Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id w9RGP1RO004463 for ; Sat, 27 Oct 2018 18:25:07 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1gGRDe-0004mZ-2f for rs_out_1@blacksheep.org; Sat, 27 Oct 2018 17:13:46 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1gGRCv-0004mQ-76 for rsgb_lf_group@blacksheep.org; Sat, 27 Oct 2018 17:13:01 +0100 Received: from smtp3web.tin.it ([212.216.176.237]) by relay1.thorcom.net with esmtp (Exim 4.91_59-0488984) (envelope-from ) id 1gGRCt-0004RQ-BB for rsgb_lf_group@blacksheep.org; Sat, 27 Oct 2018 17:13:00 +0100 Received: from feu2 (10.192.64.12) by smtp3web.tin.it (8.6.060.43) id 5B6DEBA20252F749 for rsgb_lf_group@blacksheep.org; Sat, 27 Oct 2018 18:12:54 +0200 Received: from (79.50.218.146) by webmailtin.pc.tim.it; Sat, 27 Oct 2018 18:12:54 +0200 Message-ID: <166b64cbe61.marcocadeddu@tin.it> Date: Sat, 27 Oct 2018 18:12:54 +0200 (CEST) From: "marcocadeddu@tin.it" To: Mime-Version: 1.0 X-Originating-IP: 79.50.218.146:2947 X-Spam-Score: -0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see @@CONTACT_ADDRESS@@ for details. Content preview: Hi Paul, Luis, Markus, LF let me join the topic ;-) the antenna location of Luis is something else of your Markus and Paul and much similar to mine: roof based antennas with elevated ground (in my case) and vertical ground (the water pipe) for Luis. Anyway also in my case the serie resistance of my antenna increases with rain (almost doubles). But.. Luis, probably assumes the lower impedance basing on the higher current. Luis, what kind of LPF have you adopted? Now I have a T filter with no shunting cap at the input and impedance increases with rain both with and without LPF, but if I remember correctly, when in the past I had an PI LPF with shunting input and output caps the impedance in my shack was transformed from the transmission line and LPF giving lower impedance by rain. [...] Content analysis details: (-0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [212.216.176.237 listed in list.dnswl.org] -0.0 T_RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -0.0 SPF_PASS SPF: sender matches SPF record 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (marcocadeddu[at]tin.it) 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: ee37f4b261e58bbaf6a18fc5319c092e Subject: R: Antenna resistance (Re: LF: EbNaut Autodecoder 137490 Hz: EA5DOM received) Content-Type: multipart/alternative; boundary="----=_Part_10579_6764189.1540656774756" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=HTML_MESSAGE autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false ------=_Part_10579_6764189.1540656774756 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Hi Paul, Luis, Markus, LF let me join the topic ;-) the antenna location of Luis is something else of your Markus and Paul and = much similar to mine: roof based antennas with elevated ground (in my case)= and vertical ground (the water pipe) for Luis. Anyway also in my case the serie resistance of my antenna increases with ra= in (almost doubles). But.. Luis, probably assumes the lower impedance basing on the higher curre= nt. Luis, what kind of LPF have you adopted? Now I have a T filter with no shunting cap at the input and impedance incre= ases with rain both with and without LPF, but if I remember correctly, when= in the past I had an PI LPF with shunting input and output caps the impeda= nce in my shack was transformed from the transmission line and LPF giving l= ower impedance by rain. Could be an explication? By the way, just for fate it's raining also here and I made some measuremen= t when dry again will repeat ;-) Have a funny weekend LF Marco IK1HSS =20 ----Messaggio originale---- Da: paul@n1bug.com Data: 27-ott-2018 12.34 A: Ogg: Antenna resistance (Re: LF: EbNaut Autodecoder 137490 Hz: EA5DOM recei= ved) Hi Luis, Markus, LF This is a very interesting topic for me too. My antenna resistance is very high, usually more than 100 ohms. I think there may be a few reasons. There are trees near the antenna which I presume to be lossy. My antenna ground system is not tied into the house ground, in order to minimize 120 Hz sidebands on my transmitted signal. When I tie the grounds together the level of these sidebands increases almost 20 dB. Also my RX antenna is more noisy when the TX antenna ground and house ground are tied together. I suppose this is because more noise is radiated from the TX antenna, then picked up by the RX antenna which has its own small, isolated ground. Rain has no effect on the antenna resistance, but temperature does. During summer there is little change, just minor variations. But as the temperature drops and begins to approach freezing, resistance begins to get lower. There is a big drop right around freezing or few degrees below, but resistance continues to drop with even lower temperatures, reaching minimum on the coldest winter nights. Last winter I saw it reach 40 ohms a few times. :) I am no expert but I guess the trees are partly responsible for the high resistance and the drop with freezing temperature? Anyway I can run enough power to reach calculated 1W EIRP and it's enough to be heard across that little pond. :) But here is a related question: I have calculated my EIRP to be one watt using the measured resistance, antenna parameters and current. But does this calculation include all the losses in trees? If I had the proper equipment to make field strength measurements at a distance, would I find that my EIRP is less than one watt due to the tree losses? 73, Paul N1BUG On 10/27/18 5:45 AM, Markus Vester wrote: > Hi Luis, >=20 >> Impedance drops a lot after rain >=20 > This seems unusual. I have exactly the opposite effect here: > Series resistance at 137 kHz is normally around 20 ohms > (including 5 ohms for the coil). When it rains it get worse up to > about 40 ohms, whereas best times are cold and dry winter days > with ~15 ohms when the trees are solidly frozen. So I presume > that the major contribution to my resistance are > capacitively-coupled losses in vegetation and other nearfield > environment. The ground connection itself (the "house earth" > which is connected to electric grid PE, and also pipe systems for > water supply and distict heating) seems to have a low resistance. >=20 >=20 > My only explanation for lower wet resistance would be if one were > using a separate radial system in the garden, whose connection to > ground might be better when the lawn is soaked. But I don't think > this applies to your setup at all. >=20 > Best 73, Markus >=20 > Von: VIGILANT Luis Fern=C3=A1ndez >=20 > I'm struggling > here with the antenna. Most of the time impedance rises and I > hardly run 1A RF current > > Rainy weekend here. > Impedance drops a lot after rain. Let's see how much current can > drainLast time I could see almost 4A RF. ------=_Part_10579_6764189.1540656774756 Content-Type: text/html;charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi Paul, Luis, Markus, LF

