It is a DC grounded antenna and it measures as a DC short circuit.
On Oct 20, 2008, at 7:06 PM, Fred Townsend wrote:
It is getting a little blurry here. I hope I can clarify. It is
common practice to place a DC ground on the antenna for lightning
protection. At frequency the antenna has an impedance of 50 ohms
which can not be measured with a DVM. The statement below indicates
the antenna has a DC ground but measures open. This would suggest a
fault of some kind (either between the headset and ground or at the
antenna). Therefore it is legitimate for Mr. Suter to question this
statement.
de AE6QL, Fred
--- [EMAIL PROTECTED] wrote:
From: "Paul Plack" <[EMAIL PROTECTED]>
To: <[email protected]>
Subject: Re: [Repeater-Builder] UHF Repeater Antenna -- UPDATE
Date: Mon, 20 Oct 2008 16:56:41 -0600
Is not "no measureable resistance" the same as a short? Zero ohms is
just what it should show...why would that indicate damage or defect?
----- Original Message -----
From: Jacob Suter
To: [email protected]
Sent: Monday, October 20, 2008 11:17 AM
Subject: RE: [Repeater-Builder] UHF Repeater Antenna -- UPDATE
"DC Grounded", in my experience, means the center pin and the coax
will show
a "dc short" when tested with a DMM.
Lightning? Corrosion? Manufacturing defect?
JS
> -----Original Message-----
> From: [EMAIL PROTECTED]:Repeater-
> [EMAIL PROTECTED] On Behalf Of Cort Buffington
> Sent: Monday, October 20, 2008 11:29 AM
> To: [email protected]
> Subject: [Repeater-Builder] UHF Repeater Antenna -- UPDATE
>
> Folks,
>
> *Continuation of Previous Thread: UHF Repeater Antenna Discussion*
>
> We climbed the tower on Sunday and checked things with the wattmeter
> between the Feedline and the antenna.
>
> At the bottom, we were making 75 Watts at th e duplexer output. At
the
> top, after going through 105' of LDF4.5-50A (just over 1dB of
loss), a
> PolyPhaser, and a 6' jumper of RG400 (from the duplexer to the
> PolyPhaser) we were seeing 57 Watts. I show that as about 1.2 dB of
> loss, which seems quite reasonable. The F10, at the top, showed me
> about 1.5W reflected... or 1.34:1 VSWR.
>
> The antenna is a DC grounded colinear, and we showed no measurable
> (with my DMM) resistance between the center pin and outer
conductor of
> the Hardline/Antenna combination.
>
> Right now, we're of the mind that the feedline is good.
>
> 73 DE N0MJS
>
> --
> Cort Buffington
> H: +1-785-838-3034
> M: +1-785-865-7206
--
Cort Buffington
H: +1-785-838-3034
M: +1-785-865-7206
