The Clegg Interceptor VHF Receiver
|In the 1960's, the Clegg Interceptor
receiver was a highly prized receiver by the VHF enthusiasts. It was very
sensitive and featured a low noise figure. This low noise figure was achieved
using the unique, little Nuvistor tubes which were only about twice the size of
the metal-capped transistors of the day. The most famous of the Nuvistors is
probably the 6CW4. They were used in all sorts of VHF equipment and projects
and provided VHF operators with a new tool to explore true weak signal VHF and
The receiver itself is not particularly remarkable from a circuit standpoint. It simply went about its job of pulling in weak signals and provided decent stability and selectivity. For CW, a variable bandwidth L/C audio filter is included. While not your vertical sided DSP CW filter, or even a good crystal lattice filter, it did an adequate job. Besides, if you'll notice on the mode switch, CW is not included. You just used SSB and turned on the CW filter is that was the mode of choice.
One of the things I find fascinating is the dial and it's clever calibration method. The tuning mechanism is the famous Jackson Brothers (made in the U.K.) dial system which was available for home brew projects. This tuning mechanism is silky smooth and has no noticeable backlash. The numbers in the window above the tuning knob are only a logging scale and have no relation to the received frequency other than to allow retuning precisely to a previously logged dial position. If the VFO has been linear, then this dial could have been used to produce very accurate readout of received frequency, but no attempt was made to linearize the VFO. This is obvious from the uneven 100 KHz calibration points. While this may seem crude by today's standards, it was acceptable at the time and the only really accurate receiving schemes were crystal controlled converters followed by a very accurately calibrated such as those produced by Collins.
Overall, it's an A+ receiver given the state of its peers.