Low cost - long-ish distance laser?

A funnel or short tube might help keep the dust and dirt from hitting the glass so hard. The "cave" formed by an eskimo parka is very effective at keeping wind from your face. Here's an example:

I have searched everywhere in a 50 km radius for something like that but could find nothing. I'll have to get a seamstress started on making one before next winter.

I can buy flat Gorilla glass, cut to size fairly easily. I don't want to think of the price and delivery for a curved piece.

With Gorilla glass, I'm not concerned about penetrating the glass. It's rather hard and will resist most airborne debris. It won't handle rocks, BB guns, bullets, and woodpeckers, but those are unlikely problems. The dust is held in place by static electricity. I was able to remove some of the dust by charging the glass with high voltage, and then pulling the dust away with the opposite charge on a nearby metal plate. It works nicely with the plate in front of the lens. However, when I put the charged plate behind the glass, and charged it with the same polarity on the assumption that it would repel the dust particles, nothing happened. It has some possibilities, but that will need to wait a day or three.

I did some tinkering with window glass and a small loudspeaker. I was trying to see if I could shed the dust by vibrating the glass at audio frequencies. That does work, but leaves some tiny dust particles behind. It's most effective when the window is pointed downward, which isn't going to happen. Pointed upward, it collects more dust. Also, the required glass displacement is fairly large, which would require a very flexible mounting for the glass. I could probably make this work, but I don't think it's going to be reliable, especially if the window collects a coating of grease from industrial air or a nearby emergency generator.

I also tried an air blast. Basically a manifold of air nozzles pointed at different parts of the glass from around the edge. That worked quite well, but I'm not thrilled with installing an air compressor, surge tank, and manifold on top of a mountain, and hoping that nothing will break. Too many moving parts and too many things to go wrong. However, it's the closest approximation of an alternative to a miniature windshield wiper system, so I'll look at it more closely tomorrow.

Getting rid of the dust is just part of the problem. Over a long period of time, glass collects a thin film of condensed aerosols, very fine dust particles, industrial chemicals, and exhaust fumes. Electrostatic ejection, vibration, and air blasts are not going to remove this film. Looking out my house window, I can tell it's time to wash the windows on the outside. Same with the camera window. It will take a liquid solvent like common windshield wiper fluid, to get the stuff off. Since a liquid wash and windshield wipe will also get rid of any accumulated dust, I'm favoring this solution.

Drivel: I've been emailing progress reports to the client which makes it appear that I'm actually making progress. That usually inspires a series of "oh, by the way..." requests. I was not disappointed. As of this morning, they also want to make it bullet proof, include a radiation detector, attach a weather station (they already have one), and a request that I document and patent everything. The only good news is that they finally found someone who could clean the camera window while doing other maintenance on the tower, so I'm off the hook for a while.

I can buy flat Gorilla glass, cut to size fairly easily. I don't want to think of the price and delivery for a curved piece.

With Gorilla glass, I'm not concerned about penetrating the glass. It's rather hard and will resist most airborne debris. It won't handle rocks, BB guns, bullets, and woodpeckers, but those are unlikely problems. The dust is held in place by static electricity. I was able to remove some of the dust by charging the glass with high voltage, and then pulling the dust away with the opposite charge on a nearby metal plate. It works nicely with the plate in front of the lens. However, when I put the charged plate behind the glass, and charged it with the same polarity on the assumption that it would repel the dust particles, nothing happened. It has some possibilities, but that will need to wait a day or three.

I did some tinkering with window glass and a small loudspeaker. I was trying to see if I could shed the dust by vibrating the glass at audio frequencies. That does work, but leaves some tiny dust particles behind. It's most effective when the window is pointed downward, which isn't going to happen. Pointed upward, it collects more dust. Also, the required glass displacement is fairly large, which would require a very flexible mounting for the glass. I could probably make this work, but I don't think it's going to be reliable, especially if the window collects a coating of grease from industrial air or a nearby emergency generator.

I also tried an air blast. Basically a manifold of air nozzles pointed at different parts of the glass from around the edge. That worked quite well, but I'm not thrilled with installing an air compressor, surge tank, and manifold on top of a mountain, and hoping that nothing will break. Too many moving parts and too many things to go wrong. However, it's the closest approximation of an alternative to a miniature windshield wiper system, so I'll look at it more closely tomorrow.

