Re: [Repeater-Builder] Re: Antenna cleaning solvent ???
At 2/16/2007 05:35, you wrote: Wouldn't the pitting give the antenna more surface area, broader bandwidth, and more gain? DE NU5D The pitting actually seriously impacts antenna performance as it causes ERP to drop off. What happens is instead of efficient conversion from conducted to radiated energy, you get significant losses from heat.This IIRC Aluminum Oxide is a low-loss dielectric. Unless it forms with significant impurities on the antenna, I don't see where the loss would come from. is why almost every 'extreme-duty' antenna manufacturer are now offering hard anodizing options for their mountaintop antenna products. The only way you can test for this is to do repeated far-field strength measurements over time. The antenna itself will test fine; return loss, VSWR, all look great, but it just doesn't talk as far. ...or pump a LOT of power into it use a non-contact IR thermometer to look for surface heating. Bob NO6B
[Repeater-Builder] Re: Antenna cleaning solvent ???
QST usually has some ads for antenna wax in their April 1st magazine. Try that. - -- In Repeater-Builder@yahoogroups.com, Captainlance [EMAIL PROTECTED] wrote: Auto part stores carry Aluminum wheel cleaner, it is a strong chemical that strips off oxidation and leaves a clean , raw, surface. The only problem is that raw aluminum starts to oxidize immediately. You will need to covert the antenna with a coating of clear urethane to stop this from happening . This can be done with spray or brush. Lance N2HBA - Original Message - From: John To: Repeater-Builder@yahoogroups.com Sent: Wednesday, February 14, 2007 10:16 PM Subject: [Repeater-Builder] Antenna cleaning solvent ??? What is a good cleaning solvent for aluminum repeater antennas? I have an antenna that was exposed to the weather for years and it has become pitted and dirty from the enviroment. Thanks, John
[Repeater-Builder] Re: Antenna cleaning solvent ???
Wouldn't the pitting give the antenna more surface area, broader bandwidth, and more gain? DE NU5D The pitting actually seriously impacts antenna performance as it causes ERP to drop off. What happens is instead of efficient conversion from conducted to radiated energy, you get significant losses from heat.This is why almost every 'extreme-duty' antenna manufacturer are now offering hard anodizing options for their mountaintop antenna products. The only way you can test for this is to do repeated far-field strength measurements over time. The antenna itself will test fine; return loss, VSWR, all look great, but it just doesn't talk as far. Mechanical abrasion of the surface is the only way you can get rid of pits. I guess it becomes a question of how much time you're willing to spend polishing up that antenna. Best, -Cam, VE7MMV.
[Repeater-Builder] Re: Antenna cleaning solvent ???
The antenna itself will test fine; return loss, VSWR, all look great, but it just doesn't talk as far. Mechanical abrasion of the surface is the only way you can get rid of pits. I guess it becomes a question of how much time you're willing to spend polishing up that antenna. Best, -Cam, VE7MMV. I wonder if polishing would increase the bandwidth too. All those old DB224s out there could be brought down to the low end of 2M... Laryn K8TVZ
