Should I be concerned about this setup:

Netgear AP Netgear Bridge YDI DC Injector YDI 500 milliwatt amp
Huber+Suhner planer antenna, model SPA 2400/85/17/0/V

I need the special antenna to overcome triple pane uv glass and 1 mile
to wisp.

The antenna is directional (85 degree horizontal) and my desk is right
behind the antenna. I use the set up a couple of hours a day.
Anything to be concerned about?

Should I be concerned about this setup:

Netgear AP Netgear Bridge YDI DC Injector YDI 500 milliwatt amp
Huber+Suhner planer antenna, model SPA 2400/85/17/0/V

I need the special antenna to overcome triple pane uv glass and 1 mile
to wisp.

The antenna is directional (85 degree horizontal) and my desk is right
behind the antenna. I use the set up a couple of hours a day.
Anything to be concerned about?

Well, you've got a 27 dBm radio, connected to a 17 dBi antenna. As I
read the Part 15 rules, that's just a hair over the legal limit for a
point-to-point 802.11b link - a 27 dBm radio is limited to a 15 dBi
directional antenna.

I haven't tried to do the calculations to see whether this level of RF
power is likely to be exposing you to RF levels which exceed the FCC's
human-exposure standards. I'm guessing that a lot of the power you're
transmitting is ending up bouncing off of the glass (secondary guess
is that this glass has a metallized coating?) and may be scattering
around the room.

If I were setting up a system of this sort I'd probably try to arrange
to put the antenna outdoors, and get by with a lesser amount of
transmitted power.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

You could get a small neon bulb,
spread the two wires apart (180 degrees)
then see if it lights up anywhere, if so, bad.
But this "test" is not as sensitive as it should be for exposure.
Distance has a great effect, 3 ft away Vs 9 ft away is
a factor of 9 less exposure.
(declines with 1/(r^n) where r is distance, with n range of 2 to 4)

The thing is on all the time too, unlike cellphone exposure.
Should be outside, reflective glass is partially conductive,
and reflects part of the RF too.



"Chuck Daniels" wrote in message
om...
Should I be concerned about this setup:

Netgear AP Netgear Bridge YDI DC Injector YDI 500 milliwatt amp
Huber+Suhner planer antenna, model SPA 2400/85/17/0/V

I need the special antenna to overcome triple pane uv glass and 1 mile
to wisp.

The antenna is directional (85 degree horizontal) and my desk is right
behind the antenna. I use the set up a couple of hours a day.
Anything to be concerned about?

Chuck Daniels wrote:
"I need a special antenna to overcome triple pane uv glass and 1 mile to
wisp.

Search says 2.4 - 5.8 GHz is involved. A dish has no rear radiation. Its
directivity and gain are proportional to its size and the size is
reasonable since the wavelength is in cm , less than 5 inches.

Depending on frequency and efficiency, a 6-ft dish may give more than 20
dBi gain.

Placement of the dish inside and close to the window may be convenient
for connection and obviates wind-loading. Jam up to the window may
screen the room for much of the possible reflection. Sceens could be
used to deflect other reflections.

High gain may overcome high transmission loss. It`s standard procedure
on microwave paths.

Best regards, Richard Harrison, KB5WZI

Unfortunately I can't mount the antenna outside, since I am in a
30-story building with no option for mounting things outside. If part
of the energy radiates back into the apartment is that really
dangerous or is it reasonably diffused?

Also, does the YDI amp give off a lot of energy? I just have it and
the dc injector sitting on a shelf near the antenna.

Thanks

(Richard Harrison) wrote in message ...
Chuck Daniels wrote:
"I need a special antenna to overcome triple pane uv glass and 1 mile to
wisp.

Search says 2.4 - 5.8 GHz is involved. A dish has no rear radiation. Its
directivity and gain are proportional to its size and the size is
reasonable since the wavelength is in cm , less than 5 inches.

Depending on frequency and efficiency, a 6-ft dish may give more than 20
dBi gain.

Placement of the dish inside and close to the window may be convenient
for connection and obviates wind-loading. Jam up to the window may
screen the room for much of the possible reflection. Sceens could be
used to deflect other reflections.

High gain may overcome high transmission loss. It`s standard procedure
on microwave paths.

Best regards, Richard Harrison, KB5WZI

Chuck Daniels wrote:
"If part of the energy radiates back into the apartment is that really
dangerous or is it reasonably difused?"

The latter is likely. A dish focuses the microwave energy into a narrow
beam. It is like a spotlight. I seem to remember an output of -27dBm
(1/2 watt) which is puny. Your microwave oven likely produces 1000x more
power, and this is confined to a small volume.

Some of the dish`s beam may bounce back from the glass into the room,
but it loses 22dB in the first wavelength (about 5 inches?) back from
the reflection, and then 6dB more every time the distance doubles after
that. I wouldn`t worry or if I did, I would simply interdict the energy
with suitable screening.

Most of the power developed by the microwave transmitter should reach
the antenna or be shielded from direct radiation into the transmitter
room. A microwave oven leakage meter as sold in the past by Radio Shack
can be used to detect r-f around the transmitter, in the dish beam, and
reflected from the glass. They are cheap and they work.

A 1/2-watt transmitter is no big deal. When I started working with
microwave, the set consisted of (2) 0.1 watt klystrons. One was a
repeller modulated FM transmitter. The other was a local oscillator to
mix with the received carrier from the distant transmitter in a 1N23
silicon mixer diode to feed the I-F amplifier, limiters, and
discriminator.

The above radios could carry 600 or 1200 voice channels via frequency
division multiplex over a distance of 20 or 30 miles with few problems
and with high reliability.

We later got 5-watt klystron transmitters which were superseded by all
solid-state sets. Klystrons are no limitation to power. The most
powerful vacuum tube ever made was a klystron. Klystrons serve very well
in TV transmitters of enormous power. for line-of-sight point to point
service, high power is unecessary.

Best regards, Richard Harrison, KB5WZI

On Tue, 30 Mar 2004 22:19:50 -0600 (CST),
(Richard Harrison) wrote:
Some of the dish`s beam may bounce back from the glass into the room,
but it loses 22dB in the first wavelength (about 5 inches?) back from
the reflection, and then 6dB more every time the distance doubles after
that. I wouldn`t worry or if I did, I would simply interdict the energy
with suitable screening.

Hi Richard,

This characteristic is incorrectly applied. The 22dB is not "lost,"
it is simply unavailable to a dipole that could accept the power. The
concern is with tissue absorption, not tuned, directional antenna
elements. Further, it is not "lost" given that if it is a nuisance
through reflection, there are as many re-reflection opportunities
available within the region into which it has been reflected
(provided, of course, that room is not an anechoic chamber). This,
then, renders the room into a gross dimensioned, lossy microwave oven.

Some of the reflected power will be absorbed by the walls, the
furnishings, be "lost" out the same window it reflected from; and yes,
absorbed by the turkey.

Chuck,

Our best advice has been given, carry an NE-2 neon lamp, observe it
glowing to tell when you are "done."

Let's put some real perspective to this. We are talking about all of
500mW? Let's boost that 15 fold to 7.5W, concentrate it into a patch
of 1 square inch. Now, imagine the sensation of holding a lit
christmas tree bulb (the traditional big ones). Do those prospects
bring terror? Pain? Annoyance? A mild warmth? Now turn down the
burners to that original half watt.

The common experience of a christmas past should quite capably guide
you at this point.

73's
Richard Clark, KB7QHC