Getting rid of the dust is just part of the problem. Over a long period of time, glass collects a thin film of condensed aerosols, very fine dust particles, industrial chemicals, and exhaust fumes. Electrostatic ejection, vibration, and air blasts are not going to remove this film. Looking out my house window, I can tell it's time to wash the windows on the outside. Same with the camera window. It will take a liquid solvent like common windshield wiper fluid, to get the stuff off. Since a liquid wash and windshield wipe will also get rid of any accumulated dust, I'm favoring this solution.

Drivel: I've been emailing progress reports to the client which makes it appear that I'm actually making progress. That usually inspires a series of "oh, by the way..." requests. I was not disappointed. As of this morning, they also want to make it bullet proof, include a radiation detector, attach a weather station (they already have one), and a request that I document and patent everything. The only good news is that they finally found someone who could clean the camera window while doing other maintenance on the tower, so I'm off the hook for a while.

Yes. I had forgotten about it. I even have a sample here, somewhere, maybe. I previously failed to find a vendor that could supply the coated glass, or could process some blanks. Do you have a name that can do coatings for small runs? At this time, it still seems like an R&D project.

One problem is that it requires direct UV exposure for the bug killing free radicals to be formed. The camera has programming and shades to keep direct sunlight out of the optics. There's also a safe mode function that points the camera towards the ground if it sees too much direct light. The coating idea was discarded after someone tested it by somehow pointing a camera into the sun, and predictably destroying the CCD imager. There's also some question of the durability of the coating. I'm worried about the inevitable sand storm scoring the surface.

I'm going to try and resurrect the idea and see if it can be salvaged. I like the idea of no moving parts.

Thanks.

Yes. I had forgotten about it. I even have a sample here, somewhere, maybe. I previously failed to find a vendor that could supply the coated glass, or could process some blanks. Do you have a name that can do coatings for small runs? At this time, it still seems like an R&D project.

One problem is that it requires direct UV exposure for the bug killing free radicals to be formed. The camera has programming and shades to keep direct sunlight out of the optics. There's also a safe mode function that points the camera towards the ground if it sees too much direct light. The coating idea was discarded after someone tested it by somehow pointing a camera into the sun, and predictably destroying the CCD imager. There's also some question of the durability of the coating. I'm worried about the inevitable sand storm scoring the surface.

I'm going to try and resurrect the idea and see if it can be salvaged. I like the idea of no moving parts.

Thanks.

yeah, perhps use a headlamp washer/wiper

OK, so don't modify your new antenna design for a 200 ohm output then design a 200 ohm stripline pcb to combine 4 of them with a 50 ohm output. Don't do that. btw, is a 200 ohm stripline reasonably possible? Mikek

Any idea how the corner cubes performance compares to the spheres?

It's much of a muchness, at least in the visible in dry conditions. The cube stuff suffers badly in the UV due to absorption in the plastic, and hardly works at all if the back side of it gets wet.

It's normally attached to a quilted foam backing, which protects it from rain in street-sign applications, but it isn't foolproof.

The glass bead stuff gets degraded some in the wet, but holds up better in the UV and in extreme conditions.

Cheers

Phil Hobbs

This is summer vacation for the skool so I don't know if that will be possible. However, I will ask or try email. Thanks.

Ham radio is not involved in the slightest. The short story is that I stupidly volunteered to "take a look at the problem" of their dirty camera window to see "what could be done". I interpreted that as a casual Google search for available products that might improve the situation. The client interpreted that as the start of a major R&D project. As more and more members of the staff became involved, the non-project began to grow. If I had any common sense, I would have run for my life and abandoned this time burner long ago, except I find it interesting, and if I play my cards correctly, may actually get paid for the effort. I only mentioned it because the problem was similar to Jim Thomson's zero maintenance rooftop light detector.

That's what I suspect is inside the commerical enclosures with wipers: otherwise, there is:

You don't need a PCB. Just solder all 4 coaxes together at a common coax connector. Getting the right physical separation between antennas and preventing interaction due to side lobes, will be a challenge.

Or, use three power dividers as in the common 4 bay stacked folded dipole antennas. It's one of my favorite antennas because it's center fed and therefore doesn't have the uptilt of an end fed collinear.

No. On 0.062" G10/FR4, a 200 ohm microstrip trace will be 0.001" wide. I still think a simple coaxial 4:1 balun is the way.

Self-promoting plug: A better way is to just forget the complexicated to build yagi, and switch to a much simpler and cheaper Franklin/Amos antenna: