| Author |
Message |
    
Penrider
Member
Username: Penrider
Post Number: 83
Registered: 1-2007
| | Posted on Saturday, April 21, 2007 - 1:10 pm: | 
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using the appropriate math, I built an inverted vee...17ft total length, 8ft6in per leg, feed point at 36ft...swr on my dosy libra is 1.4:1 on channel 20...I tried lowering the feed point, that Raised the swr...raising the feedpoint as much as possible to 41 feet didn't lower it below 1.4:1...adjusting the apex angle had no effect(I don't understand that part)...the angle is now approx 110degrees...should I Shorten/Lengthen the total length like tuning a mobile antenna, or is it something else?
Sean
CEF867
CVC81
"Keep smiling, it makes people wonder what you're up to!!"
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Dale
Advanced Member
Username: Dale
Post Number: 786
Registered: 12-2002
| | Posted on Saturday, April 21, 2007 - 3:11 pm: |
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im not sure about raising or lowering whip
cause ya didnt state what the swrs were on ch.1 and ch.40.check those channels that will tell ya if raising or lowering whip is needed
dale/a.k.a.hotrod
cef426
cvc#64
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Slugo4449
Intermediate Member
Username: Slugo4449
Post Number: 174
Registered: 7-2004
| | Posted on Saturday, April 21, 2007 - 3:18 pm: |
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OK, Channel 20 is 1.4:1
What is your SWR on Channel 40 and Channel 1?
Remember, the higher in frequency you go the shorter the antenna.
If it was me, I would just leave it. 1.4:1 is a good match in my book! If you want to be a perfectionist you may have to change the length of the wire.
73,
Marty |
Marconi
Advanced Member
Username: Marconi
Post Number: 699
Registered: 11-2001
| | Posted on Saturday, April 21, 2007 - 3:34 pm: |
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Try moving up and down in band, check and record what happens with SWR. Then move the antenna up or down like you did before and check it again. You are pretty close to as good as it will get on angle and the match too I think.
For me if you get that one looking much better you are probably just adding losses to the system.
I don't like the newer Dosy meters, maybe your meter is just not being affected by these small changes. You might try adding a little length to one side or the other and see what that does. I think an apex around 90 degrees is what is typicaly found to be best in affecting the SWR in any positive way.
You do not note how much feed point space you have provided either. From your measurements they are very close. That may be OK, but I always allowed at least 3-5 inches. Also try adding a 3' or 6' jumper in line to see if common mode currents are affecting the setup. If they are you might see the SWR reading changing. |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 2095
Registered: 7-2004
| | Posted on Saturday, April 21, 2007 - 5:35 pm: |
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The leg length for your resonant freq will be somewhat longer than that of a straight horz dipole.
Depends on your apex angle and how close your
leg ends are to ground.
Sometime using transmission line thats made a multiple of a half wavelength at the operating freq may help.
Or just leave it alone and enjoy it wheres it's at. Best of luck! |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 2096
Registered: 7-2004
| | Posted on Saturday, April 21, 2007 - 6:19 pm: |
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Check channels 1 and 40, then make the antenna longer or shorter as needed. |
Penrider
Member
Username: Penrider
Post Number: 84
Registered: 1-2007
| | Posted on Saturday, April 21, 2007 - 7:17 pm: |
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Marconi...what do you mean about "feed point space"??, I'm new to wire antennas in general...also, swr was 1.4 on channel 1 and 20, and almost 1.5 on channel 40...I played with the apex angle, went from less than 90degrees to over 120degrees...what puzzled me was that changing the angles had NO effect on swr, it only raised/lowered the noise floor...that's why I left it at approx 110degrees, it was the lowest noise floor.....this was purely an experiment to see if I could accomplish it, my A99 is almost flat and still runs well....if this works, great...if not, I wasted a few feet of 9913 I had laying around
Sean
CEF867
CVC81
"Keep smiling, it makes people wonder what you're up to!!"
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Tech237
Moderator
Username: Tech237
Post Number: 748
Registered: 4-2004
| | Posted on Sunday, April 22, 2007 - 9:00 am: |
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Ok here some pointers for you: -
1) SWR of 1.4:1 is fine any lowering you can make of it will make almost no difference at teh far end.
