Interview with Frank J. Kerr on 8 June 1972

Sullivan: 00:04

Okay. This is continuing with Frank Kerr on 6 August, 1972 with a delay of ten months in this interview, or an intermission of 10 months. And we all had a little bit of time to put together a few details or omissions from the earlier tape. But first of all, you said last night that the [inaudible] interferometer was also tried in New Zealand to some extent. Could you tell me about that?

Kerr: 00:36

At some stage around 1948 or 1949, just when Bolton and Stanley went across at someplace on the west coast of New Zealand. The idea being that they could look out onto the sea westwards and thus get a view of sources as they were setting instead of just rising as in Dover Heights. As far as I can recall, not a very great deal of work was done. I'm sure there's one paper or perhaps more in the Australian Journal.

Sullivan: 01:15

But you thought this might be a first example of aperture synthesis [inaudible].

Kerr: 01:19

It probably was because in fact they were looking across sources in two directions, so it can be thought of that way. They thought of it as getting two [inaudible] across a source. And in one sense, the first real example of aperture synthesis was probably Christensen's cross at Fleurs although it wasn't [inaudible] synthesized being again. It was more a question of getting two directions and then sort of taking Fourier transform imagining in one's mind what might put two things together.

Sullivan: 02:07

There's another early station, Dapto, D-A-P-T-O, I guess. What went on there?

Kerr: 02:16

Well, it came after some of the others so [inaudible]. And this is a whole series of stations in the Sydney suburban area, in the outer suburbs of Sydney. The first one is [inaudible] was Collaroy, C-O-L-L-A-R-O-Y. It was an actual Air Force radar establishment. [inaudible] It wasn't a cliff, it was a hill overlooking the sea. And that was the first place where they looked for the sun and other, and galactic radiation anyway.

Sullivan: 03:03

You mentioned that one in the previous interview.

Kerr: 03:04

And then Dover Heights followed almost immediately afterwards. It was an Army radar site, the Army had left. Then I suppose Potts Hill would have been next. It's westward of Sydney, about 10 miles, and it's an area that's owned by the Water Board. And there's a reservoir there. It's a holding reservoir as they call it. It's a [inaudible].

Sullivan: 03:38

That's the one that you see in the pictures.

Kerr: 03:40

Yes. It's got perhaps a couple days' supply of water for Sydney. The advantage of it, of course, is that it's a closed-off area [inaudible] from people [inaudible] from interference. So it was used quite a while for various things. I think the first thing there was probably a solar setup, and I think of the names were McCready and Yabsley, and a couple of Yagis set up beside the reservoir, perhaps the first. A couple of Yagis as an interferometer. And they also had a funny sort of broadside array, which I think was equatorially mounted on top of a trailer. They’re something like 15 feet in diameter or so across the rectangular, and that was used for solar work. In fact, it was used for first 21-centimeter work, wasn't it?

Sullivan: 04:51

[inaudible].

Kerr: 04:56

Because the 21-centimeter work was done in that trailer, I know, at Potts Hill. [inaudible], but think that must have been the 21-centimeter [inaudible], L-band as it was called in those days.

Sullivan: 05:18

Still is at some places.

Kerr: 05:24

It still is, of course. So Potts Hill started off on the solar work, 21-centimeter probably came next. And after these early experiments, we put up a 36-foot transit dish that could go from horizon to horizon, but it was only transit. And then the very first Mills Cross was put out there.

Sullivan: 06:09

Impressive.

Kerr: 06:10

The small experimental thing to try out the principle. Also, I suppose about three and a half meters, but it was very small and rudimentary was only, it's 400 feet long or something like that.

Sullivan: 06:26

By Mills?

Kerr: 06:27

Yes.

Sullivan: 06:28

About '52 or?

Kerr: 06:29

Say '53. And Alec Little was involved in that. He's been with his crosses for a long time. And also about that time, or starting 1950, '51 or so, the Christiansen dishes went up. First of all, one line on the east-west edge of the reservoir, and then a second line along the north-south side, so that they've got two band [inaudible] across the sun. And you've seen pictures of those [crosstalk].

Sullivan: 07:16

Yeah. Yeah.

Kerr: 07:17

Then about that time also, the solar people had, the solar spectroscopic people, that's Paul Wild, and McCready was still looking at that stage. Perhaps [inaudible] joined in.

Sullivan: 07:34

By spectroscopic you mean an interest in the broadband?

Kerr: 07:38

Yes. The first dynamic spectrograph that swept across in those days, maybe been a few seconds, but because of the type of observation they wanted as quiet as site as possible, as quiet radio-wise. So they went out, first of all to Penrith for a short period. Only about one year, and they were set up in a trailer out there. Penrith is around 40 or 45 miles west of Sydney, and that was the first dynamic spectrograph. As I say, they only stayed about a year. When I talk about trailer, it's usually an army-type trailer. It's not what you imagine as a house trailer. And then from Penrith, they wanted a more permanent site and a quieter one still, so they went down to Dapto. It's on the South Coast, shielded by mountains. [That was then?] under a mountain there. And that station existed for quite a long time from about 1954, '5, '6, or '7 until Culgoora was open.

Sullivan: 09:08

Oh, really, that long?.

Kerr: 09:09

Mm-hmm. So it was a quite long duration state station, and I got to say that rather more permanently with-- rather permanent buildings. And really, the principal, the solar dynamic spectrum work has been done at Dapto. Now they're still doing it now at Culgoora, but it's a secondary interest. So that's approximately what was done at each place. Well, the other station I haven't mentioned in this is Hornsby. That's the place where we set up our-- I had our rhombic to look at the moon, and from there it goes.

Sullivan: 09:59

You did mention it first in the other one you--

Kerr: 10:02

And after the moon echoes, Alex Shain stayed on and worked with some solar noise, but principally a cosmic noise, the survey at 19.7 megacycles at Hornsby. In the meantime, we had set up a broadside array looking face upwards for that work. And then eventually after a few years, that station was closed down, and Shain moved to Fleurs. The Fleurs already had, by this time, the first real Mills Cross, the big one, at least not as big as the present one. But the proper size [was?] about three and a half meters and was sort of made up of the dipoles. And it was in farmland, and they had to keep the cows away from the transmission lines, a few various little bits like that to [inaudible]. In fact, that particular farm, I think was one of the last places close to Sydney producing meat. It was about the time that they were phasing out that sort of thing, so it suited them to rent the place to us. They said the Mills Cross was first out there, perhaps around '54 or '5, and the Shain Cross 19.7 megacycles [inaudible]. Afterwards, it was built up on top of telephone poles. It's one of the first of a long line of arrays, which is very difficult to photograph because it's all very thin wire, so you can't see anything. And then Christiansen moved his cross work out to Fleurs. That was after Mills had invented the principle of the cross itself. And so Chris decided to use the cross on the sun instead of the [inaudible] arrangement, which was two independent lines. I suppose that was around '56 or something, too.

Sullivan: 12:46

Well, that gives me a good idea of those early stations. Thank you very much. We're being called to breakfast. That ends a short interview with Frank Kerr on 6 August, 1972, which can be considered the second interview with him on tape part number 6. The first last part of the first interview is on tape 8B.