts
are not on board here.
Now lets design the Manhattan board for
this stage. It will look nice when it gets the
same dimensions as the VFO but for HF even
this idea is not so important.
Before assembling measure the single parts
again to be sure about their values.
7. The whole text and the description of the schematic and hints on assembling and aligning were published by Peter, DL6CGC, in October 2009 in this issue of the DL QRP REPORT.
( See also radiomag FunkAmateur and www.DL-QRP-AG.de )
Peter writes that he got the idea of developing a new riglet for the
Minimal Art Session because so many transceivers are based on the direct conversion principle.
He studied literature of the 70s and designed a prototype with 99 parts.
He changed battery poles and the first MAS was over - for him.
So he got a step further and built a self oscillating mixer stage with dual
gate Fets which worked fairly well.
8. The RX part with the three staged audio amplifier. High Z phones! Filters are
commercial 10.7 Mc.More details can be found in the article mentioned above.
9. Measuring gear so far till now
is very simple: home rx, the little counter PIC 12C672P which was published by DJ3KK in SPRAT, which is not much larger than a
stamp, multi meter and this little variable oscillator (4 Cs to
combine with the basic oscillation) which came as a cheap easy
to set up kit from ELV company to test the audio amplifier. GridDip Oscillator with an injected sig at the
Filter entrance will show the audio working later.
I just found out: The earphones by ex VEB Funkwerke Leipzig have got 400 Ohms by the way which might
be useful for the original audio amplifier by Peter.
10. RX stages will be on Manhattan , too. Here the
little 1cm x 1 cm squares help to find the locations for the pads.
They are simply copied with pencil lines 1:1 from the drawing to the copper board.
The Transistor-Fet is put on only to find the distances beween the pins and pads.
Be careful when defining the two gates, drain and source due to the type.
The pads are cleaned with a glass hair brush. It would be good to find a method with a Dremel drill
to make the cleaning process a bit quicker.
DL7UWE uses his self-designed printed board, above the last stages plus audio improved by a little test Intermediate Frequency Amplifier which works pretty well.
11. Product detector BFO assembled, BF9xx and audio amplifier still missing , ready for test.
Mind that BF981 and BF 961 have the same pinning v i e w e d from the top.
I could not get the BFO oscillating first. A proved BF 961 made it possible. R in G2 stayed 100k.
You can arrange the pads on the board this way that the ends of the legs just reach the pads. So there is space left for other parts and resoldering the BF in any case will be very easy.
Test the crystals before soldering them.
--- to be continued -------------------------------