| Author |
Message |
    
Bob_p
Advanced Member
Username: Bob_p
Post Number: 560
Registered: 7-2004
| | Posted on Friday, December 10, 2004 - 3:20 am: | 
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Tech 833 thanks for helping earlier with my Questions on the I-Max. But I was just wondering if you would explain how the I-Max can cover 10 through 17 meters with a usable SWR?
I use the antenna tuner on all bands anyway just to feel safe I guess. But it seems really strange to me that the antenna can cover so much band width with that type of SWR. Am I getting false readings or something?
Thanks in advance
Bob
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Tech833
Moderator
Username: Tech833
Post Number: 911
Registered: 8-2002
| | Posted on Thursday, December 16, 2004 - 5:32 pm: |
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Hi Bob.
Well, it really isn't magic or voodoo. It is a simple unbalanced network feeding an unbalanced radiator. As input departs from resonant frequency, any reactance or resistance fluctuation is absorbed by network losses before it begins to really show on the feedpoint match. That doesn't mean it all turns to heat exactly. It means that much of the reactive component can be absorbed by other network characteristics much in the same way using large diameter material for mobile antenna coils can increase bandwidth by presenting different lengths from feedpoint to tip of whip through the coil. This is because the physical measurement of traveling the inside of the coil compared to outside are much different in length. With enough series inductance and capacitance cancelling each other out, signal losses will increase slower than matching losses. |
Bob_p
Advanced Member
Username: Bob_p
Post Number: 580
Registered: 7-2004
| | Posted on Thursday, December 16, 2004 - 6:06 pm: |
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Thanks Paul, I hate to keep asking questions about the I-Max, but I do have another one.
If the I-Max is a .64ths wave on 11 meter's How does it peroform as far a wave length on
10
12
15
17
and
20 meters?
Thank you very much in advance
Bob
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Tech833
Moderator
Username: Tech833
Post Number: 915
Registered: 8-2002
| | Posted on Friday, December 17, 2004 - 1:15 pm: |
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My pleasure, Bob.
As the frequency goes lower, it acts like a .625 (5/8 wave) and eventually a .500 (1/2 wave) until it is nnothing more than a mismatched .250 (1/4 wave) as you approach 20 meters. That really does not mean anything since you are just using it to be able to put some signal on the air on those other bands. No matter what, it is better than a dummy load! |
Bob_p
Advanced Member
Username: Bob_p
Post Number: 585
Registered: 7-2004
| | Posted on Friday, December 17, 2004 - 10:53 pm: |
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Thanks Paul That's pretty much what I was thinking, but appreciate the time and knowledge of a pro.
I guess that's why i've had such great reports on 10 meter's.
I've done pretty well on 17 meter's, making contacts from way down in South AMerica to Australia and Japan. Plus 17 meters has less noise than 15 or 20 meters. But really haven't done that well on 20 meters. So I guess a G5RV would be a decent improvement on 20 meters if not 17 meters as well.
Thanks again
Bob |
ClassA Guy (Unregistered Guest)
Unregistered guest
| | Posted on Monday, December 20, 2004 - 3:53 am: |
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Hello Paul,
I'm wondering about the lack of ground radials on the IMAX and the resulting typically higher radiation angle.
It seems to me that adding radials would provide a lower radiation angle from the IMAX, and that would be a good thing IF one were to desire to talk local, or 'ground wave'.
However, is the idea behind this antenna to be a higher gain 'skip' talking antenna with superior gain when compared to the Antron99, but with a similar high angle of radiation for the purpose of providing better DXing?
In comparing the two I've seen right about 2 'S' units gain on both
I am planning to purchase an IMAX to replace my good old HyGain Penetrator500 (which I've even beefed up to all 6061-T6) but I'm tired of the rain noise and the build-up of aluminum oxide at the junction points.
My plan is to add 1/2 wave radials which I'll make from the guy wires, adding insulators at the 1/2 wave point and which I'm expecting will provide better 50-150 mile performance- the type of QSLing I find much more challenging on 11 meters than simple ionishperical bounce, or 'skip'.
I would enjoy hearing from you with regard to whether or not you believe I'm taking the right tac in an attempt help this already cool antenna to perform even better?
BTW, I'm not hip on the commercially available ground radial kit as it only offers 1/8 wave length radials and I've read articles where differing lengths of radials were tested and 1/2 wave provided the best overall performance in the form of the highest gain, lowest angle of radiation, and closest to 50 ohm impedance at the feed point.
...and how do I get REGISTERED user status?
Thank you, C.G. |
Tech808
Moderator
Username: Tech808
Post Number: 4339
Registered: 8-2002
| | Posted on Monday, December 20, 2004 - 6:34 am: |
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CLassA_Guy,
It Very Easy to become a Registered Copper Forum Member.
