[time-nuts] WG mounting h/w (3)

[Don Latham]

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" <kScally at BYTECAN.com.au>
To: <time-nuts at febo.com>
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 <robert8rpi at yahoo.co.uk>
> Subject: Re: [time-nuts] WG mounting h/w (2)
> To: Discussion of precise time and frequency measurement
> <time-nuts at febo.com>
> Message-ID: <750194.71696.qm at web27108.mail.ukl.yahoo.com>
> 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 <kScally at BYTECAN.com.au> wrote:
>
>
> From: Kit Scally <kScally at BYTECAN.com.au>
> Subject: [time-nuts] WG mounting h/w (2)
> To: "time-nuts at febo.com" <time-nuts at febo.com>
> 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: k6rtm at comcast.net
> Subject: Re: [time-nuts] WG mounting h/w (2)
> To: time-nuts at febo.com
> Message-ID:
> <324993853.1018422.1284994721127.JavaMail.root at 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
> ------------------------------ 
>>>snip
> ------------------------------
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