Return-Path: Received: from mtain-dj10.r1000.mx.aol.com (mtain-dj10.r1000.mail.aol.com [172.19.187.146]) by air-md10.mail.aol.com (v129.4) with ESMTP id MAILINMD101-8b984d2478c7390; Wed, 05 Jan 2011 08:57:27 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dj10.r1000.mx.aol.com (Internet Inbound) with ESMTP id 0D72B380000CA; Wed, 5 Jan 2011 08:57:25 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PaTq7-0006Ml-CC for rs_out_1@blacksheep.org; Wed, 05 Jan 2011 13:55:47 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PaTq5-0006Mc-S0 for rsgb_lf_group@blacksheep.org; Wed, 05 Jan 2011 13:55:45 +0000 Received: from out1.ip09ir2.opaltelecom.net ([62.24.128.245]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PaTq3-0003kB-Dj for rsgb_lf_group@blacksheep.org; Wed, 05 Jan 2011 13:55:45 +0000 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Ai0FAMcGJE1Ok8Qt/2dsb2JhbACSDJIcc78nhUwEgWCMYw X-IronPort-AV: E=Sophos;i="4.60,278,1291593600"; d="scan'208,217";a="463598894" Received: from unknown (HELO xphd97xgq27nyf) ([78.147.196.45]) by out1.ip09ir2.opaltelecom.net with SMTP; 05 Jan 2011 13:55:33 +0000 Message-ID: <005a01cbace0$368db720$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: <4D22026B.7070908@iup.uni-heidelberg.de> Date: Wed, 5 Jan 2011 13:55:29 -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: DK7FC's "big" VLF PA Content-Type: multipart/alternative; boundary="----=_NextPart_000_0057_01CBACE0.365BAAA0" 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-global-disposition: G x-aol-sid: 3039cdbc9d0f4d2478c5731c X-AOL-IP: 195.171.43.25 ------=_NextPart_000_0057_01CBACE0.365BAAA0 Content-Type: text/plain; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable Anyone serious about LF/MF activities should consider building this am= plifier, those dabbling on these frequencies with QRP are making it ve= ry difficult for the Receive operator, causing both EAR and VISUAL dis= comfort, and anxiety when they receive nothing.=20 G3KEV ----- Original Message -----=20 From: Stefan Sch=E4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Monday, January 03, 2011 5:07 PM Subject: VLF: DK7FC's "big" VLF PA Dear group, Since a long time i wanted to publish the circuit of my "big" VLF PA= . It is titled as a 600W PA since it has never handled more power so= far, due to the power limit of my /p generator. In fact i think it wi= ll handle at least 1 kW, probably even 2 kW. As announced i will try= a 2 kW generator in my next VLF experiment and i am not afraid to use= this PA for the first test. The circuit is nothing new or very special. The mains voltage is rec= tified and stabilized by a 2.2 mF capacitor. A H bridge using 4x IRFP= 460 FETs is switching at the desired frequency. To achieve an accurat= e 50% duty cicle, a CMOS4013 is used in front of the MOSFET driver. It= is switched as a frequency divider (/2), thus the input frequency has= to be 2x the actually wanted frequency (17.94 kHz > 8.97 kHz). The dr= iver(s) are 2x IR2110. The operating frequency is about 0.1...20 kHz= (320 VDC) or 0.1...150 kHz (100 VDC). It is designed to work properly= below 9 kHz. The input waveform has to be a 12Vp rectangular waveform= , ideally. The waveform is not very critical, e.g. a sinusoidal or tri= angular waveform is no problem as well. A small transformer is used to generate a local 15V supply for the= drivers, ICs and LEDs.=20 There are several methods how the input signal can be applied. Eithe= r directly (please use an audio transformer to decouple the PC from th= e circuits ground which has mains potential!), as shown in the circuit= or via a fiber optic cable, as i do it. The fiber optic solution is= a special and (for some) strange method so i prefer to show the usual= way to do it... If the mains is used to supply the PA (much lower output impedance),= a resistor has to be used to charge the 2.2 mF capacitor. A 100 W/230= V lamp might be used. If the capacitor is charged, this resistor shoul= d be bypassed by a relay.=20 One has to take care about the output: There is no isolating transfo= rmer used so the output has main potential! Thus, a galvanic isolated= coupling winding has to be used for applying the RF to the loading co= il. No ferrite output transformer is needed! This PA is still using the first pair of FETs, there was no fault so= far. It was received in several countries that it is no problem to tr= ansmit a one hour carrier at P > 500 W. Here, the heat sink gets not= even hand warm! So the efficiency can be assumed to be almost 100%. The design can handle pretty much reactive power. It was no problem= to drive an antenna that is totally out of resonancy (kite lying on= the ground or wire suddenly disconnected due to strong pull). The actual (active) output power can be regulated continuously by ad= justing the resonance.=20 So, if one of the new VLF TX stations want to change from an audio= PA to a high power switching mode PA, this well proven design may giv= e some ideas. Just ask if something is not understood. See once again one of my very amateur like ugly hand drawings ;-) at= http://www.iup.uni-heidelberg.de/schaefer_vlf/pic/DK7FC_600W_VLF_PA.p= df Vy 73, Stefan/DK7FC PS: Once again i explicit want to say that one has to take care abou= t the parts that are on mains potential! If you are not sure about the= handling, add an isolating transformer at the 230V AC input! ------=_NextPart_000_0057_01CBACE0.365BAAA0 Content-Type: text/html; charset="ISO-8859-15" Content-Transfer-Encoding: quoted-printable
Anyone serious about LF/MF activities= should=20 consider building this amplifier, those dabbling on these frequencies= with QRP=20 are making it very difficult for the Receive operator, causing bo= th EAR and=20 VISUAL discomfort, and anxiety when they receive nothing.
G3KEV
 
