Return-Path: Received: from mtain-dk04.r1000.mx.aol.com (mtain-dk04.r1000.mx.aol.com [172.29.180.8]) by air-md06.mail.aol.com (v129.4) with ESMTP id MAILINMD061-8b884d7a52f565; Fri, 11 Mar 2011 11:51:01 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dk04.r1000.mx.aol.com (Internet Inbound) with ESMTP id 4176D3800029A; Fri, 11 Mar 2011 11:50:55 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Py5XI-00067L-Qs for rs_out_1@blacksheep.org; Fri, 11 Mar 2011 16:49:56 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Py5XH-000677-Bs for rsgb_lf_group@blacksheep.org; Fri, 11 Mar 2011 16:49:55 +0000 Received: from out1.ip09ir2.opaltelecom.net ([62.24.128.245]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Py5XF-0003b0-Eo for rsgb_lf_group@blacksheep.org; Fri, 11 Mar 2011 16:49:55 +0000 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Av4AAErheU1Ok8Nx/2dsb2JhbACCW5ISg3eNTXfCMYViBIF0jj+DBA X-IronPort-AV: E=Sophos;i="4.62,304,1297036800"; d="scan'208,217";a="471398348" Received: from unknown (HELO xphd97xgq27nyf) ([78.147.195.113]) by out1.ip09ir2.opaltelecom.net with SMTP; 11 Mar 2011 16:49:46 +0000 Message-ID: <004e01cbe00c$510320e0$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: <684332.41256.qm@web28505.mail.ukl.yahoo.com> <004201cbe003$a42e42d0$0401a8c0@xphd97xgq27nyf> Date: Fri, 11 Mar 2011 16:49:40 -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: Re: VLF G3XIZ - 12/13th March - Station Set UP - Advice Welcomed Content-Type: multipart/alternative; boundary="----=_NextPart_000_004B_01CBE00C.50AAEEC0" 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: 3039ac1db4084d7a52ef0896 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none ------=_NextPart_000_004B_01CBE00C.50AAEEC0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Chris If you are using an audio type amp then its necessary to have a Capaci= tor in series with the P winding of your matching transformer/ I do not think link windings are the best suited to this type of loadi= ng coil, but in some cases it might work. also antenna current is not a reliable guide to efficiency, more is not nec= essarily best. The tricky part is matching the TX to a resonated antenna on the freq= of interest. The antenna must be Resonant for max transfer of generat= ed RF. Some would have you believe a non resonant antenna is suitable.= =20 When resonating the antenna the indicator should be sharp if its flat= there is a problem, vy lossy ant/loading coil etc mal/g3kev ----- Original Message -----=20 From: mal hamilton=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Friday, March 11, 2011 3:47 PM Subject: LF: Re: VLF G3XIZ - 12/13th March - Station Set UP - Advice= Welcomed Chris I set my system up as follows Resonate my inv L system for the required frequency VLF or LF as req= uired. I wind a loading coil as near as possible to the required frequ= ency then connect in series with the inv L then use a signal generato= r connected to a Scope to sweep the freq area for a resonance indicate= d by minimum amplitude deflection on scope, then add turns or remove= turns 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 tra= nsformer, 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 test= ing,=20 If you do not want to use 50 ohms at TX and Ant end then you will ha= ve 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 ge= t 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 ----- 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= Welcomed LF, I shall be transmitting on VLF again over the weekend. The main purpose will be to test (and adjust) my new loading coil= therefor 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 of= f-air standard frequency, both of 10.000 . . MHz which is then passed= through 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 (se= veral kilohms). To achieve reasonable matching I use a large laminated-core mains= transformer with a step up ratio of 1:24 LOADING COIL(S) To tune out the aerial's capacitive reactance I use a series loadi= ng 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 gene= rate an aerial current of 0.15 - 0.2A The original coil's losses seemed high so to improve matters I hav= e wound another unit, this time using heavier gauge wire and of double= -layer construction. Initial results have been disappointing as I generate less aerial= current than with the old coil. The inductance necessary to achieve resonance has also fallen: fro= m ~ 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= causing the problem so I intend slowly to remove these, checking the= aerial current at intervals. AERIALS=20 I generally use my 40m inverted 'L' aerial, height 10m but have th= e facility (wind conditions being suitable) to launch balloon or kite-= assisted wires. My property borders a public playing field so I need a wind direct= ion SE - S or SW for kite operations and near still air conditions fo= r balloons. ADVICE I should be much obliged for information which will enable me to= improve the station's ERP and detectability. Can someone point me in the right direction to improve the matchin= g system, maybe using ferrite cores which are readily available ? Link coupling to the loading coil may be an option but my early at= tempts at this merely shorted out the loading coil and damaged the PA,= so I have avoided it. 73=20 Chris G3XIZ ------=_NextPart_000_004B_01CBE00C.50AAEEC0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Chris
If you are using an audio type amp then its ne= cessary to=20 have a Capacitor in series with the P winding of your matching=20 transformer/
I do not think link windings are the best suit= ed to this=20 type of loading coil, but in some cases it might work.
also
antenna current is not a reliable guide to eff= iciency,=20 more is not necessarily best.
The tricky part is matching the TX to a resona= ted antenna=20 on the freq of interest. The antenna must be Resonant for max transfer= of=20 generated RF. Some would have you believe a non resonant antenna is su= itable.=20
When resonating the antenna the indicator shou= ld be sharp=20 if its flat there is a problem,  vy lossy ant/loading coil etc
 
