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Post by crazybob on Oct 21, 2009 17:03:17 GMT -5
The locals are disscusing that on some vertical yagi's, the gamma match is above the boom, & some are mounted below the boom. Does it make a differance?  |
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Post by cbrown on Oct 22, 2009 13:02:43 GMT -5
I've seen it both ways, but I'd have to say most of the time I see it above the boom.
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Sandbagger
Administrator/The Boss 
Posts: 6,250 
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Post by Sandbagger on Oct 22, 2009 16:21:03 GMT -5
I've seen it both ways as well, and it seemingly makes no difference. When I put up my 3 element Maco, I pondered over which way to point the gamma. I finally decided to point it in the downward direction. And it was for a reason that had nothing to do with performance. I decided to point it down based on the likelihood that rain would not run into the gamma if it were pointed down.
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Post by cbrown on Oct 23, 2009 12:41:55 GMT -5
That's probably why most people point them up, so water doesn't get into the coaxial connection. That's why I always recommend coax-seal, or something like that.
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Post by crazybob on Oct 23, 2009 13:45:57 GMT -5
Here's my mudduck Jo Gunn 4 element veritcal. My gamma match is above the boom. I noticed that the Maco's were mounted below.  |
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Sandbagger
Administrator/The Boss
Posts: 6,250
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Post by Sandbagger on Oct 23, 2009 18:19:13 GMT -5
That's probably why most people point them up, so water doesn't get into the coaxial connection. That's why I always recommend coax-seal, or something like that. Well, my coax connection is horizontal to the side of the gamma, so it makes no difference which way the gamma is actually pointed, as far as water entering the coax connector is concerned. However, since the gamma is basically a trombone-style capacitor, if it's pointed up, rain can seep in between the gamma rod and the outer tube. The water can then alter the capacitance and in turn the SWR. Also if in a cold climate, the trapped water can freeze, causing the gamma to crack. Yea, you can probably drill a small drain hole at the base of the gamma tube, but pointing the gamma down takes care of it as well. |
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Post by cbrown on Oct 26, 2009 12:46:59 GMT -5
Yea, you can probably drill a small drain hole at the base of the gamma tube, but pointing the gamma down takes care of it as well. How about a urethane or silicon cap on the gamma top? |
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