[TowerTalk] Projected area of Hy-Gain beams

Tue, 18 Aug 1998 22:22:55 -0700

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spelunk.sueno wrote:

>      About 15 years ago I built something like this using a Heathkit
> weather station.  (This was the same project that used the Hoffman
> equipment boxes I mentioned in another post.)      The Heathkit unit
> provided digital outputs of windwpeed, direction, temp, pressure;
> third-party sensors provided relative humidity.  I (actually,
> engineering students working for me) wrote machine code for Apple II's
> (!!!) to read the met data and record it; BASIC was too slow.      For
> tower control today, one could use a similar system sold by folks like
> Peet Bros. as advertised in 73. (www.peetbros.com).  Bring the wind
> speed and direction from the serial port into a PC.  Use peak speed or
> average speed over some user-selected time interval to trigger
> rotator, via PC, to turn mast into wind.  If peak exceeds another
> higher threshhold, bring the (crank-up) tower down to a safer level.
> Mount the anemometer (wind-speed indicator) near the tower top; it
> won't do the mast much good to know how blustery it is on top of the
> garage.  Use opto-isolators to connect the PC to the rotator
> controller if you're home-brewing this thing.      I would caution
> against using this system as an excuse to overload a tower.  This
> ought to be used only to protect a properly designed and installed
> antenna system from damage in the event of unexpectedly high sustained
> winds.  Also, don't assume the PC (and power grid) will be operating
> during hurricane/tornado weather.      Something to think
> about.  -Gene Smar  AD3F

DavidC wrote:
>Now here is an interesting idea.  What about a wind
direction--sensor/limiter that would provide an indicator of directional

wind stress, or actual rotor control in high wind conditions to prevent
overstressing a tower?

Would this not allow one to load heavier and only be directionally
limited
as high winds dictated?  It would allow larger antennas on lighter-duty
towers, would it not?

Sounds like a new rotor control option, especially for areas plagued by
high winds.

Hmmm, the gearloose inventor in me seems to have broken loose of the
restraints!
:-)  DavidC  AA1FA

Hi guys,
Well you both read my mind. A control system such as you both have
described was on my mind and would be very useful. It would really need
some good logic behind it to perform some adjustable time based
averaging to keep the rotator from going nuts.

I mentioned this for two reasons. One was to have some of you circuit
magicians see the potential for a control system to address this
opportunity. The other, just to help everyone think about how to answer
the age old question, "Which way should I point my antenna, when the
wind blows?" I can' t count the number of discussions I've heard on
local 2M repeaters about this one. If we get information like Roger, @
Hygain has provided we can get it right, and not worry about if it is
right.

Note: The same day I received the mail from Steve that led to this post,
I got a preliminary sample of the listing of the new data from Roger.
Just a coincidence.
It is obvious to me that Roger was already working on the problem. His
announcement today was not a result of my previous comments. So, kudo's
to Roger for recognizing that we need to get this business straightened
out!

The only other thing to be considered, is the antenna torque when the
wind is broadside to the boom. If the Mfgr has placed the mast
connection at the weight balance point, we will most likely have antenna
torque at 90 Deg azimuth (some antennas have the weight balance point at
the boom center). 90 or 270 Deg may be the best place to point the
antenna for tower wind loads, but not so good for the antenna and
rotator. A tough decision! That's where an antenna torque value would be
useful.

I agree with Gene, that this approach should not be used to overload a
tower! A control system failure could be devastating. Moreover, I think
it would be hard to convince the local building code people that this is
ok.

I would rather look at it as an added safety factor. Sometimes, lesser
rated wind speed areas get unique excessive wind events. This kind of
system could keep some hardware up in the air, when the unexpected
occurs!