mal/g3kev
 
----- Original Message -----
From:=20 mal=20 hamilton
Sent: Friday, March 11, 2011= 3:47=20 PM
Subject: LF: Re: VLF G3XIZ -= 12/13th=20 March - Station Set UP - Advice Welcomed

Chris
I set my system up as follows
 
Resonate my inv L system for the required fr= equency VLF=20 or LF as required. I wind a loading coil as near as possible to= the=20 required frequency then connect in series with the inv L  then= use a=20 signal generator connected to a Scope to sweep the freq area fo= r a=20 resonance indicated by minimum amplitude deflection on scope, then= add turns=20 or remove turns to get resonance on my preferred frequency. <= /DIV>
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 tr= ansformer,=20 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=20 and S 10 - 30 turns for a 50 ohm match.
My systems are all designed for 50 ohms whic= h makes it=20 easy for testing,
 
If you do not want to use 50 ohms at TX and= Ant end then=20 you will have to design a transformer that matches say 8 ohms to hun= dreds 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 matc= hing=20 transformer between TX and Antenna that needs attention.
I hope you get the gist of this description<= /FONT>
mal/g3kev
 
----- Original Message -----
From:=20 Chr= is Osborn=20
Sent: Friday, March 11, 201= 1 1:05=20 PM
Subject: LF: VLF G3XIZ - 12= /13th 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 loa= ding=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 OC= XO or an=20 external off-air standard frequency, both of 10.000 . . MHz= =20 which is then passed through a programmable divider to= give=20 even divisions e.g.
10.000/1110 =3D 9.090 909 kHz    10.000/1112= =3D 8.992 806=20 kHz etc. . .
 
The PA is capable of giving several hundreds of watts bu= t it has a=20 low output impedance and the aerial system has a high impedance (s= everal=20 kilohms).
To achieve reasonable matching I use a large laminated-core= mains=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= loading=20 coil (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=20 wound another unit, this time using heavier gauge wire and of doub= le-layer=20 construction.
Initial results have been disappointing as I generate less ae= rial=20 current 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 consi= derably=20 more self-capacitance.
There are a few hundred turns on it which are not used and ma= y be=20 causing the problem so I intend slowly to remove these, checking= the aerial=20 current at intervals.
 
AERIALS
 
I generally use my 40m inverted 'L' aerial, height 10m but ha= ve the=20 facility (wind conditions being suitable) to launch balloon or kit= e-assisted=20 wires.
My property borders a public playing field so I need a wind= direction=20 SE - S  or SW for kite operations and near still air conditio= ns for=20 balloons.
 
ADVICE
 
I should be much obliged for information which will enab= le me to=20 improve the station's ERP and detectability.
Can someone point me in the right direction to improve the ma= tching=20 system, maybe using ferrite cores which are readily available ?
Link coupling to the loading coil may be an option but my ear= ly=20 attempts at this merely shorted out the loading coil and damaged= the PA, so=20 I have avoided it.
 
73
Chris G3XIZ
 
 
 
 
 
 
 

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