What did you use to make the inductance coil and how did you wrap it?
Looks good in the picture
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Little Tarheel II
- Thread starter K9GAS
- Start date
What did you use to make the inductance coil and how did you wrap it?
Looks good in the picture
This site here, Antenna Matching, good reading.
No. 14 enameled wire I purchase in Indy, used to wrap motors and transformers.
1" diameter by 1" long or 7-9 wraps. I used a socket on a 6" extension to hold,
that wasn't too bad to do, pretty easy. I made several out of the 10' I purchased.
No. 14 enameled wire I purchase in Indy, used to wrap motors and transformers.
1" diameter by 1" long or 7-9 wraps. I used a socket on a 6" extension to hold,
that wasn't too bad to do, pretty easy. I made several out of the 10' I purchased.
Especially since that matching coil is near that front 'mud-slinger', you might mount it behind the antenna. Or maybe encapsulate it in a piece of PVC pipe end caps. I use one a lot like that and it can certainly accumulate dirt/mud/snow/etc, even on a tool box mount. Mine (supplied with the antenna) was just a wrap or so too small, but that's easily fixed. They aren't exactly the most 'bullet-proof' thingys around so protecting them does pay off.
- 'Doc
(I like that mount.)
- 'Doc
(I like that mount.)
I'm sure there would be some affect using a sealant like that, no idea what though. I think the biggy is to keep from deforming that coil by enclosing it in something. At least that way, even if there is some affect, it shouldn't change with the weather or stuff getting on/in the coil. There's more than one way of doing that 'enclosing' so whatever or however you find easiest to do and not make drastic changes ought'a work.
Cobbling together an enclosure for the whole 'bottom' of that antenna might be one way of going about it. Would keep the thing 'cleaner' anyway.
- 'Doc
(I can think of several ways of doing that 'enclosing', but the 'doing' of it is a different story!)
Cobbling together an enclosure for the whole 'bottom' of that antenna might be one way of going about it. Would keep the thing 'cleaner' anyway.
- 'Doc
(I can think of several ways of doing that 'enclosing', but the 'doing' of it is a different story!)
Looking good. That is a pretty serious mount on that bumper! I agree with Doc about the location of the coil. The first time you run too close to a bush, it's going to get ripped off. See if you can protect it or locate it on the other side of the antenna.
From that website you shared a link with they say not to cover it with PVC, especially the gray stuff.
Further, for best results the coil should be installed as clear of surrounding sheet metal as possible, not enclosed in any material, even plastic (especially gray PVC!), and not short-tapped! When matching coils are mounted close to mounting brackets, vehicle sheet metal, enclosed in any material other than air, or have some of their winding shorted out, their performance and linearity will suffer! Incidentally, his may require relocating factory-supplied coils, or winding your own as outlined in this article.
Further, for best results the coil should be installed as clear of surrounding sheet metal as possible, not enclosed in any material, even plastic (especially gray PVC!), and not short-tapped! When matching coils are mounted close to mounting brackets, vehicle sheet metal, enclosed in any material other than air, or have some of their winding shorted out, their performance and linearity will suffer! Incidentally, his may require relocating factory-supplied coils, or winding your own as outlined in this article.
"for best results the coil should be installed as clear of surrounding sheet metal as possible, not enclosed in any material, even plastic (especially gray PVC!), and not short-tapped!"
That's well and good, but it also introduces some variations in the mounting of the antenna, and that matching coil, that can be VERY difficult to over-come. Enclosing that matching coil may result in some loss of efficiency, but I think that's probably better than the loss of the use of that antenna all together. Of course there are limits to that "give a little to get a little" thingy! I would probably bet that 'BG' would say to find another place to mount the antenna because of how you had to 'adjust' things in where it's at now. That's certainly fine, if you can do it. But what do you do if you can't? Make the 'best' of it and don't worry -excessively- about the compromise you have to make.
- 'Doc
(I agree about that particular spot being a 'not so good' place to put an antenna, at least for me. Ever walked around the 'corner' of your car/truck and 'clipped' your knee on the body/bumper? Yeah, so I wasn't paying attention, but I still got 'clipped'. 'Catching' that matching coil would probably not do it any good at all, you know?)
That's well and good, but it also introduces some variations in the mounting of the antenna, and that matching coil, that can be VERY difficult to over-come. Enclosing that matching coil may result in some loss of efficiency, but I think that's probably better than the loss of the use of that antenna all together. Of course there are limits to that "give a little to get a little" thingy! I would probably bet that 'BG' would say to find another place to mount the antenna because of how you had to 'adjust' things in where it's at now. That's certainly fine, if you can do it. But what do you do if you can't? Make the 'best' of it and don't worry -excessively- about the compromise you have to make.
- 'Doc
(I agree about that particular spot being a 'not so good' place to put an antenna, at least for me. Ever walked around the 'corner' of your car/truck and 'clipped' your knee on the body/bumper? Yeah, so I wasn't paying attention, but I still got 'clipped'. 'Catching' that matching coil would probably not do it any good at all, you know?)
good point Tim. This truck stays on highway, but it goes to hospitals, so landscape could be a issue, I didn't think of that. I put it out there as Hammer pointed to the article about getting it out away from the metal surroundings, though that didn't seem to have much affect as when it was mounted up high away from ground. I was going to try wrapping with some tape and see what the results turn out on the analyzer and see what differences show up.
