Dear denizens of the group:
im wondering is anyone here is familiar with ice sensor designs and/or has a suggestion for the construcion of a reliable method of detecting icing conditions (in free air). i know assorted commercial units are available however my budget would be about $100 per unit.
at present de-icing heater cut in below a preset temperature (or manual or remote control). it seems a waste to heat the sky all winter.
Tim
IS this a stationary application or are you deicing an airplane in flight?
antennas on towers
WTF?!?
im wondering is anyone here is familiar with ice sensor designs and/or has a suggestion for the construcion of a reliable method of detecting icing conditions (in free air). i know assorted commercial units are available however my budget would be about $100 per unit.
at present de-icing heater cut in below a preset temperature (or manual or remote control). it seems a waste to heat the sky all winter.
Tim
did i stutter?
Two words:
DOCK BUBBLER
nothing to do with boats.. i need to operate antenna de-icers
All of the de-icers I've seen have been basically "manual", though some of them are controlled automatically by temperature sensors. None have any sort of ice detector. (These are all satellite dishes.)
There is one sort of, more or less, automatic ice detection system that has been working very well in bush Alaska for the past 25 years now... We put relatively small dishes in most Alaskan villages back in the mid to late 1970's and none of them have electric deicing. When the telephones don't work, local folks automatically go thump on the back of the dish with a 2x4 to knock the snow out... It has worked like a charm.
I think he wants you to install your tower undewater so the dock bubbler can work.
im trying wax on a 3 meter dish this winter. i was going to use skiwax but after asking around i found a locally made product called collinite insulator wax.
well it would, however that would make it difficult to paint the orange and white stripes.
i have 5 AM towers in a swamp that are somewhat underwater part of the year. they are interconnected by 6' catwalks. makes for a great ground system and the vampire mosquitos make pretty good security guards.
This is probably too stupid to consider, but if the ice load onyour antenna is altering its properties, couldn't you determine that by looking at the growing impedance mismatch and take action when it reaches some limit?
If it's the mechanical load on the antenna that's a different matter. I suppose one could look at its mechanical resonating frequency, that'll change with ice load.
In airplanes we often just leave the pitot tube heater on all of the time, it sure beats having it ice up and lie about airspeed.
I've never done this, but wouldn't you need to sense temperature and relative humidity (dew point)? A quick google found
Just the first one I found. I think you could use something like this with analog outputs and a couple of op amps to detect icing conditions.
Ron
We have a novel method here that works for virtually all home antennas for Ku band satellite TV. Since the look angle for a geosynchronous satellite due south of us is only something like
12 degrees, an antenna with an offset feed horn mount can be configured so that it is actually tilted to look _down_ by a few degrees!(We don't actually get much snow, and it is all very dry powdery stuff that blows away in the wind. Hence antennas at near vertical stay fairly clear of snow anyway.)
not stupid at all, however the most common type of external wattmeters do not have a buffered analog output to sample. the meter movments are 100 uA full scale. so far all my attempts to sample them have resulted in altering the calibration and/or the zero setting of the meter movement.
the vast majariy of older transmitters do not have a reletive output for reflected power (other then the built in VSWR meter) although some of the new ones do. if the system has a main and standby transmitter it adds one more step of complexity (and therefore unreliability).
some external wattmeters have a settable trip point which is usually reserved for "plate interlock": is shuts the transmitter down rather then have it burn itself up.
the antenna portion is small compaired with the rest of the tower.
some "schools of thought" leave the heaters on 1/2 voltage (1/4 power) year round and switch to full power when needed. this requires a double throw switch or contactor.
an antenna repair this spring which involved removing, repairing pressure leaks and some heaters, and reinstalling cost $10,000 mostly in labor. and that was only a 3 bay antenna. you can see that any means to extend the lifespan of the heating elements would be a good thing.
We have a sensor at work that applies a known current to a hetaing element. If there is ice on the probe there is a change in the heating curve. Of course this is all done with a computer. Probably cost more than 100.
your comments helped me to refine my search which led me here
Tim
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