Return-Path: Received: from rly-de06.mx.aol.com (rly-de06.mail.aol.com [172.19.170.142]) by air-de01.mail.aol.com (v123.4) with ESMTP id MAILINDE013-4df49d4da6fb2; Thu, 02 Apr 2009 11:32:27 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-de06.mx.aol.com (v123.4) with ESMTP id MAILRELAYINDE062-4df49d4da6fb2; Thu, 02 Apr 2009 11:32:01 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1LpOsm-0001uT-2M for rs_out_1@blacksheep.org; Thu, 02 Apr 2009 16:31:08 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1LpOsl-0001uK-BP for rsgb_lf_group@blacksheep.org; Thu, 02 Apr 2009 16:31:07 +0100 Received: from cavuit01.kulnet.kuleuven.be ([134.58.240.43]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1LpOsi-0007aW-Pr for rsgb_lf_group@blacksheep.org; Thu, 02 Apr 2009 16:31:07 +0100 Received: from smtps01.kuleuven.be (smtpshost01.kulnet.kuleuven.be [134.58.240.74]) by cavuit01.kulnet.kuleuven.be (Postfix) with ESMTP id 0785D7B804B for ; Thu, 2 Apr 2009 17:30:24 +0200 (CEST) Received: from smtps01.kuleuven.be (localhost [127.0.0.1]) by smtps01.kuleuven.be (Postfix) with ESMTP id C98E731E703 for ; Thu, 2 Apr 2009 17:30:23 +0200 (CEST) Received: from dell-rik.fys.kuleuven.be (dhcp-10-33-85-199.fys.kuleuven.be [10.33.85.199]) by smtps01.kuleuven.be (Postfix) with ESMTP id 7FF2731E702 for ; Thu, 2 Apr 2009 17:30:23 +0200 (CEST) X-Mailer: QUALCOMM Windows Eudora Version 7.1.0.9 Date: Thu, 02 Apr 2009 17:30:25 +0200 To: rsgb_lf_group@blacksheep.org X-Kuleuven: This mail passed the K.U.Leuven mailcluster From: Rik Strobbe In-Reply-To: References: <20090402074911.6B552F3866@smtps02.kuleuven.be> <1LpKtN-16pRzc0@fwd02.t-online.de> Mime-Version: 1.0 Message-Id: <20090402153023.7FF2731E702@smtps01.kuleuven.be> X-KULeuven-Information: Katholieke Universiteit Leuven X-KULeuven-Scanned: Found to be clean X-KULeuven-Envelope-From: rik.strobbe@fys.kuleuven.be X-Karma: unknown: X-Spam-Score: 1.4 (+) X-Spam-Report: autolearn=disabled,HTML_10_20=0.945,HTML_FONT_FACE_BAD=0.452,HTML_MESSAGE=0.001 Subject: Re: LF: Tune and match the ant for 50kHz...550kHz Content-Type: multipart/alternative; boundary="=====================_84821109==.ALT" 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 X-AOL-IP: 193.82.116.20 --=====================_84821109==.ALT Content-Type: text/plain; charset="us-ascii"; format=flowed Petr, you can use a Pi filter, but I am afraid that the values might become rather inconvenient: A short (relative to the wavelength) wire antenna will act as a R-C series circuit where C is the antenna capacitance and R mainly the loss resistance. In most cases R is in the range of 10 .. 200 Ohm while Xc is in the range of 500 .. 50000 Ohm (depending on antenna length and frequency). A long wire goes with a relative small Xc but also relative small R (footprint theory), a short wire with a large Xc and large R. So in almost any case Xc >>> R. This will result in a large value for the L of the filter an relative small values for the C's. If R = 50 Ohm you would end up with Pi filter with an large (XL = Xc) and both C's = 0 (so you can omit them). 73, Rik ON7YD - OR7T At 15:15 2/04/2009, you wrote: >Hello Ha-Jo > >Thanks for your suggestion. My transmatch woud be used mainly for >RX, however, I still believe that a tuned antenna is better than >detuned one. At least it is a good preselection for RX. Most of the >RX's have just a LPF at these fq's and therefore they are >"broadband" in some way. The transmatch is then the only tuned >circuit in front of the RX. >I am still wondering whether a standard Pi network could be used? >There would be two large banks of condensers on both sides (high >voltage ones on the side of ant) switched by rotary switches. Fine >tuning would happen by the variometer in the middle. The only >disadvantage would be that on