Return-Path: Received: from mtain-dg04.r1000.mx.aol.com (mtain-dg04.r1000.mx.aol.com [172.29.65.12]) by air-de01.mail.aol.com (v129.4) with ESMTP id MAILINDE013-5ea44d7a445d10a; Fri, 11 Mar 2011 10:48:45 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dg04.r1000.mx.aol.com (Internet Inbound) with ESMTP id EDA4E380000E7; Fri, 11 Mar 2011 10:48:43 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Py4ZC-0005Hh-LW for rs_out_1@blacksheep.org; Fri, 11 Mar 2011 15:47:50 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Py4ZC-0005HY-09 for rsgb_lf_group@blacksheep.org; Fri, 11 Mar 2011 15:47:50 +0000 Received: from out1.ip08ir2.opaltelecom.net ([62.24.128.244]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Py4Z9-0002Va-14 for rsgb_lf_group@blacksheep.org; Fri, 11 Mar 2011 15:47:49 +0000 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AvoAAIfSeU1Ok8Nx/2dsb2JhbACCW5ISg3eNTXfCNoViBIF0jj+DBA X-IronPort-AV: E=Sophos;i="4.62,303,1297036800"; d="scan'208,217";a="482970733" Received: from unknown (HELO xphd97xgq27nyf) ([78.147.195.113]) by out1.ip08ir2.opaltelecom.net with SMTP; 11 Mar 2011 15:47:40 +0000 Message-ID: <004201cbe003$a42e42d0$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: <684332.41256.qm@web28505.mail.ukl.yahoo.com> Date: Fri, 11 Mar 2011 15:47:34 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: Re: VLF G3XIZ - 12/13th March - Station Set UP - Advice Welcomed Content-Type: multipart/alternative; boundary="----=_NextPart_000_003F_01CBE003.A3EDDE70" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,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: 3039ac1d410c4d7a445b6bc7 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none ------=_NextPart_000_003F_01CBE003.A3EDDE70 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Chris I set my system up as follows Resonate my inv L system for the required frequency VLF or LF as requi= red. I wind a loading coil as near as possible to the required frequen= cy then connect in series with the inv L then use a signal generator= connected to a Scope to sweep the freq area for a resonance indicated= by minimum amplitude deflection on scope, then add turns or remove tu= rns to get resonance on my preferred frequency.=20 Min deflection also corresponds to min SWR but not necessarily 1:1 at= this stage Having done this LEAVE THE ANTENNA ALONE.=20 Next, match the transmitter to the antenna with a ferrite wound trans= former, the P and S windings depend on PA Z and antenna Z A good starting point on a 3c85 type core is P - 9 turns and S 10 - 30= turns for a 50 ohm match. My systems are all designed for 50 ohms which makes it easy for testin= g,=20 If you do not want to use 50 ohms at TX and Ant end then you will have= to design a transformer that matches say 8 ohms to hundreds of ohms= at the antenna end on VLF also some sort of matching atu at the base= of the antenna to get the SWR down to 1;1 =20 Once the antenna is resonated leave it, use an ATU adjustment to get= the SWR down to 1:1 If you are having problems then its the matching transformer between= TX and Antenna that needs attention. I hope you get the gist of this description mal/g3kev =20 ----- Original Message -----=20 From: Chris Osborn=20 To: LF Group=20 Sent: Friday, March 11, 2011 1:05 PM Subject: LF: VLF G3XIZ - 12/13th March - Station Set UP - Advice Wel= comed LF, I shall be transmitting on VLF again over the weekend. The main purpose will be to test (and adjust) my new loading coil th= erefor the transmitted frequency may vary. I shall keep the reflector informed as to frequency and times that= transmissions occur should anyone wish to take a look for my signals. PRESENT STATION SET UP TX I have the option to use either an internal OCXO or an external off-= air standard frequency, both of 10.000 . . MHz which is then passed th= rough a programmable divider to give even divisions e.g. 10.000/1110 =3D 9.090 909 kHz 10.000/1112 =3D 8.992 806 kHz etc.= . . The PA is capable of giving several hundreds of watts but it has a= low output impedance and the aerial system has a high impedance (seve= ral kilohms). To achieve reasonable matching I use a large laminated-core mains tr= ansformer with a step up ratio of 1:24 LOADING COIL(S) To tune out the aerial's capacitive reactance I use a series loading= coil (inductor). The original coil was single-wound, about 600 mm diameter and has an= inductance of ~ 1.25 H With the above TX, loading coil and my 40m inverted 'L' I can genera= te an aerial current of 0.15 - 0.2A The original coil's losses seemed high so to improve matters I have= wound another unit, this time using heavier gauge wire and of double-= layer construction. Initial results have been disappointing as I generate less aerial cu= rrent than with the old coil. The inductance necessary to achieve resonance has also fallen: from= ~ 1.25H to ~ 0.75 H implying that the new coil has considerably more= self-capacitance. There are a few hundred turns on it which are not used and may be ca= using the problem so I intend slowly to remove these, checking the aer= ial current at intervals. AERIALS=20 I generally use my 40m inverted 'L' aerial, height 10m but have the= facility (wind conditions being suitable) to launch balloon or kite-a= ssisted wires. My property borders a public playing field so I need a wind directio= n SE - S or SW for kite operations and near still air conditions for= balloons. ADVICE I should be much obliged for information which will enable me to imp= rove the station's ERP and detectability. Can someone point me in the right direction to improve the matching= system, maybe using ferrite cores which are readily available ? Link coupling to the loading coil may be an option but my early atte= mpts at this merely shorted out the loading coil and damaged the PA,= so I have avoided it. 73=20 Chris G3XIZ ------=_NextPart_000_003F_01CBE003.A3EDDE70 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Chris
I set my system up as follows
 
