Token, the summary states...ASV Mk.II Developed at the Royal Aircraft Establishment at Farnborough in early 1940, ASV Mk.II differed from Mk.I mainly because it was properly engineered, and therefore much more reliable. Although called a 1.5m radar, it actually used 1.7m (176MHz). Range was up to 36 miles.
Yeah, the early ASV radars (like the Mk I) were a bit higher in frequency, above 200 MHz. The ASV Mk II was 176 MHz. The ASV Mk III was a mixture of freqs, starting with prototypes using the 176 MHz transmitter of the Mk II, but production versions ending up at much higher frequencies, up to 3 GHz. I mean the first 3 GHz Mk IIIs were made by replacing the VHF transmitter of a prototype Mk III. The Mk III had a very fractured history and documentation on it can be contradictory.
The excerpt of "When Computers Went to Sea" that I quoted makes it sound like maybe, just guessing here, the early PBY-5As were intended to have the ASV Mk I (probably the American made version, SCR-521 or ASE), and the antennas were built for that, and then ASV Mk II was installed and it was not originally realized there was a frequency mis-match.
I am fortunate enough that when I entered the field (in the 1970's) a lot of the "old hands" had first hand WW II radar experience or had been trained by those people. I actually have a lot of hands on time with WW II radars, land based, sea based, and airborne. Unfortunately, when I had the access I did not understand the history, and it was not until later when I started putting what I had been exposed to with what I could find in print. SCR-584, SCR-720, APG-2, APS-6, and ASV Mk III are a few of the WW II era radars that I have had exposure to at one time or another. But of those only the SCR-584 was in its WW II configuration, the others I was exposed to were all modified / adapted in some way to another application. For example, the APS-6 and the SCR-720 were both used mounted on trucks when I saw them.
(edit) Looking at the MIT Radlab series of books Volume 1 discusses the American made version of the ASV Mk II. For the Army it carried the designation SCR-521, and for the Navy it was called the ASE radar. This book also confirms that the ASV Mk II / SCR-521 / ASE were 176 MHz, it also states that the earlier ASV (I assume Mk I as it says no Mk number) was "near 200 Mc/sec".
T!