HF Receivers 9R-59DS and FRG-7

Trio 9R-59DS

Valve superhet receiver from Trio (Kenwood) built around 1969/1970. General Coverage from 500kHz to 30MHz with bandspread calibration over the non-WARC amateur bands. To resolve SSB and CW, BFO and Product Detector circuits and mechanical filter are provided. I got the receiver around 1974/1975 and as a young teenager I included a crystal calibration oscillator based on a 6BE6 valve and a 100kHz crystal (since replaced with a 1MHz crystal after the earlier one failed). The optional voltage regulator valve is also included, however the set does drift a little and never quite seems to settle down.
Click here for Radio Museum Info.

Yaesu FRG-7

When the Yaesu FRG-7 came out, it was the receiver I had to have. Just a dream as a teenager but eventually thirty years on, thanks to Tony G0DLX, I was lucky enough to have one. It's a fully transistorised triple-superhet receiver from Yaesu built in the late 1970s. General Coverage from 500kHz to 30MHz. It uses a Wadley Loop system to prevent drift - very effective too. Click here for Radio Museum Info.

An excellent receiver to start with but with some opportunities to enhance with mods (and lots of space to do them in!)...

Finer tuning
The early versions of the receiver had no fine tuning at all. This version does have fine tuning but it's still fairly coarse so I put a 22pF capacitor in series with the fine tune to reduce the range and so make tuning finer.

Loop Lock Light
The MHz control is tuned for the band and has to be fine tuned until loop lock is achieved. Originally the receiver shows lock by the loop lock light (a red LED) going out. This isn't very intuitive! I introduced a circuit with a two-colour LED to show green when locked and red when unlocked. The circuit was built using plain matrix board and mounted underneath (where there's lots of space). I made use of the existing white-black and white-red cables as the red and green LED anodes and provided a new cable (green) as the shared cathode connected to ground. It is described in the Yaesu FRG-7 discussion group in Yahoo. Please click on the photos below to zoom in.



Narrow IF Filter
The original 455kHz 3rd IF Filter is a Toyo LF-C6 which has a massive 6kHz bandwidth, excellent for good audio from Broadcast stations but rather poor for SSB and CW. I decided a narrower filter was essential and bought a Murata CFJ 455K14 with a bandwidth of around 2.5kHz (at 6dB down). I took the original filter off the main IF board and introduced a small varoboard bolted underneath with a standoff piller. The board containing the the two filters and a DPDT switch. The switch is mounted on the board, so not accessible in normal use of the radio. I could have used a relay and driven it from spare contacts on the front panel mode switch but decided I was unlikely to want it set back to it's wide position and have left it like this. Please click on the photos below to zoom in.



Of course leaving like that nagged at me that it would be more finished by using a relay to switch the filters. The Mode switch has two sets of spare contacts so I arranged one set to be used to switch the relay on/off. I decided that the receiver would normally be listening to SSB and so I set this up as the default and made the relay switch to the wide filter only in AM or AM/ANL modes. The relay switching cables are coloured red. Please click on the photos below to zoom in.



Transceiver conversion
Ian Keyser documented a transceiver conversion project c.1980. The ICs that he used then are all obsolete and although alternatives are available they are expensive. I had in mind using the VFO, mixing with an appropriate crystal, filtering and using this to drive a SSB transmit section. However, the VFO frequency tracks in the opposite direction of the dial frequency and this would make this project much more complicated. Sadly I now don't have plans to do the conversion.