Now that I have written the articles describing the receivers that I can use to benchmark the performance of other radios, it's a fair question to ask: what do I mean by "reference"?
Since I don't have any test equipment, I have to keep the definition simple and qualitative. Sure, I'd rather be able to measure perform in quantitative terms. But, for now, I am capable of qualitative analysis only. I hope that my background in journalism, political science, and computer science helps me to be objective and to see things for what they are, not for what I wish they would be. That said, if I think something is particularly pleasing or noteworthy, I'll remark on that, too.
It comes down to what is meant by "performance". For FM radios, my definition is composed of several attributes. Sensitivity is the ability to pick up weak signals. Selectivity is the ability to keep nearby signals separated and receivable. Image rejection is the ability to keep strong stations from generating fake signals (images) across the dial. Audio recovery is the ability to maintain the same audio level, or loudness, for both strong and weak signals. Most subjective is sound quality: does it sound good to me (and how would you define that)? And there are esthetic considerations as well.
For AM radios, the criteria are similar, but I might weigh them differently. I would also rate resistance to electrical interference and the ability to tolerate the interference generated by stations using the digital IBOC system.
I most often categorize these criteria with adjectives such as "excellent", "very good", and so on. What, generally, do I mean when I use such adjectives?
- Excellent - means performance at or near the performance I get from my reference radios. For example, Tecsun DSP-based radios such as the PL-310ET and PL-380, are categorized as "excellent" because they perform nearly as well as the NAD 4300 tuner and, possibly, may even exceed the '4300's performance as far as image rejection goes. The older but still sensitive and selective Proton 100 straddles the border between excellent performance and very good performance.
- Very good - means performance near the performance obtained from my reference radio, with deficiencies in one or more areas that barely have an effect on everyday listening. I consider the Advent 400 to have very good performance, with sensitivity and image rejection comparable to the NAD 4300, but with selectivity that is not quite up to the abilities of the 4300. While most Sony Walkman FM radios are not good at all, the first FM-only Walkman, the SRF-40W, is an exception and fits in this category. Its likely successor, the SRF-30W, is not far behind.
- Good - means performance is acceptable for everyday listening in many circumstances, but with deficiencies that are notable compared to reference receivers. The Sangean pocket radios that I have, the DT-200VX and the DT-400W have good sensitivity and selectivity on AM, and have a reasonable 4 kHz audio rolloff, but are not as sensitive or selective as a GE Superadio would be in similar circumstances. Sangean's more recent (in 2019) DSP-based models, the DT-160 and the DT-800, would be considered very good were it not for an unusually high threshold of FM signal strength required before they switch into a stereo broadcast. So, instead, they land into this category.
- Fairly good - means performance is acceptable in some circumstances, but with deficiencies that may become troublesome in others. Again, take the earlier Sangean pocket radios. Their FM sections are acceptable if you just want to receive strong local signals. But they are not selective and they don't reject images well.
- Fair - a receiver that may have a few useful attributes but generally does not perform well. Most Sony FM "walkman" radios are in this category. They sound good and often are convenient to use, but they are not selective and fail miserably at image rejection.
- Fairly poor - a receiver that would be rejected were it not for one or two useful features. The Sony SRF-42, for example, is a poor AM/FM receiver. But it does one thing really well: AM stereo, which it decodes with excellent audio quality. (I'm leaving aside the fact that there are very few AM stereo stations in operation any more.)
- Poor - unless it looks nice or has some kind of nostalgic value, forget about it. The Sony SRF-A100's FM section qualifies as a poor receiver. It sounds bad, has mediocre sound quality, almost no selectivity, and is not very sensitive. The only reason to have it is its AM section, which I would categorize as good or even very good.
Even if I'm doing a qualitative review, I still like to define the terms I'm using in a consistent way.
The reference links, by the way: