G0XAN's Amateur Radio
Station
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My station is located in the attic of my
house. The "shack" is insulated and boarded but
has no windows. So it gets very hot in summer and very
cold in winter. There are about two weeks in spring and
autumn when the temperature is OK :o) The equipment is
mainly homebrew, but I do have a TS-820 to use while I am
extending my homebrew rig (see below). If you know how to
modify a TS-820 for CW and SSB QRP, please let me know!
Carlo, IK3LMA suggests a battery and potentiometer
applied to the ALC input. I have not tried this yet, but
the manual says the ALC threshold is -6V and ALC can be
applied via the Remote or Xverter connectors. Ken WB5UYJ
suggests simply turning down the "Carrier"
control. I didn't realise this would work on SSB -
however, my power meter says it does but I haven't tried
it on air to see what the signal sounds like.
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So here's some brief descriptions of the bits and pieces
"what I built". More pictures one day...
HF Rig
- Description
- Update Winter 1999/2000
- Update Summer 2001
- Update Winter 2001/2002
- Update Spring 2002
SWR/Power Meter
ATU
Sidetone Oscillator
Aerial
Clock
HF Rig
My HF Rig is built mainly from kits from Sheldon Hands , http://www.rf-kits.demon.co.uk.
It started life as a 6m SSB rig, before I passed the Morse code
test for my HF licence. Unfortunately, I spent so much time
learning CW that although I got it built and apparantly working,
I never got a 6m aerial up so never got it on the air before
getting my HF licence. Having got hooked on CW, I decided it
wouldn't be too difficult to make the rig into an 80m CW/SSB rig,
which is what I have done. It works pretty well on CW, and I hope
to get SSB sorted out very soon.
The rig is based around the Hands RTXIF 9MHx IF/AF board which
uses the GQRP club 2.4kHz SSB filter. I have added the GQRP club
500Hz CW filter, and a Mini-Circuits monolithic amp to overcome
the terrible insertion loss! Builders beware: the CW filter is 50
Ohms (yes, FIFTY) and the SSB filter is the more usual 500 Ohms.
I added a matching transformer at each end of my additional
filter/amp board and used PIN diode switches to select between
SSB and CW.
The RTZ50 RF board is a broad-band design, so all I had to do
was change the RX and TX band-pass filters. I did this by scaling
the values in the 50MHz design to 3.5 MHz. Simple but effective!
There are other sources of filter values, eg the GQ2000 design
published in SPRAT.
The VFO/MX local oscillator board supplied for the 50MHz rig
uses a 38MHz crystal mixed with a VFO that covers a 500kHz range
between 3 and 5 MHz. It was a simple matter to retune the VFO to
the more standard 5.0 - 5.5MHz and bypass the mixer. This gave me
3.5 - 4.0MHz coverage. Of course, the VFO tunes "backwards"
but I soon got used to it.
To this basic setup I added the Hands 3.5MHz low-pass filter
and antenna changeover relay, and the RTXCO keyed 9MHz oscillator
and TX/RX control. I retuned the USB BFO for use as a CW BFO -
the crystal easily pulls far enough - leaving the LSB BFO for SSB.
I have all the bits to make a separate CW BFO, but it's way down
the list of things to do!
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Finally, I added a passive narrow AF filter from the
GQ2000 design which really does help cut out the QRM on
80m, a sidetone oscillator - a single transistor twin-T oscillator which gives a
good sinusoid from a simple design, and a permanent
supply for the audio amplifier so I could hear the
sidetone! |
So that's how the rig stands today, the main boards are fixed
in a chassis and the VFO is in a box, but the other boards are
only held in place by their connecting wires and sticky tape. I
should be ashamed I know, but metalwork never was my strong
point, and after all it works! ONE DAY it will all be boxed up
and looking pretty, but I fear that time may well be some way off.
There's always something else to "just try out before I box
it up ..."
On the list of "Things to do" are: get it working
for SSB, add an SSB AF filter, add AGC and S-meter, add filters
and switching for 20m, build a frequency display, add more bands,
and so it goes on, not forgetting to build a proper case at some
point!
Update Winter 1999/2000:
The rough note of the sidetone hinted at some undesirable RF
feedback on transmit, so I decided that a proper case was
necessary before any more work on SSB. I fabricated a case from
some large sheets of scrap aluminium I obtained from work,
avoiding the need to bend it by using aluminium angle from a DIY
shop and lots of self-tapping screws. This method was very
successful and resulted in a case that is strong enough for me to
stand on!
The Hands Electronics AGC board, which also includes a
sidetone generator and audio filter has been built.
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I have also built a multi-band filter board to take
up to 7 band-pass filters. This board will replace the
filters on the Hands RF board. It was to have been used
for transmit and receive, but after thinking about it, I
decided to build separate RX and TX filters and avoid
having too many RX/TX diode switching networks. |
Plans now include a DDS VFO for multi-band operation, but
first of all, the existing boards need to be put into the box...