2) Inverted-V should have an angle that is greater than 90. CHanging the angle does not change the swr but it will change the radiation pattern of the antenna. AT less than 90 you start to have a problem with the radiation in one leg cancelling that from the other leg due to them being 180 degrees out of phase. This is why your noise floor changed.
3) Raising an antenna will change the point of resoance to an extent. Maybe Tech833 can correct em but I seem to recall raising the feedpoint will lower the resonance of an antenna.
Here is an addition to may care to try on your experiment. Add a second inverted V aboue and parallel to your exisitng one. Attach it to the coax feeding the lower by using differing lenghts of coax 1/2 wave, 3/4 wave etc and juts see what it does to the signals. It may amaze you.
Hope this helps a little.
Simon
Tech237
KD7IEB
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Slugo4449
Intermediate Member
Username: Slugo4449
Post Number: 176
Registered: 7-2004
| | Posted on Sunday, April 22, 2007 - 2:04 pm: |
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Boy am I spoiled with an antenna analyzer.
I forgot how much work it is to just use an SWR bridge.
73,
Marty |
Penrider
Member
Username: Penrider
Post Number: 85
Registered: 1-2007
| | Posted on Sunday, April 22, 2007 - 9:52 pm: |
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wow, I thought a wire dipole was a "quickee" antenna...lol...anyways, thanks a lot guys...that's a lot of information I couldn't seem to find when I Googled it to begin with...Simon, I may just try that with two vees stacked, something else to experiment with
Sean
CEF867
CVC81
"Keep smiling, it makes people wonder what you're up to!!"
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Road_warrior
Senior Member
Username: Road_warrior
Post Number: 2097
Registered: 7-2004
| | Posted on Sunday, April 22, 2007 - 10:45 pm: |
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I was running a Horz center-fed dipole for awhile on 11 meters.
I just used a 1.1 Balun on it. |
Twowatt
Member
Username: Twowatt
Post Number: 76
Registered: 7-2005
| | Posted on Wednesday, June 20, 2007 - 8:17 pm: |
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Penrider,
If you still wanna experiment with your inverted V, try this: cut about 12-14" of wire off each end, and attach 2 pcs of tubing on each end - i.e. get 2 pcs of tubing that will fit inside the other 2 pcs, and make each end "Adjustable". (make each one 'adjustable' from about 9" to 17")
This will accomplish at least 2 things - 1) you can Adj. for the SWR/FREQ of your choice, and 2) will make the antenna more broadbanded.
ENJOY
regards |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2559
Registered: 9-2004
| | Posted on Thursday, June 21, 2007 - 12:37 am: |
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with the apex angle at 110*, the antenna will act like a horizontal dipole.
optimum angle for an inverted V is between 90-100*.
i may be mistaken, but i thought that you had to shorten the measurements used for a horizontal dipole when using it as an inverted V.
if i had an SWR of 1.4,i would leave it be, but i certainly understand the desire for perfection.
best of luck,
matt
anyone wanting a "clean signal", just look to the left and build one of these!!!
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Penrider
Intermediate Member
Username: Penrider
Post Number: 161
Registered: 1-2007
| | Posted on Thursday, June 21, 2007 - 1:58 am: |
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well, this was a while ago..have since gotten it down pat I think...may as well post it...
110* was where the lowest noise floor was(about equal to my a-99)...
the original measurements I used were based on
468/mhz then minus 5% for inverted vee...I started with 9ft legs and cut it down to match (then it was 1.4:1 across the band)...
I re-adjusted the apex to closer to 90* (raised the noise floor a lot, but now swr is 1.2:1 across the band...not sure why it changed the swr this time, when it wouldn't change it the first time???)...
I left about 8" of leg hanging past my insulators...Yes, it's adjustable and therefore
more broadbanded(using larger diameter/gauge wire will make it more broadbanded also)...But, it's a little too difficult to adjust when the feed point is 36ft up a tower and the legs are about 8ft from the sides of the tower...
In short...if you've done it before(which I have now), an inverted vee or horizontal wire dipole is a quick, cheap, easy antenna to build...but, if you Haven't done it before, it's kind of a nuisance...especially considering the results...
