... this turned up today for use as a dedicated dish for 18GHz and also to evaluate what a standard Octagon pll lnbf performs like on it, and also to take some weight off the 1.8mtr / changer.
Never had a Gibertini dish before and have to say i'm quite impressed with the build quality. I'm wondering whether to give it a quick coat of Waxol clear or similar around the hidden nuts & bolts on the back plate etc ??. Will string it later out of curiousity lol.
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I'll just share this bit of info that raised it's ugly head that "stringing" revealed with the constuction of the 1.25 Gibby ....
Although happy with the build quality and the accuracy of all the bolt holes mating up precisely with each other whilst assembling..... BUT, when it come to stringing
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Bare in mind this is going to be used at Ka.
Stringing the reflector on it's own just stood up agains't a wall had a centre string gap of about 3mm or so which surprised me a bit.
Thinking , ahh .... when it's bolted to the pre-formed back plate it will pull out the 3-4mm and be absolutely perfect ... WRONG.
The string gap increased to about 8mm !... surprised me even more and absolutely a non starter for Ka use, or any other band for that matter. The culprit was the two middle fixing bolts and the miss-shape of the two items, ... the top and bottom ones when carefully tightened up and not over-tightened were ok and did not have any impact on distorting the dish shape but the two middle ones distorted the dish shape as soon as the slightest pressure was on the dish .
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I strung the 1.25 Precision and it was absolutely spot on and rightly deserves the name "Precision Antennas".
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SO .... constructive surgery was needed on the 1.25 Gibby to get the shape back.
The two middle dish fixings were left loose whilst the remaining gap between back of dish surface and back plate metal was filled with a good quality silicone and then will be tightened up just to just the point of tension without causing distortion to dish shape.
The two outer side edges of the dish needed very very slight forward pressure to get me perfect stringing so the shown bracing was constructed.
**Does leave you pondering though as to what is the right construction method to adopt .... Go with the book constuction guide with care and end up with an 8mm string gap ?, or "string" it for perfection and alter what-ever to suit ??.
Final note: The addition of the back bracing gave the whole dish structure a more solid feeling, well worth the exercise.
A few pics to go with the words ...
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