IC-202 - Digital display

november 28, 2020 electronics, Amateur Radio

The ICOM IC-202 is a venerable amateur radio transceiver dedicated to the 144 MHz band that allows audio transmissions in BLU (Single Sideband, SSB in English) as well as in telegraphy (CW).

Some vintage advertisements :

The VFO makes it possible to cover 200 kHz. The 2 original quartz allow to cover from 144.000 MHz to 144.200 MHz, and from 144.200 MHz to 144.400 MHz. 2 other slots are available to cover 2 other portions of 200 kHz.

Here is a descriptive article from 1978 by Robert PIAT F3XY.

The frequency display on the original vernier does not allow high accuracy in reading the frequency. When switching from the call frequency (144.300 MHz) to a release frequency, if in addition the vernier has a certain offset, it is possible to lose its corresponding…

Little hack tonight with the implementation of a digital display for a venerable IC-202.

To do this, I based myself on the description of F1AFZ: Digital frequency display for IC-202.

The installation of this digital display consists in recovering the RF signal from the local oscillator and displaying it on a frequency meter-display module of this type: ebay link.

Two connectors to use:

the one on the left to connect the RF signal,
the bottom one to connect the power supply (9v to 12v).

The RF is recovered on pin J3 (J2 for ground) :

When at 12V, you might as well also get it on the IC-202 so that the display does not need a separate power supply and that it lights up at the same time as the station :

The 12V is to be recovered on this connector (pin 10) as well as the associated ground (pin 11).

All that remains is to route a small coax for the RF signal and the power cable :

Photo on the left: An existing small hole allows the power supply cable to be passed to the battery compartment. As for the coax, it easily sneaks under the LoudSpeaker and then joins the power cable. A small discreet hole on the back will be necessary to bring out the set.

The ”programming" of the display is very simple and consists simply of indicating to it the IF (Intermediate Frequency) of the IC-202, namely 10.7 MHz so that it adds it to the RF signal of the local oscillator picked up on J3. For example, on J3, the signal frequency is 133.600 MHz when the vernier indicates 144.300 MHz. It would be a shame to have such a beautiful display and to have to add 10.7 MHz in your head…

Everything happens with the 2 buttons located on the back. Here is the user manual (thank you F1AFZ!). Everything happens on page 5, successive presses on SET and on the button marked by a triangle make it possible to adjust the frequency delta to be added (10.7MHz).

First try “open belly” :

And the final result once “canned” :

And a little video preview…

For € 12 and a couple of hours, it would be a shame to deprive yourself of it!