Transatlantic Television Baird Success Part 2 – John Heys G3BDQ

The 2 KW Transmitter. Some Technical Details.

The transmitter circuit is basically a self excited oscillator employing a Mullard 0/150 valve which drives a power amplifier which uses a special high power valve which has a silica envelope. The choke (Heising) modulation employs a driver stage using a Mullard 0/150 valve which is followed by a pair of Mullard 0/250 valves in parallel. The quartz frequency control of oscillators was still in its infancy when this transmitter was designed.

transatlantic-television-baird-success-p2The 2Kw Transmitter Circuit
V1 –  Silica valve PA    V1 –  0/250 E oscillator
V3 & V4 –  0/510 audio modulator valves    V1 –  0/150  driver valve

The numbers which follow the ‘0’ of the valves denotes their power rating. Mullard power valves of that period had a glass ‘chimney’ on top which was where the vacuum evacuation pump connected during manufacture. To prevent the melting of the glass envelopes of high powered valves silica was employed instead. Pure fused quartz (silica) was introduced towards the end of WW1. This material does not expand or crack when heated and does not soften until it reaches a temperature of 1,500 C. Glass softens at about 450 C and may crack when suddenly heated or cooled.

The very high voltages for the transmitter were derived from DC generators driven by a 9 hp motor. The photo (last month) shows Logie Baird posed and pretending to adjust the filament rheostat for the big pair of 0/500 modulator valves. Ben Clapp is standing on the right and just behind his right arm stands the vertical housing for the fan cooled silica triode output triode valve. The valve between Baird and Clapp is the 0/250E valve used for the oscillator stage. The QSL card from the American station 1ARY was sent to Ben Clapp for their several QSOs across the ‘pond’ and is dated February 1925, and was sent to his Coulsdon address.

John Heys G3BDQ from Vital Spark March 2011.

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