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Captian_radio
Intermediate Member
Username: Captian_radio
Post Number: 368
Registered: 9-2004
| | Posted on Thursday, March 06, 2008 - 8:17 pm: | 
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My question concerns the GP kit for the Imax 2000.Now are the radials on the kit a quarter wave length long,8 feet 6 inches or are they some sort of linear loaded radial that are shorter?I have been doing some research on the gp kit and have found some info that states that with radials of the correct length(8foot6)quarter wave length on 11 meters lowers the take off angle from 60 degrees to 23 degrees which would be more ideal for skip and ground wave.
Anyone ever use the correct length for the radials and what were your findings.
Tnx Bob CEF451/VE1CZ
Robert L. Spicer The days of radio are just beginning!
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Road_warrior
Senior Member
Username: Road_warrior
Post Number: 2146
Registered: 7-2004
| | Posted on Friday, March 07, 2008 - 5:29 pm: |
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In the past I have run the Imax 2000 with and without the Imax GPK. Really hard to tell if it improved DX conditions for me as Dx is always changing way to much. Buy a GPK or experiment with radials and see what you come up with.
The GPK radials are not loaded.
RoadWarrior
CEF 375
Tyrone, Pa 16686 |
Dale
Senior Member
Username: Dale
Post Number: 1309
Registered: 12-2002
| | Posted on Friday, March 07, 2008 - 8:21 pm: |
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im thinking the gpk radials are the exact
same size as the top section
dale/a.k.a.hotrod
cef426
cvc#64
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Captian_radio
Intermediate Member
Username: Captian_radio
Post Number: 369
Registered: 9-2004
| | Posted on Friday, March 07, 2008 - 9:46 pm: |
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Ok then if the radials are 6 feet long than they are too short to be a true quarter wave on 11 or 10 meters so this may be a valid reason why some people are not seeing any difference when using them.I may try using 4 fiberglass whips 102 inches long seeing that they would be closer to a quarter wave on 10 and 11.If and when I do I will post my findings .
Bob CEF451/VE1CZ
Robert L. Spicer The days of radio are just beginning!
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Dale
Senior Member
Username: Dale
Post Number: 1313
Registered: 12-2002
| | Posted on Saturday, March 08, 2008 - 10:30 am: |
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there the same lenth as the top section as the imax2k.which is 8ft.
dale/a.k.a.hotrod
cef426
cvc#64
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852
Intermediate Member
Username: 852
Post Number: 457
Registered: 3-2006
| | Posted on Saturday, March 08, 2008 - 12:23 pm: |
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if your radials are only 6 feet, that sounds more like A-99 radials.. If my thinking is correct..The Imax radials are 8ft. as Dales stated.
Tommy~852~CEF 750
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Road_warrior
Senior Member
Username: Road_warrior
Post Number: 2148
Registered: 7-2004
| | Posted on Saturday, March 08, 2008 - 12:57 pm: |
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Have you read the review on the Imax GPK? If not, go to the Subscribers (Reviews) section of this forum, in product reviews, scroll down until you reach Imax 2000 GPK reviewed article. |
Road_warrior
Senior Member
Username: Road_warrior
Post Number: 2149
Registered: 7-2004
| | Posted on Saturday, March 08, 2008 - 1:04 pm: |
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I just refreshed my reading of the Imax 2000 GPK review. States in that article that the Imax GPK has (4) 6 ft radials. I no longer have mine and can not honestly remember how long they were.
RoadWarrior
CEF 375
Tyrone, PA 16686 |
Streaky
Intermediate Member
Username: Streaky
Post Number: 176
Registered: 3-2006
| | Posted on Monday, March 10, 2008 - 10:42 pm: |
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I have a home built ground plane and use 4 102" whips seems to work fine for me maybe a little longer is better?Im sure tech 833 will jump in and give us the correct answer
Streaky
CEF#805
CVC#98
WorldRadio805
The Craziest Station in the Canadian Nation
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Dale
Senior Member
Username: Dale
Post Number: 1317
Registered: 12-2002
| | Posted on Tuesday, March 11, 2008 - 6:52 pm: |
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thats what i was thinking of doing.s.s.102 whips
with a s.s. 102 top
dale/a.k.a.hotrod
cef426
cvc#64
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Road_warrior
Senior Member
Username: Road_warrior
Post Number: 2155
Registered: 7-2004
| | Posted on Wednesday, March 12, 2008 - 4:23 pm: |
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Years ago we co-phased A-99s. We tried it a few different ways. One way acted more like a beam. My friend mounted them on a boom and placed it on his tower with a rotor...LOL.
