[time-nuts] Choke Ring Pictures

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Mar 15 20:34:44 UTC 2010


For some idea of the considerations involved in selecting materials for 
and designing a radome see:
http://ia331316.us.archive.org/0/items/radarscannersand033384mbp/radarscannersand033384mbp.pdf 


A list of the properties of some dielectrics at microwave frequencies in 
inluded.


Bruce

Bob Camp wrote:
> Hi
>
> Any idea what the funnel was made out of? Some plastics aren't real great at
> microwaves...
>
> Bob
>
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Brian Kirby
> Sent: Sunday, March 14, 2010 8:50 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Choke Ring Pictures
>
> The home made choke ring was calculated and the pie/cake pans came
> close.  I think somebody all ready pointed at it, but Unavco or NASA had
> the dimensions to about 6 or 8 common choke ring reflectors on line.
>
> They are aluminum cake pans - I bought them in a crafts store.  They are
> one inch apart between the rings.   They are 2 inches deep at the rims.
> The outside pan is 12 inches (measured inside).  Next is 10 inch,  then
> 8 inch, then 6 inch, and 4 inch.
>
> When making them, I found the center of each pan and then drilled them.
> Then I used a bolt to hold them all together except for the very center
> unit.  Then I drilled two holes about and inch from the center and used
> thin long bolts to  attach them to a piece of square tubing on the
> bottom.   The alignment bolt was removed from the center hole and
> drilled out larger to pass the antenna coax thru.    The very center
> pan, I used epoxies to glue the antenna too and I used a clamp to hold
> it in place.   Then the  coax was pass thru a hole I drilled out thru
> the center holes of the other pans.   Then I glued the antenna pan to
> the other pans and used several blocks of wood to center the pan and a
> big piece of pipe and weights as a clamp to hold it down while it was
> curing.   The square tubing was aligned into a  laser level mount and
> epoxied and that allows the unit to be attached to a tripod.  The mount
> has three adjusting screws that allows the antenna to be leveled.   I
> used the units in pairs when surveying and always aligned then north in
> an attempt to bias out centering differences.
>
> The first unit mounted on the house roof did have a drainage problem the
> first time it rained.  I drilled 1/8 holes inside of each ring to let it
> run out.  That was not the worst problem.  A bird decided it would make
> a good home and started building a nest on it when I went on vacation.
> I bought a large plastic funnel and inverted it and glued it inside of
> the outer ring to stop that.
>
> The antenna is the common Antenna97 from Motorola, the coax was cut at
> about one foot (I think it was originally 18 feet long) and a connector
> was attached.  I then used a very low loss coax (1/2 inch heliax) about
> 40 feet long to bring it into the basement.
>
> Brian - KD4FM
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>    





More information about the time-nuts mailing list