Update Summer 2001:
After 18 months of neglect (I was busy doing other things) the
rig is finally beginning to take shape. I am now making a
concerted effort to get it boxed up and working, although I am
sure it will never really be "finished" :o)
A multi-band low-pass filter board has been designed and
built, which will handle all bands from 3.5 to 50MHz. The IF
filter board has been rebuilt with a new PCB and relay switching
for CW/SSB and TX/RX. Diode switching just seemed to end up with
too many bias resistors and blocking capacitors so I wasn't
convinced it was the best way to go...
Much drilling of metal is taking place now and I have all of
the board fixings in place for the top side of the enclosure,
plus the low-pass filter board which sits on the back wall. A
prototype front panel is being put together to check that
everything really does fit before making the final panel!
Plans for the DDS VFO have been revived. It will consist of a
200MHz AD9857 which has a 14-bit DAC which should help overcome
some of the performance problems associated with earlier DDS VFOs.
The DDS will be controlled by a PIC 16F876 which has much more to
offer than the fantastic but somewhat limited 16F84. However, I
need to write some software, build a programmer ... more jobs to
add to the list ...
The AD9857 comes in a 0.65mm pitch 80-pin quad flat pack
package, so watch this space to see how I get on with mounting it
on a home-made PCB!
Update Winter 2001/2002:
The PIC and DDS hardware has been designed and the (long) task
of writing the software has begun. The boards will not be made
until the software is written, just in case the design changes...
I expect the software development to progress slowly, since there
is more to life than writing software!
When everything is working, I will publish the design here. If
you can't wait and wish to collaborate on the software, please
drop me a line and we can sort something out.
Update Spring 2002:
With the software outline designed, I was happy that the
hardware design was OK, so I built the PIC PCB. I have started
writing the software now and so far I can display a message on
the LCD. Progress indeed! :o)
The DDS PCB is still to be built, and there's a good bit more
software to write yet!
SWR/Power Meter
This is another kit, this time from C.M.Howes. Very
straightforward and seems to work well. I did notice that it
seemed to swallow some of my power on 2m when it was left in-line
as a power meter.
ATU
My QRP ATU is a homebrew CLC circuit. I was lucky to get two
variable capacitors of roughly the right value at a reasonable
price. The coil was wound on a piece of 38mm plastic pipe, the
sort used for waste water. To keep the turns tight I drilled a
double row of holes along the pipe and wound short lengths of
wire between each pair of holes. The wire finished by going down
one hole and up the opposite one to lock it in place. The next
piece of wire was then joined to the first , forming a tap, and
wound round to the next pair of holes. The coil dimensions were
arrived at by referring to a variety of texts and making
something about the right size and number of turns using the
materials available. There are about 4 turns between each tap, 12
taps in all. One day a 12-way switch will select which tap is
used, but for now a croc' clip on a flying lead suffices!
Aerial
Now this proves that almost anything can, and frequently does,
work!
I wanted to work 80m because I got my licence at the bottom of
the sunspot cycle and I only get to operate at night. Work and
children keep me occupied during the day. Unfortunately I have a
VERY small garden, so I just strung up as much wire as I could. I
eventually managed to get 70' (about 20m) out in a very strangely
bent shape, with the highest point about 35' (12m) above the
ground. The aerial starts at the ATU (at least there are no
feeder losses!) and the first 8' is in the house (far from ideal).
The next 15' is vertical, then a 35' almost-horizontal run to the
end of the garden, with the final 12' sloping down at about 45
degrees. However, it does work! My homebrew rig has managed QSOs
over Europe from Norway to Spain. I borrowed a rig when I was
first licenced - an elderly TS520 - and with that I worked USA,
Canada and the Canary Islands on 20m, and Asiatic Russia on 40m.
All this with 5W CW to a grotty bit of wire too close to the
ground, and at the bottom of the solar cycle!
I did have the ubiquitous G5RV (the most popular 80m antenna
in Britain?), but since it is 102 feet long, and my garden is
somewhat less than that, some ingenuity was called for. The
centre section of each half was folded into triangles, 0.75m on
each side. 4 triangles compressed 12m of antenna into a 4m space.
The idea came from an old copy of "Practical Wireless"
and the theory is that the triangular folding is non-inductive.
It looks a bit strange, but it seemed to work.
I'm not sure the G5RV was really working that well. It was
been replaced by a 20m dipole which does fit on my property in a
straight line! It only works on 20m, but it does work. QSOs (100W
SSB) with Thailand, Azerbaijan, USA, and Venezuala prove it!
In the quest for multiband operation, half a W3DZZ was
constructed and used as an inverted L against earth. It works
fairly well, but I suspect the earth connection could be better.
More work required!
Update Winter 1999/2000:
The ground connection is to two pieces of copper (water pipe)
earth rods hidden in the flower bed, connected by some very heavy
braid. During the CQ WW WPX contest, I worked Argentina, Brazil,
USA and Canada on 21MHz (100W SSB), so it must be working fairly
well!
Clock
This is an RS Components digital clock module that I was given
when it became surplus to requirements at work. Since it always
reads UTC it has no adjustments on the outside, all the time-setting
switches are hidden inside.
Last updated: 16 March 2002
Email me at gary.aylward@ntlworld.com
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