Return-Path: Received: from mtain-me06.r1000.mx.aol.com (mtain-me06.r1000.mx.aol.com [172.29.96.142]) by air-de06.mail.aol.com (v127_r1.1) with ESMTP id MAILINDE064-5eb94b9531ed29f; Mon, 08 Mar 2010 12:20:45 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-me06.r1000.mx.aol.com (Internet Inbound) with ESMTP id 50C1238000140; Mon, 8 Mar 2010 12:20:43 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Nogbo-0000zo-Bz for rs_out_1@blacksheep.org; Mon, 08 Mar 2010 17:19:12 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Nogbn-0000zf-PM for rsgb_lf_group@blacksheep.org; Mon, 08 Mar 2010 17:19:11 +0000 Received: from imr-da04.mx.aol.com ([205.188.105.146]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Nogbm-0004EE-BX for rsgb_lf_group@blacksheep.org; Mon, 08 Mar 2010 17:19:11 +0000 Received: from imo-ma04.mx.aol.com (imo-ma04.mx.aol.com [64.12.78.139]) by imr-da04.mx.aol.com (8.14.1/8.14.1) with ESMTP id o28HIoOH007102 for ; Mon, 8 Mar 2010 12:18:50 -0500 Received: from MarkusVester@aol.com by imo-ma04.mx.aol.com (mail_out_v42.9.) id l.cf7.732f3d22 (37142) for ; Mon, 8 Mar 2010 12:18:45 -0500 (EST) Received: from smtprly-me02.mx.aol.com (smtprly-me02.mx.aol.com [64.12.95.103]) by cia-ma03.mx.aol.com (v127_r1.2) with ESMTP id MAILCIAMA034-b2cf4b953170152; Mon, 08 Mar 2010 12:18:45 -0500 Received: from webmail-m018 (webmail-m018.sim.aol.com [64.12.101.102]) by smtprly-me02.mx.aol.com (v127.7) with ESMTP id MAILSMTPRLYME026-b2cf4b953170152; Mon, 08 Mar 2010 12:18:40 -0500 References: <2CDE578A1E1B49AF96D61BB5D91FA03D@White><20100308082209.1C973F3862@smtps02.kuleuven.be><8CC8CC36E425927-1F28-913E@webmail-d097.sysops.aol.com> <20100308160521.5A32AF3865@smtps02.kuleuven.be> To: rsgb_lf_group@blacksheep.org Date: Mon, 08 Mar 2010 12:18:40 -0500 In-Reply-To: <20100308160521.5A32AF3865@smtps02.kuleuven.be> X-MB-Message-Source: WebUI MIME-Version: 1.0 From: Markus Vester X-MB-Message-Type: User X-Mailer: Webmail 30746-STANDARD Received: from 194.138.39.61 by webmail-m018.sysops.aol.com (64.12.101.102) with HTTP (WebMailUI); Mon, 08 Mar 2010 12:18:40 -0500 Message-Id: <8CC8CFA87EEE662-4A8C-CE75@webmail-m018.sysops.aol.com> X-Spam-Flag:NO X-AOL-SENDER: MarkusVester@aol.com X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001,UNPARSEABLE_RELAY=0.001 Subject: Re: LF: 12 km on Dream(ers) Band - TX loss calculation Content-Type: multipart/alternative; boundary="--------MB_8CC8CFA8814FC72_4A8C_19CEF_webmail-m018.sysops.aol.com" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.1 required=5.0 tests=HTML_FONTCOLOR_UNKNOWN, 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 x-aol-global-disposition: G x-aol-sid: 3039ac1d608e4b9531eb64dd X-AOL-IP: 193.82.116.20 ----------MB_8CC8CFA8814FC72_4A8C_19CEF_webmail-m018.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="us-ascii" Dear Rik, LF, the reason why I prefer series feeding is that the amplifier current drops= when the antenna falls out of resonance, either due to arcing, or detunin= g by wind (or pieces falling off). With a tap at a few turns or light indu= ctive coupling, the detuned load would be seen nearly as a short circuit.= There are ways around this, either by parallel-resonating the small coupl= ing coil with a large capacitance (ie. bandfilter coupling, which also pro= vides a convenient variable impedance match), or inserting a lowpass filte= r having about 90 degrees phase shift. =20 In the first round of 9 kHz experiments, Walter (DL2LF), Geri (DK8KW) and= myself all have attempted to use large ferrite cores. In principle you ca= n come to a more compact and higher Q coil. But when going to large voltag= es, there are two types of difficulties: Core saturation introduces additi= onal hysteresis losses, accompanied by current-dependent inductance which= made tuning "jumpy". To mitigate that, you basically need a large iron cr= oss section and a large air gap. The other issue was voltage breakdown bet= ween the "hot" end and the partly conductive core material.=20 I think my coil wire is actually .2 mm copper diameter, about 0.55 ohms/m.= The ten sections were wound separately on their food containers using a= "converted electrical lemon squasher", and series connected externally af= ter assembly. Best 73, MArkus -----Urspruengliche Mitteilung-----=20 Von: Rik Strobbe An: rsgb_lf_group@blacksheep.org Verschickt: Mo., 8. Mrz. 2010, 17:05 Thema: Re: LF: 12 km on Dream(ers) Band - TX loss calculation Hello Marcus, could the loss in the impedance transformer be avoided by tapping the load= ing coil ? I just had a look at the "copper wire tables" and 0.2mm OD wire (actually= 0.15mm copper) has a resistance of 1 Ohm/m. Quite a challenge to get 830= m wire on the coil without breaking the wire :-). Would it also work with less (but thicker) wire and a ferrite core ? The ferrite core will introduce some additional loss, but on the other han= d you will have less (and thicker) wire reducing the copper losses. But I= am not sure what the overall effect will be. 73, Rik ON7YD At 11:44 8/03/2010, you wrote: Dear Rik, LF, =20 yes these numbers are pretty much where I arrived in my calculations. Ther= e is some loss in the transformer, about 1024* 0.25 ohm from the primary= and 60 ohm in the secondary, adding up to 315 ohm series loss. Thus anten= na resistance at 9 kHz would be more like 700 ohm. The same antenna has a= much lower resistance on 137 kHz, around 35 ohms normally, and down to 28= ohms in cold and dry weather. This includes the LF coil resistance (RF li= tz wire, Q ~ 700, Rcoil ~ 7 ohm). The large difference indicates that capa= citively coupled losses from high-resistance objects (trees, roof etc.) ar= e probably dominating at 9 kHz.=20 =20 BTW I just noticed an error in the the 9 kHz coil description, it actually= has 10 sections, 500 turns each (back to kindergarten then to learn count= ing to ten ;-). Skin effect is probably still neglegible with the thin 0.2= mm wire, but there may be some eddy current loss (proximity effect) in th= e overlapping layers. Best 73, Markus -----Urspruengliche Mitteilung-----=20 Von: Rik Strobbe An: rsgb_lf_group@blacksheep.org Verschickt: Mo., 8. Mrz. 2010, 9:22 Thema: Re: LF: 12 km on Dream(ers) Band Hello Marcus, first of all congrats with your achievement. Based on the numbers you gave I tried to figure out the loss resistance at= 9kHz: - 35W and 0.135A would give 1920 Ohm.=20 - with a 32/1 transformer the TX (audio amp) would be loaded with 1.8 Ohm Assuming that the loss at 9kHz is slightly more than the DC loss (let's sa= y 900 Ohm) the "ground loss" (including greenery and buildings) would be= about 1 kOhm. Can you confirm this figures ? 73, Rik ON7YD ----------MB_8CC8CFA8814FC72_4A8C_19CEF_webmail-m018.sysops.aol.com Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset="us-ascii"

