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VK3ABK > WLAN 26.09.03 09:45l 46 Lines 2072 Bytes #999 (0) @ WW
BID : 2136_VK3KAY
Read: GUEST DB0FHN OE5RCO DK5RAS DO1SLP DO6NP
Subj: WLANs etc on 2.4GHz
Path: DB0FHN<DB0RGB<DB0MRW<OK0PKL<OK0PCC<OK0NAG<OK0PPL<DB0RES<ON0AR<VK3KAY
Sent: 030926/0719Z @:VK3KAY.#WEV.VIC.AUS.OC #:2136 [Wendouree] $:2136_VK3KAY
From: VK3ABK@VK3KAY.#WEV.VIC.AUS.OC
To : WLAN@WW
Hello Ari, Mark, Barry, and others.
My 'Hello' is directed to Ari VK3PKT who's bulletin directed to Mark VK3JMA,
raises the worry about the increasing activity on the '2.4GHz' ISM band.
It is an increasing problem of interference in this shared band, and the
Ham satellite reservation is worth conserving as the received signal strength
from AO-40 and others is at 'DX strength'. This is why I have steered clear
of the WiFi possibilities for 'Ham bands'. I understand that the transmit
frequency is software controlled, and so depends on a PC clock using a rather
simple, not temperature controlled, crystal oscillator.
But having said that, it should be understood that with the lower microwave/
upper UHF bands (2.4GHz is UHF) line of sight is assumed and directional
antennas are essential for Ham activities. These two requirements make the
transmit power far less important. Having spent the majority of my Ham days,
and nights!, on VHF/UHF, I can assure you that the rules rate 'height' of the
antennas (and line of sight follows) as number one consideration. This is
followed by 'height' again as number two and three! No question.
We all know of the telemetry from space, received over millions of kilometres
using high gain antennas, and relativly low transmit power. Nothing beats a
clear path: and path loss with directional antennas at 2.4GHz is very low.
At this wavelength, we do not have water vapour, cloud or rain drop loss that do
attenuate the real microwaves. But the path must be well clear of ground
objects to prevent disturbance to the signal path. Many line of sight contacts
are made with milliwatts radiated power and a gain antenna.
An interference problem comes about when an antenna must be omnidirectional
or the beam must be wide angle for whatever reason. Then, refraction and
reflection will cause phase delay and severe signal loss. There is no real
substitute for a good antenna at a respectable height.
This may be of interest and worth considering.
73. Dick. VK3ABK.
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