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In article ,
] writes: why were the transmitters of "twin" receiver/transmitter combos, such as the R-4/T-4 pair, designed with separate supplies? First off, some receiver/transmitter pairs put the power supply in side the transmitter as well as the receiver. This was more common before about 1960 than after. In fact, before WW2 it was common for receivers to have separate supplies! Several reasons: Size/weight/minaturization: The power supply for a 100-200 watt transmitter like the T-4 is much larger and heavier than the power supply for the matching R-4. In order to keep the tx and rx to the same size and about the same weight, the transmitter power supply was made external. As rigs got smaller, this became more and more of an issue because most power supply parts could not be made much smaller. Heat: The heat produced in tube rigs is always a concern, and transmitters produce lots from the final tubes to begin with. Making the power supply external eliminated having to deal with the heat from it. Magnetic fields: The power transformer and filter choke(s) have magnetic fileds around them which can induce hum in various components and wiring. The fields are much stronger in a transmitter like the T-4X because the power level is much higher than in a receiver. Cost/manufacturing considerations: IIRC, the same power supply that was used with the TR-4 was used with the T-4. This saved the Drake folks the cost of designing a power supply into the T-4. It also reduces the *apparent* cost of the T-4X. (Same sort of marketing gimmick that has an item priced at $599.99 instead of $600 - they think we're so math-impaired that we'll be more inclined to buy the "less expensive" item.) Homebrewing/existing supply/upgrading: Some hams might want to save money by building their own power supplies (they aren't complicated). Others might have a TR-4/AC-4 setup, and then decide to get the R-4/T-4 compbo for the shack and use the TR-4 mobile. Such a move would require buying a DC supply for the car and just the R-4/T-4X for the shack, since the AC supply was already on hand. Brand loyalty is/was a big thing with manufacturers, so being able to offer inducements like that was a selling point. (And the TR-4 could still be used in the shack). 73 de Jim, N2EY |
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