 
----- Original Message -----
Sent: Monday, January 03, 201= 1 5:07=20 PM
Subject: VLF: DK7FC's "big"= VLF PA

Dear group,

Since a long time i wanted to publ= ish the=20 circuit of my "big" VLF PA. It is titled as a 600W PA since it has= never=20 handled more power so far, due to the power limit of my /p generator= . In fact=20 i think it will handle at least 1 kW, probably even 2 kW. As announc= ed i will=20 try a 2 kW generator in my next VLF experiment and i am not afraid= to use this=20 PA for the first test.

The circuit is nothing new or very spe= cial. The=20 mains voltage is rectified and stabilized by a 2.2 mF capacitor. A= H bridge=20 using 4x IRFP 460 FETs is switching at the desired frequency.= To=20 achieve an accurate 50% duty cicle, a CMOS4013 is used in fro= nt of the=20 MOSFET driver. It is switched as a frequency divider (/2), thus the= input=20 frequency has to be 2x the actually wanted frequency (17.94 kHz >= 8.97=20 kHz). The driver(s) are 2x IR2110. The operating frequency is= about=20 0.1...20 kHz (320 VDC) or 0.1...150 kHz (100 VDC). It is desi= gned to=20 work properly below 9 kHz. The input waveform has to be a 12Vp recta= ngular=20 waveform, ideally. The waveform is not very critical, e.g. a sinusoi= dal or=20 triangular waveform is no problem as well.
A small transformer is= used to=20 generate a local 15V supply for the drivers, ICs and LEDs.
There= are=20 several methods how the input signal can be applied. Either directly= (please=20 use an audio transformer to decouple the PC from the circuits ground= which has=20 mains potential!), as shown in the circuit or via a fiber optic cabl= e, as i do=20 it. The fiber optic solution is a special and (for some) strange met= hod so i=20 prefer to show the usual way to do it...

If the mains is used= to supply=20 the PA (much lower output impedance), a resistor has to be used to= charge the=20 2.2 mF capacitor. A 100 W/230V lamp might be used. If the capacitor= is=20 charged, this resistor should be bypassed by a relay.

One ha= s to=20 take care about the output: There is no isolating transformer= used so=20 the output has main potential! Thus, a galvanic isolated coup= ling=20 winding has to be used for applying the RF to the loading coil. No= ferrite=20 output transformer is needed!

This PA is still using the= first pair=20 of FETs, there was no fault so far. It was received in several= countries=20 that it is no problem to transmit a one hour carrier at P > 500= W. Here,=20 the heat sink gets not even hand warm! So the efficiency can be assu= med to be=20 almost 100%.
The design can handle pretty much reactive power. It= was no=20 problem to drive an antenna that is totally out of resonancy (kite= lying on=20 the ground or wire suddenly disconnected due to strong pull).
The=20 actual (active) output power can be regulated continuously by adjust= ing the=20 resonance.

So, if one of the new VLF TX stations want to cha= nge from=20 an audio PA to a high power switching mode PA, this well proven desi= gn may=20 give some ideas. Just ask if something is not understood.

See= once=20 again one of my very amateur like ugly hand drawings ;-) at http://www.iup.uni-he= idelberg.de/schaefer_vlf/pic/DK7FC_600W_VLF_PA.pdf

Vy= =20 73, Stefan/DK7FC

PS: Once again i explicit want to say that= one has to=20 take care about the parts that are on mains potential! If you are no= t sure=20 about the handling, add an isolating transformer at the 230V AC=20 input!
------=_NextPart_000_0057_01CBACE0.365BAAA0--