REFLECTOR: nav antenna

[Douglas Holub]

I meant to say, how many dB down were you at 113 MHz when the antenna was 
1-5/8" shorter.

Doug Holub
----- Original Message ----- 
From: "Steve Goldman" <steve at fatcatair.com>
To: "'Velocity Aircraft Owners and Builders list'" <reflector at tvbf.org>
Sent: Saturday, December 01, 2007 1:32 PM
Subject: REFLECTOR: nav antenna


> So I'm hoping to finally glass my first wing surface tomorrow and I
> just finished installing the nav antenna. When I glassed my winglets a
> year ago I did't have an antenna analyzer. This year I happen to have
> borrowed one. I tested my comm antennas and they're ok, not tuned to
> the center of the band, but not bad. As I expected the comms ended a
> little long which would seem to be likely given the way they are
> constructed.
>
> So I was surprised today when I measured the tuned freq. of the nav
> antenna and found the center is 122mhz. Although I have an EE degree
> I'll admit to not taking the transmission lines class so I'm no expert
> on antennas. A quick search of the net found a page that calculates
> dipole length and inverted V's like the nav appears to be. Giving that
> page the length of the leg (22- 13/16) shows that 122mhz is a
> reasonable center freq. Since the nav band is 108-118 a center of 113
> works out to a leg about 1-5/8 inches longer. So I made the antenna
> that length and tested it and it does center at 113.
>
> So I'm wondering if anyone else has checked their antenna like this.
> Until tomorrow I'll stil have time to trim if what I'm doing is wrong
> even though it seems ok.
>
> -- 
> Steve Goldman
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