Resonate my inv L system for the required freq= uency VLF or=20 LF as required. I wind a loading coil as near as possible to the= required=20 frequency then connect in series with the inv L  then use a signa= l=20 generator connected to a Scope to sweep the freq area for a reson= ance=20 indicated by minimum amplitude deflection on scope, then add turns or= remove=20 turns to get resonance on my preferred frequency.
Min deflection also corresponds to min SWR but= not=20 necessarily 1:1 at this stage
Having done this LEAVE THE ANTENNA ALONE.
 
Next, match the transmitter to the=20 antenna  with a ferrite wound tran= sformer, the=20 P and S windings depend on PA Z and antenna Z
A good starting point on a 3c85 type core is= P - 9 turns=20 and S 10 - 30 turns for a 50 ohm match.
My systems are all designed for 50 ohms which= makes it=20 easy for testing,
 
If you do not want to use 50 ohms at TX and An= t end then=20 you will have to design a transformer that matches say 8 ohms to hundr= eds of=20 ohms at the antenna end on VLF also some sort of matching atu at= the base=20 of the antenna to get the SWR down to 1;1  
 
Once the antenna is resonated leave=20 it,  use an ATU adjustment to get the SWR down to= =20 1:1
If you are having problems then its the matchi= ng=20 transformer between TX and Antenna that needs attention.
I hope you get the gist of this description
mal/g3kev
 
----- Original Message -----
From:=20 Chris= Osborn=20
Sent: Friday, March 11, 2011= 1:05=20 PM
Subject: LF: VLF G3XIZ - 12/1= 3th March -=20 Station Set UP - Advice Welcomed

LF,
 
I shall be transmitting on VLF again over the weekend.
 
The main purpose will be to test (and adjust) my new loadi= ng=20 coil therefor the transmitted frequency may vary.
I shall keep the reflector informed as to frequency and times= that=20 transmissions occur should anyone wish to take a look for my=20 signals.
 
PRESENT STATION SET UP
 
TX
 
I have the option to use either an internal OCXO= or an=20 external off-air standard frequency, both of 10.000 . . MHz whi= ch is=20 then passed through a programmable divider to give even= divisions=20 e.g.
10.000/1110 =3D 9.090 909 kHz    10.000/1112 =3D= 8.992 806 kHz=20 etc. . .
 
The PA is capable of giving several hundreds of watts but= it has a=20 low output impedance and the aerial system has a high impedance (sev= eral=20 kilohms).
To achieve reasonable matching I use a large laminated-core mai= ns=20 transformer with a step up ratio of 1:24
 
LOADING COIL(S)
 
To tune out the aerial's capacitive reactance I use a series lo= ading coil=20 (inductor).
The original coil was single-wound, about 600 mm diameter and= has an=20 inductance of ~ 1.25 H
With the above TX, loading coil and my 40m inverted 'L' I= can=20 generate an aerial current of  0.15 - 0.2A
 
The original coil's losses seemed high so to improve matters I= have wound=20 another unit, this time using heavier gauge wire and of double-layer= =20 construction.
Initial results have been disappointing as I generate less aeri= al current=20 than with the old coil.
 
The inductance necessary to achieve resonance has also fallen:= from=20 ~ 1.25H to ~ 0.75 H implying that the new coil has conside= rably more=20 self-capacitance.
There are a few hundred turns on it which are not used and may= be causing=20 the problem so I intend slowly to remove these, checking the aerial= current at=20 intervals.
 
AERIALS
 
I generally use my 40m inverted 'L' aerial, height 10m but have= the=20 facility (wind conditions being suitable) to launch balloon or kite-= assisted=20 wires.
My property borders a public playing field so I need a wind dir= ection SE=20 - S  or SW for kite operations and near still air conditions fo= r=20 balloons.
 
ADVICE
 
I should be much obliged for information which will enable= me to=20 improve the station's ERP and detectability.
Can someone point me in the right direction to improve the matc= hing=20 system, maybe using ferrite cores which are readily available ?
Link coupling to the loading coil may be an option but my early= attempts=20 at this merely shorted out the loading coil and damaged the PA, so= I have=20 avoided it.
 
73
Chris G3XIZ
 
 
 
 
 
 
 

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