The Labgear LG300 5 band transmitter by Ken Brooks G3XSJ Settling down for a winter reading of 1950’s RSGB Bulletins, the image of a large and handsome piece of amateur radio equipment stared out from the front pages. For years and years this same piece of equipment appeared, symbolising the stability of the era. Even the captions were alluring with scripts like “A real man’s transmitter.” The haunting image was in fact the Labgear LG300, a chunky, classically designed 150 watt rig in a steel cabinet with chrome handles giving it a very businesslike appearance. |
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Adverts for the LG300 first appeared in the RSGB Bulletin in January 1955, illustrating what was presumably their prototype which had round meters. By March 1955 the price had been revealed as 47gns, (£49.35), less 813 valve. Much emphasis was placed on the TVI proofing of the instrument. This was in the days of rapid TV growth, and with transmissions on band 1, TVI was a real problem for amateurs. The September 1955 Bulletin advert played on those fears with the eye catching caption “Sorry OM but I’ll have to close down now - T/V starts in 5 minutes” . In January 1956 a photograph of the companion
power supply and modulator first appeared, suggesting that its
development might have been an afterthought. Skipping through the years,
the final advert appeared in May 1961. The price was now 66 gns, (still
less 813!), and a new address was given along with affiliation to the
PYE group of companies. Presumably PYE marketing decided there were
insufficient returns from advertising
what was then becoming a time expired product. Description
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The Labgear LG300— PSU/Modulator on the left hand side, RF unit on the right |
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Band switching is accomplished at low level by wafer switches in the multiplier, and by a separate tank circuit switch. The tank circuit switch is of massive ceramic construction but spoiled by a fragile diecast detent mechanism. Considerable torque is need to overcome the detents. With two switches needed to select a band Labgear issued a cautionary note in their instructions warning users against multiplying in the PA. Acquisition and
rehabilitation Tuning up |
It had been noticed that drive levels varied between
bands and before activating the PA it was expected that full RF output
would not be obtained, but with EHT applied and when tuning up the pi
network, the rig delivered the full 150 watts of RF into a dummy load.
This could be easily exceeded at the expense of signal quality. I have not yet air tested it, mainly because of slothfulness on my part sorting out the transmit/receive arrangements, but its capability is not in doubt. Overall, the LG300 is a fascinating piece of equipment and I believe there are already a few in VMARS members’ hands. Despite its robust appearance some parts have a distinctly hand built look about them and there are physical weaknesses in a couple of areas. With care, these can be overcome, and my limited experiences go to prove that 1950’s technology can be resurrected with relative ease. In their time these were very expensive items of equipment and perhaps treasured possessions of their fortunate owners. They have probably survived because there is very little to go wrong that cannot be repaired. I look forward to running this one up and having real contacts using it, but to be completely authentic my radio room carpet should be replaced with lino, I should take to wearing a sports jacket with leather elbow pads, and I should take up smoking a pipe! |
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View of the PA compartment |
Rear view of the PSU/modulator cabinet—plenty of heavy metal here! |
This article and pictures copyright © Ken
Brookes G3XSJ
and may not be reproduced elsewhere without permission.
HTML conversion Colin Guy G4DDI.