From: Rik Strobbe <Rik.Strobbe@fys.kuleuven.be>
To: "rsgb_lf_group@blacksheep.org" <rsgb_lf_group@blacksheep.org>
Date: Wed, 3 Aug 2011 21:38:43 +0200
Thread-Topic: Antennas
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Subject: LF: RE: Antennas
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Hi Chris,

the quality of the received signal it determined by it's SNR. So if you hav=
e an antenna where QRM/QRN are at a higher level than the RX noise it makes=
 no sense to get a larger antenna (=3D produce more signal and noise).
As QRM / QRN on 137kHz and even on 500kHz is rather high even with a small =
antenna you will get more QRM / QRN and it will perform as well as a big an=
tenna.
So it seems absolutely normal to me that a small whip will performp as well=
 as a big wire antenna (for RX !).
More important that size might be other properties such as directivity (eg =
with a loop you can null out a QSM source).

I do use my "big" TX antenna for RX, but do need to attenuate the signal by=
 at least 20dB to avoid RX overloading.

73, Rik  ON7YD - OR7T

________________________________
Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org=
] namens Chris [c.ashby435@btinternet.com]
Verzonden: woensdag 3 augustus 2011 20:08
Aan: RSGB LF Group
Onderwerp: LF: Antennas

Hi Mal and LF,
Well, all I can say is that here the signal to noise ratio on RX is better =
on my PA0RDT than it is on my long wire (inverted 'L'). I have always thoug=
ht this a bit strange, quite often weak signals that cannot be seen on the =
wire are perfectly copied on the PA0RDT. This applies from 136kHz to 3.8MHz=
. I cannot see what else it can be other than local noise/QRM level. 80m is=
 another prime example where the noise has gradually got worse over the yea=
rs here.
Vy 73,
Chris, G4AYT, Whitstable, Kent.

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<div>Hi Chris,</div>
<div>&nbsp;</div>
<div>the quality of the received signal it determined by it's SNR. So if yo=
u have an antenna&nbsp;where QRM/QRN are at a higher level than the RX nois=
e it makes no sense to get a larger antenna (=3D produce more signal and no=
ise).</div>
<div>As QRM / QRN on 137kHz and even on 500kHz is rather high even with a s=
mall antenna you will get more QRM / QRN and it will perform as well as a b=
ig antenna.</div>
<div>So it seems absolutely normal to me that a small whip will performp as=
 well as a big wire antenna (for RX !).</div>
<div>More important that size might be other properties such as directivity=
 (eg with a loop you can null out a QSM source).</div>
<div>&nbsp;</div>
<div>I do use my &quot;big&quot; TX antenna for RX, but do need to attenuat=
e the signal by at least 20dB to avoid RX overloading.</div>
<div>&nbsp;</div>
<div>73, Rik&nbsp; ON7YD - OR7T&nbsp;</div>
<div dir=3D"ltr"><font color=3D"#000000" size=3D"2" face=3D"Tahoma"></font>=
&nbsp;</div>
<div style=3D"DIRECTION: ltr" id=3D"divRpF343390">
<hr tabindex=3D"-1">
<font color=3D"#000000" size=3D"2" face=3D"Tahoma"><b>Van:</b> owner-rsgb_l=
f_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Chris [c=
.ashby435@btinternet.com]<br>
<b>Verzonden:</b> woensdag 3 augustus 2011 20:08<br>
<b>Aan:</b> RSGB LF Group<br>
<b>Onderwerp:</b> LF: Antennas<br>
</font><br>
</div>
<div></div>
<div>
<div><font size=3D"2" face=3D"Arial">Hi Mal and LF,</font></div>
<div><font size=3D"2" face=3D"Arial">Well, all I can say is that here the s=
ignal to noise ratio on RX is better on my PA0RDT than it is on my long wir=
e (inverted 'L'). I have always thought this a bit strange, quite often wea=
k signals that cannot be seen on the
 wire are perfectly copied on the PA0RDT. This applies from 136kHz to 3.8MH=
z. I cannot see what else it can be other than local noise/QRM level. 80m i=
s another prime example where the noise has gradually got worse over the ye=
ars here.</font></div>
<div><font size=3D"2" face=3D"Arial">Vy 73,</font></div>
<div><font size=3D"2" face=3D"Arial">Chris, G4AYT, Whitstable, Kent.</font>=
</div>
</div>
</div>
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