From 2SZ to Z-4AA October 18/19th Part 2 – By John Heys G3BDQ

The amateur radio scene in 1924 centered around simple regenerative receivers, and self excited power oscillators which coupled into Marconi antenna systems. Most of the distance record breaking stations used input powers of more than 250 watts.

Cecil Goyder’s transmitter at Mill Hill was no exception and for his record breaking contact with New Zealand he employed a pair of Mullard 0/250 triodes in parallel working as a Hartley oscillator on a wavelength of about 90 metres. To get the high voltage power supply needed, a sychronised motor driven mechanical rectifier together with a valve diode was used. His smoothing circuit had just a 12H LF choke with a couple of capacitors. There was a 2 uF input capacitor and just 1 uF of final smoothing. In 1924 Goyder had no way to properly monitor his output signal for tone, stability or chirp and relied upon the RF current meter in the antenna lead to tune up for ‘maximum smoke’. A rather poor photo of the transmitter reveals that there was no meter to measure the current to the oscillator valves. He cleverly avoided the use of a wide spaced high voltage tuning capacitor by having a fixed capacitor which could be connected across various turns on the oscillator coil. This coil was made with quarter inch diameter copper tubing and had 18 turns. No chassis or breadboard was used to construct the transmitter; components being fixed to the bench or positioned up above on a small shelf.

the-transmitter-part2-2 the-transmitter-part2-1The synchronised rectifier was on a small stool standing close to the transformers of the high voltage power supply. To get the best output into his antenna Goyder had to select seven coil tapping points before starting operations, a procedure which must have taken up a considerable time. Keying the transmitter and getting a side tone to help his Morse sending would have been quite a problem. I feel that the only way to key his transmitter was to key, via a suitable relay, the AC mains input to the high voltage transformer. This relay could also have additional connects that could switch in a buzzer to operate when the key was pressed.

One can only imagine what the 2SZ signal sounded like, and Bell  (Z-4AA) wrote “UR QSA RAC sigs” (Raw AC tone) on his QSL card confirming the historic contact. The frequency drift during and between overs must have been considerable and his simple TRF receiver had to be switched off when the transmitter operated. This send/receive switching must have made quite lengthy intervals between overs. Goyder’s power output can only be guessed at, but was perhaps quite low and at best between 25 and 30% of the input power. His valves had low purveyance and despite using an anode voltage of 2,500 would at best only draw about 200 mA of anode current (500 watts) so I think the output power was little more than 120 – 170 watts and possibly less.

Just a few years after this notable contact, Goyder was using and advocating the use of quartz crystal frequency control and the use of CO-PA transmitter circuits. This revolution in transmitter stability allowed the use of narrow bandwidth receivers like the superhet. The normal 10 watts input power imposed upon most British operators became enough to then allow long distance working when conditions were favourable, something that was impossible when employing free running oscillator transmitters.

The antenna used at Mill Hill by 2SZ was a typical amateur Marconi, for resonant Hertzian radiators were not being used at that time. At the School a couple of 25ft masts were arranged with one at each end of the building which allowed an antenna height of 45 ft. British Licence conditions then (and even for a short time after WW2) only allowed the use of 100 ft long aerials. This included any top wire or wires and the down lead. At Mill Hill there was a top made up with five parallel wires fixed to 12 ft wooden spreaders and a 5 wire ‘sausage’ using circular spreaders which descended for 45 ft to the radio room. The earthing system included an 8 wire counterpoise which also had a cage lead in. The 2SZ transmitter was not directly connected to either earth or the counterpoise. This is not like present earthing practice. I think Goyder was afraid that his counterpoise arrangement would be jeopardized if a real earth was connected to his antenna circuit.

By John Heys G3BDQ – Vital Spark April 2013.

Return to the index of Vital Spark articles.

G3MGQ’s Month on the Air

Prepared by the clubs RSGB trainer, G3MGQ, you will find the latest DX contests including the ones to shoot for as well as ones to give a wide berth. Why not download the latest edition of Month on the Air and enjoy your DX just that little bit more.

Become a member of HERC

Join the Hastings Electronics and Radio Club.

Why not join one of the largest and most established Radio clubs in the South East of England? Very low joining cost, and free for a year to new licencees.

Vital Spark Archive

Vital Spark newsletter articles

Take a look through a large selection of articles written by club members over the years which have been published in the monthly Vital Spark newsletter .

Used Ham Radio Equipment

View HERC's Used Ham Radio Equipment for sale list..

Every four weeks, HERC's Used Ham Radio Equipment for sale list is updated on the site. Bookmark the gear for sale page to re-visit easily and take advantage of the used equipment on sale through the club.

Club Photographs

HERC Image Galleries.

Here is the official HERC photograph archive which contains multiple image galleries spanning several decades since the club was formed many years ago. Enjoy the images!

UK Amateur Radio Repeaters

UK repeaters

Click button above for full list, or a local repeater callsign below for info.

GB3EB 2m in Uckfield- Active
MB6EB 2m DStar Node in Eastbourne - Active
MB6RY Wires-X DigiGate in Broad Oak - Active
GB3HE 70cm in Hastings - Active
GB7HE 70cm DStar in Hastings - Coming soon
GB3ZX 70cm in Eastbourne - Low Power
GB3JT 23cm ATV in Hastings - NoV cleared
GB7RY 70cm X-Wires Repeater Rye - Active
GB7ES Eastbourne - DSTAR Rpt. - Active
GB3ES 2m in Hastings - Active

For a complete list of repeaters, head over to
the UK Amateur Radio repeaters list.

Popular pages

Get your amateur radio licence - Find out more about amateur radio licence training.
Month on the Air - G3MGQ's popular monthly DX contest/expedition list.
Wilf Gaye Memorial Cup - The clubs annual operating event in the memory of Wilf Gaye M0GYE.
St. Richard's College Buildathon/STEM/ARISS - HERC attends St. Richard's Catholic College for their various events surrounding the Tim Peake ARISS contact.
G3BDQ - John Hey's Rare QSL Cards.
Sussex Electronics Radio Fair - SERF Sussex Electronics Radio Fair 2016.
Vital Spark - A selection of articles re-published from the Vital Spark.
RSGB News - Find out how to get RSGB news on your mobile or PC.
Experimenters Corner - A selection of Proteus projects by Bob Gornal (G7DME)
BBADL - Bath Based Distance Learning Course.
Conquest Hospital Radio - Presented by HERC member Antony (G4CUS).
Radio Rallies 2016 - An up to date list of radio rallies scheduled for 2016.
Club QSL Cards - A selection of QSL cards the club has received over the years.
Other Newsletters - Excellent newsletters and magazines from other clubs.
TX Factor episodes - Take a look at the TX Factors YouTube videos.
John Taplin - A bio of the late John Taplin.

Amateur Radio Resources

Other Radio Clubs & RAYNET

BSARS - Brede Steam Amateur Radio Society

RAYNET - The Hastings and Rother RAYNET Group.

HERC members sites

Sigord - Gordon Sweet
Hastings Radio Comms - Andrew Haas-Campbell
Hoofbags - Liz Costa

Categories