The HF-sony icf sw 100 service manual was the replacement for the HF-125 and offered a few minor changes over its predecessor including slightly different case styling and different feet and some small technical changes including finer tuning steps – changed from 15. 6Hz in the HF-125 to 7.
The demands made on a short wave receiver when used in the western hemisphere, and particularly in Europe, are great indeed. Such a receiver has to be capable of resolving weak signals in a welter of almost unbelievably strong transmissions, and provide high sensitivity at the same time as high immunity to overload. The HF-225 has been designed specifically to give the dedicated short wave listener a receiver which fulfills all his requirements, whilst doing it within an attractive price. The performance of the HF-225 approaches that of professional receivers costing up to ten times its price, and the simple appearance of the HF-225 hides a very comprehensive specification. The HF-225 short wave receiver was conceived, designed and is ‘Made in Britain’ for the DX enthusiast.
Its ability to perform on a crowded band with strong adjacent stations was a major consideration in its design. The HF-225 is also easy to use, the controls being simple and sensible. Essential bandwidth filters which are often options on other equipment are fitted as standard. Unnecessary frills are not included and their omission is deliberate. Operating modes are AM, USB, LSB and CW. Operating the HF-225 is refreshingly simple. Two buttons, one marked up, the other down, select the correct megahertz and you tune to the required frequency using a large heavy knob with a thoughtfully provided finger recess.
The tuning rates relate to a simple design concept of two stations per knob revolution on each mode. Tuning on SSB and CW is in 8 Hz steps. This allows extremely accurate resolution of SSB signals and ECSS reception of AM. Mode selection is by a front panel switch. Initial filter selection is automatic and dependent on mode.
Checking the filter in use is easy, a momentary press of the FILTER SELECT button and the frequency display changes to indicate the current filter width, another press of the button identifies the next filter on the display and at the same time switches to it. Repeated pressing of the button switches in the other filters in turn. To further enhance reception other facilities are included. A noise blanker is permanently in circuit to deal with vehicle ignition interference, 20 dB of R. HF or LF cut tone control can be applied to the audio output. The HF-225 has 30 memories which store receiver frequency settings.