David Macnaughton and his Fascinating World of Amateur Radio



Please Scroll (16 items)

























AM on 29 MHz With David VK2BA

Megan, NSW, Australia - Grid Square QF69

  Click image to view full size 


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:    


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. 

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"



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.





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: