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Znut
| | Posted on Saturday, July 27, 2002 - 1:15 pm: | 
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Here is my plan so far:
I have a roll of 3/4" aluminum tubing (fortunate, aye). Using the formula L=1005/f(mhz) it will be 37' before turning it into a loop. I think I should be able to make it round, instead of square or delta shaped. This will allow me to use shorter spreaders, reducing the overall weight. I will simply hang it in a tree and anchor it in whichever direction, probably east-west. It will have a pattern similar to a dipole, broadside in both directions.
My question for the forum is, can you folks help me figure out how to match the impedance (approx. 100 ohms) and unbalance it to feed with coax. I don't want to buy a 2:1 balun or commercial gamma match. I want to build as much of the system as I can myself, except for suggestions from you folks. I'm looking to balance efficiency with cost effectiveness.
Thanks,
Znut |
Znut
| | Posted on Saturday, July 27, 2002 - 7:44 pm: |
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I guess I should ask if anybody is interested in antenna projects. I'm taking this one on because I want a horizontally polarized antenna to talk to a couple of you folks on the flatside. I chose a quad/loop/delta configuration because they have much less static on receive.
Znut |
Deadly Eyes
| | Posted on Saturday, July 27, 2002 - 11:04 pm: |
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Re Z.....
You can drop that aluminum off at my house on ....err err sorry.
Seriously the formula is correct to determine the feet of the loop. As to shape you can use a circle, square or a triangle having sides of equal length. Just try to avoid making it into a skinny long rectangle.
How to feed it is simple. The easiest way is to use a quarter wave matching section of 70 ohm coax. Attach the center of the quarter wave matching section to one end of the loop and the shield to the other end of the loop. The formula for determining the length of a 70 ohm coax matching section is as follows: One wave Length in feet equals 984 times the velocity factor or the coax divided by the frequency in Mhz. Divide the answer you get by 4 and make the matching section this length. You want to make a quarter wave matching section. If the 70 ohm coax used has that hard plastic material to separate the center from the shield then the velocity factor should be .66. If the 70 ohm coax used has that soft spongey material then the velocity factor should be .80.
Use any length of 50 ohm coax and attach the center to the center and the shield to the shield on the other end of the matching section.
The antenna orientates itself per the half opposite the feed point. So if you put the feed point on the vertical side it will be vertical orientated. If you put it on the horizontal side it will be horizontal. If you put the feed point on a corner (of a square shape) it will be half vertical and half horizontal.
One more thing, if you put the antenna in a vertical orientation physically it will transmit out and away. If you put it in a horizontal orientation physically it will be a cloud warmer antenna/shorter range.
The antenna will transmit broadside to the plane of the loop.
I hope I did not confuse you too much.
Signed
Lover of the
loop antenna
DE
The quarter wave |
Znut
| | Posted on Saturday, July 27, 2002 - 11:11 pm: |
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OK, see, my friend Taz has a Moonraker. It operates on Vert/ and Horiz polarity. A dipole or some other horizontally polarized antenna situated just right would allow me to communicate with him (again) as well as some other folks who are also fond of the Copper Forum.
Another objective of this project is to do a little homebrewing. Just too see the results!
I can mix and match different aproaches and through trial and error achieve something. I'd rather use some of you folk's wisdom and get the antenna on the air, especially with your help.
I promise to be honest with all the details and should be able to post some pics.
Call me "just trying to use the forum for the enjoyment of CB radio" but every component of our system is important. I hope homemade equipment can be a part of the discussion here.
Znut |
Znut
| | Posted on Saturday, July 27, 2002 - 11:54 pm: |
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Hey DE,
I am counting on standing the loop up and feeding it from the bottom (horizontal feed).
I appreciate you participating here!
I considered a 'Q' section as you have mentioned. I like the simplicity but despise the bandwidth. It would work great though to talk to Taz on Ch. 17 and maybe a few channels either way.
Awsome! I may use a section of 75 ohm coax for the 'Q' section, slightly longer just to try her out.
COOL!
Thanks,
Znut |
Taz
| | Posted on Sunday, July 28, 2002 - 7:32 pm: |
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bruce
| | Posted on Sunday, July 28, 2002 - 9:33 pm: |
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neat i wonder if it might work on 6? |
Marconi
| | Posted on Monday, July 29, 2002 - 12:27 am: |
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Hey Znut, why not try to feed your loop direct feed. You may find the match is not as bad as you might think. Depending on the nature of the source information on the impedance, the 3/4" tubing could help lower the impedance somewhat anyway. In fact you could probably tune the impedance down a little by adjusting the length a bit. Chances are you will find this thing resonant at a bit shorter than you might think. If the match is bad, you could always use the 1/4 transformer noted already. If the transformer reduces the impedance to from 100 ohms to 50 ohms, I would not worry about the bandwidth, you should be better off if you tune the antenna to resonance where you want it.
If you have a need to tune some, making adjustments to the length, think about it a little. You should be able to figure out how to make those adjustments very easily using a little smaller or larger tubing and hose clamps.
Balancing the feed may make for a tighter figure 8 pattern than it would otherwise be, but that may not be a problem with the round shape anyway.
Keep us posted on your progress
Marconi |
Znut
| | Posted on Monday, July 29, 2002 - 10:14 pm: |
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Well,
Where do I begin?
OK, I goofed, the tubing which I was told was 3/4" aluminum tubing is actually 1/2" 75ohm(I think) hardline. Coax! I was surprised when I retrieved it from storage.
I cut 37 feet of it and formed it into sort of a loop around a pine limb. I fed it with rg 58 coax with about 6' of it wound into a 9 turn coil at the feedpoint.
Check this out: 1.5:1 (1 megahertz bandwith, CH. 20 being the center!) Excellent receive, but NO contacts yet. However, it is situated east - west and most of the activity is around the Great Lakes. I'm in middle Georgia.
Well, I'll wait for Taz to contact me on flatside channel 17. Unless somebody wants to try.
I think I need to put the spreaders on and match it for it to work really well.
Any signal reports?
Znut |
Znut
| | Posted on Monday, July 29, 2002 - 10:20 pm: |
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By the way Marconi, you and DE both suggested trying it out. I got farther doing just that than looking for the magic bullet. Now I am even more encouraged and I will figure out how to match the impedance.
Thanks!
Znut |
DE
| | Posted on Monday, July 29, 2002 - 10:41 pm: |
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Re Bruce....
If you are going to make an antenna for 6 meters why not try a Quagi (SP?).
For those who do not know this antenna is a beam antenna that has a quad reflector a quad driver section and all yagi directors.
The advantage is that the quagi has more gain over that of a yagi of the same size. Or at least that is what the books say. |
Znut
| | Posted on Monday, July 29, 2002 - 10:42 pm: |
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OK,
I just talked to a fellow in Illinois, near ST Louis, barefoot on 37 LSB on my 2510.
This is going to be a GREAT antenna! I can't wait to perfect it!
Znut |
Marconi
| | Posted on Tuesday, July 30, 2002 - 12:35 pm: |
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Znut, you indicate the loop is hardline and that it may be 75 ohm coax. That fact has nothing to do with your matching issue. In this case the coax is simply acting like a conductive radiator.
If you have a 1.5:1 SWR and the loop shows some bandwidth, then that should be good enough.
You may find tying the shields and the center conductor together on each leg individually, will give you a larger radiator crossection and that should lower the impedance match a bit closer to 50 ohms also. Making the radiator thicker should also require you to make the loop a bit shorter as well, in order to remain resonant at the frequency of choice.
Marconi |
bruce
| | Posted on Tuesday, July 30, 2002 - 12:40 pm: |
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DE correct no doubt a " quagi" is a good antenna but im intrested in seeing how he does with this loop I used and love a simple SQUALO its too bad they are not made anymore. |
707
| | Posted on Tuesday, July 30, 2002 - 5:37 pm: |
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znut-
are we gonna get some pics of this thing??? |
Znut
| | Posted on Tuesday, July 30, 2002 - 5:45 pm: |
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I didn't think it would Marconi. I found a 1.5:1 balun at AES for under $20, but for now I'm going to hang out. I just have it looped around a branch to see how it works and if I really want to fool with it. I need to try to make some more contacts (hint). If Taz used his Y messenger he and I could coordinate since we already have had contact before and have something to compare notes with. I am considering building a closed loop about 5% larger and mounting it on a boom behind this loop, about 6'. Viola! A 2 element (round) quad.
