| Author |
Message |
    
26 OP 141 (Unregistered Guest)
Unregistered guest
| | Posted on Thursday, November 11, 2004 - 4:36 am: | 
|
Hi,
Anyone out there explain this antenna on how it radiates? Its two antenna's in one, split between two coils but only one feed at bottom.
9.5M long and in excess of 7DB gain according to the instructions I have with it.
It just about outperforms every other antenna Ive tried,including the Hygain Golden Penetrator which I also own.
If you have a BIG MAC or any other antenna from HAM INTERNATIONAL get in touch.
Tech guys Im really interested how this thing works eletrically.Keep it simple.
TNX
TIM
26 Orient Pirate 141
|
Gonzo
Intermediate Member
Username: Gonzo
Post Number: 100
Registered: 9-2004
| | Posted on Thursday, November 11, 2004 - 9:32 am: |
|
Please type out the web address. Without providing a link.
31.5 feet long is 7/8 wave, but I am still sceptical on any manufacturers "gain" figures.
And 7/8 wave should not be any better than a 5/8 wave, in fact worse, unless all of the minor lobes could be compressed effectively towards ground. Or unless this is a stacked 1/2 wave vertical, which doesn't quite add up.
More info please. Its called a Big Mac?? wait till McDonalds hears about that! |
Gonzo
Intermediate Member
Username: Gonzo
Post Number: 101
Registered: 9-2004
| | Posted on Thursday, November 11, 2004 - 9:34 am: |
|
Also
Tim, When do you monitor Tim Freq; 27.535 USB??
UT time??
Maybe we can try and scream at each other, I am on the east coast. NY/VT. |
Bruce
Senior Member
Username: Bruce
Post Number: 1754
Registered: 9-2003
| | Posted on Thursday, November 11, 2004 - 3:12 pm: |
|
Hummmmm sounds like a crude 11 meter ringo ranger using a phaseing stub ( coil ) and phaseing 2 1/2 waves. As for 7 db of gain you would have to phase 3 of the 1/2 wave sections not 2. even then the close spacing would cancel out some of the gain ..... like happings in the ringo antennas. True multi stacked antennas are hard to find except at VHF/UHF and most are incased in fiberglass.
|
26 OP 141 (Unregistered Guest)
Unregistered guest
| | Posted on Thursday, November 11, 2004 - 10:50 am: |
|
Hi Gonzo,
Its called a Big Mac for sure. It was made in Belgium in the early 80's and is the biggest vertical I know. I will scan instruction manual and upload tomorrow.
Im on 27.535 USB most weekends either in the mobile or at home. Just call me if you here the skip up from the UK.
here is the link:-
pageperso.aol.fr/Daviken/Antennes/Antennes.htm
pageperso.aol.fr/Daviken/Ham+International+Home2+English.htm
|
Gonzo
Intermediate Member
Username: Gonzo
Post Number: 103
Registered: 9-2004
| | Posted on Thursday, November 11, 2004 - 6:35 pm: |
|
I did notice that the page you mentioned, said that this antenna was top heavy, not very stable and did not have any more gain then the 5/8 wave antenna. From the description I gathered (even though my french is a little weak)that they were not impressed with this antenna, and measured only 5.3 DB gain.
It appears that this antenna is a J-pole design, with a 1/2 wave above a 1/4 wave section, with some sort of matching coil between the elements, and 6 horizontal radials. |
Gonzo
Intermediate Member
Username: Gonzo
Post Number: 104
Registered: 9-2004
| | Posted on Thursday, November 11, 2004 - 6:54 pm: |
|
They also measured a 1/2 wave at 6DB gain, so now I am pretty skeptical. These other designs that are 3/4, 7/8, J-pole's & similar, have never impressed me that much, they tend to add unnecessary weight and complexity to try and out-do a 5/8 vertical. I do not think any of them are ever that successful.
And as Bruce said stacked vertical's on 11 meters is a little hard to do, unless you have a permanent 100 foot tower laying around your yard |
26 OP 141 (Unregistered Guest)
Unregistered guest
| | Posted on Friday, November 12, 2004 - 6:16 am: |
|
Hi Gonzo,
Its called a Big Mac for sure. It was made in Belgium in the early 80's and is the biggest vertical I know. I will scan instruction manual and upload tomorrow.
