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10 meter mobile antenna
I just bought a 10 meter mobile rig (25 watt old radio shack rig).
I was planing on cutting down a 102" CB whip to 10 meter band. Anyone know of any type of antenna that would work better? Thanks Joe KI4ILB |
10 meter mobile antenna
Merlin-7 KI4ILB wrote:
I just bought a 10 meter mobile rig (25 watt old radio shack rig). I was planing on cutting down a 102" CB whip to 10 meter band. Anyone know of any type of antenna that would work better? I used a 10M Hamstick on my Ranger pickup with good results. Mark AA7TA |
10 meter mobile antenna
Have you heard of a 10 meter mobile antenna??
Hamstix, Hustler, et al make them. Lot easier than trying to cut steel. Merlin-7 KI4ILB wrote: I just bought a 10 meter mobile rig (25 watt old radio shack rig). I was planing on cutting down a 102" CB whip to 10 meter band. Anyone know of any type of antenna that would work better? Thanks Joe KI4ILB |
10 meter mobile antenna
"Dave" wrote in message ... Have you heard of a 10 meter mobile antenna?? Hamstix, Hustler, et al make them. Lot easier than trying to cut steel. Yeah, that should take all of a couple of minutes. W4OP |
10 meter mobile antenna
Anyone know of any type of antenna that would work better? As long as you only cut it as much as needed to move it up into the ten meter band it will still be a full length quarter wave antenna. No, there is almost nothing you could get that is better..... provided you mount it in the center of your roof. Now, the interesting question becomes, "If you don't mount it in the most optimum location, how much is it degraded, and would a loaded antenna mounted in the center of your roof be any better?" Realistically speaking, a center loaded (approximately 60 inch long) antenna mounted on the trunk or roof is a very good compromise. K2XT |
10 meter mobile antenna
All those commercial antennas will work better at thinning your wallet.
But not at getting your signal out. The only way you'd improve over the signal from a cut-down CB whip (2 minutes work with a hacksaw) is to either make the antenna directional in azimuth which would decrease the signal in other directions, or try making a collinear array. And I seriously doubt that you could get any noticeable gain from a collinear without making it too tall to be practical. I'm glad that some hams are still willing to reach for the hacksaw instead of the wallet. Go for it! Roy Lewallen, W7EL Dave wrote: Have you heard of a 10 meter mobile antenna?? Hamstix, Hustler, et al make them. Lot easier than trying to cut steel. Merlin-7 KI4ILB wrote: I just bought a 10 meter mobile rig (25 watt old radio shack rig). I was planing on cutting down a 102" CB whip to 10 meter band. Anyone know of any type of antenna that would work better? Thanks Joe KI4ILB |
10 meter mobile antenna
Dale Parfitt wrote: "Dave" wrote in message ... Have you heard of a 10 meter mobile antenna?? Hamstix, Hustler, et al make them. Lot easier than trying to cut steel. Yeah, that should take all of a couple of minutes. W4OP I could probably torch that bugger off in about 15 seconds.. :/ Might look kinda funky on the tip though. I agree. What is has is about as good as he's going to get. As long as it's grounded to the car well, preferably on the body somewhere, it's going to work great. Any other whip is probably going to be inferior as far as a 1/4 design. But it is possible for a roof mounted half size whip to equal a full 1/4 wave with a lower or poor ground. I'd use a bumper mount as a last resort. A side body mount with a ball mount, or even trunk mount would work a lot better. That whip on a roof would brown the food. Not very practical though as far as trees and drive thru's. A trunk mount is possible though. Heck, my mobile antenna is way tall. But I don't really care about looks much.. I recently bought a third small car to save gas when I don't need to drive the trucks. I put it's antenna mount on the trunk lid with reinforced plating underneath to keep from ripping the trunk lid apart. Hondas have thin sheet metal... :/ My 11 foot antenna would flex that thing like crazy with no plating underneath. Wouldn't last 3 hours before I ripped a hole in the trunk. I had to do the same with a monte carlo I once drove. MK |
10 meter mobile antenna
Thanks everyone
It will be mounted to the side rail of my Dodge 1500 4 door along with the 6 foot coliner for 2m and the 11 meter whip. Yes it has a CB in it. I need the CB for talking to truckers when I go into hurricane hit areas a day or two after the hurricane. Finding out what roads are open, last place to get fuel etc... Now all I need to figure out is how to keep the 10 meter and 11 meter antennas from interacting too bad or place them in such a way that the interaction does something that is usefull... Joe |
10 meter mobile antenna
Merlin-7 KI4ILB wrote:
Now all I need to figure out is how to keep the 10 meter and 11 meter antennas from interacting too bad or place them in such a way that the interaction does something that is usefull... Here's an idea. Use the 11 meter antenna for 10 meter operation by switching in a series capacitor. All you need to do is to neutralize the small amount of inductive reactance on 10m caused by the antenna being a tad too long. The capacitor could be switched in and out by a relay. I get a value of ~330 pf to perform that function. The SWR on 10m will actually be better than it is on 11m. Or you could use the capacitor with the second 102 inch vertical without having to cut it. -- 73, Cecil http://www.w5dxp.com |
10 meter mobile antenna
In message , Cecil
Moore writes Merlin-7 KI4ILB wrote: Now all I need to figure out is how to keep the 10 meter and 11 meter antennas from interacting too bad or place them in such a way that the interaction does something that is usefull... Here's an idea. Use the 11 meter antenna for 10 meter operation by switching in a series capacitor. All you need to do is to neutralize the small amount of inductive reactance on 10m caused by the antenna being a tad too long. The capacitor could be switched in and out by a relay. I get a value of ~330 pf to perform that function. The SWR on 10m will actually be better than it is on 11m. Or you could use the capacitor with the second 102 inch vertical without having to cut it. I did exactly this (20 years ago). I used a variable compression trimmer capacitor to check that I could actually get a low SWR, measured it, and fitted the nearest value disc ceramic (rated at 500VDC). I think it was 330pF. No problems with 40W. Ian. -- |
10 meter mobile antenna
OK where can I buy a 330pf cap? Its only a 25 watt rig but I would like a
bit of overkill. ****es me off that Radio Shack is a cell phone store now. I used to be able to walk into Radio Shack and the person there would understand what you needed. Now if it does not have to do with cell phones or car audio they just give you this dumb look.. Thanks Joe vertical without having to cut it. I did exactly this (20 years ago). I used a variable compression trimmer capacitor to check that I could actually get a low SWR, measured it, and fitted the nearest value disc ceramic (rated at 500VDC). I think it was 330pF. No problems with 40W. Ian. -- |
10 meter mobile antenna
Merlin-7 KI4ILB wrote:
OK where can I buy a 330pf cap? Make it a silver mica or doorknob. I get mine at an electronics supply store in Bryan, TX, close to Texas A&M. Where are you located? -- 73, Cecil, http://www.qsl.net/w5dxp |
10 meter mobile antenna
"Now if it does not have to do with cell phones or car audio they
just give you this dumb look.. " Heh.. went into my local Radio Shack and asked if they had any antenna masts in stock. Guy goes and looks on the shelves. I say "I'd like a TV mast, it's in the back if you have it, it's ten feet long" Guy looks on the shelves some more, points to the mast brackets. I'm like, "It's a ten feet long piece of steel pipe it wouldn't be out here, it isn't out here, it wouldn't fit out here, it's in the BACK." I look it up on the internet on the computer in the store and show them that yes, they do have them in stock. Of course, he doesn't think they've got any. Twenty minutes after I walk in, I'm finally leaving with a five foot and a ten foot mast section which they, of course, had. Guy is just incredulous that I'm going to walk out of the store with a ten foot piece of pipe. They then ask me if I need a cell phone ;-) Dan |
10 meter mobile antenna
"Merlin-7 KI4ILB" wrote in message . .. I just bought a 10 meter mobile rig (25 watt old radio shack rig). I was planing on cutting down a 102" CB whip to 10 meter band. Anyone know of any type of antenna that would work better? Thanks Joe KI4ILB A 1/8wl antenna mounted in the center of your roof will probably work better than the 1/4 lambda antenna on the bumper. |
10 meter mobile antenna
On Thu, 26 Oct 2006 22:53:48 GMT, "Merlin-7 KI4ILB"
wrote: OK where can I buy a 330pf cap? Its only a 25 watt rig but I would like a bit of overkill. ****es me off that Radio Shack is a cell phone store now. I used to be able to walk into Radio Shack and the person there would understand what you needed. Now if it does not have to do with cell phones or car audio they just give you this dumb look.. Thanks Joe I've been able to mail order most any electrical part from Mouser. No minimum order. And it puts you on the list for their huge catalog. bob k5qwg vertical without having to cut it. I did exactly this (20 years ago). I used a variable compression trimmer capacitor to check that I could actually get a low SWR, measured it, and fitted the nearest value disc ceramic (rated at 500VDC). I think it was 330pF. No problems with 40W. Ian. -- |
10 meter mobile antenna
It would not be mounted on the bumper.
My thinking is that since the first 1/3 of an antenna does the most radiating, get it as far away from any metal (broadside) that you can. It would be mounted in a stake-hole (one of the 4 square holes in each corner of the truck bed. Joe A 1/8wl antenna mounted in the center of your roof will probably work better than the 1/4 lambda antenna on the bumper. |
10 meter mobile antenna
Ok which one would you recommend?
http://www.mouser.com/search/Refine.... f&N=1323038+0 Thanks joe I've been able to mail order most any electrical part from Mouser. No minimum order. And it puts you on the list for their huge catalog. bob k5qwg vertical without having to cut it. I did exactly this (20 years ago). I used a variable compression trimmer capacitor to check that I could actually get a low SWR, measured it, and fitted the nearest value disc ceramic (rated at 500VDC). I think it was 330pF. No problems with 40W. Ian. -- |
10 meter mobile antenna
"Merlin-7 KI4ILB" wrote in message . .. Ok which one would you recommend? http://www.mouser.com/search/Refine.... f&N=1323038+0 Thanks joe I've been able to mail order most any electrical part from Mouser. No minimum order. And it puts you on the list for their huge catalog. bob k5qwg vertical without having to cut it. I did exactly this (20 years ago). I used a variable compression trimmer capacitor to check that I could actually get a low SWR, measured it, and fitted the nearest value disc ceramic (rated at 500VDC). I think it was 330pF. No problems with 40W. Ian. I once saw a 102" whip on a motor home that had literally been wound into a 4 " dia coil about half way up! It looked like one of those CB "big coil" trucker antennas except it was all in one piece. I can only surmise that he heated it and wound it around some sort of form. It shortened the thing down to less that 5 feet. But, then, wouldn't that take the temper out of the steel and make it flop over the next time it was hit? There was also no evidence of heating, either; it looked like it had been formed at the beginning of its life. Anybody ever see anyone do this before. If so, how was it done? 73 Jerry -- |
10 meter mobile antenna
"Merlin-7 KI4ILB" wrote in message .. . It would not be mounted on the bumper. My thinking is that since the first 1/3 of an antenna does the most radiating, get it as far away from any metal (broadside) that you can. It would be mounted in a stake-hole (one of the 4 square holes in each corner of the truck bed. Joe A 1/8wl antenna mounted in the center of your roof will probably work better than the 1/4 lambda antenna on the bumper. To each his own, but I don't agree with the "bottom" of the antenna doing the radiating. :) The bottom, *if* I understand it correctly--and I am not here to prove anything or start a flame war (I ain't got time for that ;) )--is the voltage portion, the top would be the current (RF) portion. Witness what happens if you grab an antenna (dipole. The current at the ends can reach levels to produce serious burns! Grab a mobile antenna below the loading coil while transmitting. You won't feel a thing! Grab it at or above the coil, it will burn the hell out of you ( X-numbers of milliamps of RF current). The next thing is, IMHO, if your antenna is radiating from the bottom, WHY would you even NEED the rest of the antenna? LOL! Next there's those pesky ground proximities that tend to "grab" a signal and just spoil everything. Now I am not trying to start a war, prove anyone wrong, annoy anyone, or engage in a "I'm-smarter-than-you-and-I'm-not-gonna-yield" etc, etc. I'll yield because it is 1) not important to me) and 2) cuz I ain't got time to get into a theory war today! ;) But, I am just of the opinion that the RF is where the thing will burn the crap out of you if you grab it!!! I've been burnt plenty of times, and it ain't pleasant!!! 73 Jerry |
10 meter mobile antenna
Jerry wrote:
The bottom, *if* I understand it correctly--is the voltage portion, the top would be the current (RF) portion. Nope, for a 1/4WL mobile antenna, the feedpoint is the high current, low voltage point. The tip top is the low current, high voltage point. The thing that tends to bite us is the high voltage. Consider that the top portion of a mobile antenna can be a low-radiation top hat while the bottom of the antenna (high current section) is radiating very well. -- 73, Cecil http://www.w5dxp.com |
