HAM RADIO NOSTALGIA PAGE
AM on 29 MHz With David VK2BA
Megan, NSW, Australia - Grid Square QF69
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VIEW MY 10M AM LOGS
My 10 Metre AM log - stations I have worked in Solar Cycle
23:
My 10 Metre AM log - stations I have worked in Solar Cycle 24:
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The
modulator of my home brew 29 MHz transmitter - a pair of 813's glowing
like the setting sun
If
conditions are suitable, I operate most days from about 2100Z until
after change of day when the band fades out to the US (about 0200Z)
generally on 28.990 AM with the beam pointed towards
United States. I am happy to talk to any station that I can hear, and
will go to any lengths to give a contact to the weakest of stations. My
best effort was to work WB5UGT when he was running one watt of AM, and
he had a good readable signal. Sometimes I receive interference from CB
transmissions and other illegal transmissions within the amateur band. I
believe that the best thing that amateurs can do is to use the band.
Let's fill it up with activity and that way the CB'ers and others will
go elsewhere - hopefully back to where they should be.
See you on
10 AM!.
The main operating position at VK2BA
Megan - A small farming community near Coffs Harbour
David VK2BA beside the home brew 813 29Mhz transmitter
In Australia
it is very hard to obtain on old boat anchor for restoration. So if you
want to run a tube transmitter with high level plate modulation you
really need to make it yourself. This transmitter runs a single 813 on
29MHz providing about 100W output. I run it lightly to maximize the tube
life and rely on the antenna to make up the E.R.P. The transmitter RF
tube line-up is: 12BY7 (Crystal oscillator and/or doubler), 2E26 (doubler),
2E26 (driver), 813 (PA). The transmitter has been run consistently now
for some years. The cabinet still needs some black wrinkle paint and
the controls still need to be engraved. I guess when band conditions
drop off I can do some of those things.
The modules
are from bottom up:
1: 1400
volt power supply
2:
Modulator with AB1 813's
3:
Control and meter panel
4:
Exciter unit
5: 10
Metre PA with single 813.
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Originally,
I used a Yaesu FT757GX as a VFO. The low level 29 MHz output from the
FT757GX drove a little divider unit, consisting of a pair of 6AM6's as
amplifiers, a TTL IC (7074) dividing by 4 and then driving a 12BY7
amplifier at 7.225 MHz. This was a good arrangement as I had a nice
accurate frequency readout at 29MHz, but the transmitter was driven at
7.250MHz. A similar arrangement could easily be used to drive a Viking 2
or any other boat anchor transmitter that needs drive to be multiplied
to the final output frequency. I have now constructed a VFO using a
Command transmitter tuning capacitor and a 12AV7 Franklin oscillator
driving two class A amplifiers. To indicate frequency I have added a
frequency counter to the VFO. It drives the BA300 with 7.250 Mhz.
That lovely
D104 microphone and the four large meters in the transmitter were
provided by Smitty, KD4AF. Smitty also sent out other components
including a modulation transformer and a meter and crystal switch from
a Viking 2, which I used in a previous home brew 10 metre AM project. I
am very grateful for the assistance not only from Smitty, but from other
10 metre AM'ers as well. It is not easy to source vintage components in
VK, and the help that I received has put the AM station on the air.
The modulator unit
The PA unit with the 813
Exciter
unit of the "BA300"
MY VIKING II
I have now
obtained a Viking II, generously provided by Smitty KD4AF. I have made
some modifications to the audio and the old rig is now on air. It has
made some contacts into US on 29MHz but I generally keep it on 40 Metres
where there is a little local AM activity. I will take a photo of the
unit shortly and place it on this site.
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