Look at the Top Left hand corner of the forum here and you will see:
Forum Membership
Register
Forum Rules
All you have to do is CLICK on Register and fill out the Information.
You will then be sent an e-mail with a link in it that you will need to click on to activate your new acct.
Hope this helps,
Lon
Tech808
CEF808
N9OSN
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Tech833
Moderator
Username: Tech833
Post Number: 917
Registered: 8-2002
| | Posted on Monday, December 20, 2004 - 11:20 am: |
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I will take one point at a time.
"It seems to me that adding radials would provide a lower radiation angle from the IMAX, and that would be a good thing IF one were to desire to talk local, or 'ground wave'. "
Since this is a CB forum, and the Imax is marketed as a CB antenna, and CB is limited to 150 miles transmission (by FCC rule), then my comments regarding ground planes has been directed toward that user base. Not only will a lower takeoff angle help ground wave coverage, it will also help with distance sky wave.
"However, is the idea behind this antenna to be a higher gain 'skip' talking antenna with superior gain when compared to the Antron99, but with a similar high angle of radiation for the purpose of providing better DXing? "
No. It is designed to be a higher performance antenna than the A99 all-around, but still retain the simplicity of installation like the A99.
"I'm not hip on the commercially available ground radial kit as it only offers 1/8 wave length radials and I've read articles where differing lengths of radials were tested and 1/2 wave provided the best overall performance in the form of the highest gain, lowest angle of radiation, and closest to 50 ohm impedance at the feed point. "
1/2 wave ground radials will not make a bit of difference over 1/4 wave radials ina counterpoise installation like this. If you were to bury the ground radials (as in a ground mounted, base fed vertical) then your statement would be correct. Do not get hung up on ground radial length on an antenna with a matching network like the Imax. It will make zero difference. In a 1/4 ground plane without a ground tap, it makes a slight (SLIGHT!) difference in base impedance. The same impedance change could be made by using 1/4 wave radials and adding more radials to equal the same total length of wire used in fewer 1/2 wave radials. |
Gonzo
Intermediate Member
Username: Gonzo
Post Number: 144
Registered: 9-2004
| | Posted on Monday, December 20, 2004 - 3:22 pm: |
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ClassA Guy :"I am planning to purchase an IMAX to replace my good old HyGain Penetrator500"
I like the Imax2000 and have both of those antennas. However The IMAX has MORE noise than the Hygain, not less. It will put out about almost the same,at least not a very noticeable difference. The Hygain out-hears the IMAX, due to lower noise. I would clean the Hygain.
----------------------------------------------
If you do but an Imax:
The IMAX is not designed the same as the Hygain aluminum antenna, and therefore as tech883 said putting ground radials on it (unless the antenna is really low) will NOT make any difference. Aluminum ground planes like the Hygain...need a ground counter-poise to work correctly and lower the angle of radiation. The Imax radiates differently and does not need the radials, since the lower half of the antenna is the ground.
----------------------------------------------
tech883 is also correct in stating 1/4 wave ground radials will work just as good as 1/2 wave ground radials. But in your case with the IMAX leave them off.
-------------------------------------------
Lastly the IMAX2000 is VASTLY superior to the A99. But expecting to change from an Hygain Penetrator to an Imax200 and expecting to have a large difference in local ground wave communication is just not gonna happen. |
ClassA Guy (Unregistered Guest)
Unregistered guest
| | Posted on Tuesday, December 21, 2004 - 3:31 pm: |
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Thanks for the replies, I found this:
http://mars.comportco.com/~w5alt/antennas/ant-radials.html
about radials. Cool test, but I'm not sure what the difference might be when using a .625/.64 length antenna, as the article is a test using a .25 or 1/4 wave.
No "Register" or
"Forum Rules" viewable in my browser window...??? http://www.copperelectronics.com/discus4/messages/29/76128.html?1103342029 |
Tech808
Moderator
Username: Tech808
Post Number: 4349
Registered: 8-2002
| | Posted on Tuesday, December 21, 2004 - 6:28 pm: |
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ClassA_Guy,
As soon as you get on the Copper Forum BEFORE you click on anything you will see on the Left Hand Side:
Forum Membership
Register
Forum Rules
Discussion
Topics
Last 3 Hours
Last Day
Last Week
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Getting Started
Formatting
Troubleshooting
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Search
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User List
Users Online
Edit Profile
CEF Net
Membership List
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CB & Ham Lingo
Modification List
Links
Copper Main Page
All you have to do is CLICK on Register and sign up.
Then you wil receive an e-mail with a link in it you will need to click on to activate your account.
What SERVER are you Using?