10 meter mobile antenna
The current at the
ends can reach levels to produce serious burns! Grab a mobile antenna below the loading coil while transmitting. You won't feel a thing! Grab it at or above the coil, it will burn the hell out of you ( X-numbers of milliamps of RF current). Jerry, It's the high-voltage bits that bite you because your skin resistance is so high it takes some substantial voltage to drive a noticable current through you, but it doesn't take much current to give you a nasty burn. The high-current parts of the antenna don't have enough voltage to burn you. Dan |
10 meter mobile antenna
"Jerry" wrote in message ... "Merlin-7 KI4ILB" wrote in message . .. Ok which one would you recommend? http://www.mouser.com/search/Refine.... f&N=1323038+0 Thanks joe I've been able to mail order most any electrical part from Mouser. No minimum order. And it puts you on the list for their huge catalog. bob k5qwg vertical without having to cut it. I did exactly this (20 years ago). I used a variable compression trimmer capacitor to check that I could actually get a low SWR, measured it, and fitted the nearest value disc ceramic (rated at 500VDC). I think it was 330pF. No problems with 40W. Ian. I once saw a 102" whip on a motor home that had literally been wound into a 4 " dia coil about half way up! It looked like one of those CB "big coil" trucker antennas except it was all in one piece. I can only surmise that he heated it and wound it around some sort of form. It shortened the thing down to less that 5 feet. But, then, wouldn't that take the temper out of the steel and make it flop over the next time it was hit? There was also no evidence of heating, either; it looked like it had been formed at the beginning of its life. Anybody ever see anyone do this before. If so, how was it done? 73 Jerry -- Wouldnt be that hard to do, You can retemper the steel if it gets soft and the discoloring will buff off. tempering metal takes some specific knowledge and experience. Ive done it to tools and had some success but I have also made them to brittle and they break. Of course it may have been one of those big coil antennas |
10 meter mobile antenna
"Jimmie D" wrote in message .. . "Jerry" wrote in message ... "Merlin-7 KI4ILB" wrote in message . .. Ok which one would you recommend? http://www.mouser.com/search/Refine.... f&N=1323038+0 Thanks joe I've been able to mail order most any electrical part from Mouser. No minimum order. And it puts you on the list for their huge catalog. bob k5qwg vertical without having to cut it. I did exactly this (20 years ago). I used a variable compression trimmer capacitor to check that I could actually get a low SWR, measured it, and fitted the nearest value disc ceramic (rated at 500VDC). I think it was 330pF. No problems with 40W. Ian. I once saw a 102" whip on a motor home that had literally been wound into a 4 " dia coil about half way up! It looked like one of those CB "big coil" trucker antennas except it was all in one piece. I can only surmise that he heated it and wound it around some sort of form. It shortened the thing down to less that 5 feet. But, then, wouldn't that take the temper out of the steel and make it flop over the next time it was hit? There was also no evidence of heating, either; it looked like it had been formed at the beginning of its life. Anybody ever see anyone do this before. If so, how was it done? 73 Jerry -- Wouldnt be that hard to do, You can retemper the steel if it gets soft and the discoloring will buff off. tempering metal takes some specific knowledge and experience. Ive done it to tools and had some success but I have also made them to brittle and they break. Of course it may have been one of those big coil antennas Nope! I went over and looked at it from one foot away. One single CB whip wound into about a 3-4" coil about halfway up. Looked pretty good, too. I just don't know how he did it; never seen that done before. 73 Jerry |
10 meter mobile antenna
On Mon, 23 Oct 2006 01:12:09 GMT, "Merlin-7 KI4ILB"
