If I remember aright, every flange should mate to a choke. that's how to
keep the joints from giving bad stuff...
Don
----- Original Message -----
From: "Kit Scally" <[email protected]>
To: <[email protected]>
Sent: Wednesday, September 22, 2010 8:34 PM
Subject: [time-nuts] WG mounting h/w (3)
Robert,
Many apologies for giving you the "big snip" (!) - replying to TN postings
when receiving via "Digest mode" leaves room for such mishaps.
I'm not familiar with 5/32" dowels or how well they fit in WG mounting
holes. One major problem is European IEC & US-MIL spec'd flanges have
varying size holes! 5/32 is 0.156 - this dowel may/may not fit WR75
(0.144 or 0.161) but will be "loose" on WR90 (0.169). Then there's metric
& imperial variations ...
What I can say with confidence that if you're building a WG run with 20-30
flanges (ie an HPA hybrid combiner) using disparate makes of hardware and
don't take anal care with tapered pins on each and every joint, you <will>
end up with dB's of ppk ripple when the assembly is swept end-end. This
is well-nigh impossible to reduce without re-aligning every flange. If
the system has only a few mating flanges, other methods may be OK.
I can appreciate how shoulder screws reduce the degree of craft assembly
skill and assembly time required - certainly less messy than pins ! Thick
flanges don't seem to be in common use in satellite earth stations.
(BTW - do dowels wear with use?)
Rgds,
Kit
VK2LL
*****************
Message: 4
Date: Mon, 20 Sep 2010 18:44:37 +0000 (GMT)
From: Robert Atkinson <[email protected]>
Subject: Re: [time-nuts] WG mounting h/w (2)
To: Discussion of precise time and frequency measurement
<[email protected]>
Message-ID: <[email protected]>
Content-Type: text/plain; charset=iso-8859-1
I think you are a snip too soon. My original post said "If you have to use
screws, at least align two diagonal holes with 5/32" dowels while nipping
up the ?first two screws". Taper pins are also OK of the taper is slight
and flanges are not too thick. Don't tighten the first two screws too
tight at first to aviod warping the flange.?In aircraft installations I've
designed have used shoulder screws because they were specified by the
equipment manufacturer.
?
Robert G8RPI.
--- On Mon, 20/9/10, Kit Scally <[email protected]> wrote:
From: Kit Scally <[email protected]>
Subject: [time-nuts] WG mounting h/w (2)
To: "[email protected]" <[email protected]>
Date: Monday, 20 September, 2010, 9:19
Hi,
Well, still not strictly, strictly true !?
In Ku & K? band earth stations I've worked in, I've never seen shoulder
screws used, although the equipment used was mainnly from the USA.?
Next to you precision adaptors, SMA torque wrenches etc in your personal
goodie box are sets of tapered pins, about 35-40mm long - that fit various
diameter WG mounting holes (the old metric vvs Imperial issue again).
You insert a pair of pins on diagonal corners then add bog-standard SS
hardware to the opposite diagonals & tighten.? The tapered pins are then
removed and replaced with another pair of screws/nuts.? This ensures
absolute (?) internal WG slot alignment.? There are a few variations on
this theme if you must have absolutely minimum RL within that section of
guide or if one guide face is threaded.? Hex-headed bolts are usually
used.
That may explain why shouldered bolts are seldom seen.
Tapered WG pins fall into the 99.9999% unobtainium class of materials.
Kit
VK2LL
Message: 2
Date: Mon, 20 Sep 2010 14:58:41 +0000 (UTC)
From: [email protected]
Subject: Re: [time-nuts] WG mounting h/w (2)
To: [email protected]
Message-ID:
<324993853.1018422.1284994721127.javamail.r...@sz0110a.emeryville.ca.mail.comcast.net>
Content-Type: text/plain; charset=utf-8
Another mystery solved!
My (late) father-in-law spent most of his career at Varian-Eimac, mostly
working on TWTs, BWOs, and the occasional magnetron. In one batch of his
goodies, along with the H&S SMA torque wrench, was a little box with some
tapered metal pins! I've wondered what those were for, and now I know!
He was very happy when his daughter brought home someone who knew what
vacuum tubes were, even if he did think that the RF work I did as a ham,
even the 144 and 440 MHz stuff, was still practically DC...
Bob K6RTM
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