If I come across any radio that will operate on the 40 MHz band, I like to keep a record of it here on the blog. One such radio is the ELTING 8000 which was a 1980's vintage radio that was built in Yugoslavia. It was also manufactured by RIZ.
This low-band VHF radio used FM modulation and had a maximum of ten crystal-controlled operating channels.
In the example shown above which is the base version, it is set up for simplex operation on 40.775 MHz, 41.220 MHz, 41.775 MHz and 42.200 MHz. The specified range of the radios was from 40.7 MHz to 42.4 MHz.
This is an internal view of the radio. The mains power supply can be seen quite clearly on the right. You can also make out the crystals just left of centre.
This is the view from the other side and as you can see, there is a second PCB.
The frequency chart below shows how the crystal frequencies were selected...
The transmit frequency is a 12th multiple of a crystal operating at about 3.5 MHz. Possibly something like X3 first, select the third harmonic and then multiply that by 4.
For this radio to operate on say 40.680 MHz (which is the centre of the 40 MHz ISM band - Industrial, Scientific, Medical), a crystal of 3.390 MHz is required for transmit.
To receive on 40.680 MHz, then a 51.380 MHz crystal is required (receive frequency plus 10.7 MHz IF).
There were several versions of the 8000 series... 1) 8000F for fixed operation, 2) 8000M for mobile and 3) 8000P for portable.
The RF output power of each one was 10 watts. There was also a hand portable version called the 8000/1.5P with a 1.5 watt output.
Some of these radios are available on the second hand market and might be a way to get going on just one select frequency on the 40 MHz band.
1) Crowave Blog