Bruce, my loop is a full wave hanging vertically. A squalo is basically a half wave dipole formed into a circle, triangle, or square. I would love to get a stacked pair or four for my 6 meters! Horizontal polarity and omni directional with gain! Great for the Sideband and slowscan TV nets!
I'll be back,
Znut |
Znut
| | Posted on Tuesday, July 30, 2002 - 6:18 pm: |
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Yes 707, my buddy says he'll bring his digital camera by as the antenna takes shape. Right now it is in a crude phase. See previous posts. If it rains now, which it is about to, I won't be using it at all any more today because it is a bare metal loop hanging in a branch against the tree and may short and detune. Hopefully this storm's bark is worse than it's bite. No pun intended (well, maybe).
By the way 707, are you anywhere west of me. Say about 500 - 1000 miles? I'm in middle GA. (hint) If you have yahoo messenger here's my email. ejd682001@yahoo.com
Znut |
Taz
| | Posted on Tuesday, July 30, 2002 - 6:20 pm: |
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heh, i do use it znut!
Just i use a different name _obi_wan_ |
707
| | Posted on Wednesday, July 31, 2002 - 10:43 pm: |
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Znut- yes, I'd say we could probably do it, based on skip the past few days. It seems to be coming from your neck of the woods. I would be interested to see how it would go between your loop and my inverted L.
Thru Friday, I'll have the radio on in the morning between 7a and 9a CST, then after 6p on 27.385 lsb. Let me know if you want to use a different channel ;-) |
Taz
| | Posted on Thursday, August 01, 2002 - 2:21 am: |
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38, lsb. I wouldnt mind trying to make the contact myself. |
Phineas
| | Posted on Friday, August 02, 2002 - 6:31 pm: |
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Bruce
I use a home brew horizontal loop on 6. Works quite nicely on ssb.
Phineas |
bruce
| | Posted on Saturday, August 03, 2002 - 12:20 pm: |
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I ran for 20 years 4 stacked squailos great omidirectinal antenna too bad they are not made anymore.... they even made one for 10-11 meters and 2 and 44o but the 6 meters ones stack worked as well as a small beam. |
Znut
| | Posted on Monday, August 05, 2002 - 5:52 pm: |
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I talked to 707 on this thing, middle GA to south TX.
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Znut
| | Posted on Monday, August 05, 2002 - 6:02 pm: |
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Talked from middle GA to southern TX with 707 on this thing.
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Znut
| | Posted on Monday, August 05, 2002 - 6:05 pm: |
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Taz
| | Posted on Tuesday, August 06, 2002 - 8:21 am: |
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looks like a nice size loop |
707
| | Posted on Tuesday, August 06, 2002 - 12:14 pm: |
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Not bad for a couple of homebrew antennas. Loop to Inv L., and neither one over 8-9 ft. up. Znut was doing about S8-9 on a peak, with tons of QRN and bumpy conditions. |
Znut
| | Posted on Thursday, August 08, 2002 - 6:06 pm: |
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I have decided to use a balun to match my new antenna. I hope to build a frame and get a pole this weekend but it looks a little "iffy" due to overtime for work.
I'm pretty sure I am going to build a reflector and make a beam. Do you folks think 1 1/4 inch PVC will be ok for a frame? The boom will only be about 6 feet long. The spreaders will be about 12 ft. (the diameter of the loops).
I received the parts for the balun today, but will not begin to make it until I get the antenna up and get my pal to bring his antenna analyzer over so I can tune the antenna and determine the impedance of it so I can wind the transformer to match the ant. to coax. Remember, I said I won't buy a balun? I didn't say I wouldn't buy the stuff to make one. I read from a couple sources that the antenna's pattern is affected by the feedpoint so I wanted to make sure I balanced the feedpiont.
'Nuff for now.
