Return-Path: Received: from rly-da07.mx.aol.com (rly-da07.mail.aol.com [172.19.129.81]) by air-da04.mail.aol.com (v126.13) with ESMTP id MAILINDA042-a7f4b27aac2167; Tue, 15 Dec 2009 10:27:30 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-da07.mx.aol.com (v125.7) with ESMTP id MAILRELAYINDA077-a7f4b27aac2167; Tue, 15 Dec 2009 10:26:59 -0500 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NKZFy-0006Bb-J1 for rs_out_1@blacksheep.org; Tue, 15 Dec 2009 15:24:10 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NKZFx-0006BS-Vp for rsgb_lf_group@blacksheep.org; Tue, 15 Dec 2009 15:24:09 +0000 Received: from out1.ip03ir2.opaltelecom.net ([62.24.128.239]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NKZHL-0006L6-RD for rsgb_lf_group@blacksheep.org; Tue, 15 Dec 2009 15:25:39 +0000 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AmwFAJI5J0tcHB8h/2dsb2JhbACCJ9ZChCsEgWI X-IronPort-AV: E=Sophos;i="4.47,400,1257120000"; d="scan'208,217";a="203298463" Received: from unknown (HELO xphd97xgq27nyf) ([92.28.31.33]) by out1.ip03ir2.opaltelecom.net with SMTP; 15 Dec 2009 15:25:42 +0000 Message-ID: <001d01ca7d9a$dbedc9b0$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: <38A51B74B884D74083D7950AD0DD85E828AC7C@File-Server-HST.hst.e-technik.tu-darmstadt.de> Date: Tue, 15 Dec 2009 15:25:39 -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-Karma: unknown: X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: LF: Re: AW: Re: "Gain" between qrss3 and qrss10 / PA design Content-Type: multipart/alternative; boundary="----=_NextPart_000_001A_01CA7D9A.DB9CC380" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.2 required=5.0 tests=HTML_50_60,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 ------=_NextPart_000_001A_01CA7D9A.DB9CC380 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable An old scrap Line output transformer 3C5 material from a tube TV will= handle 1 Kw of RF and costs nothing. For my LF and MF TX the LOPT came out of my junk box. mal/g3kev ----- Original Message -----=20 From: Stefan Sch=E4fer=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Tuesday, December 15, 2009 2:51 PM Subject: LF: AW: Re: "Gain" between qrss3 and qrss10 / PA design Hello Jim! First i want to say that i am glad to meet you here. Do you remember= our QSO in 2004? And mni tnx for your article to the tuning meter (an= d others)! I have built it 2003 and it is for me the most useful measu= ring device on LF at all! Yes, on 137kHz a half bridge is also a good idea since the losses ar= e quite small. But, for a half or full bridge like in these decca tran= smitters, one needs an output ferrite core that can handle the whole= output power. I think these are expensive (?), not easy to get and co= uld be driven into saturation when dimensioned well. In my class e PA= I use a single (!) IRFP360 that costs 1,9 Euro in the moment. This PA= can easily handle 1kW with an efficiency of more than 96%. In the who= le PA circuit, no ferrite cores are used, just two iron powder cores= for the output filter. The driver is one cheap ICL7667, available for= 1,1 Euro. All Capacitors are of the type wima FKP1 (2kV version), cos= ts are below 1 Euro. So, I think a half bridge is more expensive? Best 73 and hope for another QSO!!! Stefan / DK7FC -----Urspr=FCngliche Nachricht----- Von: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@= blacksheep.org] Im Auftrag von James Moritz Gesendet: Dienstag, 15. Dezember 2009 15:15 An: rsgb_lf_group@blacksheep.org Betreff: LF: Re: "Gain" between qrss3 and qrss10 / PA design Dear Stefan, LF Group, A much better choice of circuit topology for QRO transmitters using= an=20 off-line rectified mains PSU of about 330V is the half- or full brid= ge,=20 voltage-mode class D, as used in the "Decca" PAs, and G4JNT's off-li= ne=20 design. Here the peak voltage across each MOSFET is only equal to th= e DC=20 supply voltage, so cheap 500V Mosfets designed for off-line SMPSUs= are=20 ideal. The class E and push-pull current-mode class D designs are be= tter for=20 relatively low voltage supplies, say < 40V. The limitation on TX power that can be used at LF with a vertical an= tenna is=20 the antenna voltage, roughly Iant * XCant. In my experience, corona= =20 breakdown becomes a problem in the 10 - 20kV range with a wire anten= na. So=20 to use high power, and so achieve high antenna current and ERP, you= need=20 high antenna capacitance. Also, the voltage will be increased if the= antenna=20 loss resistance is low. I found that, with an 10m high inverted L an= tenna of=20 about 50m of wire in total, I could run 1.2kW reliably, provided car= e was=20 taken to eliminate sharp ends, narrow spacings, etc. in the antenna= and=20 tuner. This resulted in up to 5A antenna current, and about 17kV on= the=20 antenna wire. Even so, I have to increase the antenna height in orde= r to=20 approach 1W ERP. At 500k, the antenna impedance is much lower, and= =20 efficiency also usually higher, so TX power is less of a problem. In my experience, DX contacts using QRSS30 are quite practical, give= n a=20 large supply of strong coffee! But with longer dot periods, good pro= pagation=20 does not last long enough to complete even a minimal QSO. Cheers, Jim Moritz 73 de M0BMU ------=_NextPart_000_001A_01CA7D9A.DB9CC380 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
An old scrap Line output transformer= 3C5=20 material from a tube TV  will handle 1 Kw of RF and costs=20 nothing.
For my LF and MF TX the LOPT cam= e out of my=20 junk box.
mal/g3kev
 