Getting a good earth ground seems to be the key with screwdrivers, and getting them low and good connection to the frame seems to be the key. That's what the Tarheel support stressed as to where I had before was problematic. This box has all kinds of good ground plane, it's all metal, but it wasn't getting an earth ground. This has been a learning experience. Mounted on that front bumper seemed ideal as it's connected to frame directly and there's nice wide flat metal going to frame, supports, that make a good rf/dc ground as well. An interesting side note, is the high bands are affected somewhat if the 80/40 is not set correctly. I had it set to 50ohm x=0 reactance and 1.1 on 80 and close to that on 40m and the higher bands were affected in the sense that 20m was a little above 2.1:1 and higher loss and seventeen was not as bad but not as close as I wanted. When I followed the article and Tarheels direction and got the 80/40 closer to 40 ohm x=0 1.1 swr the higher bands fell right into place. I don't have it perfect 80 is more like 47 ohm. If I squeeze the coil tighter 80 gets closer to 40 ohm.
I just don't remember if that means I need lengthen or shorten the coil? I'll post a pic on here how it was mounted before I moved it.
I'm surprised though, that just a one outer wrap on the coil would mess it up as the wire is coated already. I was thinking this would be great to keep the coil in shape. I can see the guys at the truck wash blasting that coil out of shape as well.
I'm going to do some fine tuning this weekend and some more strapping as I have some light rf still, especially if I run the mic over 20%. I hate to see rf, I just want an over mod report.
Doc, I was worried a little about one of us taking some flesh off as well. It doesn't seem to be a problem as you see that antenna very well, yikes it's big, and naturally walk away from it.
This is the way I had it mounted prior. The angle of the pic doesn't show, but the decoupler was around 3" above the roof, which was fine by Tarheel's specs, but was just to far from the ground. The cap hat wasn't going to work though, too close to metal roof. I tried raising it to no avail. The height as it was with a 4' whip was still at lower position near 15' and at 80m would have been about 16' 6".
Getting a good earth ground seems to be the key with screwdrivers, and getting them low and good connection to the frame seems to be the key. That's what the Tarheel support stressed as to where I had before was problematic. This box has all kinds of good ground plane, it's all metal, but it wasn't getting an earth ground. This has been a learning experience. Mounted on that front bumper seemed ideal as it's connected to frame directly and there's nice wide flat metal going to frame, supports, that make a good rf/dc ground as well. An interesting side note, is the high bands are affected somewhat if the 80/40 is not set correctly. I had it set to 50ohm x=0 reactance and 1.1 on 80 and close to that on 40m and the higher bands were affected in the sense that 20m was a little above 2.1:1 and higher loss and seventeen was not as bad but not as close as I wanted. When I followed the article and Tarheels direction and got the 80/40 closer to 40 ohm x=0 1.1 swr the higher bands fell right into place. I don't have it perfect 80 is more like 47 ohm. If I squeeze the coil tighter 80 gets closer to 40 ohm.
I just don't remember if that means I need lengthen or shorten the coil? I'll post a pic on here how it was mounted before I moved it.
I'm surprised though, that just a one outer wrap on the coil would mess it up as the wire is coated already. I was thinking this would be great to keep the coil in shape. I can see the guys at the truck wash blasting that coil out of shape as well.
I'm going to do some fine tuning this weekend and some more strapping as I have some light rf still, especially if I run the mic over 20%. I hate to see rf, I just want an over mod report.
Doc, I was worried a little about one of us taking some flesh off as well. It doesn't seem to be a problem as you see that antenna very well, yikes it's big, and naturally walk away from it.
This is the way I had it mounted prior. The angle of the pic doesn't show, but the decoupler was around 3" above the roof, which was fine by Tarheel's specs, but was just to far from the ground. The cap hat wasn't going to work though, too close to metal roof. I tried raising it to no avail. The height as it was with a 4' whip was still at lower position near 15' and at 80m would have been about 16' 6".
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There are always going to be a few compromises with mobile antennas, no way around that at HF. If you are moving, then the lower mounted antenna would probably be the better of the two. If you were stilling still, the higher mounted antenna would then probably be best. That's just one of 'those' things about practicality and long(er) antennas.
The idea with any loaded antenna is to get that loading coil/device away from any metal that will affect it. A coil will be more affected by being beside metal than being above metal. So moving that high mounted antenna higher and getting all of it above metal would be the best way of going about it. It's also probably the least practical thing you can do. So, you compromise. All things considered, your bumper mount is probably the best that's possible in your particular situation. Not the best in the world, but the best -possibility- you have available.
Now... if I could only figure some reasonably good way of putting that @#$ screwdriver antenna on my HHR... oh well.
- 'Doc
The idea with any loaded antenna is to get that loading coil/device away from any metal that will affect it. A coil will be more affected by being beside metal than being above metal. So moving that high mounted antenna higher and getting all of it above metal would be the best way of going about it. It's also probably the least practical thing you can do. So, you compromise. All things considered, your bumper mount is probably the best that's possible in your particular situation. Not the best in the world, but the best -possibility- you have available.
Now... if I could only figure some reasonably good way of putting that @#$ screwdriver antenna on my HHR... oh well.
- 'Doc
Yeah it really is the only real place for that thing. In hind sight, I would have went for the 75HP and put it on the hood, that probably would have been better. Nice thing about a work truck I would have drilled a hole for a ball mount.
Hey also, I wrapped electrical tape around the coil and saw no change on the 259b. I fine tuned it and moved the coil to a more protected spot. Took it to the truck wash last night as they did their thing and no movement on the coil so everything is good. Thanks, Jerry
Hey also, I wrapped electrical tape around the coil and saw no change on the 259b. I fine tuned it and moved the coil to a more protected spot. Took it to the truck wash last night as they did their thing and no movement on the coil so everything is good. Thanks, Jerry
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