wrote: I just bought a 10 meter mobile rig (25 watt old radio shack rig). I was planing on cutting down a 102" CB whip to 10 meter band. Anyone know of any type of antenna that would work better? Thanks Joe KI4ILB I know this is an old post, but I only just now found and read it, so I hope it is of interest to someone, if not the original poster. Now that that's over, (whew) I installed a 102" SS whip, spring, and ball mount I got from Rat Shack on the side of my 94 Plymouth Sundance's left rear fender, (the trunk lid is fiberglass so I couldn't mount it there) and it works great as it was. I got a near perfect match across the 10 meter band without a tuner and I didn't have to trim it one iota. If I needed, there is a little room for adjustment in the mount as the whip is secured with a hex head set screw in the mount. That should give enough wiggle room to get a decent match without having to cut the whip. I have a tuner, (a Drake MN-4) I use in the car, but I use in bypass mode for 10 meters. It will tune the whip from 20 through 10 meters with an SWR typically under 1.5:1 on all those bands. It won't tune to a useable SWR for anything lower in frequency than 20 meters though, so I will have to come up with another antenna that I can hopefully use with the same mount for 40, and hopefully through 80 meters. Again, I know this is a reply to a nearly 7 month old post, but I hope it is of use to someone anyway. Rob |
10 meter mobile antenna
"Rob" wrote in message ... On Mon, 23 Oct 2006 01:12:09 GMT, "Merlin-7 KI4ILB" wrote: I just bought a 10 meter mobile rig (25 watt old radio shack rig). I was planing on cutting down a 102" CB whip to 10 meter band. Anyone know of any type of antenna that would work better? Thanks Joe KI4ILB I know this is an old post, but I only just now found and read it, so I hope it is of interest to someone, if not the original poster. Now that that's over, (whew) I installed a 102" SS whip, spring, and ball mount I got from Rat Shack on the side of my 94 Plymouth Sundance's left rear fender, (the trunk lid is fiberglass so I couldn't mount it there) and it works great as it was. I got a near perfect match across the 10 meter band without a tuner and I didn't have to trim it one iota. If I needed, there is a little room for adjustment in the mount as the whip is secured with a hex head set screw in the mount. That should give enough wiggle room to get a decent match without having to cut the whip. I have a tuner, (a Drake MN-4) I use in the car, but I use in bypass mode for 10 meters. It will tune the whip from 20 through 10 meters with an SWR typically under 1.5:1 on all those bands. It won't tune to a useable SWR for anything lower in frequency than 20 meters though, so I will have to come up with another antenna that I can hopefully use with the same mount for 40, and hopefully through 80 meters. Again, I know this is a reply to a nearly 7 month old post, but I hope it is of use to someone anyway. Rob Thanks, I have my home up for sale, so I have not had time to mount the 10 meter rig in my truck yet. Besides the rig is in storage 300 miles away from here. I hope my home sells soon, I had to take down my tower and pack up most everything I own to show the house... I think I am going thru withdrawl... Im glad to hear that it works well, I may toss the analiser on the 11 meter whip that is already on the truck. If it works out I may only need to add an antenna switch. I only use the 11 meter rig durring hurricane season but it would be nice not to need to change antennas when I do need it. The truck also has a 2 meter colinear on it thats 6 feet tall or so. I would not mind adding another HF antenna but 2 long antennas on it is enough. Thanks again Joe |
10 meter mobile antenna
"Rob" wrote in message ... On Mon, 23 Oct 2006 01:12:09 GMT, "Merlin-7 KI4ILB" wrote: I just bought a 10 meter mobile rig (25 watt old radio shack rig). I was planing on cutting down a 102" CB whip to 10 meter band. Anyone know of any type of antenna that would work better? Thanks Joe KI4ILB I know this is an old post, but I only just now found and read it, so I hope it is of interest to someone, if not the original poster. Now that that's over, (whew) I installed a 102" SS whip, spring, and ball mount I got from Rat Shack on the side of my 94 Plymouth Sundance's left rear fender, (the trunk lid is fiberglass so I couldn't mount it there) and it works great as it was. I got a near perfect match across the 10 meter band without a tuner and I didn't have to trim it one iota. If I needed, there is a little room for adjustment in the mount as the whip is secured with a hex head