----- Original Message -----
Sent: Tuesday, December 15,= 2009 2:51=20 PM
Subject: LF: AW: Re: "Gain"= between qrss3=20 and qrss10 / PA design

Hello Jim!

First i want to say that i am glad= =20 to meet you here. Do you remember our QSO in 2004? And mni tnx for= your=20 article to the tuning meter (and others)! I have built it 2003 and= it is for=20 me the most useful measuring device on LF at all!

Yes, on 137kHz a half bridge is=20 also a good idea since the losses are quite small. But, for a half= or full=20 bridge like in these decca transmitters, one needs an output ferrite= core that=20 can handle the whole output power. I think these are expensive (?),= not easy=20 to get and could be driven into saturation when dimensioned well. In= my class=20 e PA I use a single (!) IRFP360 that costs 1,9 Euro in the moment.= This PA can=20 easily handle 1kW with an efficiency of more than 96%. In the whole= PA=20 circuit, no ferrite cores are used, just two iron powder cores for= the output=20 filter. The driver is one cheap ICL7667, available for 1,1 Euro. All= =20 Capacitors are of the type wima=20 FKP1 (2kV version), costs are below 1 Euro. So, I think a half= bridge is=20 more expensive?

Best 73 and hope for another=20 QSO!!!

 

Stefan / DK7FC

 

 

-----Urspr=FCngliche=20 Nachricht-----
Von: owner-rsgb_lf_group@blacksheep.org=20 [mailto:owner-rsgb_lf_group@blacksheep.org] Im Auftrag von James=20 Moritz
Gesendet: Dienstag, 15. Dezember 2009 15:15
An:=20 rsgb_lf_group@blacksheep.org
Betreff: LF: Re: "Gain" between qrss= 3 and=20 qrss10 / PA design

 <= /P>

Dear Stefan, LF=20 Group,

 <= /P>

A much better choice= of circuit=20 topology for QRO transmitters using an

off-line rectified ma= ins PSU of=20 about 330V is the half- or full bridge,

voltage-mode class D,= as used in=20 the "Decca" PAs, and G4JNT's off-line

design. Here the peak= voltage=20 across each MOSFET is only equal to the DC

supply voltage, so ch= eap 500V=20 Mosfets designed for off-line SMPSUs are

ideal. The class E an= d push-pull=20 current-mode class D designs are better for

relatively low voltag= e supplies,=20 say < 40V.

 <= /P>

The limitation on TX= power that can=20 be used at LF with a vertical antenna is

the antenna voltage,= roughly Iant *=20 XCant. In my experience, corona

breakdown becomes a= problem in the=20 10 - 20kV range with a wire antenna. So

to use high power, an= d so achieve=20 high antenna current and ERP, you need

high antenna capacita= nce. Also, the=20 voltage will be increased if the antenna

loss resistance is lo= w. I found=20 that, with an 10m high inverted L antenna of

about 50m of wire in= total, I could=20 run 1.2kW reliably, provided care was

taken to eliminate sh= arp ends,=20 narrow spacings, etc. in the antenna and

tuner. This resulted= in up to 5A=20 antenna current, and about 17kV on the

antenna wire. Even so= , I have to=20 increase the antenna height in order to

approach 1W ERP. At= 500k, the=20 antenna impedance is much lower, and

efficiency also usual= ly higher, so=20 TX power is less of a problem.

 <= /P>

In my experience, DX= contacts using=20 QRSS30 are quite practical, given a

large supply of stron= g coffee! But=20 with longer dot periods, good propagation

does not last long en= ough to=20 complete even a minimal QSO.

 <= /P>

Cheers, Jim=20 Moritz

73 de M0BMU

 <= /P>

 <= /P>

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