How a filter-type HF SSB transceiver works. The PCM Hawk transceiver pictured here was built in the 1980s and has 10 fixed crystal-controlled channels between 2 and 8 MHz. I haven't measured the RF output power but my estimate is somewhere between 50 and 100 watts. The intermediate frequency is 1.650 MHz. Crystals are be 1.65 MHz above the desired transmit and receive frequency. The SSB signal generated is lower sideband, but because it is subtracted it becomes upper sideband, which is the general standard. Widely used in outback Australia (4 wheel drive, school of the air, flying doctor etc) these transceivers were simple, rugged and designed for use (and abuse) by non-radio people. Until satellite phones, radios like these were the only connection with the outside world. Though most radio amateurs prefer frequency agile equipment so they can operate across the whole band, converting a set like this is still a great project. Luckily the set fitted has channels for 2, 4 and 6.9 MHz so very little work is needed for use on 1.8, 3.5 and 7 MHz. The main problem is the upper sideband which is not generally used on these amateur bands - lower sideband is preferred. To fix this you can change the mixing scheme (so you add the 1.650 MHz IF so don't invert the sideband) but this requires some tuned circuit changes. Or you can leave the mixing as is and change the 1.650 MHz carrier crystal so it's below, not above the filter's passband. It requires a lot of effort to swing a 1.650 MHz crystal down to 1.647 MHz, but it can be done by (i) adding an extra crystal in parallel, (ii) adding a lot of series indductance and (iii) fiddling with capacitor value(s) in the oscillator. ... https://www.youtube.com/watch?v=9saTnTsAe4U

Testing an LED light for interference on 144 MHz FM. PS: If you liked this video please consider supporting Amateur Radio VK3YE by: * Subscribing on YouTube * Checking my books page at https://books.vk3ye.com​​​​​​​​​​​​​​​​ * Shopping on Amazon via: https://amzn.to/3iiDQXv, or * Shopping on eBay via: https://ebay.us/i9DuWP (then if you buy something I'll get a small commission at no cost to you) ... https://www.youtube.com/watch?v=H8twPwskQNI