set screw in the mount. That should give enough wiggle room to get a decent match without having to cut the whip. I have a tuner, (a Drake MN-4) I use in the car, but I use in bypass mode for 10 meters. It will tune the whip from 20 through 10 meters with an SWR typically under 1.5:1 on all those bands. It won't tune to a useable SWR for anything lower in frequency than 20 meters though, so I will have to come up with another antenna that I can hopefully use with the same mount for 40, and hopefully through 80 meters. Again, I know this is a reply to a nearly 7 month old post, but I hope it is of use to someone anyway. Rob The long antenna probably tunes up on 10M because of the fiberglass trunk lid. Had the lid been metal it would have been the responsibel for the largest portion of the capacitance needed to resonate the antenna. Without this capcitance the antenna will need to be longer than normal to achive resonance on 10M. One advantage of this that you have noted is a better match to 50 ohms. Longer antenna = greater L, fibergllass lid = less capacitance which gives a higher LC ratio at resonance. Jimmie |
10 meter mobile antenna
"Jimmie D" wrote in message ... "Rob" wrote in message ... On Mon, 23 Oct 2006 01:12:09 GMT, "Merlin-7 KI4ILB" wrote: I just bought a 10 meter mobile rig (25 watt old radio shack rig). I was planing on cutting down a 102" CB whip to 10 meter band. Anyone know of any type of antenna that would work better? Thanks Joe KI4ILB I know this is an old post, but I only just now found and read it, so I hope it is of interest to someone, if not the original poster. Now that that's over, (whew) I installed a 102" SS whip, spring, and ball mount I got from Rat Shack on the side of my 94 Plymouth Sundance's left rear fender, (the trunk lid is fiberglass so I couldn't mount it there) and it works great as it was. I got a near perfect match across the 10 meter band without a tuner and I didn't have to trim it one iota. If I needed, there is a little room for adjustment in the mount as the whip is secured with a hex head set screw in the mount. That should give enough wiggle room to get a decent match without having to cut the whip. I have a tuner, (a Drake MN-4) I use in the car, but I use in bypass mode for 10 meters. It will tune the whip from 20 through 10 meters with an SWR typically under 1.5:1 on all those bands. It won't tune to a useable SWR for anything lower in frequency than 20 meters though, so I will have to come up with another antenna that I can hopefully use with the same mount for 40, and hopefully through 80 meters. Again, I know this is a reply to a nearly 7 month old post, but I hope it is of use to someone anyway. Rob The long antenna probably tunes up on 10M because of the fiberglass trunk lid. Had the lid been metal it would have been the responsibel for the largest portion of the capacitance needed to resonate the antenna. Without this capcitance the antenna will need to be longer than normal to achive resonance on 10M. One advantage of this that you have noted is a better match to 50 ohms. Longer antenna = greater L, fibergllass lid = less capacitance which gives a higher LC ratio at resonance. Jimmie He mounted the antenna on the fender (because the trunk was fiberglass). With that in mind, how does the trunk lid being fiberglass lessen the capacitance of the circuit? Doesn't the fender 'take the place' of the trunk lid? I would reccommend someone using a metal trunk lid as a mounting surface to install some copper wire jumpers from the lid to the rest of the body. Some folks even go ahead and install copper jumpers to join all parts of the body to each other and to the frame, motor, and neg battery terminal. |
10 meter mobile antenna