the lower end of range (say 50 or 100 >kHz) the vario inductivity would be too low and tuning would be >difficult (woolly), while on the higher end (550 kHz), it would be >too high, tuning would be rather sharp and losses in the vario also >rather high. >Could this work? > >73, Petr > >----- Original Message ----- >From: hajo.brandt.dj1zb@t-online.de >To: rsgb_lf_group@blacksheep.org >Sent: Thursday, April 02, 2009 1:15 PM >Subject: Re: LF: Tune and match the ant for 50kHz...550kHz > >Dear Petr, > >I guess the easiest solution would be to seperate receiving and transmitting. > >For receive it is not necessary at all to tune the antenna. I am >using my LF T-antenna for receive from 10 kHz to 30 MHz (in addition >I also have an untuned wire loop covering 10 kHz to at least 500 >kHz, pointing to the north). Tuning the antenna would just increase >the antenna noise too, as SM6BHZ has also told me. You may just need >somewhat more amplification before the rx, and possibly an rx >preselection before this preamplifier. > >Concentrating on just tuning the antenna for transmitting on either >136 kHz or 500 kHz would be much easier. > >And, by the way, the "sphere in sphere" variometer has a big >drawback: Its Q is quite OK at maximum inductivity but very poor at >its minumum. Explanation is simple. Just assuming the resistance of >the wire being constant, at low inducitivity the relation XL to R >becomes very poor. > >OK? > >73 Ha-Jo, DJ1ZB > > > "Rik Strobbe" schrieb: >Hello Petr, > >50-550kHz seems a "big shot". >If you want to tune (bring to resonance) the antenna using a >variometer it would need a ratio of (550/50)^2 = 121. >The variometer I use on 500kHz has a range of 40-450uH, thus a ratio >of 11. The variometer comes from an 500kHz marine transmitter and it >would be rather complex to build a copy (mechanical). >Running low power you could use a parallel LC circuit. One end to >the antenna and the other end to ground. The TX is connected to a >tap at the coil, close to ground. You can tune the antenna to >resonance by changing C (variable capacitor) and match to 50 Ohm by >changing taps on the coil. I did that with success in the early days >on 136kHz, but I could run only 30W power before the capacitor >(plate distance 2mm) started arcing. >Now you will need a capacitor with a ratio of 121, but that is not >so hard: most variable capacitors have a range of 20 or better and >you can put some fixed capacitors in parallel (via switches). > >73, Rik ON7YD > >At 09:26 2/04/2009, you wrote: >>Hi all, >> >>I want to make a small transmatch (RX, TX up to 10 Watts, or so) to >>tune LW 41 m (or smaller T-ant) in the range 50 ... 550 kHz. >>I am not too good in theory... but I believe that the most >>efficient system is the popular loading coil (home made variometer, >>and taps to find 50 Ohms match). >>The simple variometer (cylindrical coil in another cylindrical >>coil) is easy to make and works fine on 136kHz. However, it is >>possible to change inductance in the range about 1:2 or 1:3 only, >>not much better. Therefore the redudant inductance is too high to >>fetch the ant to resonance on 550 kHz. >>Solution would be to make a more sophisticated variometer (best: >>sphere in sphere) to reach the ratio 1:10 or so. >>Or, to use a different kind of network. Pi network, L network or T >>network. BTW I would also prefer to use a rotary switch and solder >>twenty condensers rather than to make twenty taps on a coil wound >>with litz wire... >> >>How did you solve this yourself? >> >>Thanks, 73, Petr, OK1FIG >> >> >> > > >Disclaimer: >http://www.kuleuven.be/cwis/email_disclaimer.htm >for more information. > > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm --=====================_84821109==.ALT Content-Type: text/html; charset="us-ascii" Petr,

