[time-nuts] Choke Rings and Points North
jimlux at earthlink.net
Wed Dec 17 08:49:16 EST 2014
On 12/17/14, 4:36 AM, Bob Camp wrote:
>> On Dec 17, 2014, at 1:07 AM, Chuck Harris <cfharris at erols.com> wrote:
>> I would venture that the extent of the magic was to note the physical
>> center of the array, and call that the phase center.
>> As long as you always orient the antenna in the same direction, any
>> errors that might exist in the real phase center will be consistent,
>> and could be corrected for by noting the offset from a benchmark.
> I’m afraid that’s what they do as well. Just spin it and see what a dial indicator reads sort of thing. I think that I’d want something that actually did some microwave tests ….
The UNAVCO data is an actual RF test.
And from a manufacturing standpoint, I would imagine that typical
tolerances are better than 0.001" (25.4 microns). Changes much bigger
than that would show up as VSWR changes, which *is* something that they
check in manufacturing.
The Leica "artichoke" multiband choke ziggurats (they're not flat, so I
have a hard time calling it a "ring") are cast and then machined.
Casting isn't what I would think is a precision operation, but it
probably is real consistent from unit to unit.
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