While leafing through some old RSGB Bulletins (now RadCom)
I came across a letter written by Robert Tarr G3PUR.
In the letter, Bob explained how the 70MHz a.m. calling frequency
- 70.260MHz - came about in the Summer of 1962; all of 40 years ago.
While leafing through some old RSGB Bulletins (now RadCom)
I came across a letter written by Robert Tarr G3PUR.
In the letter, Bob explained how the 70MHz a.m. calling frequency
- 70.260MHz - came about in the Summer of 1962; all of 40 years ago.
A group of amateurs from England's south coast, initially Robert Tarr G3PUR, Fred Robins G3GVM and Don Hayter G3JHM, brought some military surplus B44 Mk.1 receivers and put them on 70MHz. A pair of crystals from the very first batch they ordered are shown on the right.
There is some debate as to exactly why 70.260MHz was chosen as the calling and operating frequency but whatever, Summer 2002 marks the 40th anniversary of 70.260MHz.
It seems appropriate to celebrate this triumph of serendipity over the best efforts of the band planners by digging-out all those old 70MHz a.m. rigs and putting them on the air. See you on 70.260!
I've been contacted by Kevin Ravenhill G1HDQ, who is looking for 70MHz (a.m. if possible) contacts. Kevin is located near Axminster in E. Devon and has a Pye Reporter plus a Pye A200 amplifier. He's been in contact with other 4m enthusiasts at www.70mhz.org and tells me:
"Among those interested are G0WJR (who operates portable/mobile most Sunday mornings, mainly from hilltops around the Bristol area and would like more AM QSOs), GW1SXT in Pontypool, and G3TCU in Surrey. "Also, Norman 5B/G1JJE can run 100W AM into a 6-ele from Cyprus and is willing to give it a go, so this could make life interesting if conditions are right...."Kevin's E-mail address is: hdq-at-btinternet-dot-com. (Please replace the '-at-' and the '-dot-'. Anti-spam measure.)
Many battery-powered, valved radio sets are still working happily,
and most of their components can still be obtained should they fail.
Unfortunately, the same cannot be said for the batteries they use.
Anyone who has an old battery can always remove the battery's innards
and replace them with modern batteries.
But for those of us who don't have the real thing, help is now at hand.
The combination of modern electronics and NiMH cells means that high voltages can be generated efficiently from low voltage sources. And now there's a web site on the Internet that has scans of obsolete batteries.
All you have to do is download the image you want and print it full-size on a colour printer. As the images are not all to scale, you'll ned to know the size of the battery you're trying to recreate. To help I've put some battery data on my Data and Documents page.
The images below show two (cosmetic only) batteries made in this way. The Radio is a Vidor CN381B 'Radio Attache'.
Please, anyone who has a battery that isn't manufactured any more, can you preserve both the outer case and the connector. Also, if anyone has any detailed battery information (engineering data and the like, the sort of thing that equipment and radio designers would have needed), can they preserve that also.
The site mentioned above is a good start, but I'd like to see a permanent, comprehensive collection of battery data assembled and as much information as possible made available on the Internet. Maybe a contemporary battery manufacturer could be persuaded to host the site. Any takers?
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