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 w5SMXeOj016525 for ; Fri, 29 Jun 2018 00:33:43 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1fYfNp-0001dd-Je for rs_out_1@blacksheep.org; Thu, 28 Jun 2018 23:27:21 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1fYfNo-0001dU-0Y for rsgb_lf_group@blacksheep.org; Thu, 28 Jun 2018 23:27:20 +0100 Received: from know-smtprelay-omc-11.server.virginmedia.net ([80.0.253.75]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91_59-0488984) (envelope-from ) id 1fYfNl-0001mo-DZ for rsgb_lf_group@blacksheep.org; Thu, 28 Jun 2018 23:27:18 +0100 Received: from MPC ([82.41.138.247]) by cmsmtp with ESMTPA id YfNkf6j5yRWceYfNkfGYaP; Thu, 28 Jun 2018 23:27:16 +0100 X-DKIM-Result: Domain=blueyonder.co.uk Result=Signature OK X-Originating-IP: [82.41.138.247] X-Authenticated-User: mhsw02331@blueyonder.co.uk X-Spam: 0 X-Authority: v=2.3 cv=EPmyLGRC c=1 sm=1 tr=0 a=rq8qAeMNggrfRlaOSPne8A==:117 a=rq8qAeMNggrfRlaOSPne8A==:17 a=x7bEGLp0ZPQA:10 a=r77TgQKjGQsHNAKrUKIA:9 a=wV9FcBFsAAAA:8 a=pGLkceISAAAA:8 a=0asuyQz37scfaMuiYjoA:9 a=QEXdDO2ut3YA:10 a=F3M5lZpKAAAA:8 a=j4if3XbOOR2C0Fv4uVQA:9 a=0utE35UvD8WQXpyI:21 a=_W_S_7VecoQA:10 a=S9tSBiJD-_FMqjcyfT7e:22 a=slCku8JSH3TyizEDQ3pD:22 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=blueyonder.co.uk; s=meg.feb2017; t=1530224836; bh=bCw0dJNuglN6UWoCqi0p9miRUf023XbwtSZG6apFdVQ=; h=From:To:Subject:Date; b=f7jKdtqHDeliNECIlcXSGZ/TKgitf/xsXz9zE4jJa3QjRWEeUcRUTPvgFrba24e88 1hBjtnzXi9vB1VJotei1Sm5anHENLnDLJFALNRsxUMnIopq3ChCBJgZjxSgZJXJ9/4 G64+/mz9dZuW1VOSCV1yaFwgrLXYZQOoFkz6VIWthFq4KYGl5QzrpQXXZ7knrmJHF6 INaPso/R8qgNdRgHycXIVWd/NrX/++sVPTOtgVRj6sr42Xa5fNZ7jeBraGUw3pL0jJ zXKkFQhhl9ZbtpT2e1oT8Zk5+6uaq9irI8nQADvP35a96m9YeqQjDEThfBsS0tJHOB V+EKEfW/BbyKg== Message-ID: From: "Mark" To: Date: Thu, 28 Jun 2018 23:27:16 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 16.4.3528.331 X-MimeOLE: Produced By Microsoft MimeOLE V16.4.3528.331 X-CMAE-Envelope: MS4wfBCkt6vWX0nj3R4ddF8wPdAOLA/SZXJ4HgXwth8sWx0oHAz9iyPToRkr6Ok6ocd7ivdqwLkQbvYDhN5Wfgn8bUNnFEUnR2Ee9Fas7wIHfXIFF6NSo3KN 5azAB9ir/XWmrAr+COFnsWIypgTzUtOeky7lyCq6WCL9SEgYRhe7qKMMHMbLh+75GIWQz0gJf5Ny9g== 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 All The technique used for MF broadcast systems to combine 2 or more transmitters into a single antenna is valid here. This is not a ‘1 loading coil’ solution, but is relatively easy to implement as there is no interaction between legs. Build a parallel tuned circuit for each frequency you want to use. These are referred to as rejectors. The 2 rejectors are joined at the antenna driving point each leg goes to the equipment. ie the MF Rx is passed through the LF rejector to the antenna and vice versa Each rejector will have a very high impedance at its resonant frequency but have a series reactance that is manageable at the pass freq. You then add this series reactance at the pass frequency to the driving point impedance (it helps if you can measure this and consider in series reactance format) The pass reactance is easily calculated for the rejector. You can then match each leg at the wanted frequency with no significant interaction between the legs of combiner / diplexer Many broadcast antennas at MF are electrically short and often it is helpful to add a pre-match element at the driving point a shunt C or series L or whatever minimises the subsequent matching requirements on both legs. Matching is commonly done with Pi or T matching sections for ease of adjustment and improved harmonic rejection, although a simple L match would suffice on receive. [...] 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 [80.0.253.75 listed in list.dnswl.org] -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: 7117f452ff11af9bac782a916713f0d7 Subject: LF: Re: Can I match 2 frequencies with one loading coil? Content-Type: multipart/alternative; boundary="----=_NextPart_000_02B6_01D40F37.8D3118D0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.7 required=5.0 tests=HTML_20_30, HTML_FONTCOLOR_UNSAFE,HTML_MESSAGE,MISSING_OUTLOOK_NAME 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. ------=_NextPart_000_02B6_01D40F37.8D3118D0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Hi All The technique used for MF broadcast systems to combine 2 or more = transmitters into a single antenna is valid here. This is not a =E2=80=981 loading coil=E2=80=99 solution, but is = relatively easy to implement as there is no interaction between legs. Build a parallel tuned circuit for each frequency you want to use. These = are referred to as rejectors. The 2 rejectors are joined at the antenna driving point each leg goes to = the equipment. ie the MF Rx is passed through the LF rejector to the = antenna and vice versa Each rejector will have a very high impedance at its resonant frequency = but have a series reactance that is manageable at the pass freq. You then add this series reactance at the pass frequency to the driving = point impedance (it helps if you can measure this and consider in = series reactance format) The pass reactance is easily calculated for the rejector. You can then = match each leg at the wanted frequency with no significant interaction = between the legs of combiner / diplexer Many broadcast antennas at MF are electrically short and often it is = helpful to add a pre-match element at the driving point a shunt C or = series L or whatever minimises the subsequent matching requirements on = both legs. Matching is commonly done with Pi or T matching sections for = ease of adjustment and improved harmonic rejection, although a simple L = match would suffice on receive. This technique allows transmitters at very high powers (50-100kW or so) = on 2 or more frequencies to use one antenna. It will work on receive = just as well enabling a proper 50 j0 ohm resistive match ( if that is = actually needed ) for n frequencies, you need n-1 rejectors in series = for each leg before the matching section If you decide to try this on Transmit, watch out for the increased = =E2=80=98circulating currents=E2=80=99 in the rejectors due to the = passed transmission. Currents and voltages in the C and L of a rejector = are larger than the expected current in the equivalent pass reactance. Mark GM4ISM From: Andy Talbot=20 Sent: Thursday, June 28, 2018 8:32 PM To: LineOne=20 Subject: Re: LF: Can I match 2 frequencies with one loading coil? Try this, but you'll have to adjust iteratively:=20 Bands referred to as LF and MF First make your LF loading coil so it resonates the antenna as it = stands. Now make an MF loading coil. The problem is that t=3Dwhen = both are connected to the antenna teh lower value MF one shunts teh LF. = So add series C to the MF one to make a series tuned circuit, increasing = the L to keep the system at resonance. The net effect now, at LF will = be an increased value of X shunting it. As your additional C reduces = and L increases, the residual at LF across the LF coil goes up. Now = adjust teh LF colil to bring it to resonance, then go back and redo the = MF L or C. Iterating between teh two until they both go. I'ts a complicated setup, with two frequencies and three variables to = play with - so an infinite set of values to end up with, but if I were = doing it, I'd make up a spreadsheet and play around with values until a = workable solution that resonated both antennas was found and looked OK. = Once resonated you can bring them to a match if needed. But on Rx just = resonating them ought to suffice Or use a circuit analysis prog. =20 Andy=20 www.g4jnt.com On 28 June 2018 at 20:04, Chris Wilson wrote: Hello Mal, Thanks Mal and Stefan, but Mal, I want to listen to and decode both = bands at the same time on 2 different receivers, sharing the one antenna. I tried shorting out the loading coil but LF reception is much poorer. Not sure how much of an effect no loading coil has at MF ,but suspect a loading coil to resonate would be pretty helpful? Thursday, June 28, 2018, 7:55:55 PM, you wrote: > I use aircore loading and matching > Use 2 coils and SW between them for desired band > G3KEV --=20 Best regards, Chris mailto:dead.fets@gmail.com ------=_NextPart_000_02B6_01D40F37.8D3118D0 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable
 
