kl7aj
02-27-2008, 05:47 PM
A local ham here spent a great deal of money and time on an H.F. installation on his SUV. Everything was built like a brick outhouse. First-class installation in every regard. Everything was done "right."
Alas, my friend had a very disappointing signal on 75 meters. He asked for my advice. I pointed out his bumper mounted, base loaded 8 foot whip.
I asked my friend how long his antenna was. He said "eight feet".
"Oh, really now", I taunted. "Look at the bottom five feet of that. It runs right up next to the steel body of your SUV, two inches away. What you ACTUALLY have is five feet of transmission line and three feet of antenna...the part that extends above your SUV roof. Not only that, but your loading coil is practically TOUCHING the body of your SUV, and it's a long, thin coil, making everything worse. You'd be MUCH better off with a three foot whip on the roof of your SUV, and a short-fat loading coil in the clear. You're totally wasting 5 feet of antenna."
"But this tunes EVERYWHERE!" my friend protested.
"Yeah. So does a dummy load," I retorted. I could see the dejection in his face. After all, he DID do a fine piece of craftsmanship. And it looked pretty cool, too.
"So," I continued. "Do you want to be jack of all bands or master of one?"
After considerable frowning and pondering, the verdict was rendered. "I'm mainly on 75 meters, I guess."
"I thought so," I said. "Tell ya what. You keep your antenna here...it's still better than 50% of the stuff on the road. But let's ADD a dedicated 75 meter, roof mounted whip with a REAL loading coil. That way, you can compare them both. And you'll get to look like the FCC as well. Fair enough?"
To make a long story short, my friend did just as I suggested, and he is a happy camper....literally.
So, you CAN have your cake and eat it too. :)
eric
Alas, my friend had a very disappointing signal on 75 meters. He asked for my advice. I pointed out his bumper mounted, base loaded 8 foot whip.
I asked my friend how long his antenna was. He said "eight feet".
"Oh, really now", I taunted. "Look at the bottom five feet of that. It runs right up next to the steel body of your SUV, two inches away. What you ACTUALLY have is five feet of transmission line and three feet of antenna...the part that extends above your SUV roof. Not only that, but your loading coil is practically TOUCHING the body of your SUV, and it's a long, thin coil, making everything worse. You'd be MUCH better off with a three foot whip on the roof of your SUV, and a short-fat loading coil in the clear. You're totally wasting 5 feet of antenna."
"But this tunes EVERYWHERE!" my friend protested.
"Yeah. So does a dummy load," I retorted. I could see the dejection in his face. After all, he DID do a fine piece of craftsmanship. And it looked pretty cool, too.
"So," I continued. "Do you want to be jack of all bands or master of one?"
After considerable frowning and pondering, the verdict was rendered. "I'm mainly on 75 meters, I guess."
"I thought so," I said. "Tell ya what. You keep your antenna here...it's still better than 50% of the stuff on the road. But let's ADD a dedicated 75 meter, roof mounted whip with a REAL loading coil. That way, you can compare them both. And you'll get to look like the FCC as well. Fair enough?"
To make a long story short, my friend did just as I suggested, and he is a happy camper....literally.
So, you CAN have your cake and eat it too. :)
eric