Znut |
Znut
| | Posted on Friday, August 09, 2002 - 8:17 pm: |
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Ok, I need some help.
So far I have learned how to make a 4:1 and 1:1 balun. I also know the theory behind a choke type balun. However, I am a only beginning to learn.
I know this, the ratio of impedance (ie. 2:1) is the square of the ratio of turns on the transformer/choke (1.4:1).
I am trying to figure out how to wind and tap a 2:1 balun. Not just a transformer, needs to be 50 ohms unbalanced(coax) to approximately 100 ohms(balanced), a balun.
Would somebody point me in the right direction with this? I appreciate the help.
I have already used you folks' advice with impressive results.
I love this forum!
Znut |
Znut
| | Posted on Wednesday, September 11, 2002 - 10:44 pm: |
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OK,
I'm makin' a beam. A 2 element quad. I'll have pics soon.
I'll also want some radio checks.
Wish me luck with my project.
Znut |
Deadly Eyes
| | Posted on Thursday, September 12, 2002 - 12:07 am: |
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Re Z
Rather than use a balun try the following common method of feeding a loop antenna, a quarter wave matching section of 70 ohm coax.
Using the following math cut a piece of 70 ohm coax...
Length in feet = (984 x velosity factor) divided by the frequency (used to make the loop) in mhz. The velosity factor is .6 if the insulation on the 70 ohm coax is the hard plastic type and .8 if the insulation is the soft foam type.
Add a couple of inches to the calucated length and make pigtales on both ends of the 70 ohm matching section.
Attach the center conductor of the 70 ohm coax to one end of the loop and attach the shield to the other side of the loop.
Attach a piece of 50 ohm coax (any length) to the other end of the 70 ohm matching section--shield to shield, center conductor to center conductor.
This will bring the SWR for the design frequency down to 1.5 or lower over a large range of frequencies.
For 70 ohm matching section you can even use discarded cable TV coax. BUT if you do, you will find, as I did, that when you wrap aluminum and copper together and apply signal you cook up corosion. But in a pinch it will do just fine.
Item 2, size of reflector/director...
The reflector shoud be 5% longer than the loaded section. The director should be 5% shorter than the loaded section.
Later
DE |
Znut
| | Posted on Thursday, September 12, 2002 - 10:13 am: |
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Thanks DE,
I may try that with the a 1:1 balun. See, the ant is balanced and I need to unbalance it to match with coax. I could wrap 6 feet of coax for a choke right at the antenna instead but I already have the materials for the choke type balun so I might as well utilize them.
Roger on the element lengths. Already cut. I'm assembling the frame now with 1 1/2" PVC. The spacing is going to be 78" between elements (boom length).
Take Care,
Znut |
Znut
| | Posted on Thursday, September 12, 2002 - 10:42 pm: |
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Moderator(s):
Should I begin a new thread, since this project evolved into a beam?
Thanks,
Znut
Forummaster Note : You may if you like but it isn't absolutely necessary. If you think that someone might be more inclined to read it now or later if it was under a different subject header then create a new subject. |
bruce
| | Posted on Friday, September 13, 2002 - 12:21 pm: |
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Hey ZNUT hear's your next project but make it for CB ! And yes you can stack them!
http://www.ssbusa.com/wimowheel.html
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Znut
| | Posted on Friday, September 13, 2002 - 7:21 pm: |
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Thank you,
I appreciate the advice and the cheers from you folks. With an antenna with some gain I'll be talking to some of you soon, I've already talked to 2 on the forum (Taz and 707). That is the main goal of this project.
I was influenced to go flatside for many reasons but my decision was catalyzed the last time I talked to Taz on the air. I was talking to him with an a-99 and he with the moonraker. Our best results were with his beam on the horiz polarity. I'm sure that maybe his ant. was better tuned on the flat, that is natural because of the detuning of the vertical by the tower/mast.
Okay, I decided to make some sort of SIMPLE antenna with some sort of directional characteristics. First I was gonna try a dipole. A fellow ham (please, no blasting about the ham part) mentioned a loop (square, delta or round) because they are very unsusceptible to terrestrial (manmade and ground) noise. It worked and has less static than I could have imagined. I made a short contact with 707 with it and was encouraged. He has an inverted L and my loop is 8 feet off the ground. So I decided to complicate things a little and make a beam and I am walking a fine line between a simple beam and one with more contraptions than the space station. You know, I want a 1:1 swr and the optimum pattern and front to back ratio of a 4 element beam.