Im on 27.535 USB most weekends either in the mobile or at home. Just call me if you here the skip up from the UK.
here is the link:-
pageperso.aol.fr/Daviken/Antennes/Antennes.htm
pageperso.aol.fr/Daviken/Ham+International+Home2+English.htm
|
hypower (Unregistered Guest)
Unregistered guest
| | Posted on Friday, November 12, 2004 - 9:51 am: |
|
Hi, I am a friend of Tim,s and had a Big Mac. It was a 7/8 wave colinear consisting of a 5/8 wave section over a 1/4 wave with a phasing coil in between. what I would like to know from anyone who understands colinears is how long does the phasing coil need to be (maybe an 1/8th or 1/4 wave?) does the top 5/8 section need to be approx 22ft including this coil or is the coil length in addition to the top element? and also how do you tune/SWR such an antenna when bulding one? I can get it to SWR at 1.1 but never know if I should adjusting the 1/4 or 5/8 section. should I try to tune the bottom 1/4 wave section before adding the phasing coil and 5/8 upper radiator? any help or info greatly received. PS it had vetical radials on the bottom section to lower the radiation angle to below that of a standard 5/8 wave. This along with its stacked design gave it the extra gain. |
Bruce
Senior Member
Username: Bruce
Post Number: 1757
Registered: 9-2003
| | Posted on Friday, November 12, 2004 - 12:14 pm: |
|
This is the same idea as the Hustler CGT144 144 MHz, 5.2 db, 7 ft. ant. I run them on 2 meters and MURS. If the CB one works as well 5db of gain is about right. Now on the 2 meter one you cut a SMALL part of the bottom part and check SWR to make sure it is going in the right direction .... THEN trim the top slightly and recheck. I have used these since the early 70's and its a very good antenna and fairly cheep. |
Gonzo
Intermediate Member
Username: Gonzo
Post Number: 105
Registered: 9-2004
| | Posted on Friday, November 12, 2004 - 3:07 pm: |
|
I understand a little better now, but I think you may be confusing terms a bit. It now sounds like a standard 5/8 wave antenna, with a matching coil network similar to a Hy Gain Penetrator (this is needed to provide 50 ohms). The difference being that this antenna used a 1/4 wave bottom section and radials to provide ground.
So, if this is the case and I am reading right:
This antenna is not a "stacked" design
The coil in the end of the 5/8 wave vertical section is not a "phasing coil"...it is a matching network coil.
The reason the gain was the same as a 5/8 wave antenna...is that it IS a 5/8 wave antenna with a complex set of ground radials and 1/4 wave bottom section.
This BTW is somewhat similar to the Imax2000 antenna with ground plane kit.
-----------------------------------------
Using the term 7/8 wave would sound impressive but would in essence be a 5/8 wave antenna.
--------------------------------------------
To answer your questions: If you can get SWR of 1.1 what is the problem???
If you were to build one; you would shorten or lenghten the top section. The bottom section would need to remain 1/4 wavelenght.
---------------------------------------------
Again this design seems to be heavy, bulky and probably not the most stable. I know that they were trying to lower the angle of radiation by providing a bottom 1/4 wave section and ground radials, but this probably has minimal effect, as long as the antenna was put up high enough.
--------------------------------------------
This is the same as adding a ground plane kit to a Imax2000 that is already 54 feet in the air. This would also accomplish very little.
|
hypower (Unregistered Guest)
Unregistered guest
| | Posted on Saturday, November 13, 2004 - 2:07 pm: |
|
Thanks for help Gonzo. It said in the owners manual it is a 7/8 wave. A 5/8wave over a 1/4wave (in phase) It had two large external coils. A matching coil at the base and what they called a phase adapting coil between the 1/4 and 5/8 sections. This antenna was approximately 31 feet in length. I have never used an omni diectional which performed like this and I have tried most including Avanti sigma4, penetrator, I-max etc. Hence you can see my enthusiasm to try and build one. Using an MFJ antenna analyser I finally got my homebrew version up and working but I know something is not right somewhere.why I mentioned the SWR is because I can get it to SWR ok at slightly different lengths. As you can tell I have very little experience in antenna building but I have had a great interest in CB radios and antennas for over 20 years. Anymore info anyone?
Regards Dave.. |
Gonzo
Intermediate Member
Username: Gonzo
Post Number: 106
Registered: 9-2004
| | Posted on Sunday, November 14, 2004 - 1:12 pm: |
|
Hey more power to you Dave, thats great that you are building antennas. Now that you described the antenna a little more. There was an antenna (The Franklin Antenna)which was usually a 1/2 wave vertical "stacked" design, followed by a 1/4 wave shorted stub for "phase" reversal. This in effect lowered the angle of radiation very successfully. Ground radials and a matching circuit was added as well on similar designs. I do remember reading that this antenna was very limited as far as frequency.
----------------------------------
I also think Bruce maybe right, the design he points out is a similar one, that could also be used with ground radials I believe. The antenna he points out is a rigid coaxial design, which in effect is very simialr to the Franklin Antenna.
-------------------------------
Please let us know how you do, and email me with any details if you wish |
