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 w9SFVHBV012934 for ; Sun, 28 Oct 2018 16:31:18 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1gGmxF-00087d-E9 for rs_out_1@blacksheep.org; Sun, 28 Oct 2018 15:26:17 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1gGmx7-00087U-7B for rsgb_lf_group@blacksheep.org; Sun, 28 Oct 2018 15:26:09 +0000 Received: from mout02.posteo.de ([185.67.36.66]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91_59-0488984) (envelope-from ) id 1gGmx4-0006ft-Bu for rsgb_lf_group@blacksheep.org; Sun, 28 Oct 2018 15:26:07 +0000 Received: from submission (posteo.de [89.146.220.130]) by mout02.posteo.de (Postfix) with ESMTPS id 779902400E5 for ; Sun, 28 Oct 2018 16:26:04 +0100 (CET) X-DKIM-Result: Domain=posteo.de Result=Signature OK DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.de; s=2017; t=1540740364; bh=mvfyCwjdLtK6KZFE2rNrwxPqDLXtw8SO/vVjqCefYSw=; h=Date:From:To:Subject:From; b=WRh2ywfJwuB0VWDNQiHpQzhgbHcBEAWOdvK9k9TMo35kOB+bOlbreGBTb/EPCFGPG uzB/+kxBvAWdVIss9FgjxK5NKlNFv/TeN5L/52VWb8i4GjsdnGrGbP3PR76rLJ50NF JNnh4p41stTf4bGerSUHpC42gIX04VImijErMwSQUFOn0eoSoOedvLH338jnbW0+w9 bH+ze+ZE3n5qKSXH2hltGTUBI2JYGfHkLYdblSiWmC7ZdH5zdnNu9NnWiP8e+EJssy LU8ee623qKIGFRSFIQzn2hN3B7TM2Bdu3vhfeyXplr9EfuzPiLZMQyeRw282T4BJFj /eY0mkOqW6x0w== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 42jhQM6CKDz9rxK for ; Sun, 28 Oct 2018 16:26:02 +0100 (CET) Message-ID: <5BD5D50A.4060405@posteo.de> Date: Sun, 28 Oct 2018 16:26:02 +0100 From: DK7FC User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <166b64cbe61.marcocadeddu@tin.it> <6DB8451D7F3D3947A5918808A59621EA0867FDA1@servigilant.vigilant.local> In-Reply-To: <6DB8451D7F3D3947A5918808A59621EA0867FDA1@servigilant.vigilant.local> X-Spam-Score: -2.3 (--) 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 Luis, Am 27.10.2018 23:11, schrieb VIGILANT Luis Fernández: > Hi All, LF > > Interesting topic. Also happens in MF but in LF it gets more critical. > Must be a nightmare at VLF :( Here it is more critcal on MF than on LF. At VLF it is quite uncritical because the coil's resistance is a major part of the overall losses. > Other intringuin detail. When it is dry and impedance rises to >100 > Ohm the only way to hardly reach 1A RF > is to detune the antenna. I have to set the resonant peak at 138Khz > and then at 137,5 get even higher impedance > and high SWR, but the antenna current rises and so the radiated signal. How do you measure the antena current? Are you sure the waveform still looks like a sine? > All this at the cost of more amps > consumed by the PA and higer voltage at antenna feed. Running the > antenna at the optimum resonance makes > almost no RF current, even considering that this is the minimum > impedance point. Hm, are you sure your antenna has 50 Ohm when it is resonated? Otherwise you may need a transformer to transform it to 50 Ohm. Or your LPS is not working properly. What power output do you get when using a 50 Ohm dummy load? And what efficiency? [...] Content analysis details: (-2.3 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at http://www.dnswl.org/, medium trust [185.67.36.66 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 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: 961b72438de48e5ba6ae15a9c530febb Subject: Re: Antenna resistance (Re: LF: EbNaut Autodecoder 137490 Hz: EA5DOM received) Content-Type: multipart/alternative; boundary="------------040402080700090902050205" 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 This is a multi-part message in MIME format. --------------040402080700090902050205 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Hi Luis, Am 27.10.2018 23:11, schrieb VIGILANT Luis Fernández: > Hi All, LF > > Interesting topic. Also happens in MF but in LF it gets more critical. > Must be a nightmare at VLF :( Here it is more critcal on MF than on LF. At VLF it is quite uncritical because the coil's resistance is a major part of the overall losses. > Other intringuin detail. When it is dry and impedance rises to >100 > Ohm the only way to hardly reach 1A RF > is to detune the antenna. I have to set the resonant peak at 138Khz > and then at 137,5 get even higher impedance > and high SWR, but the antenna current rises and so the radiated signal. How do you measure the antena current? Are you sure the waveform still looks like a sine? > All this at the cost of more amps > consumed by the PA and higer voltage at antenna feed. Running the > antenna at the optimum resonance makes > almost no RF current, even considering that this is the minimum > impedance point. Hm, are you sure your antenna has 50 Ohm when it is resonated? Otherwise you may need a transformer to transform it to 50 Ohm. Or your LPS is not working properly. What power output do you get when using a 50 Ohm dummy load? And what efficiency? 73, Stefan > > About the LPF, this is really the only part of the Ropex PA still in > use. This is a link to the schematic with the LPF > https://www.dropbox.com/s/ejn5stuz7vban7u/Ropex%20Schematic.JPG?dl=0 > > Have not tried without LPF. The analyzer measurements are made > directly to antenna. But may be a good idea to > make them with the LPF inserted and see what happens > > 73 de Luis > EA5DOM > > ------------------------------------------------------------------------ > *De:* owner-rsgb_lf_group@blacksheep.org > [owner-rsgb_lf_group@blacksheep.org] en nombre de marcocadeddu@tin.it > [marcocadeddu@tin.it] > *Enviado:* sábado, 27 de octubre de 2018 18:12 > *Para:* rsgb_lf_group@blacksheep.org > *Asunto:* R: Antenna resistance (Re: LF: EbNaut Autodecoder 137490 Hz: > EA5DOM received) > > 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. > > 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 funny weekend LF > > Marco IK1HSS > > > ----Messaggio originale---- > Da: paul@n1bug.com > Data: 27-ott-2018 12.34 > A: > 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 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, > > > >> Impedance drops a lot after rain > > > > 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. > > > > > > 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. > > > > Best 73, Markus > > > > Von: VIGILANT Luis Fernández > > > > 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. > > > --------------040402080700090902050205 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Hi Luis,

