"Jerry Martes" wrote in message
news:gbNmi.4641$BI5.3525@trnddc07...

"szilagyic" wrote in message
ups.com...
Hello,

Recently we purchased a cellular yagi dual band antenna to help our
signal strength on a Sierra 860 AirCard with Cingular/AT&T, in hopes
of improving the speed of the card at our home. We are having
horrible results and cannot get it to work correctly. The antenna is
a CCM brand 24 dB dual band yagi (824-896Mhz & 1870-1950Mhz); it was
purchased from he (
http://www.easystreetelectronics.com...PROD&ProdID=71
). It is attached to a 30 ft RG58U coax cable that runs back to a TNC-
to-FME adapter, then to the Sierra card. We tried the antenna at a
test location where we know where the tower is at, about 2 miles away,
and can get 90% signal strength with the stock antenna there. When we
attached the yagi and moved it in small increments to each side until
we honed in on the exact spot, the highest signal strength we can get
is about 50-60%. I was assuming we should be able to get 100% signal
strength easily since the stock antenna already gets 90%.

We tried the yagi at another location where we only get about 30%
signal strength with the stock antenna. We do not know where the
tower is at so we started in one spot and went in 5 degree increments
in a complete circle, noting the signal strength at each stop. The
highest we were able to get is about 20%.

We must be missing something here, as I don't see why the yagi has
less signal strength than the stock antenna. I have not tested the 30
ft cable or ends yet, but it was factory made and appears to be fine
(no kinks, etc). The yagi is mounted on a PVC pole, and the elements
of the antenna are vertically oriented, and it the beam is parallel
with the ground.

Can anybody help us or provide some tips??? Are we using the right
antenna? Right now we are completely stumped, and would really like
to get this figured out.

Thank you very much for all feedback and help on this matter...

--
Chris


Hi Chris

The performance of your "24 dB Yagi" doesnt surprise me. I have doubts
about the accuracy of the antenna's specs. It wouldnt surprise me to
learn that the CCM antenna had only 10 dB gain over the "stock" antenna.
And coax line loss can vary from manufacturer to manufacturer. Some
brands of RG 58 could have more than 13 dB in the high frequency band.
It could be very difficult to build an antenna with 24 dB Minimum gain
thruout the frequency range 824 to 896 MHz and 1870 to 1950 MHz with one
feed point. A 23 dB "gain" antenna will have a very narrow radiation
pattern beam width. That would require a fairly large antenna at the low
frequency end of your band.


.


I have a yagi made for a radio modem by a reputable manufacturer. Design
frequency is near 900Mhz 13db(i/d/?) gain and it iis about 6 ft long, maybe
longer. Connection is via a very short piece if 1/4 inch coax which also
includes a ferrite bead BALUN. Reccomended connection is via low loss coax.I
think it was last used with LMR900, about 100ft. The antena was removed from
service due to poor perforamce and replace wiht a parabloic antenna, I
belive the gain of this antenna was about 19 db again of uncertain
reference. I hope this gives an idea of what a proper idea for the
application should be..

Jimmie