Hope this Helps,
Lon
Tech808
CEF808
N9OSN
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ClassA Guy (Unregistered Guest)
Unregistered guest
| | Posted on Tuesday, December 21, 2004 - 6:50 pm: |
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...Found it.
I found this forum through a search on Google and I had to remove all but http://www.copperelectronics.com in order to start over and find the right hand menu you were referring to.
I think you should add a 'HOME' selection to these forum pages so others could be automatically taken there in the future, as this might help eliminate some confusion.
Thank you,
C.G. |
Bob_p
Advanced Member
Username: Bob_p
Post Number: 606
Registered: 7-2004
| | Posted on Monday, December 27, 2004 - 2:30 am: |
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Tech 833
Hi Paul, about the radials in your review you say they will reduce noise. I am using the I-Max as you know on my new HF rig, and it's pretty quite on 10 and 12 without the radials, but on 15,17 and 20 the noise goes up to an irratating level on 20 meters. I was wondering if the radials would help reduce the noise on those bands?
By the way the way I ended up grounding the I-Max was to use a #10 solid copper wire and ran it from the base of the antenna to a water spigot in the back yard,( from the spigot to the main is about 60 feet) and then I took two 12 foot #14 solid copper wires and ran them away from the ground opposed from each other, and burried them about 3"'s under ground facing east/west long ways. I don't know if it will help, but figured it couldn't hurt.
Thank you in advance, and hope you and your had a wonderful Christmas.
73
Bob |
Tech833
Moderator
Username: Tech833
Post Number: 921
Registered: 8-2002
| | Posted on Monday, December 27, 2004 - 11:47 pm: |
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Bob,
On 20m, the Imax GPK will make no difference. Your ground scheme sounds great! |
Bob_p
Advanced Member
Username: Bob_p
Post Number: 613
Registered: 7-2004
| | Posted on Tuesday, December 28, 2004 - 1:16 am: |
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Thanks Paul, I already have the GPK, but don't have anyone to climb up and on the second story to install it. I thought about hiring someone to do it for me if the thing would drop the noise level on 20 meters. But I guess with all the filtering the radio has, the antenna is really quite on 10 and 12 anyway.
Thanks for letting me know what’s up, and I am very glad to hear the ground is doing what I had hoped. I spent most of the day today adding another wire to it, so it now has three 12-foot radials coming off of the spigot. I was told the more the merrier, so I had to go into the neighbors yard for the third wire, up here there are no lawns, just pine needles and rocks! When I finished I noticed a slight change in the SWR, but nothing very obvious.
Again thank you very much and I hope you and yours have a happy and prosperous New Year
Bob
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Tech833
Moderator
Username: Tech833
Post Number: 926
Registered: 8-2002
| | Posted on Tuesday, December 28, 2004 - 4:59 pm: |
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Glad to help.
My ground system consists of somewhere between 20 and 40 buried copper wires (I forget) of various lengths, some around 300 feet long. They leave the base of the tower at all angles and are distributed sorta equally. Where the wires intersect the foundation of the house and the equipment building, they are soldered to large diameter copper wires around the foundation. The ground wires are bonded to the wire mesh in the foundation under my wife's playhouse.
My noise floor is unmeasureable. My gear only goes down to -120 dB/m. I do hear grunge around the 80m band but not near as much as some of the people I talk to. |
Bob_p
Advanced Member
Username: Bob_p
Post Number: 617
Registered: 7-2004
| | Posted on Tuesday, December 28, 2004 - 10:35 pm: |
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Tech 833
Hi Paul and thanks for the advice.
I wish I could get the antenna that quite. I'll bury some more wires at the connection point where the antenna meets the water pipe. On 10 and 12 meters where the antenna is really designed to work it really is quite, so I need to make the investment into a good antenna. I've been looking at the Gap Eagle DX, and a few others. But I would like to get a cheap wire up except the size and orientation of my lot makes a wire pretty much a bust. The lot is only 25X100 with the narrow side facing east and west. So unless I figure out how a vertical wire works, I’m stuck buying an expensice muti-band vertical.
Anyway thank you very much for the compliment on the grounding, I will add more wires to the ground ASAP. Oh by the way is 3 inches or so deep enough for the ground wires?
Thanks again
Bob
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Tech833
Moderator
Username: Tech833
Post Number: 927
Registered: 8-2002
| | Posted on Wednesday, December 29, 2004 - 6:03 pm: |
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3 inches is not really deep enough. Try 6 to 12 inches. For AM broadcast installations, we aim for 18 to 24 inches.