73, Kurt

--
YagiStress - The Ultimate Software for Yagi Mechanical Design
Visit http://www.freeyellow.com/members3/yagistress

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<HTML>
&nbsp;

spelunk.sueno wrote:
<BLOCKQUOTE TYPE=CITE>&nbsp;&nbsp;&nbsp;&nbsp; About 15 years ago I built
something like this using a Heathkit weather station.&nbsp; (This was the
same project that used the Hoffman equipment boxes I mentioned in another
post.)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; The Heathkit unit provided digital
outputs of windwpeed, direction, temp, pressure; third-party sensors provided
relative humidity.&nbsp; I (actually, engineering students working for
me) wrote machine code for Apple II's (!!!) to read the met data and record
it; BASIC was too slow.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; For tower control
today, one could use a similar system sold by folks like Peet Bros. as
advertised in 73. (<A HREF="http://www.peetbros.com">www.peetbros.com</A>).&nbsp;
Bring the wind speed and direction from the serial port into a PC.&nbsp;
Use peak speed or average speed over some user-selected time interval to
trigger rotator, via PC, to turn mast into wind.&nbsp; If peak exceeds
another higher threshhold, bring the (crank-up) tower down to a safer level.&nbsp;&nbsp;
Mount the anemometer (wind-speed indicator) near the tower top; it won't
do the mast much good to know how blustery it is on top of the garage.&nbsp;
Use opto-isolators to connect
the PC to the rotator controller if you're home-brewing this thing.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
I would caution against using this system as
an excuse to overload a tower.&nbsp; This ought to be used only to protect
a properly designed and installed antenna system from damage in the event
of unexpectedly high sustained winds.&nbsp; Also, don't assume the PC (and
power grid) will be operating during hurricane/tornado weather.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
Something to think about.&nbsp;&nbsp;-Gene
Smar&nbsp; AD3F&nbsp;</BLOCKQUOTE>
DavidC wrote:
 >Now here is an interesting idea.&nbsp; What about a wind
 direction--sensor/limiter that would provide an indicator of directional
 wind stress, or actual rotor control in high wind conditions to prevent
 overstressing a tower?

Would this not allow one to load heavier and only be directionally limited
 as high winds dictated?&nbsp; It would allow larger antennas on lighter-duty
 towers, would it not?

Sounds like a new rotor control option, especially for areas plagued
by
 high winds.

Hmmm, the gearloose inventor in me seems to have broken loose of the
 restraints!
 :-)&nbsp; DavidC&nbsp; AA1FA
 &nbsp;

Hi guys,
 Well you both read my mind. A control system such as you both have
described was on my mind and would be very useful. It would really need
some good logic behind it to perform some adjustable time based averaging
to keep the rotator from going nuts.

I mentioned this for two reasons. One was to have some of you circuit
magicians see the potential for a control system to address this opportunity.
The other, just to help everyone think about how to answer the age old
question, "Which way should I point my antenna, when the wind blows?" I
can' t count the number of discussions I've heard on local 2M repeaters
about this one. If we get information like Roger, @ Hygain has provided
we can get it right, and not worry about if it is right.

Note: The same day I received the mail from Steve that led to this post,
I got a preliminary sample of the listing of the new data from Roger. Just
a coincidence.
 It is obvious to me that Roger was already working on the problem.
His announcement today was not a result of my previous comments. So, kudo's
to Roger for recognizing that we need to get this business straightened
out!

The only other thing to be considered, is the antenna torque when the
wind is broadside to the boom. If the Mfgr has placed the mast connection
at the weight balance point, we will most likely have antenna torque at
90 Deg azimuth (some antennas have the weight balance point at the boom
center). 90 or 270 Deg may be the best place to point the antenna for tower
wind loads, but not so good for the antenna and rotator. A tough decision!
That's where an antenna torque value would be useful.

I agree with Gene, that this approach should not be used to overload
a tower! A control system failure could be devastating. Moreover, I think
it would be hard to convince the local building code people that this is
ok.

I would rather look at it as an added safety factor. Sometimes, lesser
rated wind speed areas get unique excessive wind events. This kind of system
could keep some hardware up in the air, when the unexpected occurs!

<P>73, Kurt
<BR>&nbsp;

<P>--
<BR>YagiStress - The Ultimate Software for Yagi Mechanical Design
<BR>Visit <A HREF="http://www.freeyellow.com/members3/yagistress">http://www.freeyellow.com/members3/yagistress</A>
<BR>&nbsp;</HTML>

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