Bruce,
Thank you for this point. I've seen Mu metal competitors but I can't
tell what the case is made from.
Pretty much everybody I've seen on this has had to make some kind of
allowance for getting the RF out.
I drilled a hole for an SMA connector and had it exit on the digital
half of the chassis (not the "physics" half), as they're separated by a
very large bar, perhaps brass. It has a few ways to get wires through,
but it didn't seem to be a good idea.
The SMA is a jumper I bought on eBay from a Chinese manufacturer, with
an IPX connector on one end and the SMA bulkhead on the other.
Hirose U.Fl and IPX are said to be compatible, but it didn't look like
it wanted to stay down, so I tacked a wire to the head of the IPX
connector put a brass 2-54 nut on a nearby post to ensure mechanical
connection. I think this is better than soldering open coax to the
connector, but given the short size and low frequency (10 Mhz) it's
probably not a concern.
So, I probably did something bad to the magic Mu metal annealing by
drilling a hole, but it's as far as I could get over on the digital side
of the brass divider. At this point I have nothing calibrated that I
can measure the device with and see if there's any small magnetic
influence, but perhaps someday I will, or maybe someone else would like
to compare with another device sometime.
It might have been possible to re-purpose a pin from the existing RS232
connector, and perhaps others who buy this same run of device may want
to investigate that.
Leigh.
Bruce Griffiths wrote:
Leigh L. Klotz, Jr WA5ZNU wrote:
So far I've seen
http://www.dd1us.de/Downloads/precise%20reference%20frequency%20rev%200_4.pdf
If the case is Mu metal or similar then the modification shown in the
above article will likely destroy its magnetic shielding properties
(unless its annealed in a hydrogen atmosphere at 400C for several hours
after machining).
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