let me join the topic ;-)
the antenna l= ocation of Luis is something else of your Markus and Paul and much similar = to mine: roof based antennas with elevated ground (in my case) and vertical= ground (the water pipe) for Luis.
Anyway also in my case the serie resi= stance of my antenna increases with rain (almost doubles).
But.. Luis, p= robably assumes the lower impedance basing on the higher current.
Luis, = what kind of LPF have you adopted?
Now I have a T filter with no shuntin= g cap at the input and impedance increases with rain both with and without = LPF, but if I remember correctly, when in the past I had an PI LPF with shu= nting input and output caps the impedance in my shack was transformed from = the transmission line and LPF giving lower impedance by rain.

Could = be an explication?

By the way, just for fate it's raining also here = and I made some measurement when dry again will repeat ;-)

Have a fu= nny weekend LF

Marco IK1HSS
 

----Messaggio originale----
Da: paul@n1bug.com
Data: 27-ott-2018 12.3= 4
A: <rsgb_lf_group@blacksheep.org>
Ogg: Antenna resistance (Re= : LF: EbNaut Autodecoder 137490 Hz: EA5DOM received)

Hi Luis, Markus= , LF

This is a very interesting topic for me too.

My antenna = resistance is very high, usually more than 100 ohms. I
think there may b= e a few reasons. There are trees near the antenna
which I presume to be = lossy. My antenna ground system is not tied
into the house ground, in or= der to minimize 120 Hz sidebands on my
transmitted signal. When I tie th= e grounds together the level of
these sidebands increases almost 20 dB. = Also my RX antenna is more
noisy when the TX antenna ground and house gr= ound are tied together.
I suppose this is because more noise is radiated= from the TX
antenna, then picked up by the RX antenna which has its own= small,
isolated ground.

Rain has no effect on the antenna resist= ance, but temperature does.
During summer there is little change, just m= inor variations. But as
the temperature drops and begins to approach fre= ezing, resistance
begins to get lower. There is a big drop right around = freezing or
few degrees below, but resistance continues to drop with eve= n lower
temperatures, reaching minimum on the coldest winter nights. Las= t
winter I saw it reach 40 ohms a few times. :)

I am no expert bu= t I guess the trees are partly responsible for the
high resistance and t= he drop with freezing temperature?

Anyway I can run enough power to = reach calculated 1W EIRP and it's
enough to be heard across that little = pond. :)

But here is a related question: I have calculated my EIRP t= o be one
watt using the measured resistance, antenna parameters and curr= ent.
But does this calculation include all the losses in trees? If I had=
the proper equipment to make field strength measurements at a
distan= ce, would I find that my EIRP is less than one watt due to the
tree loss= es?

73,
Paul N1BUG



On 10/27/18 5:45 AM, Markus Ves= ter wrote:
> Hi Luis,
>
>> Impedance drops a lot afte= r rain
>
> This seems unusual. I have exactly the opposite eff= ect here:
> Series resistance at 137 kHz is normally around 20 ohms> (including 5 ohms for the coil). When it rains it get worse up to> about 40 ohms, whereas best times are cold and dry winter days
>= ; with ~15 ohms when the trees are solidly frozen. So I presume
> tha= t the major contribution to my resistance are
> capacitively-coupled = losses in vegetation and other nearfield
> environment. The ground co= nnection itself (the "house earth"
> which is connected to electric g= rid PE, and also pipe systems for
> water supply and distict heating)= seems to have a low resistance.
>
>
> My only explanat= ion for lower wet resistance would be if one were
> using a separate = radial system in the garden, whose connection to
> ground might be be= tter when the lawn is soaked. But I don't think
> this applies to you= r setup at all.
>
> Best 73, Markus
>
> Von: VIGI= LANT Luis Fern=C3=A1ndez
>
> I'm struggling
> here with = the antenna. Most of the time impedance rises and I
> hardly run 1A R= F current
>
> Rainy weekend here.
> Impedance drops a lot= after rain. Let's see how much current can
> drainLast time I could = see almost 4A RF.



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