The poor man’s choke-ring GPS antenna
Description
The outer
container, gold color, originates from a 35mm KODAK 600ft motion picture
negative film canister.
Film labs
have plenty of them to spare, as film is spliced into larger rolls after it has
undergone development.
The inner
NIVEA tin can, blue color, may be a bit difficult to find, as it is more than
two decades old.
Nowadays,
plastic ones probably have replaced them, thing that makes them unsuitable for
this purpose.
The
interesting thing about the pair is that the two pieces share almost the same
depth/height.
The outer
ring is 41mm, while the inner 40mm, thus forming a single groove choke ring.
Optimally,
the groove depth should be a bit larger than ë/4, which for L1 = 1575MHz equals 47,6mm.
Commercially
available, L1 only, designs have as a ballpark 50mm.
The norm
for topographic/geodetic grade choke ring antennas is ~63 mm, as they have to
cater for L1,
but also for the lower frequency L2=1227MHz.
.
The GPS
patch antenna is magnetically attached onto the NIVEA box
The two
pieces are assembled together through a bolt & nut,
which also
fixes a metallic nipple beneath for placing the assembly on top of a steel rod.
Comparison
A-B tests with a disk ground plane of equal diameter have not been made