We also experimented with different top sections and GPK radials. Never noticed much of a difference that I can remember. Curious to know what you guys come up with the Imax 2000.
RoadWarrior
CEF 375
Tyrone, PA 16686 |
Captian_radio
Intermediate Member
Username: Captian_radio
Post Number: 373
Registered: 9-2004
| | Posted on Wednesday, March 12, 2008 - 9:34 pm: |
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Dale the top of the Imax should be about 96 inches,if you add a 102 inch whip it would lower the resonant freq somewhat maybe down below 24 mhz.I would be interested to see how it would work with the longer top.It could also place more stress on the lower sections and cause it to fail.
Bob CEF451/VE1CZ
Robert L. Spicer The days of radio are just beginning!
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Dale
Senior Member
Username: Dale
Post Number: 1324
Registered: 12-2002
| | Posted on Thursday, March 13, 2008 - 5:58 pm: |
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hmm.didnt think about that.well could just trim the whip too 96inches and/or adjust tuning rings
dale/a.k.a.hotrod
cef426
cvc#64
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Maxgain
Junior Member
Username: Maxgain
Post Number: 48
Registered: 3-2007
| | Posted on Friday, April 04, 2008 - 8:14 am: |
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The ground plane kit radials for both the imax 2000 and the A 99 are all about 5 feet in length.
Proper radials for 11 meters are supposed to be almost 9 feet in length.
I don't understand how an antenna manufacturer can sell radials for an 11 meter antenna that are not even close to what a quarter wavelength should be, they should be about 9 feet long each.
The top section of an A-99 is about 5 or 6 feet in length.
The top section of an Imax 2000 is about 8 feet in length. |
Tech808
Moderator
Username: Tech808
Post Number: 15610
Registered: 8-2002
| | Posted on Friday, April 04, 2008 - 8:33 am: |
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Maxgain,
Check out the Topics Titled:
Copper Talk
» Subscriber (Preview)
» Product Reviews
» A99 Exposed Base Antenna
and
Copper Talk
» Subscriber (Preview)
» Product Reviews
» Imax 2000 Exposed Base Antenna
and
Copper Talk
» Subscriber (Preview)
» Product Reviews
» Imax 2000 Ground Plane Kit Reviewed
and it may help answer all of your questions. 
Lon~Tech808
CEF#0808/HAM#001/CVC#0002
Tech808@copperelectronics.com
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Canal_digger
Junior Member
Username: Canal_digger
Post Number: 19
Registered: 1-2008
| | Posted on Thursday, May 29, 2008 - 10:48 am: |
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I have read in several places that bending the 4 ground planes upwards to 30 degrees helps with take-off angle, etc. How about going the full 90 degrees (really 0 degrees) like other typical alum. ground plane antennas? Shouldn't that work as well or better than having the 30 degree down dip? |
Twa77
Intermediate Member
Username: Twa77
Post Number: 142
Registered: 1-2003
| | Posted on Thursday, May 29, 2008 - 6:57 pm: |
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i bent mine up and have been talking more skip than ever. cuold be an improvement could be plain ol conditions |
Chrisbama351
New member
Username: Chrisbama351
Post Number: 7
Registered: 2-2018
| | Posted on Thursday, April 02, 2020 - 5:41 pm: |
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I'm curious what everyone's results came out to be? Longer radials? different angle? |
Tech833
Moderator
Username: Tech833
Post Number: 2453
Registered: 8-2002
| | Posted on Saturday, April 04, 2020 - 4:13 pm: |
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Change the angle per the article, and let it rip!
