|
Post by MonkeyMan on Sept 15, 2016 10:16:48 GMT -5
So as I'm waiting for our addition to be completed (had a slow start thanks to the knuckleheads at borough hall) I remain antenna-less and have been thinking about alternatives to the IMAX eyesore. I have in my possession two stainless 102" whips and was wondering how I might be able to put these to use.
I've seen different mounts which allow for two whips to be configured as a dipole, either vertically, horizontally and inverted 'V', but quite frankly antenna theory is not strong suit so I figured I'd throw this up for discussion.
|
|
|
Post by cbrown on Sept 15, 2016 12:48:47 GMT -5
If it were me, I'd go with the inverted V. Most people setting up an vertical dipole mess up the radiating pattern by not having the feed coax 90° to the antenna.
|
|
Sandbagger
Administrator/The Boss
Posts: 6,247
|
Post by Sandbagger on Sept 15, 2016 13:19:45 GMT -5
So as I'm waiting for our addition to be completed (had a slow start thanks to the knuckleheads at borough hall) I remain antenna-less and have been thinking about alternatives to the IMAX eyesore. I have in my possession two stainless 102" whips and was wondering how I might be able to put these to use. I've seen different mounts which allow for two whips to be configured as a dipole, either vertically, horizontally and inverted 'V', but quite frankly antenna theory is not strong suit so I figured I'd throw this up for discussion. Well, do you want to have something that looks unobtrusive, or do you want to put out a good signal? In most cases you can't have both. A single 102" whip on the rain gutter will work (I used one for the first 5 years that I was up here), but it's not going to work as well as the Imax. You can also make a dipole from two opposing 102" whips, but that is nearly as long as the Imax, and mounting it is more problematic than the IMax or a gutter mounted whip.
|
|
Sandbagger
Administrator/The Boss
Posts: 6,247
|
Post by Sandbagger on Sept 15, 2016 13:50:21 GMT -5
If it were me, I'd go with the inverted V. Most people setting up an vertical dipole mess up the radiating pattern by not having the feed coax 90° to the antenna. Inverted V configurations are horizontally polarized. That might work well for skip, but it will suck eggs for local work.
|
|
|
Post by MonkeyMan on Sept 15, 2016 14:48:26 GMT -5
Well, do you want to have something that looks unobtrusive, or do you want to put out a good signal? In most cases you can't have both. A single 102" whip on the rain gutter will work (I used one for the first 5 years that I was up here), but it's not going to work as well as the Imax. You can also make a dipole from two opposing 102" whips, but that is nearly as long as the Imax, and mounting it is more problematic than the IMax or a gutter mounted whip. Not really worried about how it looks, good signal is the priority. Just thinking about trying something different with what I already have "in stock" and if it doesn't work out I can simply put the IMAX back up. So if I went with the vertical dipole configuration I'd have to come off the vertical mast at a 90 degree angle, correct? Any rule of thumb as to how far off the vertical mast?
|
|
Sandbagger
Administrator/The Boss
Posts: 6,247
|
Post by Sandbagger on Sept 15, 2016 18:45:26 GMT -5
Well, do you want to have something that looks unobtrusive, or do you want to put out a good signal? In most cases you can't have both. A single 102" whip on the rain gutter will work (I used one for the first 5 years that I was up here), but it's not going to work as well as the Imax. You can also make a dipole from two opposing 102" whips, but that is nearly as long as the Imax, and mounting it is more problematic than the IMax or a gutter mounted whip. Not really worried about how it looks, good signal is the priority. Just thinking about trying something different with what I already have "in stock" and if it doesn't work out I can simply put the IMAX back up. So if I went with the vertical dipole configuration I'd have to come off the vertical mast at a 90 degree angle, correct? Any rule of thumb as to how far off the vertical mast? If you remember the old "Trik-Stik" antenna, it was a simple dipole that had a horizontal mounting boom, at the feedpoint in the middle, that held the antenna about 2 or 3' away from the mast. And you just attached the coax to the antenna at the center and ran it along the boom, and down the mast. You can do the same thing with a hunk of wood (2X4) and just attach the 2 whips to it and fashion some way of attaching the coax to them, and you can nail another 2X4 at a 90 degree angle from the two whips and go from there.....
