So I thought that I would search here on this site, apparently the namesake of the aforementioned scale, and in so doing could not find anything.
So I posted on the forum thinking that maybe I missed something.
Evidently there is not an eHam Scale. Which is fine.
As I mentioned before I'll bet that what is being referred to as an "eHam Scale" is a misnomer for the ratings of a product in our Product Reviews. Example. Take a look here at HF Amplifiers category: http://www.eham.net/reviews/products/10
Note the 3rd column labled "Average Rating". This is a numerical average of each review rating as submitted by reviewers.
It seems likely that someone (not from eHam) has applied the term "Scale" to the review ratings to describe the implied product quality as shown by the review ratings.
Our ratings are described on the product review submission page when someone submits a product review:
5 - Great!
4 - Good
3 - OK
2 - Needs help
1 - Poor
0 - Awful!
73 Phil NA4M
eHam Product Reviews Manager