Dear Rik, LF,
 
the reason why I prefer series feeding is that the amplifier current= drops when the antenna falls out of resonance, either due to arcing, or= detuning by wind (or pieces falling off). With a tap at a few turns or li= ght inductive coupling, the detuned load would be seen nearly as a short= circuit. There are ways around this, either by parallel-resonating the&nb= sp;small coupling coil with a large capacitance (ie. bandfilter coupl= ing, which also provides a convenient variable impedance match), or insert= ing a lowpass filter having about 90 degrees phase shift.  =
 
In the first round of 9 kHz experiments, Walter (DL2LF), Geri (DK8KW)= and myself all have attempted to use large ferrite cores. In princip= le you can come to a more compact and higher Q coil. But when going to&nbs= p;large voltages, there are two types of difficulties: Core saturation int= roduces additional hysteresis losses, accompanied by current-dependent ind= uctance which made tuning "jumpy". To mitigate that, you basically need a= large iron cross section and a large air gap. The other issue was voltage= breakdown between the "hot" end and the partly conductive core material.=
 
I think my coil wire is actually .2 mm copper diameter, about 0.55 oh= ms/m. The ten sections were wound separately on their food containers usin= g a "converted electrical lemon squasher", and series connected externally= after assembly.
 
Best 73,
MArkus


-----Urspruengliche Mitteilung-----
Von: Rik Strobbe <rik.strobbe@fys.kuleuven.be>
An: rsgb_lf_group@blacksheep.org <rsgb_lf_group@blacksheep.org>
Verschickt: Mo., 8. Mrz. 2010, 17:05
Thema: Re: LF: 12 km on Dream(ers) Band - TX loss calculation

Hello Marcus,<= br>
could the loss in the impedance transformer be avoided by tapping the load= ing coil ?
I just had a look at the "copper wire tables" and 0.2mm OD wire (actually= 0.15mm copper) has a resistance of 1 Ohm/m. Quite a  challenge to ge= t 830m wire on the coil without breaking the wire :-).
Would it also work with less (but thicker) wire and a ferrite core ?
The ferrite core will introduce some additional loss, but on the other han= d you will have less (and thicker) wire reducing the copper losses. But I= am not sure what the overall effect will be.

73, Rik  ON7YD


At 11:44 8/03/2010, you wrote:
Dear Ri= k, LF,
 
yes these numbers are pretty much where I arrived in my calculations. Ther= e is some loss in the transformer, about  1024* 0.25 ohm from the pri= mary and 60 ohm in the secondary, adding up to 315 ohm series loss. Thus= antenna resistance at 9 kHz would be more like 700 ohm. The same antenna= has a much lower resistance on 137 kHz, around 35 ohms normally, and down= to 28 ohms in cold and dry weather. This includes the LF coil resistance= (RF litz wire, Q ~ 700, Rcoil ~ 7 ohm). The large difference indicates th= at capacitively coupled losses from high-resistance objects (trees, roof= etc.) are probably dominating at 9 kHz.
 
BTW I just noticed an error in the the 9 kHz coil description, it actually= has 10 sections, 500 turns each (back to kindergarten then to learn count= ing to ten ;-). Skin effect is probably still neglegible with the thin 0.2= mm wire, but there may be some eddy current loss (proximity effect) in th= e overlapping layers.

Best 73,
Markus


-----Urspruengliche Mitteilung-----
Von: Rik Strobbe <rik.st= robbe@fys.kuleuven.be>
An: rsgb_lf_group@blackshe= ep.org <rsgb_lf_gro= up@blacksheep.org>
Verschickt: Mo., 8. Mrz. 2010, 9:22
Thema: Re: LF: 12 km on Dream(ers) Band

Hello Marcus,

first of all congrats with your achievement.
Based on the numbers you gave I tried to figure out the loss resistance at= 9kHz:
- 35W and 0.135A would give 1920 Ohm.
- with a 32/1 transformer the TX (audio amp) would be loaded with 1.8 Ohm<= br> Assuming that the loss at 9kHz is slightly more than the DC loss (let's sa= y 900 Ohm) the "ground loss" (including greenery and buildings) would be= about 1 kOhm.
Can you confirm this figures ?

73, Rik  ON7YD

 
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