If your lot narrow dimention faces E and W, then a center fed dipole is exactly what you need! If I misunderstand you, where a dipole across the length would be pointing the wrong way, why not try a sloper? With a good ground system, slopers have a nice low angle of radiation and are slightly directional whichever way the wire points (off the end!). That might be just what you need. Alpha Delta makes a multi-band sloper. If you want max performance on 10/11 meters, your could trim the 30m wire for 10m and it will work well. |
Bob_p
Advanced Member
Username: Bob_p
Post Number: 621
Registered: 7-2004
| | Posted on Wednesday, December 29, 2004 - 7:04 pm: |
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Thanks Paul, I will be using the I-Max for 10, and 12,meters. I hate to say it, but I haven't used 11 meters since I bought the Kenwood.
Will the water spigot work for a ground on the Sloper? I understand you said the ground scheme sounded great for the I-Max but just want to be sire it will do the trick for a sloper.
Thanks as always
Bob
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Tech291
Moderator
Username: Tech291
Post Number: 24
Registered: 11-2004
| | Posted on Wednesday, December 29, 2004 - 9:45 pm: |
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Bob,
Maybe this site will give you some food for thought.
http://mars.comportco.com/~w5alt/antennas/notes/ant-notes.php?pg=1
tech291
CEF#291
kc8zpj |
Bob_p
Advanced Member
Username: Bob_p
Post Number: 622
Registered: 7-2004
| | Posted on Thursday, December 30, 2004 - 12:26 am: |
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Tech291 thanks I read some of the information at the site and it was interesting. I get the impression that with the ground I have I should be fine.
I have another question though.
If I were to use a G5RVjr. (51 feet long, 25.5 feet each leg) set up as an inverted V, would 25 feet apart at the base be usable?
I know it's a pretty steep V but it's an option that would give me the east west orientation I need.
Thanks in advance
Bob
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Tech833
Moderator
Username: Tech833
Post Number: 929
Registered: 8-2002
| | Posted on Thursday, December 30, 2004 - 2:22 pm: |
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It will work O.K. Not great, just O.K. A sloper would work better in that case. |
Bob_p
Advanced Member
Username: Bob_p
Post Number: 624
Registered: 7-2004
| | Posted on Thursday, December 30, 2004 - 4:18 pm: |
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Tech 833
Thanks Paul.
That's great, I can easily point the Sloper east and have it terminate into the water pipe. I was hoping the G5RV jr. inverted V might be a decent option because its really the cheapest option available. But I know your advice is solid as a rock, so I'll go with the sloper without question, except on which one to use.
I know I've been asking way too many questions and appreicate your patience. But it should be coming to and end.
I've been looking at three different slopers, The Spi-Ro VS-53 which covers 10,15,20,40 and 80 meters at 1/4 wave on each band, and is 42 feet long. Then the Alpha Delta model DX-B that covers 30-160 meters and is 60 feet long. The web site doesn't mention anything about 20 meters or below. So I'm not too sure about usng it. The I-Max can handle 10,12,15, and 17 if it has too. But since the Spi-Ro has 10 through 80 meter coverage, I've been looking at primarily at the Spi-Ro V-53 since it covers thoughs bands. They also have a VS-64, that covers 10,15,20,40,80,and 160 meters, and is 72 feet long. But from what I've heard people say I'm not sure if I would use 160 meters.
SO I am thinking about using the I-Max for 10, 12, meters and possibly 15, and 17 meters. With either the V-53 or the VS-64 that would give me full 1/4 wave or better coverage on 10,12,15,17,20,40,and 80 or 160 meters.
http://www.spiromfg.com/vertical_slopers.htm
However if you say I should go with the Alph-Delta DX-B, I will not hesitate. But I need at least 20 meter coverage, because the I-Max really goes a poor job there.
Again thank you very much. Your advice has been a real blessing.
Bob
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Tech833
Moderator
Username: Tech833
Post Number: 930
Registered: 8-2002
| | Posted on Thursday, December 30, 2004 - 11:02 pm: |
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No sweat Bob.
I am sorry, I am not familiar with the Spi-Ro antennas. From the website, they look O.K. I am not a real big fan of traps myself, so I would lean toward the Alpha Delta and cutting the 30m wire for 20m. However, for limited space, the Spi-Ro looks good to me. Let me know how it works! |
Bob_p
Advanced Member
Username: Bob_p
Post Number: 627
Registered: 7-2004
| | Posted on Friday, December 31, 2004 - 2:28 am: |
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Tech833
Thanks Paul.
I'm going to give it some thought, and when I get something in the air, I'll let you know ASAP.
The Spi-Ro Company has a wire antenna without traps that can be used as a sloper. And it covers all bands between 10 and 160 meters. It uses a balanced feed line instead of coax, but I have an antenna tuner so that's not a problem. I just need to find out how it would work compared to the antenna that is designed specifically as a sloper.
Again thank you for your time and your patience.
I hope you and yours have a great New Year.
Bob
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