[CQ-Contest] Re: 2 dB more?

[Marijan Miletic, S56A]

Dr. Matjaz Vidmar, S53MV, professor of electromagnetics at Ljubljana
University
points out that hams are not aware of a very simple relation:

Antenna gain is a  product of directivity and efficiency.

Unless one doesn't use resistive loads for broadbanding antenna, poor traps
or grounding system for verticals, HF efficiency is very close to 100%.

Special receiving antennas are another story.

73 de Mario, S56A, N1YU

----- Original Message -----
From: "Tom Rauch" <w8ji at akorn.net>
To: <cq-contest at contesting.com>; "Salina Physician Anesthesia" <spa at tri.net>
Sent: Monday, December 31, 2001 12:41 AM
Subject: Re: [CQ-Contest] Re: 2 dB more?


>
> > I have been using a KT-36XA in the last few contests.  Joke is that
> > I've basically only worked 10M as I am really a DXer first and don't
> > like getting a run going as I can't handle the mess.  However, it is
> > nice to call into a pile and get in on the first call.  And then there
> > are the weak stations that plead for a contact and they are in the QRN
> > with syllables only.  A few dB more and?  Or would I just find another
> > layer?
>
> The common myth is if you have more antenna "gain" the gain also
> improves reception. That isn't true, unless you have a relatively
> "insensitive" receiver.
>
> The **directivity** of the antenna system determines the receiving
> ability, not the "gain". Directivity does NOT include losses, it is
> only a measure of the peak response in the direction of signals
> compared to noise or unwanted signal response from other
> directions.
>
> There is a little article about this on www.w8ji.com under receiving
> arrays, and while it deals mainly with 160 it also applies to other
> bands.
>
> The only time gain, or reduction of loss, helps is when the your
> system is limited by noise in the feedline or receiver.
>
> We need to compare pattern differences, rather than gain, for
> receiving. Odds are very good you won't see anywhere near the
> receiving S/N improvement that you see "gain" difference. many
> times a lower gain antenna system is a better receiving system
> than higher gain systems.
>
> Transmitting is another story, and even one or two dB can be major
> in how a weak signal sounds. A couple dB is actually well over one
> "S" unit marking on the meters of almost all receivers when signals
> are weak. Most receiver meters are very non-linear low on the
> scale.
>
> When you are weak, that two dB will seem more like several dB. If
> your signal is anywhere near strong, it won't mean anything unless
> you are in a pileup with other equally strong stations.
>
> Myself, I'd look at all options before changing the antenna!
> 73, Tom W8JI
> W8JI at contesting.com
>
>
> --
> CQ-Contest on WWW: http://lists.contesting.com/_cq-contest/
> Administrative requests: cq-contest-REQUEST at contesting.com
>


--
CQ-Contest on WWW: http://lists.contesting.com/_cq-contest/
Administrative requests: cq-contest-REQUEST at contesting.com