TW Nuvistor Converters
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TW Nuvistor Converters

These converters used the RCA 6CW4 miniature nuvistor which had a remarkably good low noise performance and this unit replaced the Cascode converter previously produced by TW. The nuvistor converters had approximately 30dB gain and 70dB I.F. rejection.

The photographs above show a TW 2m nuvistor converter, this particular one having its own built in power supply (which retailed at £15), but they were also supplied without a built in P.S.U. (which retailed at 11 gns.). For those of you too young to remember, a guinea was £1 and 1 shilling, equivalent to £1:05 in today's currency. These converters were available with a choice of I.F.s (e.g. 28-30MHz, 4-6MHz etc).

The photograph above left shows the 'innards' of the converter with all the components mounted on the lid and the P.S.U mounted in the box. The nuvistor can be clearly seen on the photograph above right (just to the right of the Belling Lee antenna socket). My thanks to Howarth GW3TMP for the converter and the original photographs.

According to an advert from 1964, a 4m version was also available (again with a choice of I.F.s) .

Vern M0WQR has kindly sent in some photographs of a TW nuvistor converter that he acquired at a rally (May 2011) for the princely sum of  £2.

As may be seen from the photograph alongside, this particular unit seems to have gained some extra ventilation and is missing the on/off switch and  the indicator lamp.

I am not altogether sure what I.F. this unit is using, the marked crystal frequency being 7680kc/s.

I recently acquired another 2m TW nuvistor converter but this one does not have a built in power supply (photos below).

This particular unit uses  a 28 - 30MHz I.F.  The circuitry is in remarkably good condition, but it does look as if, at some stage, a Belling Lee socket has been mounted on the top plate.

In September 2017, a friend of mine overheard a conversation on 80m in which mention was made that an item of TW equipment had been seen at a recent event held at Finningley Amateur Radio Society near Doncaster. I emailed the club and promptly received a reply from Martin M0HOM who confirmed that the club had a piece of TW equipment that had been donated to the club through a SK.  From his description it seemed likely that it was a TW converter and this was confirmed when Martin sent me a photograph.

The unit is a TW nuvistor converter for the 2m band. The FT243 crystal is marked as 6450 kc (6.45MHz) meaning that the converter is intended for use with a receiver tuning approximately 28 - 30MHz to give coverage of 144-146MHz .

According to Martin, the converter was given some ‘volts’ and after checking the heater current being drawn HT was applied with no apparent problems. After a mad search for Belling Lee connector converters,  a 2m antenna and a suitable receiver were connected and the TW2 was successfully converting again!  Magic !!!

Martin went on to say that when listening to GB3VHF using his Yaesu FT-100 via the converter it was sounded better on that RX than on the clubs FT-847 shack rig. You can listen for yourself here      

FARS are proud to be able to display it in their museum, and think that it is fantastic to have the option to actually use it, and not just look at it.

Photograph above provided by Martin M0HOM and used courtesy of Finningley Amateur Radio Society (FARS).