Gerard's Homebrew Cymometer

591
Item nr.

Homebrew Cymometer Cymometer

External digital tuning

**Data for Homebrew Cymometer**
Production	The Netherlands, 2024. Price was 16.
Bands	LW through SW.
Semi- conductors	Cymometer.
Cabinet	Plastic.
Power	AC 230V@2.3W.

The Design

Imprecise indication of tuned frequency is the major limitation of analogue receivers for Shortwave DX-ing. I have installed digital frequency readouts in several radio's and oscillators, like my Sloper, the Genometer, a Philips BX660X tuner, a Jennen Trio JR-102, and a Pye Seafarer. This little unit is a separate Cymometer, built in a scrapped alarm clock, that can be used with any tube radio as a set top.

The little unit has banana jacks on the back, and I made a cable to connect it with a radio. The best point is the grid of the oscillator triode. Connect the "hot" (red) wire with that pin, and the black wire with clip to an earth nearby. For the Noval ECH81/UCH81, use pin 9. For the Locktal ECH21/UCH21, use pin 3. For the Rimlock ECH42/UCH42, use pin 4, and be careful not to short anything with the sharp and tight shielding around the tube base.

Obtained	1/2024 from own construction.
Condition	8.
Value (est.)	15€.

This Object

Digital alarm clocks consume 1.5 to 2.0 Watts of energy, must be reset twice a year, take space on the bedside table, and offer just a day program. They are still found new in shops, but also for 1 or 2 euro's in thrift stores.

You can take out all you don't need, and are left with a nice box that perfectly fits a six-digit cymometer, and readily built-in 6V power supply.

Cymometers can be connected to the oscillator of a radio. You can make a soldered connection (with small capacitor); experiments with capacitive coupling by a cap over the mixer tube worked out unreliable. My Philips BX480A has the 6300kHz point marked precisely on the dial. Clearly, connecting anything to the oscillator circuit may introduce capacity and decrease the frequency. Connecting the meter to the triode plate, this 6300kHz point tunes to about 5900kHz, a decrease of 400kHz (or 6%) that causes a definite misalignment and decrease in sensitivity. Connecting the meter to the triode grid decreases frequency to 6284kHz, just a decrease of 16kHz that can be safely ignored. This experiment indicates that the triode grid, not plate, is the point to connect the Cymometer.

Part of Gerard's Radio Corner.
Generated by SiteBuilder on 26/2/2024 by Gerard (g.tel@uu.nl)