Hi All
The technique used for MF  broadcast systems to combine 2 or = more=20 transmitters into a single antenna is valid here.
This is not a =E2=80=981 loading coil=E2=80=99 solution, but is = relatively easy to=20 implement as there is no interaction between legs.
Build a parallel tuned circuit for each frequency you want to use. = These=20 are referred to as rejectors.
The 2 rejectors are joined at the antenna driving point each leg = goes to=20 the  equipment.  ie the MF Rx  is passed through the LF=20 rejector  to the antenna and vice versa
Each rejector will have a very high impedance at its resonant = frequency=20 but  have a  series reactance  that is manageable at = the =20 pass freq.
You then add this series reactance at the pass frequency to the = driving=20 point impedance (it helps if you  can measure this and  = consider in=20 series reactance format)
The pass reactance is easily calculated for the rejector. You can = then=20 match each leg at the  wanted frequency with no significant =20 interaction between the  legs of  combiner / diplexer
Many broadcast antennas at MF are electrically short and often it = is=20 helpful to add a  pre-match  element at the driving = point  a=20 shunt C or series L or whatever  minimises the subsequent matching=20 requirements on both legs. Matching is commonly done with Pi or T = matching=20 sections for ease of adjustment and improved harmonic rejection, = although a=20 simple L match would suffice on receive.
 