"Hal Rosser" wrote in message ... "Jimmie D" wrote in message ... "Rob" wrote in message ... On Mon, 23 Oct 2006 01:12:09 GMT, "Merlin-7 KI4ILB" wrote: I just bought a 10 meter mobile rig (25 watt old radio shack rig). I was planing on cutting down a 102" CB whip to 10 meter band. Anyone know of any type of antenna that would work better? Thanks Joe KI4ILB I know this is an old post, but I only just now found and read it, so I hope it is of interest to someone, if not the original poster. Now that that's over, (whew) I installed a 102" SS whip, spring, and ball mount I got from Rat Shack on the side of my 94 Plymouth Sundance's left rear fender, (the trunk lid is fiberglass so I couldn't mount it there) and it works great as it was. I got a near perfect match across the 10 meter band without a tuner and I didn't have to trim it one iota. If I needed, there is a little room for adjustment in the mount as the whip is secured with a hex head set screw in the mount. That should give enough wiggle room to get a decent match without having to cut the whip. I have a tuner, (a Drake MN-4) I use in the car, but I use in bypass mode for 10 meters. It will tune the whip from 20 through 10 meters with an SWR typically under 1.5:1 on all those bands. It won't tune to a useable SWR for anything lower in frequency than 20 meters though, so I will have to come up with another antenna that I can hopefully use with the same mount for 40, and hopefully through 80 meters. Again, I know this is a reply to a nearly 7 month old post, but I hope it is of use to someone anyway. Rob The long antenna probably tunes up on 10M because of the fiberglass trunk lid. Had the lid been metal it would have been the responsibel for the largest portion of the capacitance needed to resonate the antenna. Without this capcitance the antenna will need to be longer than normal to achive resonance on 10M. One advantage of this that you have noted is a better match to 50 ohms. Longer antenna = greater L, fibergllass lid = less capacitance which gives a higher LC ratio at resonance. Jimmie He mounted the antenna on the fender (because the trunk was fiberglass). With that in mind, how does the trunk lid being fiberglass lessen the capacitance of the circuit? Doesn't the fender 'take the place' of the trunk lid? I would reccommend someone using a metal trunk lid as a mounting surface to install some copper wire jumpers from the lid to the rest of the body. Some folks even go ahead and install copper jumpers to join all parts of the body to each other and to the frame, motor, and neg battery terminal. Which do you think will offer more capacitance to the antenna, a metal trunk lid wich is a 90 degrees to the antenna and relaatively wide or the narrow fender that falls away from the antenna quickly. Jimmie |
10 meter mobile antenna
snip He mounted the antenna on the fender (because the trunk was fiberglass). With that in mind, how does the trunk lid being fiberglass lessen the capacitance of the circuit? Doesn't the fender 'take the place' of the trunk lid? I would reccommend someone using a metal trunk lid as a mounting surface to install some copper wire jumpers from the lid to the rest of the body. Some folks even go ahead and install copper jumpers to join all parts of the body to each other and to the frame, motor, and neg battery terminal. I am the king of grounding.. One note on that...most tail pipes on cars/trucks are hung with rubber hangers in the middle of them so that they can flex. What you end up with is a large diameter pipe (sometimes they match up on a frequency that you use), mostly around 10 meter band but I guess It could be any number of frequency's depending on the length of pipe) I have found cases where the radio was picking up, what sounded like ignition noise but after the tail pipe was grounded in a couple of places, the noise dissapeared. Joe |
10 meter mobile antenna
Which do you think will offer more capacitance to the antenna, a metal trunk lid wich is a 90 degrees to the antenna and relaatively wide or the narrow fender that falls away from the antenna quickly. Jimmie But he said the trunk lid was fiberglass - not metal - so the fender is the better choice. I know a metal trunk lid would be better - but there was not on available. Read his Original post again. |
10 meter mobile antenna
"Hal Rosser" wrote in message ... Which do you think will offer more capacitance to the antenna, a metal trunk lid wich is a 90 degrees to the antenna and relaatively wide or the narrow fender that falls away from the antenna quickly. Jimmie But he said the trunk lid was fiberglass - not metal - so the fender is the better choice. I know a metal trunk lid would be better - but there was not on available. Read his Original post again. Read my post again, I was commenting on why the long(27Mhz) antenna tuned up on 10M. I he had a metal lid he would have had to trim the antenna. Jimmie |
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