Return-Path: Received: (qmail 13042 invoked from network); 3 May 2000 14:06:56 -0000 Received: from unknown (HELO post.thorcom.com) (212.172.148.70) by bells.core.plus.net.uk with SMTP; 3 May 2000 14:06:56 -0000 Received: from majordom by post.thorcom.com with local (Exim 3.02 #1) id 12mzia-0008UR-00 for rsgb_lf_group-outgoing@blacksheep.org; Wed, 03 May 2000 15:01:36 +0100 Content-Transfer-Encoding: 8bit Received: from bob.dera.gov.uk ([192.5.29.90]) by post.thorcom.com with esmtp (Exim 3.02 #1) id 12mziY-0008UM-00 for rsgb_lf_group@blacksheep.org; Wed, 03 May 2000 15:01:34 +0100 Received: by bob.dera.gov.uk; (8.8.8/1.3/10May95) id PAA29367; Wed, 3 May 2000 15:04:32 +0100 (BST) X-Priority: 3 X-MSMail-Priority: Normal Received: (qmail 6183 invoked from network); 3 May 2000 14:57:42 -0000 Received: from gauntlet.mail.dera.gov.uk (172.16.9.10) by baton.dera.gov.uk with SMTP; 3 May 2000 14:57:42 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: by gauntlet.mail.dera.gov.uk; id NAA05067; Wed, 3 May 2000 13:46:40 GMT Received: from unknown(146.80.11.40) by gauntlet.mail.dera.gov.uk via smap (3.2) id xma005039; Wed, 3 May 00 13:46:14 GMT Received: from frn-gold-1.dera.gov.uk (unverified) by mailguard.dera.gov.uk (Content Technologies SMTPRS 4.1.5) with ESMTP id for ; Wed, 3 May 2000 15:05:23 +0100 Received: by FRN-GOLD-1 with Internet Mail Service (5.0.1460.8) id <2J0905MJ>; Wed, 3 May 2000 14:59:52 +0100 Message-ID: <3617AC3245C2D1118A840000F805359C017528B4@pdw-mercury-1.dera.gov.uk> From: "Talbot Andrew" To: rsgb_lf_group@blacksheep.org Subject: LF: RE: LF Amplifiers etc Date: Wed, 3 May 2000 14:59:50 +0100 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.0.1460.8) Content-Type: text/plain; charset=iso-8859-1; format=flowed Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Sender: Thanks for that, you've just saved me some work. I'm playing with a TDA2005 bridge audio amplifier for 10 watts off a 12v rail (since I had one spare), but that older device is a bit prone to instability into anything other than a perfect resistive load. The simplicity of the LM1875 circuitry makes the effort of using a 30V rail (via a switch mode PSU from 12V) worthwhile. Farnell do this device too, and also I see in their catalogue the LM1876 which appears to be a pair of '1875 types in one package. 50 watts from a bridge perhaps ? On the subject of linear amps. I'm also investigating the idea of a pulse width mod. voltage controller for class D PAs. Then by separating out envelope and phase information from complex modulation waveforms, an efficient PA could be used without the trouble of going through SSB driver stages and probably a transverter. The authors of a lot of the modem software could hopefully be persuaded to make amplitude and phase info available separately. Watch this space. Andy G4JNT > ---------- > From: Andre' Kesteloot[SMTP:akestelo@bellatlantic.net] > Reply To: rsgb_lf_group@blacksheep.org > Sent: 2000-05-03 13:17 > To: rsgb_lf_group@blacksheep.org > Cc: lf-amrad > Subject: Re: LF: beacon power control > > Rik Strobbe wrote: > > > [...] > > As the beacon is meant to be low-power (10mW and less) a relative > small TX > > power can be used (50 Watts and less), so it can easily be > overdimensioned > > to provide extra safety. > > Maplin has a small class A amplifier using a LM 1875 that easily puts > out 25 > watts at 136 Khz. It is stable, has automatic current limiting and > overheating > protection. Because it operates in class A, the output can be > controlled simply by a step attenuator at the _input_ of the > amplifier. > -- The Information contained in this E-Mail and any subsequent correspondence is private and is intended solely for the intended recipient(s). For those other than the recipient any disclosure, copying, distribution, or any action taken or omitted to be taken in reliance on such information is prohibited and may be unlawful.