The Harris RF-505A is a synthesized-tuning full-coverage longwave-thru-shortwave receiver from the early 1970s. Tuning to 100 Hz resolution is accomplished via six 10-position rotary switches, one switch per decade from Tens-MHz down to Hundreds-Hz. The switch-based tuning tends to make this receiver unappealing for SWL’ing and band-scanning activities. There is a continuous-tune VFO mode that can be switched in, but it only spans 10KHz so is only useful for tweaking up an individual station.

The frequency range is specified as 1.6 to 30 MHz (which is the range of the preselector), but with the preselector off, the receiver will operate down to below 100 kHz with reduced gain (sensitivity is 2 uV at 100 kHz). The first IF is 156 MHz, the second 500 kHz, using Collins mechanical filters. The first mixer is a diode ring mixer, and there is no RF amplifier apart from a 2N5179 in the optional preselector. Despite this the receiver achieves a sensitivity of 0.25 uV. The second mixer is a dual gate FET. The receiver dynamic range is more than 125 dB.

The 505A is capable of ISB operation, so has two independent IF amplifiers, detectors and audio stages. There are USB and LSB mechanical filters, one in each of the IFs, while one IF also has a 10kHz AM filter, the other a 500 Hz CW filter (however, this one is missing this option). While there is only one speaker amplifier, selectable between IF channels, there are two independent line-level audio outputs and two internally lit ‘S’ meters! The Noise Blanker option is not installed in this receiver.

I’ve made two modifications to this set; Firstly, the set was not supplied with a power cord so I’ve installed a permanent power cord and by-passed the AC cord connector. This is visible on the photo of the rear of the set. Secondly, I’ve replace the drive chain for the VFO adjustment with a rubber “O” ring. The drive chain used plastic beads on a steel wire and over time the plastic breaks down and the chain drive no longer works. A rubber “O” ring was found to provide an ideal solution. I’ve never had to use the VFO anyway. I think it’s there more for CW ops and since this set does not have the CW filter installed it’s never been used for that. More details pertaining to this modification and whole lot more info on the 505A are available here: http://madrona.ca/e/radio/HarrisRF505A/index.html

This set is in perfect working order and other than a small scratch by the right side rack mounting tabs, is in mint condition.

Would prefer pick-up in London, but can discuss other options.