[time-nuts] Choke Ring Pictures
Robert Atkinson
robert8rpi at yahoo.co.uk
Sun Mar 14 22:10:53 UTC 2010
Most light alloy cake tins are anodised, so getting consistent contact could be a problem. It's hard to remove the anodising and leave an even surface..
Robert G8RPI.
--- On Sun, 14/3/10, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
From: Magnus Danielson <magnus at rubidium.dyndns.org>
Subject: Re: [time-nuts] Choke Ring Pictures
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Date: Sunday, 14 March, 2010, 21:42
Joe Gwinn wrote:
>>
>> Date: Sun, 14 Mar 2010 21:09:00 +0100
>> From: Magnus Danielson <magnus at rubidium.dyndns.org>
>> Subject: Re: [time-nuts] Choke Ring Pictures
>> To: Discussion of precise time and frequency measurement
>> <time-nuts at febo.com>
>> Message-ID: <4B9D425C.2050307 at rubidium.dyndns.org>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> Bob Camp wrote:
>>> Hi
>>>
>>> Wedding cake pans normally come in 1" increments and are either 2" or 3" deep. Sets are 2" increments on the diameter:
>>>
>>> http://cooksdream.com/store/wedding-round.html
>>>
>>>
>>> http://www.hubert.com/store/products.asp?CAWELAID=126235277&A=SB%2E58369%2E10738&Dn=0&An=966+966&Au=Presentation+Id&Ntt=10738&N=966+966&src=chanadv&Ntx=mode+matchall&D=10738&Ntk=SKU
>>>
>>> The height would be fairly easy to adjust. The diameter not so much so.
>>>
>>> Looks like 2 and 2.5" are typical dimensions for the depth. ~1" looks pretty typical for the width. A 2" deep / 2" diameter step set looks like it would do a pretty good job . It won't be accurate enough to be perfect. Without a 3D EM program it would be tough to figure out just what the errors would do to you.
>>
>> With 2.5" depth and 14", 12", 10", 8" and 6" diameter pans you are not
>> completely in a different world from some antennas:
>>
>> http://facility.unavco.org/project_support/permanent/equipment/antennas/ant_cals.html
>>
>> Evaluating the performance may be a different thing.
>>
>> One thing to care about is the leakage between the pans if you just stick them inside each other.
>
> I'd be tempted to use EMI gaskets between the pans, except that contact will soon be lost as the aluminum grows a nice oxide layer. But it may not be necessary to make DC electrical contact, as the capacitance between the metal layers may suffice to act as a short at 1.5 GHz. A thin sheet of mylar (or a heavy anodization layer) between would help this along, by increasing the capacitance.
However it is done, you want it to be fairly stable. Evenly distributed screws against a stable platform like a steel-plate should do it.
An alternative is to TIG them together.
Cheers,
Magnus
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