[time-nuts] Choke Ring Pictures

[Joe Gwinn]

>
>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.

Joe Gwinn