| Author |
Message |
    
Scoobydoo
Member
Username: Scoobydoo
Post Number: 73
Registered: 8-2005
| | Posted on Sunday, February 26, 2006 - 8:41 pm: | 
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Hi everyone, What exactly is a gamma match? I have heard of them being used on Maco V5/8's. I plan on using a Maco v5/8 when I put up my new antenna mast. Does the gamma match make it easier to tune the swr's? Thanks in advance for the help. |
Marconi
Advanced Member
Username: Marconi
Post Number: 612
Registered: 11-2001
| | Posted on Monday, February 27, 2006 - 11:32 am: |
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It is a feeder, that is able to feed an antenna where the antenna itself is completely at ground potential, meaning the whole antenna, elements, hub, boom, and mast, are all hooked in some way to the earth.
It is suitable to use in yagi style beams that use "Plumbers Delight" construction techniques to improve the stabality of system without the use of a prone to failure insulators, as is noted in the V-5/8. |
Tech833
Moderator
Username: Tech833
Post Number: 1230
Registered: 8-2002
| | Posted on Monday, February 27, 2006 - 12:27 pm: |
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A gamma is just a shunt feed system with some series capacitance to offset feedpoint inductance such as that found on a center fed grounded half wave dipole. |
Scoobydoo
Member
Username: Scoobydoo
Post Number: 74
Registered: 8-2005
| | Posted on Thursday, March 02, 2006 - 2:17 am: |
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So if I use this on my V5/8 will I adjust it for SWR instead of adjusting the length of the antenna? Will it be easiar to adjust my SWR? That would be a plus. Where does it attach on the antenna? Sorry, still a little confused about how it works and what it does. Thanks for the help. |
Rldrake
Intermediate Member
Username: Rldrake
Post Number: 102
Registered: 1-2006
| | Posted on Thursday, March 02, 2006 - 10:52 pm: |
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It attachs at the feedpoint and the radiator element.
Some of the antenna manufacturer's websites have pictures of their antennas with a good view of it. |
Tech833
Moderator
Username: Tech833
Post Number: 1241
Registered: 8-2002
| | Posted on Friday, March 03, 2006 - 11:23 am: |
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A gamma will not work well, if at all on a V-5/8. A gamma has series capacitance but on a 5/8 vertical fed at the base, you actually need a little bit of series inductance. |
Wayne
Member
Username: Wayne
Post Number: 51
Registered: 12-2001
| | Posted on Sunday, March 05, 2006 - 12:39 pm: |
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Hello everyone what a great topic, seems like everything worked out with the location of this topic. Hear we go I am in the process of getting a larger gamma match, but a friend of mind was telling me I can save some extra dollars by using my driver element as a gamma match hes getting ready to move away and I might not get to his place to see his antenna before he moves, so is there anyone hear can help me with this question. And it can only be used with yagi style beams. Also are there any antenna books that could help me . Most likely it would have to come under HAMS BOOKS thanks |
Tech833
Moderator
Username: Tech833
Post Number: 1246
Registered: 8-2002
| | Posted on Sunday, March 05, 2006 - 4:40 pm: |
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Pick up the ARRL Antenna Book from your local bookstore or online. Everything I have told you can be found in there. |
Funtimebob
Intermediate Member
Username: Funtimebob
Post Number: 175
Registered: 5-2002
| | Posted on Monday, March 06, 2006 - 10:23 am: |
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Curious...., The wolf .64 uses a gamma match. the nov 1960 QST had a big write up on a 5/8 wave antenna fed with one. would love to get a chance to go to the main public library and see if I could pull a copy of the article off microfilm if they have it... |
Tech833
Moderator
Username: Tech833
Post Number: 1253
Registered: 8-2002
| | Posted on Monday, March 06, 2006 - 8:29 pm: |
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The Wolf .64 does NOT use a gamma match. It uses a ring shunt match. The part of the ring between the tap and the vertical radiator cancel out the inductance, and there is no capacitor in series with the power shunt.
A Gamma by definition has series capacitance. A Simple parallel shunt feed LOOKS like a Gamma but does not have the series capacitance. Is THAT would you were talking about? |
Funtimebob
Intermediate Member
Username: Funtimebob
Post Number: 176
Registered: 5-2002
| | Posted on Thursday, March 09, 2006 - 12:31 am: |
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quoted from his web site,
"To further its ability to handle lightning, the bottom of the radiator element is connected directly to ground and RF is fed through a gamma match."
hmmmm..... |
Tech833
Moderator
Username: Tech833
Post Number: 1264
Registered: 8-2002
| | Posted on Thursday, March 09, 2006 - 12:50 pm: |
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The website is using the term incorrectly. |
Marconi
Advanced Member
Username: Marconi
Post Number: 626
Registered: 11-2001
| | Posted on Thursday, March 09, 2006 - 10:46 pm: |
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833, if what you say is so, then isn't it the same on all the Maco beams as well, even though they claim to be gamma fed they are not? |
Tech833
Moderator
Username: Tech833
Post Number: 1266
Registered: 8-2002
| | Posted on Friday, March 10, 2006 - 10:32 am: |
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The Maco beams ARE gamma fed. The gamma match has an insulator between the two pieces of tubing that make up the gamma unit. |
Marconi
Advanced Member
Username: Marconi
Post Number: 628
Registered: 11-2001
| | Posted on Friday, March 10, 2006 - 12:05 pm: |
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Well I don't see the .64 as you describe 833. The .64 uses no insulator at the base, and there is a capacitor inside of the gamma matcher that allows feeding of this one or else you would have a direct short in feeding. The .64 is all connected to the earth ground.
I do see the .50_11M just as you describe and it is insulated from the earth ground where the main raidating element attaches to the base mount. I believe you have these two antennas confused. The .50_11M has a ring coil like the V5/8 and the main radiating element sits inside of an insulator that is inside of the base mount serving as a capacitor for adjusting the reactance of this antenna, similar to the V5/8. |
Tech833
Moderator
Username: Tech833
Post Number: 1268
Registered: 8-2002
| | Posted on Saturday, March 11, 2006 - 9:56 am: |
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I must have them confused. |
