I bought two kinds of COTS equipment. One was from Sharper Image catalog. I
don't recall the other. This was over 20 years ago. I helped a friend build
a system subsequently using Radio Shack piezo-electric horn tweeters which
we drilled for drainage. This too was 20 years ago. We bread boarded a
signal source using 555/556 timer chips and small power amp. I don't recall
the ckt exactly but could recreate it probably from an old Signetics
applications manual if provided a copy (mine faded into oblivion years ago.)
This isn't rocket surgery or brain science. You just want an ultrasonic
signal high enough in frequency to not be heard by humans, say at least
22-23 KHz (I used to hear up to 21.5 KHz, yes I could hear ultrasonic
alarms, bats feeding, etc.) and loud enough to be terrifically annoying to
birds. Don't waste power with freqs above the tweeter's capability (maybe
30-35 KHz) I haven't looked into tweeters for ultrasonic reproduction for
decades but expect them to still be readily available. A simple BUT LOUD
ultrasonic signal ramped up and down annoys birds. One way to get the
signal is a VCO ckt modulated by a sawtooth generator (see application notes
for 555 and or 556 chip) Feed this into an amp capable of a few to several
watts (you don't need mega watts to annoy birds) thence into efficient
speakers with ultrasound capability (used to be cheap at Radio Shack as
Hi-Fi tweeter horns)
Additional sophistication is to use an IR motion detector to turn the unit
on (like a security light ckt energizing your power supply. It worked for
cats and dogs but isn't always reliable for birds. At least the ones I tried
(way back when) were not always sensitive enough for small birds. Larger
birds will likely be "seen." Here is where you look into circuits like those
used for safety purposes on your automatic garage door opener. If you break
the LED beam you are detected or put another timer stasge in it and have it
turn on for several seconds then off for a while and back on. A duty cycle
of say 10% should be plenty say on for 6 seconds and off for 54 or whatever
you like. The trick is to not just turn it on for long periods as the
feathered nuisances can get used to just about anything steady state.
Something coming on LOUD every little while has a good startle effect.
Pseudo random sequence would be terrific if your skill is up to it.
Need more info? Try Google first then if you really are stuck for ideas,
ask here again.
Patrick
-----Original Message-----
From: Grant Saviers
Sent: Friday, January 04, 2013 7:26 PM
To: Patrick Greenlee
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] Bye Bye Birdies
Patrick
Please suggest some stocking suppliers and models.
Grant KZ1W
On 1/4/2013 10:52 AM, Patrick Greenlee wrote:
Plastic owls and rubber snakes work for some folks but are not universally
successful.
Ultrasonic emissions have a much higher success record. Ultrasonic waves
are easy to "beam" directionally which permits a ground or near ground
level installation with the transducer(s) aimed up to where the birds like
to perch. Aiming the sound upward keeps from disturbing the dogs and
cats.
These devices are available COTS for relatively little money or easily
built by the electronic savvy. Mine have lasted for many years and still
work well. Some of these devices offer choices on the type of output. A
randomly occurring warble tone similar to the "yelping style" public
safety sirens (but of course in the ultrasonic spectrum) seems to work
best. Having it come on at random intervals works best and keeps the birds
from getting used to it.
Inexpensive "tweeters" of the horn variety work well, especially if the
design lends itself to accepting a drain hole for water (well... it is
aimed up) Alternatively an enclosure with a hard flat reflective surface
to aim the beam upward will work.
I have used these for many years with great success, not only for birds
but other pests as well when coupled with IR motion detector including
cats and dogs who used to think my yard a public restroom and the odd
skunk, raccoon, armadillo, or opossum.
Patrick AF5CK
iginal Message----- From: Jim Lux
Sent: Saturday, December 29, 2012 5:16 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Bye Bye Birdies
On 12/28/12 9:11 PM, Bob K6UJ wrote:
Another option for bird control is to get one of the plastic owls and put
him up on the tribander.
My results were negative, evidently the birds in our area aren't scared
of owls because the owl didn't help at all.
When i took it down I discovered the birds had crapped all over it. :-)
my in-laws experience with their vineyard was that birds are discouraged
by novelty and change. reflective ribbons one week, owls the next, etc.
That doesn't lend itself to antennas
the other strategy which seems to work quite well is to make what ever
it is "not sittable on". those funky plastic spiky things or
string/monofilament.
Of course, neither of the latter are particularly easy to do on
something like a multielement beam, especially if you want it to last
for decades.
For ordinary wire antennas.. I suppose, if you use strong enough copper
clad steel, the birds can just sit on the wire forever.
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