This technique allows transmitters at very high powers (50-100kW or = so) on=20 2  or more  frequencies to use one antenna. It will work on = receive=20 just as well enabling a  proper 50 j0 ohm resistive  match ( = if that=20 is actually needed )  for n frequencies, you need n-1 rejectors in=20 series  for each leg before the matching section
 
If you decide to try this on Transmit, watch out for the  = increased=20 =E2=80=98circulating currents=E2=80=99 in the rejectors due to the = passed transmission. Currents=20 and voltages in the C and L of a rejector are larger than the  = expected=20 current in the equivalent  pass reactance.
 
Mark GM4ISM
 
 
 
 
Sent: Thursday, June 28, 2018 8:32 PM
To: LineOne
Subject: Re: LF: Can I match 2 frequencies with one loading=20 coil?
 
Try this, but you'll have to adjust iteratively:=20
Bands referred to as LF and MF
 
First make your LF loading coil so it resonates the antenna as it=20 stands.    Now make an MF loading coil.  The problem = is that=20 t=3Dwhen both are connected to the antenna teh lower value MF one shunts = teh=20 LF.  So add series C to the MF one to make a series tuned circuit,=20 increasing the L to keep the system at resonance.   The net = effect=20 now, at LF will be an increased value of X shunting it.  As your = additional=20 C reduces and L increases, the residual at LF across the LF coil goes=20 up.    Now adjust teh LF colil to bring it to resonance, = then go=20 back and redo the MF L or C.  Iterating between teh two until they = both=20 go.
 
I'ts a complicated setup, with two frequencies and three variables = to play=20 with - so an infinite set of values to end up with, but if I were doing = it, I'd=20 make up a spreadsheet and play around with values until a workable = solution that=20 resonated both antennas was found and looked OK.  Once resonated = you can=20 bring them to a match if needed.   But on Rx just resonating = them=20 ought to suffice
 
Or use a circuit analysis prog.     =
 
Andy=20
 
 
On 28 June 2018 at 20:04, Chris Wilson <dead.fets@gmail.com> wrote:


Hello=20 Mal,

Thanks Mal and Stefan, but Mal, I want to listen to and = decode=20 both bands
at the same time on 2 different receivers, sharing the = one=20 antenna. I
tried  shorting out the loading coil but LF = reception is=20 much poorer.
Not  sure how much of an effect no loading coil = has at MF=20 ,but suspect
a loading coil to resonate would be pretty=20 helpful?

Thursday, June 28, 2018, 7:55:55 PM, you = wrote:

> I=20 use aircore loading and matching
> Use 2 coils and SW between = them for=20 desired band
> G3KEV







--
Best=20 = regards,
Chris         &n= bsp;           &nb= sp;     =20 mailto:dead.fets@gmail.com


 
= ------=_NextPart_000_02B6_01D40F37.8D3118D0--