Keep after me to have a realistic perspective Marconi! Thanks.
The frame is almost done. I was hoping to complete it this weekend but that tropical storm thing is making it rain here in GA. When it is complete I'll have some photos. Within a week or so of finishing the frame you guys should HEAR me on the finished antenna, hopefully.
Znut |
Znut
| | Posted on Monday, September 16, 2002 - 7:01 pm: |
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Oh man!
The spreaders are assembled for each element. My drill battery has seen better days and won't drill through thin wall PVC. Gonna try right after it charges again and see how many holes I can get done. Then we can fit the elements, put them on the boom and put it in/on the air.
The 1/2" holes are actually for the elements, just thread it through and it'll be nice and secure.
Znut |
Znut
| | Posted on Thursday, September 19, 2002 - 9:28 pm: |
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The elements are mounted on the spreaders.
The antenna is about the same size as a PDL II.
I hope to talk to some of you on it Saturday or Sunday night.
I'm starting with the ant. cut long and fed directly with coax, wound into a choke.
I still have to glue the boom part of the PVC and raise it. I'm surprised how light and sturdy the whole thing is.
Znut |
Znut
| | Posted on Saturday, September 21, 2002 - 9:13 pm: |
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I just talked to Taz.
I wanna talk some more DX.
I have to talk on lower channels until I tune the antenna some more.
Znut |
707
| | Posted on Wednesday, September 25, 2002 - 5:36 pm: |
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I'll be listening for you this weekend, Sat and Sun or hook up with me online then and we'll coordinate from there. Also... Where's the PICS man??? We gotta have antenna project pics.
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Taz
| | Posted on Wednesday, September 25, 2002 - 8:42 pm: |
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How did you get that photo of my house? |
Tech833
| | Posted on Thursday, September 26, 2002 - 10:21 am: |
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That is a shortwave station, I have been there. The curtain arrays look really neat in that photo! Although, it makes the arrays looks much closer than they really are. That site is on several acres of land. I'm not sure if the exact location is public or not. I can ask and if so, I will share the location with you if you are interested. It is in the U.S. |
Taz
| | Posted on Thursday, September 26, 2002 - 9:02 pm: |
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Well then you can say you have been to my house then. You must have been the guy driving the pacer with the rat shack radio?
There are major size stations in texas and oklahoma |
Taz
| | Posted on Thursday, September 26, 2002 - 9:03 pm: |
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hehe what do all those antennas do?? how tall are the towers?
and most of all where does he work? |
Znut
| | Posted on Thursday, September 26, 2002 - 10:24 pm: |
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Uh, I would say he's broadcasting. Literally. |
Tech833
| | Posted on Thursday, September 26, 2002 - 10:51 pm: |
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If you mean 'he' to mean V.O.A., then 'he' works for the United States Government.
Like I said, that is a shortwave station transmitter site. If I recall, it operates several transmitters on varied frequencies from 2.5 to around 15 MHz. Bandswitching takes only a couple of minutes.
Those are curtain arrays. The towers are around 250 or 300 feet AGL (I do not recall the exact height). |
707
| | Posted on Friday, September 27, 2002 - 2:40 pm: |
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Ok, fine...I give. The picture is WVHA, Scotts Corners(near near Greenbush, 20m NE of Bangor, ME) at 68.34W/45.09N
It is not VOA, but at last count, operated by either World Harvest or the Adventists. |
Tech833
| | Posted on Saturday, September 28, 2002 - 11:39 am: |
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Yes, you are correct. It is the Adventists. My error. |
Znut
| | Posted on Wednesday, October 02, 2002 - 7:05 pm: |
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Here are the basic mechanical specs.
The elements are made of 1/2 inch 75ohm aluminum hardline, the type you see attatched to the overhead powerlines to carry cable TV signals. The spreaders that hold the elements are made of 1 1/2" O.D. thin wall PVC. The boom is made of 1 1/2" high pressure (thicker wall) PVC.
