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Message |
    
Marconi
Intermediate Member
Username: Marconi
Post Number: 335
Registered: 11-2001
| | Posted on Saturday, January 29, 2005 - 1:11 pm: | 
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Is there a resonanting quality in a gamma match device or does it simply provide insulation and a connection for coax to a typically grounded radiator?
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Ferd1605
New member
Username: Ferd1605
Post Number: 4
Registered: 1-2005
| | Posted on Sunday, January 30, 2005 - 3:19 am: |
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The gamma match is a system to feed the antenna to 50 ohm unbalanced coax . The driven element must be a bit shorter that normal to use a gamma match . The good thing about a gamma match is the simple "plumers delight" desighn and a DC ground . In easy terms , a gamma is a capacitor and a tuning rod . the capacitor section is the smaller rod { with insulation} inside the larger rod . |
Tech833
Moderator
Username: Tech833
Post Number: 977
Registered: 8-2002
| | Posted on Sunday, January 30, 2005 - 10:56 am: |
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To expand on the great answer from Ferd,
You can build a gamma with either the internal mechanical capacitor you normally see, or also a regular tuning capacitor in series with the shunt. Either way, it is electrically the same, but the internal mechanical capacitor is by far the best for strength and power handling and weather resistance.
The mechanical capacitor is formed by the insulation used between the outer metal tubinng and the inner metal tubing that slides in and out for adjustment. Sliding the two rods changes the capacitance (and the feedpoint reactance) and the shunt (shorting bar) changes the resistance. You can 'load up' almost anything with a gamma. |
Marconi
Intermediate Member
Username: Marconi
Post Number: 340
Registered: 11-2001
| | Posted on Sunday, January 30, 2005 - 11:00 am: |
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You are right Ferd. I was wondering this because it seems that there is more to a gamma than just the parts that allow one to insulate a DC grounded driven element and be able to adjust it to reach out and tap a matching point on the element.
Technical stuff tells us that diameter, length, and spacing are vitally important to their effectivness. That sounds like that it is not just and insulating connection that is able to transfer energy.
Thanks! Just curious. |
Tech833
Moderator
Username: Tech833
Post Number: 983
Registered: 8-2002
| | Posted on Tuesday, February 01, 2005 - 9:55 am: |
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The tubing diameters affect the capacitor value. If you were to use a standard paddle tuning cap in series with a wire to the feedpoint tap, then wire diameter would be of no concern. Changing the diameter of either the tubing or the insulator (dilectric) material changes the capacitor value. |
Marconi
Intermediate Member
Username: Marconi
Post Number: 345
Registered: 11-2001
| | Posted on Tuesday, February 01, 2005 - 11:59 am: |
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Thanks to everyone for the comments. |