you can use a Pi filter, but I am afraid that the values might become rather inconvenient:
A short (relative to the wavelength) wire antenna will act as a R-C series circuit where C is the antenna capacitance and R mainly the loss resistance.
In most cases R is in the range of 10 .. 200 Ohm while Xc is in the range of 500 .. 50000 Ohm (depending on antenna length and frequency).
A long wire goes with a relative small Xc but also relative small R (footprint theory), a short wire with a large Xc and large R.
So in almost any case Xc >>> R. This will result in a large value for the L of the filter an relative small values for the C's.
If R = 50 Ohm you would end up with Pi filter with an large  (XL = Xc) and both C's = 0 (so you can omit them).

73, Rik  ON7YD - OR7T


At 15:15 2/04/2009, you wrote:
Hello Ha-Jo
 
Thanks for your suggestion. My transmatch woud be used mainly for RX, however, I still believe that a tuned antenna is better than detuned one. At least it is a good preselection for RX. Most of the RX's have just a LPF at these fq's and therefore they are "broadband" in some way. The transmatch is then the only tuned circuit in front of the RX.
I am still wondering whether a standard Pi network could be used? There would be two large banks of condensers on both sides (high voltage ones on the side of ant) switched by rotary switches. Fine tuning would happen by the variometer in the middle. The only disadvantage would be that on the lower end of range (say 50 or 100 kHz) the vario inductivity would be too low and tuning would be difficult (woolly), while on the higher end (550 kHz), it would be too high, tuning would be rather sharp and losses in the vario also rather high.
Could this work?
 
73, Petr
 
----- Original Message -----
From: hajo.brandt.dj1zb@t-online.de
To: rsgb_lf_group@blacksheep.org
Sent: Thursday, April 02, 2009 1:15 PM
Subject: Re: LF: Tune and match the ant for 50kHz...550kHz

Dear Petr,

I guess the easiest solution would be to seperate receiving and transmitting.

For receive it is not necessary at all to tune the antenna. I am using my LF T-antenna for receive from 10 kHz to 30 MHz (in addition I also have an untuned wire loop covering 10 kHz to at least 500 kHz, pointing to the north). Tuning the antenna would just increase the antenna noise too, as SM6BHZ has also told me. You may just need somewhat more amplification before the rx, and possibly an rx preselection before this preamplifier.

Concentrating on just tuning the antenna for transmitting on either 136 kHz or 500 kHz would be much easier.

And, by the way,  the "sphere in sphere" variometer has a big drawback: Its Q is quite OK at maximum inductivity but very poor at its minumum. Explanation is simple. Just assuming the resistance of the wire being constant, at low inducitivity the relation XL to R becomes very poor.

OK?

73 Ha-Jo, DJ1ZB


  "Rik Strobbe" <rik.strobbe@fys.kuleuven.be> schrieb:
Hello Petr,

50-550kHz seems a "big shot".
If you want to tune (bring to resonance) the antenna using a variometer it would need a ratio of (550/50)^2 = 121.
The variometer I use on 500kHz has a range of 40-450uH, thus a ratio of 11. The variometer comes from an 500kHz marine transmitter and it would be rather complex to build a copy (mechanical).
Running low power you could use a parallel LC circuit. One end to the antenna and the other end to ground. The TX is connected to a tap at the coil, close to ground. You can tune the antenna to resonance by changing C (variable capacitor) and match to 50 Ohm by changing taps on the coil. I did that with success in the early days on 136kHz, but I could run only 30W power before the capacitor (plate distance 2mm) started arcing.
Now you will need a capacitor with a ratio of 121, but that is not so hard: most variable capacitors have a range of 20 or better and you can put some fixed capacitors in parallel (via switches).

73, Rik  ON7YD

At 09:26 2/04/2009, you wrote:
Hi all,
 
I want to make a small transmatch (RX, TX up to 10 Watts, or so) to tune LW 41 m (or smaller T-ant) in the range 50 ... 550 kHz.
I am not too good in theory... but I believe that the most efficient system is the popular loading coil (home made variometer, and taps to find 50 Ohms match).
The simple variometer (cylindrical coil in another cylindrical coil) is easy to make and works fine on 136kHz. However, it is possible to change inductance in the range about 1:2 or 1:3 only, not much better. Therefore the redudant inductance is too high to fetch the ant to resonance on 550 kHz.
Solution would be to make a more sophisticated variometer (best: sphere in sphere) to reach the ratio 1:10 or so.
Or, to use a different kind of network. Pi network, L network or T network. BTW I would also prefer to use a rotary switch and solder twenty condensers rather than to make twenty taps on a coil wound with litz wire...
 
How did you solve this yourself?
 
Thanks, 73, Petr, OK1FIG
 
 
 


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