|
On Sun, 9 Jan 2005 16:35:20 -0500, "Jack Painter"
wrote: Guys, the last time I checked, this was not rec.car.battery. We're talking about antennas and RF, not DC connections to your car battery. Using grease, even outside the made connection, will eventually penetrate the spaces. Maybe this doesn't matter to the 50-100w user, but it matters to high power connections, the most notable of which is lightning. Here in the UK I'll think you'll find the lightning conductors have greased joints. I always thought it was the origin of the term 'greased lightning'.... (only joking) -- from Aero Spike |
"Spike" wrote in message ... On Sun, 9 Jan 2005 16:35:20 -0500, "Jack Painter" wrote: Guys, the last time I checked, this was not rec.car.battery. We're talking about antennas and RF, not DC connections to your car battery. Using grease, even outside the made connection, will eventually penetrate the spaces. Maybe this doesn't matter to the 50-100w user, but it matters to high power connections, the most notable of which is lightning. Here in the UK I'll think you'll find the lightning conductors have greased joints. I always thought it was the origin of the term 'greased lightning'.... Plus, of course, the issue isn't so much the power as the current when thinking of high resistance connections. The cranking current drawn via a car battery terminal is around 100A. If the grease ingress caused a high resistance connection, the car wouldn't start. In practice, ungreased connections tend to 'go high' due to corrosion. -- Brian Reay www.g8osn.org.uk www.amateurradiotraining.org.uk FP#898 |
"Spike" wrote Here in the UK I'll think you'll find the lightning conductors have greased joints. I always thought it was the origin of the term 'greased lightning'.... (only joking) -- from Aero Spike That is funny. But since this has now become rec.batteries.car (just kidding): The reaction from battery acids, air and dirt are minimized with grease. But mechanics who grease the inside of the cable-clamp and outside of the battery post *before the connection is made* are not helping the electrical connection - they're applying preventative maintenance for idiots - who never clean their battery posts. Conductive paste is much more expensive than grease. Those who know what they are doing use the former. Conductive paste is specified in US Lightning protection (NEC-70/NFPA-780), and grease is not allowed to be used in any mechanical connection there. Back to antennas for a moment, we all know that grease (or conductive pate) does not provide waterproofing of any kind. And most of you will accept that grease is a dialectric, not a conductor. But after making a mechanical joint with conductive paste (ensuring no air enters the joint, and conductivity remains per the connected materials), and proper waterproofing is applied, you have a safe and maintenance-free joint that will last for years. Or it would anyway, if the same codes didn't require you to expose and mechanically tighten every such joint once a year. That's why the expensive exothermic (welding) of all grounding electrode conductor joints becomes a savings in the long run. Unfortunately that is never practical along rooflines up on masts and towers. So those mechanical joints must provide as little impedance as possible, and survival of the equipment depends on this. Because all transmitter antenna radials automatically become a part of the lightning protection system, the materials used should be the best you could afford, not the cheapest you can find. And the connections should likewise be the best possible. The transmission system will be more efficient, and safer. Jack Painter Virginia Beach, Virginia |
On Sun, 9 Jan 2005 22:51:14 +0000, "Ian White, G3SEK" wrote:
wrote: get a mechanised pizza cutter to make the wire slots and place it on the wheel of a wheel barrow Art, you're a genius! SM2CEW's website describes a radial plough which attaches to the back of a tractor, and can lay a full-sized Top Band radial in 2 minutes. I had been lamenting the lack of a Volvo tractor (or the space to lay such long radials) but a blade attached to a wheelbarrow might just do it... or even to the lawn mower. Opens up a whole new perspective on mowing the lawn. Jock. -- "Education is a progressive discovery of our own ignorance." - Will Durant |
On Sun, 9 Jan 2005 22:51:14 +0000, "Ian White, G3SEK"
wrote: wrote: get a mechanised pizza cutter to make the wire slots and place it on the wheel of a wheel barrow Art, you're a genius! SM2CEW's website describes a radial plough which attaches to the back of a tractor, and can lay a full-sized Top Band radial in 2 minutes. I had been lamenting the lack of a Volvo tractor (or the space to lay such long radials) but a blade attached to a wheelbarrow might just do it... or even to the lawn mower. I just checked one of my catalogs from a restaurant supply store (Bridge Kitchenware in New York City), and I notice they sell pizza cutters with wheels as big as 5 inches in diameter. If you used hose clamps to attach the handle of a pizza cutter to the end of a broom handle, I bet that would make a dandy lawn slit cutter for laying radials. Bob k5qwg |
