Hi Roy,
Thanks for the answer. Please don't think I'm trying to be "smart",
just curious about these things and not knowledeable enough.
Roy Lewallen wrote:
Toni wrote:
I've seen here before suggestions about using a tuned loop to increase
the gain of radio controlled clocks. Do you think this could also be
used to increase the gain of a gps receiver?
No. If you were to increase the gain of your GPS antenna, either by
redesign of the antenna or by an external parasitic structure of some
sort, it would have to result in a narrower pattern. So you'd reduce the
reception in some directions.
When talking about loop antennas people talk about "capture area".
Whatever that is, this seems to be what makes a ferrite bar antenna
more sensitive than the equivalent simple coil tuned to the same freq.
I know that by using a ferrite bar you are narrowing the pattern, but
I'd think that the main gain does not come from the pattern narrowing
but from "capture area increase" (again, please bear with my ignorance,
these are only my thoughts on what I've read on the Web)
I know one can not have more than 0 dB with full omni, I just guess the
minimalistic antenna in pocketable gps is way below 0 dB and could
maybe be improved a little.
0 dB relative to what?
An isotropic antenna;
AFAIK a perfect isotropic antenna would have 0 dB
gain
Once you get the desired coverage angle, the only way to improve the
reception of the GPS is to improve the receiver signal/noise ratio. The
only way you can do that from outside the GPS is to use an external
antenna with a preamp having a lower noise figure than the GPS's receiver.
Please let me doubt that. For a given coverage angle you can't make
better than a perfect antenna, but you can certainly make worst (think
of a T2FD).
I'm not sure what the "high loss antenna" is. If you mean the GPS
antenna, it's not high loss at all, but is likely very efficient. If
it's a patch antenna, you can't model it at all with EZNEC. But even if
it's a quadrifilar helix, you can't model it with one segment.
I dont know how efficient they are, but I do know that normal
commercial patch antennas are noticeably less efficient than helical
ones, and then, for the helicals, I doubt that something aprox 1/10 wl
is anything close to efficient. If this was to be true I'd love to
build an equivalent 6.5 ft. helix to work on 20m!
73s, Toni