The driven element, the one with the coax hooked to it is 35 feet 7 inches. It is capable of about 1 1/2 feet of adjustment but right now it is tuned as high as I can tune it without trimming the loop part. I have it fed at the bottom so it is horizontally polarized (flatside). I wound 9 turns, about 6 or 7 feet of coax into a choke right at the feedpoint to prevent the RF from radiating from the coax itself.
The reflector is 37 feet 4 inches. It is capable of about 3 feet of adjustment.
The boom is 6 feet 6 inches long.
The height is almost 21 feet to the boom. However, the bottom of the elements are only about 8 feet from the roof of my home with metal siding and metal roof. I don't think that is detuning the antenna too much though.
I have about a 1.2 to 1 SWR on channel 20. I don't know for sure if that is where the antenna is most resonant/efficient. It has nice bandwidth. SWR is under 2:1 from 26.45 to 27.65!
I will make a balun when I can get an analyzer on it and tune it more precisely and determine the exact impedance at resonance. I think this will improve the radiation pattern.
I don't really have any info about the gain or pattern other than the fact that it is directional. All of my results are based on DX. I have had some stations come in 5 or more s-units over my A-99. HR 2510's don't have a very nice s-meter. Yes, I do have a switch to do side by side conparison. When I find a local station with a horizontally polarized antenna I may be able to get an idea of what the radiation pattern looks like.
Overall I am very happy with the results. I used it this past Saturday during the DX-A-THON so there are 3 of you who have heard it on the air. 2 during the event Saturday and one other from a contact the week before, see related threads for details.
As promised, here are pictures.
Znut
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Znut
| | Posted on Wednesday, October 02, 2002 - 9:32 pm: |
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BTW,
50k is low res!
Znut |
Taz
| | Posted on Wednesday, October 02, 2002 - 9:52 pm: |
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almost looks like a pdl-2 |
Znut
| | Posted on Wednesday, October 02, 2002 - 11:00 pm: |
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I can email slightly better pics if anybody wants.
Znut |
Znut
| | Posted on Thursday, October 03, 2002 - 11:05 pm: |
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Here are the basic mechanical specs.
The elements are made of 1/2 inch 75ohm aluminum hardline, the type you see attatched to the overhead powerlines to carry cable TV signals. The spreaders that hold the elements are made of 1 1/2" O.D. thin wall PVC. The boom is made of 1 1/2" high pressure (thicker wall) PVC.
The driven element, the one with the coax hooked to it is 35 feet 7 inches. It is capable of about 1 1/2 feet of adjustment but right now it is tuned as high as I can tune it without trimming the loop part. I have it fed at the bottom so it is horizontally polarized (flatside). I wound 9 turns, about 6 or 7 feet of coax into a choke right at the feedpoint to prevent the RF from radiating from the coax itself.
The reflector is 37 feet 4 inches. It is capable of about 3 feet of adjustment.
The boom is 6 feet 6 inches long.
The height is almost 21 feet to the boom. However, the bottom of the elements are only about 8 feet from the roof of my home with metal siding and metal roof. I don't think that is detuning the antenna too much though.
I have about a 1.2 to 1 SWR on channel 20. I don't know for sure if that is where the antenna is most resonant/efficient. It has nice bandwidth. SWR is under 2:1 from 26.45 to 27.65!
I will make a balun when I can get an analyzer on it and tune it more precisely and determine the exact impedance at resonance. I think this will improve the radiation pattern.
I don't really have any info about the gain or pattern other than the fact that it is directional. All of my results are based on DX. I have had some stations come in 5 or more s-units over my A-99. HR 2510's don't have a very nice s-meter. Yes, I do have a switch to do side by side conparison. When I find a local station with a horizontally polarized antenna I may be able to get an idea of what the radiation pattern looks like.
Overall I am very happy with the results. I used it this past Saturday during the DX-A-THON so there are 3 of you who have heard it on the air. 2 during the event Saturday and one other from a contact the week before, see related threads for details.
Scroll up the thread for some pictures.
Znut |
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