Spike wrote in
: On Sun, 09 Jan 2005 15:52:22 GMT, David Edmonds wrote: Maybe it's the installation and not supplying that is under question - though typically our government bring in a silly law such as this - while they know that there is no right of entry to inspect. The problem arises when you try to sell your house. A prospective purchaser's solicitor will ask for the certificates for any work you admit to having been done post Jan 1. So you don't admit to any! |
"Brian Reay" wrote in
: "Spike" wrote in message ... On Sun, 9 Jan 2005 16:35:20 -0500, "Jack Painter" wrote: Guys, the last time I checked, this was not rec.car.battery. We're talking about antennas and RF, not DC connections to your car battery. Using grease, even outside the made connection, will eventually penetrate the spaces. Maybe this doesn't matter to the 50-100w user, but it matters to high power connections, the most notable of which is lightning. Here in the UK I'll think you'll find the lightning conductors have greased joints. I always thought it was the origin of the term 'greased lightning'.... Plus, of course, the issue isn't so much the power as the current when thinking of high resistance connections. The cranking current drawn via a car battery terminal is around 100A. If the grease ingress caused a high resistance connection, the car wouldn't start. In practice, ungreased connections tend to 'go high' due to corrosion. It's not normally grease, it's vaseline, which is conductive. I don't know how vaseline behaves at RF, though. Maybe not too well? |
Bob
The idea is to not mess up the lawn PLUS controlling the depth of the cut. When the slicer is on the wheel the main weight of the barrow is directly over the slicer thus making it easir to slice the lawn at a controled depth reducing the possibility of jamming at a lower depth. The whole idea is not to mess up the lawn and by taking some flower pots from one end and changing them over at the other end will look like you are working hard in the garden and shaming the neigbors in front of yjeir wifes. Cheers Art I might add I used a tractor system when I did mine which also inserted the wire but you just don't mess with an English lawn or you will lose the impression of perfection and where wifes are known to use treezers for the final touch. Reminds me of a story where a yank admired a particular lawn at some notable tourist site. He asked the ground keeper how he could duplicate it when he got home, Certainly the groundskeeper replied but firt you must start the lawn several centeries ago! "Bob Miller" wrote in message ... On Sun, 9 Jan 2005 22:51:14 +0000, "Ian White, G3SEK" wrote: wrote: get a mechanised pizza cutter to make the wire slots and place it on the wheel of a wheel barrow Art, you're a genius! SM2CEW's website describes a radial plough which attaches to the back of a tractor, and can lay a full-sized Top Band radial in 2 minutes. I had been lamenting the lack of a Volvo tractor (or the space to lay such long radials) but a blade attached to a wheelbarrow might just do it... or even to the lawn mower. I just checked one of my catalogs from a restaurant supply store (Bridge Kitchenware in New York City), and I notice they sell pizza cutters with wheels as big as 5 inches in diameter. If you used hose clamps to attach the handle of a pizza cutter to the end of a broom handle, I bet that would make a dandy lawn slit cutter for laying radials. Bob k5qwg |
|
"Alun" wrote in message ... Plus, of course, the issue isn't so much the power as the current when thinking of high resistance connections. The cranking current drawn via a car battery terminal is around 100A. If the grease ingress caused a high resistance connection, the car wouldn't start. In practice, ungreased connections tend to 'go high' due to corrosion. It's not normally grease, it's vaseline, which is conductive. I don't know how vaseline behaves at RF, though. Maybe not too well? If it isn't in the the current path (ie between the mating surfaces) and also not acting as an unwanted path (eg between the earth clap and the antenna), does it matter? OK, you may get some local absortion of RF energy, but how much grease are you going to use? Not enough to absorb much RF and the mass of grease (or vaseline) will be far less than other unquantified RF conductors and absorbers in the vicinity. You need to look at things like this in the context of the problem. -- Brian Reay www.g8osn.org.uk www.amateurradiotraining.org.uk FP#898 |
| All times are GMT +1. The time now is 09:31 AM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
RadioBanter.com