[time-nuts] GPS backup for the stationary time and frequencyuser
billj at ieee.org
Fri Oct 8 15:52:36 UTC 2010
Magnus Danielson wrote:
> On 10/08/2010 03:35 AM, jmfranke wrote:
>> When I said the feed would work, I was meaning it would work if LHC.
>> The illustrations and text imply you could just place a normal GPS
>> receiver at the feed location, but the polarization would be wrong.
> Which was what I reacted on...
> I am by no means a practical antenna expert, and the EM-theory is a
> bit fuzzy on the edges, but I do distinctly recall that signal is RHC
> and reflections becomes LHC so an antenna with RHC orientation will
> provide some first-degree damping of the LHC reflections. For this
> antenna setup the intended RHC signal is reflected and should become
> LHC... just as the interference... so it relies on the antenna gain of
> the dish to out-perform the other reflections for the half-space
> receiver that a normal GPS antenna is. The choke ring for a dish head
> has a distinct different pattern (forming an inner cone rather than
> flat space).
> So, a normal antenna would kind of work since the antenna gain would
> overcome the poor LHC supression of a simple RHC antenna... yay.
> If an LHC antenna was used instead... now we are talking.
So a dish reflector and a sub reflector and the GPS receiver at the dish
would work? What is that
configuration called? I can't remember at this early hour.
More information about the time-nuts