[NLRS] Tower Mounted Video Camera Immune to the sun.

[Dr. Gerald N. Johnson]

Like a level, the tricky thing with a camera mount is alignment with the 
main lobe of tha antenna. Much easier with a looper than an offset dish. 
Some advocate laying the offset dish on its side, then the elevation 
angle is clear while azimuth is debated. Since my last 10G+ outing I 
mounted a couple of linear levels on my dish, one for lateral tilt and 
the other for elevation. I made the elevation mount adjustable and set 
it for level on Saturday where the dish peaked on Saturday. On Sunday I 
noticed signals peaked sometimes with the bubble at the end of the tube, 
or nearly to the end of the tube, not centered.

On a tropo path, skinning the horizon does not always produce the 
strongest signal. Sometimes signals are absorbed by that skinning of 
crops and trees and there would be more signal to the scattering volume 
if the antenna elevation was raised. The chart in the International 
Microwave Handbook does not take surface skimming losses into account. 
It only plots the losses from the bend at the mutual scattering horizon 
and the effects of raising or lower the antenna elevation angle to 
change that scattering angle.

Sometimes the other station is illuminating higher in the sky and you 
have to tilt up to have a decent shared scattering volume at a workable 
distance. On a tropo path we are always encountering trade offs from 
square law loss effective from the distance of antenna to the scattering 
volume, scattering angle in the mutual scattering volume, variations in 
the atmospheric density gradient, and humidity gradient, and local 
losses from skimming earth, crops, trees, and structures. All of which 
make predicting the exact elevation angle at a given minute (or second) 
difficult. For the strongest signal we want the scattering volume to be 
equal distance from the two stations.

This last weekend rover signals varied way more than enough to notice by 
ear between beaconing dots, often as much as moving the dish 5 or 10 
degrees by hand which made it difficult for precise aiming. Moving very 
slowly and waiting through the rapid fades made for better path 
performance for the QSO. And that was for a 18" offset dish. The 
adjacent 36" dish often didn't work as well because aiming was too critical.

Sometimes with ducting and inversions the elevation angle of arrival is 
elevated. I've been told by old old timers from AT&T Long Lines that on 
some circuits they mounted two dishes at each end of a path. One for the 
normal 4/3 earth radius and another one tilted up 4 or 5 degrees to 
catch conditions when the refraction was more the 4/3 earth radius 
normal density gradient refraction. For some circuits they found that 
extra refraction often enough they just broadened the elevation pattern 
by using two dishes with shared receivers and power.

73, Jerry, K0CQ

On 9/20/2013 6:42 PM, Steve N4PZ wrote:
>
>
> Hello All I put the camera inside a piece of PVC pipe abt 2 inche
> diameter and cap up both ends. On one end glue (RTV, smells like
> vinigar) a piece of glass on a hole cut in the cap. Put the glass on
> OUTSIDE of the cap or snow will build up on the edge outside and cut
> off part of your camera view. The relay goes inside the PVC pipe also
> obviously. Make sure to drill a small hole or two on the lowest part
> of the PVC pipe for drainage but not big enough for wasps to get
> inside, Remember, if you skip the relay inside the PVC pipe to
> isolate the camera when it is turned off you WILL, GUARANTEED, very
> soon buy a new camera as the first wild thunder storm passes. Hi Hi.
> Once you have cameras on all your antennas like I have you will feel
> blind if one fails. Even on my tropo antennas. I can see trees
> blocking certain paths that I never suspected. On microwave dishes I
> have vertical adjust on my tropo dishes. You would be amazed how
> easily you can find your dish pointing into the ground or way up
> above the actual horizon. A level can lie. Trust me. Point your dish
> at the setting sun and with a vertical adjustment I’ll bet 50% of all
> microwave dishes aren’t on the horizon. Also on a 300 mile path on
> 5760 I found peak signal not on the horizon but several degrees above
> it. Try a camera. You will wonder how you ever did without it. 73
> Steve N4PZ
>
>