Archived from groups: alt.internet.wireless (
More info?)
In article <t32Rc.279$5_.63@newsr2.u-net.net>, Paul A Bristow
<pbristow@hetp.u-net.com> writes
>"Jeff Liebermann" <jeffl@comix.santa-cruz.ca.us> wrote in message
>news:us97h0h6athg7h7rdtbaeu50ip2c1kefno@4ax.com...
>> On Fri, 6 Aug 2004 12:38:10 +0100, "Paul A Bristow"
>> <pbristow@hetp.u-net.com> wrote:
>>
>> >Tests with a multimeter show <10 ohm resistance between the outer and the
>> >centra of the coax cable to the roof. To me, this suggests a short in
>the
>> >coax cable up to the antenna. I would expect the antenna to appear to
>have
>> >infinite DC resistance.
>>
>> Nope. If the yagi antenna has a gamma match or a T-match (balanced
>> pair of Gamma matches), it will show infinite impedance because the
>> driven element feed goes through a coaxial capacitor. However, a
>> Hairpin match (also known as a Beta match), will exhibit a dead short.
>> If the driven element is a closed loop as in a folded dipole or loop
>> yagi, you will also see a dead short.
>> >My installer assures me this 'zero' DC resistance is normal (and
>recommends
>> >a 5 Ghz setup at much higher cost).
>>
>> No comment without some clue as to what you are trying to accomplish,
>> what you have to work with, and why 2.4Ghz is deemed inadequate.
>
>My installer says:
>The problem, as we told you at install time, isn't really a question of
>signal strength, it's a question of distance. 2.4GHz signals
>
>take a finite time to travel over distance, and the MAC layer of the 802.11b
>protocol has quite tight timing restrictions. This is
>
>why most manufacturers quote 100s of metres rather than kilometers for the
>operation of their equipment. We have found ways to
>
>increase this tolerance, but only within reason, signals simply take too
>long to reach you and return within acceptable limits.
Really?, Well lets see most manufactures only quote hundreds of yards
because they only intend such equipment to work over short distances
with the built in aerials provided.
Well we've used it at 5 Km and had no problems at all!. With external
aerials of course..
>
>Fitting a higher gain antenae will achieve 2 x things, it'll take you over
>the 20db maximum permitted power output in the UK, and
>
Well that depends on a number of things inc cable and connector losses
etc anyway at that range you shouldn't need such gain. Are you sure the
path is really line of sight?...
>it'll probably bring the pole down in the first storm, what it won't do is
>improve your signal timing (and hence the quality of your
>
>service).
>
Well put up a stronger pole then, silly argument!..
>The only real solution is to upgrade to 5.8GHz which has half the wavelength
>and much more leniant MAC timings, making distances of
>
>xx kilometers quite possible. This is no problem, but 5.8G equipment is
>expensive as it is not widely adopted, involving an
>
>additional cost of around £ 250.00. We can however guarantee that it will
>work or we won't install it (5.8GHz tends to be all or
>
>nothing, it works or it doesn't, there is no half way house as with
>802.11b).
>
>I'm about 4 km away from the TV tower with clear line of site (no trees or
>anything in the Fresenel zone).
It seems to me that theres another reason behind this somewhere perhaps
their system is congested at 2.4 or some other reason.....
>
>Views on this please.
>
>Thanks
>
>
>
>Paul
>
>
>
>
>
--
Tony Sayer