Am 27.10.2018 23:11, schrieb VIGILANT Luis Fernández:
Hi All, LF

Interesting topic. Also happens in MF but in LF it gets more critical. Must be a nightmare at VLF :(

Here it is more critcal on MF than on LF. At VLF it is quite uncritical because the coil's resistance is a major part of the overall losses.
Other intringuin detail. When it is dry and impedance rises to >100 Ohm the only way to hardly reach 1A RF
is to detune the antenna. I have to set the resonant peak at 138Khz and then at 137,5 get even higher impedance
and high SWR, but the antenna current rises and so the radiated signal.
How do you measure the antena current? Are you sure the waveform still looks like a sine?
All this at the cost of more amps
consumed by the PA and higer voltage at antenna feed. Running the antenna at the optimum resonance makes
almost no RF current, even considering that this is the minimum impedance point.
Hm, are you sure your antenna has 50 Ohm when it is resonated? Otherwise you may need a transformer to transform it to 50 Ohm. Or your LPS is not working properly. What power output do you get when using a 50 Ohm dummy load? And what efficiency?

73, Stefan



About the LPF, this is really the only part of the Ropex PA still in use. This is a link to the schematic with the LPF

Have not tried without LPF. The analyzer measurements are made directly to antenna. But may be a good idea to
make them with the LPF inserted and see what happens

73 de Luis
EA5DOM

De: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] en nombre de marcocadeddu@tin.it [marcocadeddu@tin.it]
Enviado: sábado, 27 de octubre de 2018 18:12
Para: rsgb_lf_group@blacksheep.org
Asunto: R: Antenna resistance (Re: LF: EbNaut Autodecoder 137490 Hz: EA5DOM received)

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.

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 funny weekend LF

Marco IK1HSS
 

----Messaggio originale----
Da: paul@n1bug.com
Data: 27-ott-2018 12.34
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 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,
>
>> Impedance drops a lot after rain
>
> 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.
>
>
> 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.
>
> Best 73, Markus
>
> Von: VIGILANT Luis Fernández
>
> 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.



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