|
|
|
Post by thejerk on Sept 17, 2016 10:09:15 GMT -5
I ran a horizontal dipole made from two 102 inch whips...the droop of the whips gave a semi-inverted vee, which worked well for skip and ok for local...two mirror mount brackets on a stub of pipe worked for me...
|
|
|
Post by BBB on Sept 17, 2016 10:51:17 GMT -5
|
|
Sandbagger
Administrator/The Boss
Posts: 6,247
|
Post by Sandbagger on Sept 18, 2016 18:08:18 GMT -5
Those co-phaser boxes are getting rare as hen's teeth. Pete's had a lot of fun with his......
|
|
|
Post by cbrown on Sept 21, 2016 13:32:49 GMT -5
Inverted V configurations are horizontally polarized. That might work well for skip, but it will suck eggs for local work. Since local 11M activity here is rare, I assumed it would be for other areas too. I'd try the vertical dipole for local, although a good 1/4 wave ground plane would probably be better.
|
|
Sandbagger
Administrator/The Boss
Posts: 6,247
|
Post by Sandbagger on Sept 21, 2016 13:49:16 GMT -5
Inverted V configurations are horizontally polarized. That might work well for skip, but it will suck eggs for local work. Since local 11M activity here is rare, I assumed it would be for other areas too. I'd try the vertical dipole for local, although a good 1/4 wave ground plane would probably be better. 1/4 wave Dave would probably agree, although he also has a horizontal dipole for skip..... Interestingly enough a dipole supposedly has more gain than a 1/4 wave vertical, but I suspect differences in radiation angles might make real world performance comparisons that favor the 1/4 wave in certain circumstances.
|
|
|
Post by MonkeyMan on Sept 21, 2016 14:25:19 GMT -5
I ran a horizontal dipole made from two 102 inch whips...the droop of the whips gave a semi-inverted vee, which worked well for skip and ok for local...two mirror mount brackets on a stub of pipe worked for me... I may try this for fun. It seems to be the easiest as far as mounting is concerned and I believe I have a couple mirror mounts laying around out in the shed.
|
|
|
Post by cbrown on Sept 23, 2016 15:21:02 GMT -5
1/4 wave Dave would probably agree, although he also has a horizontal dipole for skip..... Interestingly enough a dipole supposedly has more gain than a 1/4 wave vertical, but I suspect differences in radiation angles might make real world performance comparisons that favor the 1/4 wave in certain circumstances. Isn't the Starduster basically a 1/4 wave? I know a lot of people that had them and they really liked them.
|
|
Sandbagger
Administrator/The Boss
Posts: 6,247
|
Post by Sandbagger on Sept 23, 2016 18:07:21 GMT -5
1/4 wave Dave would probably agree, although he also has a horizontal dipole for skip..... Interestingly enough a dipole supposedly has more gain than a 1/4 wave vertical, but I suspect differences in radiation angles might make real world performance comparisons that favor the 1/4 wave in certain circumstances. Isn't the Starduster basically a 1/4 wave? I know a lot of people that had them and they really liked them. Yep. As far as I can tell, the Starduster had a 1/4 wave radiator and 3 1/4 wave radials. The only difference between it and a standard 1/4 wave antenna is the radial droop is much steeper on the Starduster. There's no way that configuration should be able to produce the rated 5.0db advertised gain figure. Yes, the people who had them swore by them. They had a broad SWR bandwidth and no coils, so it could take all the power the amps of the day could throw at them. I never had the opportunity to try one, but I suspect that at my location, I would probably have experienced similar results to the Astro Plane that I had, which got blown away by the 5/8th wave GP that replaced it.
|
|
|
Post by MonkeyMan on Sept 24, 2016 11:32:36 GMT -5
|
|
|
Post by thejerk on Sept 24, 2016 17:19:13 GMT -5
Mine had two flat mirror mounts, which made it easier
I also used a short bolt for the counterpoise (short bolt and an antenna lug) and had a coil of coax (about ten wraps of RG8 on the bottom half of a 5 gallon bucket for structure).