I can't even begin to actually calculate Gain, but Observed results against an A-99 without the GPK are...
Almost identical receive strength, and slightly Less TX locally(mobile to base with my wife, all she knows is louder or quieter)...
It does the job, and kept me on the air when the a-99 got full of water...but just about Any other antenna that I've tried is better...
Maybe someday I'll try an endfed vertical or sloping longwire
Sean
CEF867
CVC81
Ham252--KE5OZI
(pic is of me and LilBritches-cef899)
"Keep smiling, it makes people wonder what you're up to!!"
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Vanillagorilla
Senior Member
Username: Vanillagorilla
Post Number: 1029
Registered: 4-2005
| | Posted on Sunday, July 01, 2007 - 2:41 pm: |
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Local communication should likely fall short because your likely cross polarized. Your talking on Horiz while the local is likely vertical? Expect that. You probably will not see that much difference in DX conditions Sean.
I built a very simple Double Bazooka Dipole 3 yrs ago and had 10g solidcore soldered to the ends...about 12" worth each. To adjust SWR I simply wrapped the ends over itself in coils which also left me a nice hoop to tie to. Worked well in a Pine tree inverted to 90 degrees with the feed only 20ft up. Super quiet and talked well to 25mi. Never did do any DX with it but was fun learning.
Next I want to try inverted "L" long wire OR Offset dipole for 20m.
Keep playing with it. Its what keeps the hobby alive....although YOU may end up grayer 
Hank~CEF559/CEFHAM242
11mtr Northeast Net Control
Eastern Long Island NY
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Mikefromms
Advanced Member
Username: Mikefromms
Post Number: 997
Registered: 6-2003
| | Posted on Tuesday, July 03, 2007 - 1:28 pm: |
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You'll have fun on ssb.
Mikefromms |
Hyperno_1979
Intermediate Member
Username: Hyperno_1979
Post Number: 382
Registered: 12-2005
| | Posted on Saturday, July 14, 2007 - 3:25 am: |
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You can find them in kit form for $14 on internet auction sites. Apparently they don't even need tuning. I might try one myself....
CEFFFCEF
Bob
CEF703/CVC26
269 Hunter Valley
27.355 lsb.
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Maxgain
Junior Member
Username: Maxgain
Post Number: 37
Registered: 3-2007
| | Posted on Wednesday, September 12, 2007 - 5:37 pm: |
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Why are you wasting your time building an inverted V for 11 meters? It is going to be bi-directional , little if any gain ,non rotatable, and any currently available CB base vertical will easily outperform it.
Inverted V's are better off on the lower HF ham bands. |
Goat373
Intermediate Member
Username: Goat373
Post Number: 354
Registered: 3-2005
| | Posted on Wednesday, September 12, 2007 - 10:08 pm: |
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still thinking of that inverted L aye hank?
Brian
CEF574
KI4LXH
"If it aint broke, dont fix it....and lord dont throw no bricks!"
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Penrider
Intermediate Member
Username: Penrider
Post Number: 207
Registered: 1-2007
| | Posted on Wednesday, September 12, 2007 - 7:23 pm: |
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LOL..if you noticed from all the posts, it was just to see if I could. Obviously I can. Even with it's shortcomings it was still equal to on local and slightly better on DX from my A-99. Plus even considering Labor, with materials it cost less than $20 to build it. It's hanging off my tower below my new 5/8wave ground plane as a spare. It kept me on the air when my a-99 died, and it will do so again I'm sure.
Sean
CEF867
Two tin cans and a string, it's still a contact...BTW, I need my can back when we're done!
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N8fgb
Junior Member
Username: N8fgb
Post Number: 37
Registered: 5-2002
| | Posted on Sunday, September 30, 2007 - 10:41 pm: |
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A horizontal dipole is 72 ohms at the feedpoint,and bidirectional.An inveryed V is close to 50 ohms and is omnidirectionl,which is why some prefer it.Both are balanced antennas,and the feedline is unbalnced coax,which is why a balun helps.Balun -balanced to unbalanced.
Rich |
