[Antennas] Only dumb question is the one not asked
Reginald Mackey
[email protected]
2002年3月29日 13:17:32 -0800
I ground my shields from all my coax on the 8 foot ground rod just outside
the home where also the station ground goes. There is no long lead, it is
almost a direct connection.
----- Original Message -----
From: "Harvey&Bessie" <[email protected]>
To: <[email protected]>
Cc: <[email protected]>
Sent: Friday, March 29, 2002 12:06 PM
Subject: Re: [Antennas] Only dumb question is the one not asked
> The impedance right at the feed point is (when SWR is low) close to 50
> ohms. the coiled co-ax near the feed point forms an RF-choke only for
> the outer conductor (the field of the inner conductor is entirely
> contained within the outer conductor acting as a shield) so, the RF
> "seeing" a higher impedance (several hundred ohms) in the path down the
> outer conductor, as compared to the 50-ohm impedance of the inner
> conductor, does not travel down the outside of the outer conductor.
> As for connecting a "ground" directly to the outer conductor at the feed
> point -- how would you propose doing that? The antenna, hopefully, is
> elevated some distance from earth -- the source of any true ground
> connection -- any wire lead you connect there has to have considerable
> length to get to "ground." It is still ground for DC, but not for RF. In
> fact if it is exactly (or nearly) one-quarter wavelength long it is no
> ground at all but an open circuit at RF!
> Harvey/W4TG
>> - - -
>> Your moderator for this list is:
> Larry Wilson KE1HZ [email protected]
> _______________________________________________
> Antennas mailing list
> [email protected]
> http://mailman.qth.net/mailman/listinfo/antennas
>