Hi Ken
Note when I modeled the 16 element I did so as a series of dipoles fed
in phase rather than use the coax/crossover design.
I felt like checking your statement about being unable to receive in the
front yard. At around 45 degrees down from the antenna the NEC2 output
says that you'll get a lobe between 20 and 30dB down from an isotropic
(or 35-45dB down from the max gain) I'll admit my near close in signal
theory doesnt really exist but a path of 800m has about 106dB of loss.
If you knock that back to 12 metres (6dB every time you halve) you have
about 70dB path loss. If you then take a WAP kind of power level of
around 10dBm the RX signal at 12m with a halve wave is going to be
around (10-70-25) -85dBm. This kind of corelates with the lowest usable
signal for WiFi! There ya go!
I like the URL you sent as being more predictable/easier to construct
that using bits of coax. Keep in mind that progressively longer and
longer colinears are more and more critical to build and the
construction method that is being used is not really optimal in the area
of spacing between elements. You could probably pick a much better
design. I think however that you need to sit back and consider what you
are trying to achieve. Are you setting up a personal WiFi LAN for others
to use or just for specific contacts? If you are wanting to work in one
direction (or use a rotator) it might be more effective to use a corner
reflector and maybe 4 elements in phase. This will be much less critical
in construction. Remoting the WAP will make a lot of sense too as
you'll lose the line loss! Comments?
Cheers Bob
Ken Bessler wrote:
Wow - that's sharp! It explains why I lost the signal in my front yard.
How about this version?
http://martybugs.net/wireless/collinear.cgi
I just built it out of a coat hanger, soldered to the old coax
feedpoint from the last "experiment". It performs pretty good
but I calculate 2.14db of losses in the line. Something my
back of the set antennas don't have to deal with.
What about expanding the above antenna?
Ken KG0WX