Otherwise, pretty simple concept...
|
|
|
Post by thejerk on Sept 24, 2016 17:21:20 GMT -5
Remove the backing plate of that one mount, and flip the other mirror mount in its place. Make it a zee mount, with the pipe in between the halves.
|
|
Sandbagger
Administrator/The Boss
Posts: 6,247
|
Post by Sandbagger on Sept 24, 2016 19:28:13 GMT -5
Need longer bolts for the bracket, and a couple washers and a nut for the counterpoise. Comments, tips, advice? One thing that I noticed is that you can't have the dipole elements electrically connected to the mount/mast, the elements need to be isolated. This isn't hard to do if you keep the plastic washers for both sides of the mirror mounts. But you can't use the type of connector that accepts a PL-259 connector as that is designed to put the center contact of the coax to the whip, and the shield to the mount, which in a mobile installation, will be your ground counterpoise. But this won't work, if you are trying to make a horizontal dipole. What you need to do is connect the center contact of the coax to one element, and the shield to the other element and keep the mount insulated from both whips. Standard spade lug connectors should do the trick. Like this:
|
|
|
Post by MonkeyMan on Sept 25, 2016 9:05:27 GMT -5
Hmm, so I can't use the PL259 and then "hard mount" the counterpoise?
Insulate both whips from the mount, center to one, sheild to the other, correct?
|
|
Sandbagger
Administrator/The Boss
Posts: 6,247
|
Post by Sandbagger on Sept 25, 2016 15:55:42 GMT -5
Hmm, so I can't use the PL259 and then "hard mount" the counterpoise? Insulate both whips from the mount, center to one, sheild to the other, correct? You've got it!
|
|
|
Post by MonkeyMan on Sept 26, 2016 16:57:04 GMT -5
So to keep this "budget friendly" by utilizing what I have on the shelf, I insulated the PL259 ground from contact with the mount, then put a lightening arrestor inline which will connect ground directly to the counterpoise. For that I have a lug type stud mount on order. If this scheme isn't doable I can very easily replace the SO239 stud for the driven element with a bolt and a lug connector.
|
|
Sandbagger
Administrator/The Boss
Posts: 6,247
|
Post by Sandbagger on Sept 26, 2016 18:06:46 GMT -5
So to keep this "budget friendly" by utilizing what I have on the shelf, I insulated the PL259 ground from contact with the mount, then put a lightening arrestor inline which will connect ground directly to the counterpoise. For that I have a lug type stud mount on order. If this scheme isn't doable I can very easily replace the SO239 stud for the driven element with a bolt and a lug connector. A bit Mickey Mouse, but it should work.
|
|
|
Post by MonkeyMan on Sept 26, 2016 18:40:13 GMT -5
M-i-c... 'C' is for cheap
|
|
|
Post by BBB on Sept 29, 2016 12:08:53 GMT -5
This radio should work with that setup then
|
|
|
Post by thejerk on Oct 1, 2016 12:35:15 GMT -5
I will try to take a a picture of mine today...
|
|
|
Post by doctor on Oct 10, 2016 8:22:32 GMT -5
If you want to build a el-cheapo antenna, go to youtube and look up I think it was grasshopper or cricket and he shows how to build a cb antenna using 102 inch whip, I built one and it works good. It is the youtube by cricket, 102 inch whip.. DOCTOR/795 www.youtube.com/watch?v=bolyErI2888
|
|
|
Post by MonkeyMan on Oct 16, 2016 19:11:29 GMT -5
Had a few spare minutes today... Also picked up longer bolts so that it has room to fit on a mast. And I located the short, aluminum mast I've been looking for. It's holding up a section of fence between the shed and building next door.
|
|
Sandbagger
Administrator/The Boss
Posts: 6,247
|
Post by Sandbagger on Oct 17, 2016 11:51:10 GMT -5
Had a few spare minutes today... Also picked up longer bolts so that it has room to fit on a mast. And I located the short, aluminum mast I've been looking for. It's holding up a section of fence between the shed and building next door. That looks like it'll work just fine. Just make sure you keep it away from other objects that can detune it or disrupt the radiation pattern. Up in the clear air at 36' (or more) would be great.
|
|
|
Post by MonkeyMan on Oct 17, 2016 12:58:50 GMT -5
Had a few spare minutes today... Also picked up longer bolts so that it has room to fit on a mast. And I located the short, aluminum mast I've been looking for. It's holding up a section of fence between the shed and building next door. That looks like it'll work just fine. Just make sure you keep it away from other objects that can detune it or disrupt the radiation pattern. Up in the clear air at 36' (or more) would be great. 36', really?! I couldn't even get close to that. Hmm...
|
|
|
Post by BBB on Oct 17, 2016 15:31:01 GMT -5
Unless you use it horizontal, then height is not so much a concern...
|
|