“Those who hear not the music, think the dancer mad”
Kingsdon Kit

40 Metre - Kingsdon Transmitter Kit Construction


Following the successful completion of the Midney Receiver I was keen to start the matching transmitter!

Construction - Session 1 - Supply and Control Parts

I read all the detailed instructions! Then divided up the components by their values to check everything is present and to speed assembly. Construction proceeds well, certainly aided by a bottle of Waggledance and the practice of building the Midney. Most of the first two sections were completed.

Learning Points

Construction - Session 2 - CW TR Control Parts and Sidetone Circuits

Kingsdon Circuit Board
Circuit Board

Completed the supply and control parts from Session 1 and tested OK, the relay clicking in when expected!
Then fitted the muting parts and the CW TR Control parts (C109 onward) which needed some careful checking as this was a "bare" area of the board. Needing a rest from construction it was time for a Carlsberg Export and some Mince Pies.
Tested the CW TR section and fitted the sidetone circuit parts. Following this marathon soldering session the board was checked and two capacitors with the "wrong" values were found, these were removed and "correct" value ones soldered in.. Only to find they were correct after all!
Time for a Grolsch and supper. Running through the tests after supper, various voltages were not correct! One resistor was missing and a capacitor was wrong way round !! (Positive to earth). These problems were quickly corrected and then everything tested OK.

Learning Points

Construction - Session 3 - Speech Amp

Only a few parts for this section. I carefully checked the placement of the TR104 transistor as the centre lead has to be bent forwards, so care is needed to ensure it does not touch the topside earth!

Construction - Session 4 - Modulator and Filter

Soldered the few remaining components from Session 3 and tested OK. Then on to the Modulator and Filter stage, where had not placed all the components before I soldered them.. So had great difficulty fitting the 602 IC! I had also mislaid the 47pf capacitor needed to complete this stage. Finished with a bottle of Tanglefoot.

Learning Points

Construction - Session 5 - Modulator and Filter

Rechecked work from Session 4 and fitted the 47pf capacitor. Seeking an interlude from the project I decide to build the Dummy Load needed to test the Kingsdon!

Construction - Session 6 - Modulator and Filter

Rechecked work from Session 5 and soldered some missing earths! Then soldered in the remaining components for this stage. Curiously C121 cap was already fitted.. Does this mean a 10uf capacitor is missing somewhere else.. This will need to be checked. Mystery solved C121 appears twice in the instructions ! Would have made more progress, but there was such a good evening of television, Independence Day and Beverly Hills Cop 2

Construction - Session 7 - Driver Stage

Rechecked and tested Session 6, all OK! (A chance to try out my new magnifying lamp from Maplin!) Settled down for a Fish and Chip supper washed down with some splendid Chablis.. Fitted the next driver stage parts then read the Toriod winding instructions..

Construction - Session 8 - Driver Stage

Toroid Closeup
Toroid Transformer Closeup

Soldered in the next set of components then reread the L102 toriod winding instructions. Once read again things were clearer. Time to get down to twisting wire. The target was 4 turns per 25 mm, but I found it difficult to see the start and end of a turn.. So this was on a best efforts basis! Next threaded the twisted wire through the ferite core and organised the wire outputs, a fiddly job requiring some care.

Kingsdon And Scotch
Kingsdon And Scotch

Supper and a glass of Highland Park Scotch. Next wound and fitted the band specific toroid (Getting used to winding) and the TR105 with heat sink. Transmitter components now completed !

Construction - Session 9 - Testing

Finished installing the components, which proceeded very smoothly then joined the Kingsdon to the Midney by soldering coax braid across the board joint. This worked well.
However I hit a snag! on page 6 "adjusting the standing current in TR105". Applying current to the rig caused the relay to click in immediately. I checked the current it was drawing, but then put the probes on live and earth "before" switching to volts. The bench PSU cut out.
I emailed Tim, who promptly replied with some suggestions..

Learning Points

Construction - Session 10 - Testing

Tom (G4BYE) kindly took a look at the rig. The TR101 transistor was dead and there was no 8Volt supply as the LK100 link had been removed! These issues were resolved and the tests then completed successfully.
Checking back regarding LK100, the link had been removed as the earlier instructions "If the 8 Volt line has been connected, this junction should be 4 Volts.." seemed to indicate it was no longer required. It is explicitly removed later in the instructions!

Learning Points

Construction - Session 11 - Connecting to the Midney

Installed the key socket, mike socket and tune switch. The board to board connections were made across the back of the board as this was easier than threading thin cable through holes only to have them shorting to earth on the topside of the board and being generally difficult!! (Only the control socket and switch wires were threaded through the board).

Construction - Session 12 - Testing

Powered up again and the PSU cut out. Next removed the 12v link on to Midney, The PSU did not cut out. Some further investigation ensued. Reconnected the 12v and 8v links, all seemed OK. Tested voltages and sidetone in the Tune and Net switch positions, OK. Then wired up the antenna to check the RX, no signals. Then turned down the sidetone to check the Tune position RX mute, it did not seem to work. So a few things to check..

Construction - Session 13 - Testing

Tom (G4BYE) had been very helpful in explaining a few things and in finding a daft mistake - The Carrier Insertion Oscillator link from the RX was soldered to "point C" I soldered it to the wrong side of C.. an earth pad !!! as you can imagine this compromised the RX somewhat.. It must have been late..

Construction - Session 14 - Testing

Tom and I followed through the CIO, VFO and mixer on the scope. We got a good CW sine wave, but only on one frequency. As the tuning was changed the signal agained other components!

First CW Contact!

Tom rang me on Sunday morning to say that he had added a small resistor to the xxx coil which resolved the tuning problems. He then followed through the setup instructions again for the filters and adjusted the sidetone drive, the rig now gave a good CW sine wave across the tuning range!
Very keen to try it out he connected it to a basic wire antenna and heard a CW station in Hull (XXX) calling, so he called them and nearly fell off his chair when they replied!! Splendid!!

Construction - Session 15 - First Voice Tests

Initial Voice Testing
Initial Voice Testing

Another Sunday evening! Following the success of the CW testing it was time to start voice testing. Prior to carrying out any "On Air" testing it was important to get a basic setup and to understand what effected what!
Tom (G4BYE) loaned me a basic microphone, a short wire was installed ready to ground the PTT and the dummy load connected. Using the Kenwood to monitor (Whilst held against my ear to avoid feedback!) I switched the rig into "Tune", after a little tuning a good tone was heard. I then switched to "operate" , grounded the PTT and spoke into the microphone!
After further adjustment of the mic gain and tuning I could hear myself clearly through the Kenwood! I adjusted the mic gain further and listened to the effects of tuning "across" the SSB signal.
All ready for some "On Air" testing!!


Construction - Session 16 - First Voice Tests



To Follow.