Your radio 'Mythbuster' since 1998
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Ke0koy
Junior Member
Username: Ke0koy
Post Number: 16
Registered: 12-2018
| | Posted on Monday, April 06, 2020 - 11:30 am: |
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Consider a vertical dipole with the coax ran up through the bottom element to the feed point. Now consider taking the tip of the bottom element and start stretching it out so its fanned out at the end. This increases the capacitance and makes the element electrically longer (physically shorter) for a given frequency. If we dice up that bottom conical element into sections, now its starting to look like a ground plane antenna. When you change the angle of the radiators, you are changing the feed point impedance. The radiation resistance is closest to 50ohm (when reactance is canceled out) as the angle approaches 45 degrees. Its easy to tune out a little capacitance with an inductor when the radiation resistance is already 50ohm (if there even is a capacitive component). Once you change the resistive portion of the radiator, now you need to find a tapping point on the coil to transform the complex impedance as you are no longer simply removing reactance.
My sirio827 has radials at 0° (perpendicular to the radiating element) and it works great. Every night here in northern Minnesota (no propagation enhancement) I talk to a guy about 50 miles away 5x5 on 12w. I agree with canal_digger on the takeoff angle, although it shouldn't be the thing that keeps you off the air. My sirio antenna is a 5/8, and since the antenna already needs a matching network, whether Rr is 50ohm, 70ohm or 36ohm really doesn't matter as the match transforms it to 50ohm anyhow. |
Tech833
Moderator
Username: Tech833
Post Number: 2455
Registered: 8-2002
| | Posted on Thursday, April 09, 2020 - 12:47 pm: |
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KE0KOY,
You're right about the angle of the radials changing the feedpoint impedance on a 1/4 wave vertical, however not on a 5/8 wave.
Changing the angle of the radials on a 5/8 wave vertical, especially when the radials are less than 1/4 wave long (as in the case of the Imax GPK), changes the takeoff angle but has almost no effect on the feedpoint impedance, as long as the radials remain below the end point of the vertical.
In the case of the Imax GPK, I took the antenna and radial kit to an antenna test range and spun the antenna and plotted it's vertical radiation pattern. After seeing the COR much too high above horizon for a 5/8 wave, I started changing the angle of the radials to obtain a better takeoff angle and vertical radiation pattern. It's all documented in the review published on Copper's website and in the print magazine (at the time).
Your radio 'Mythbuster' since 1998
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Ke0koy
Junior Member
Username: Ke0koy
Post Number: 17
Registered: 12-2018
| | Posted on Thursday, April 09, 2020 - 3:04 pm: |
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I will try to find that review, thanks! My sirio holds the radials with set screws so taking them off and replacing them with ones I can bend without guilt for experimentation should be easy. Ill have to try that this summer! |
Tech833
Moderator
Username: Tech833
Post Number: 2456
Registered: 8-2002
| | Posted on Friday, April 10, 2020 - 2:12 pm: |
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Here it is- http://www.copperelectronics.com/discus4/messages/7750/20506.html?1023340740
That was 18 years ago. Yikes!!
Your radio 'Mythbuster' since 1998
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Ke0koy
Junior Member
Username: Ke0koy
Post Number: 18
Registered: 12-2018
| | Posted on Friday, April 10, 2020 - 5:41 pm: |
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I just finished up trying this with my 5/8 Sirio827 and I lost almost 1dB. It did increase the bandwidth of the antenna (cool) and also affected the feed point impedance (enough to be concerned with it, not cool).
I have put the before and after antenna scans and a detailed explanation of what I did on google drive for anyone interested.
https://drive.google.com/open?id=1RKRleDS7Vy-Ba34RDcLzWByYt3Viw-qt |
Chrisbama351
Junior Member
Username: Chrisbama351
Post Number: 11
Registered: 2-2018
| | Posted on Monday, April 13, 2020 - 7:45 pm: |
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Are 1/4 wave length radials better than the 6' Imax gpk radals?
Is longer better?
Does length effect the best degree of angle?
What diameter home made radials are the most efficient? |
Tech833
Moderator
Username: Tech833
Post Number: 2458
Registered: 8-2002
| | Posted on Tuesday, April 14, 2020 - 12:20 am: |
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Chrisbama351,
I deleted the 3 other posts you made with this exact same text (copied/pasted into 4 threads) but leave this because it is relevant here.
On an Imax 2000, the radial length is not critical. Changing the 60" radials to 108" elements won't change anything.
Longer is not better. As you approach 18' long, they become invisible, like they aren't there at all.
Diameter doesn't matter either. Diameter changes the Q slightly for the radiating element, but not for the radials.
Your radio 'Mythbuster' since 1998
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