[time-nuts] Choke Ring Pictures

[Brian Kirby]

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