Return-Path: X-Spam-DCC: paranoid 1170; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-0.0 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_MESSAGE,HTML_TINY_FONT autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id u099qcuJ032742 for ; Sat, 9 Jan 2016 10:52:38 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1aHq8t-0006Jg-03 for rs_out_1@blacksheep.org; Sat, 09 Jan 2016 09:49:03 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1aHq8s-0006JX-Ep for rsgb_lf_group@blacksheep.org; Sat, 09 Jan 2016 09:49:02 +0000 Received: from mail-wm0-f45.google.com ([74.125.82.45]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.86) (envelope-from ) id 1aHq7o-00084s-Cg for rsgb_lf_group@blacksheep.org; Sat, 09 Jan 2016 09:49:01 +0000 Received: by mail-wm0-f45.google.com with SMTP id f206so161671148wmf.0 for ; Sat, 09 Jan 2016 01:47:41 -0800 (PST) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=oefu3vowUz5ZZeeCf8TDBLbHnDe1GGfl+8uyOoJaULg=; b=XVOdkeiaW/skPkZmg2gJfFfNBPqiW30NJOYRQZM8Q+aeIC02gF8moSU4hvF0Ikpe5d YRYrzWfYoLqzXHcbTJyo+SCaWdXhxVTxEkKP0t1SIetnnsX9yCiUnq71yQx+E+Tc5+WO +4U7Ghitb3MQ6LO/DR5cojt+U72wpEXLI5NqCNPjfguGd/Zgo4hMsJU2AgbKR2p8k+VK LByyQO79BJZj9+Y0Mde+Ns19T5YWKNAmvc1yv87A6CEDrjGhTKyHszfei9aLXfX/7C+8 QzzucR1YdFWV4K37Klijc2e2pDB3McU+htzjPWglCk1MZ/O8DCTFa35usy88LlmEuqix V/Tg== MIME-Version: 1.0 X-Received: by 10.28.134.147 with SMTP id i141mr3525254wmd.87.1452332859153; Sat, 09 Jan 2016 01:47:39 -0800 (PST) Received: by 10.28.150.6 with HTTP; Sat, 9 Jan 2016 01:47:39 -0800 (PST) In-Reply-To: <15225aa896a-5493-6387@webprd-m74.mail.aol.com> References: <00f101d14a6f$82452590$86cf70b0$@com> <15225aa896a-5493-6387@webprd-m74.mail.aol.com> Date: Sat, 9 Jan 2016 09:47:39 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@yahoogroups.co.uk, rsgb_lf_group@blacksheep.org X-Scan-Signature: 3a87dabb458a71c2beb9bfdeedcdf30e Subject: LF: Re: [rsgb_lf_group] Linear Amp for LF Content-Type: multipart/alternative; boundary=001a114432ae2a630a0528e39805 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-Scanned-By: MIMEDefang 2.56 on 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 6228 --001a114432ae2a630a0528e39805 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable With the re-interest there appears to be in WOLF, and the gradual moving on with processing and data comms technology, it might be time to revisit modes that require a bit of linearity. Its well known that idPSK and coherent modes in general will offer an immediate 3dB advantage over non-coherent modes. However, in many practical situatins they are let down by the non linear processing needed to recoder carrier coherency and symbol timing. So non-coherent - FOR PRACTICAL PURPOSES wins. Recent tests using EBnaut show just what can be done if the need for carrier / clock recovery are removed (by using ultra stable sources) , so there may be some mileage to be gained by looking again. The magic point to reach is to make sure the advantages gained by coherency, in terms of S/N and hence transmitted power for any given path, offset the reduced efficiency of a linear PA stage. Typically 85% (class-E) down to to 45% (Class AB). So we really need to make sure our new data modes give us that extra 2 to 3dB. Which, judging by EBnaut with its simple BPSK mayty be possible. Once linear amps are in use, then the route to faster data in a given narrow bandwidth opens up - and more scope for espreimentation. As an aside - I am wondering if a speeded up version of WOLF might work for the higher microwavbe bands. Say 1000B/s or even faster BPSK with all the processing overhead of WOLF. Andy G4JNT On 9 January 2016 at 09:14, David G0MRF g0mrf@aol.com [rsgb_lf_group] < rsgb_lf_group@yahoogroups.co.uk> wrote: > > > Hi Terry. > > Ask away...You have almost read my mind....... > > I've been looking at the class D circuit in detail over the past few > weeks....FETs obsolete....SWR detector not quite right etc. > I've even used it on its limits to make a nice QSO with SV on 630m last > weekend. - Got so hot the snubber resistor on one of the drains fell off > > I plan on producing around 50 boards if my Chinese manufacturer hasn't > gone bust in the stock market crash.... > However, I'm not sure the linear board has much sales potential as CW / > WSPR / JT9 can all be done with non linear amplifiers. > > Also, the recently introduced power FETs are all optimised for rapid > switching in power supply applications. That's very different from 15yrs > ago when the Vg and Id transfer characteristics were much more 'linear' i= n > nature. > > What do you think?? > > David > > > -----Original Message----- > From: 'Terry GW0EZY' gw0ezy@sky.com [rsgb_lf_group] < > rsgb_lf_group@yahoogroups.co.uk> > To: rsgb_lf_group > Sent: Fri, 8 Jan 2016 23:51 > Subject: RE: [rsgb_lf_group] Linear Amp for LF > > > Hi David > > I don=E2=80=99t suppose you would consider making some more PCBs for your > amplifier=E2=80=A6=E2=80=A6.? > > Sorry =E2=80=93 I couldn=E2=80=99t resist asking! > > 73 Terry > > *From:* rsgb_lf_group@yahoogroups.co.uk [ > mailto:rsgb_lf_group@yahoogroups.co.uk = ] > > *Sent:* 08 January 2016 23:25 > *To:* rsgb_lf_group@yahoogroups.co.uk > *Subject:* Re: [rsgb_lf_group] Linear Amp for LF > > > Hi Andy. > > If it helps, I found a series combination of a silicon diode and a > schottky diode has the correct characteristic to compensate for a FET in > linear service. - Avoiding components in the source. > I just put them at the lower end of a potential divider chain that > developed the bias voltage. > Worth a try perhaps > > 73 > > David > > > -----Original Message----- > From: Andy Talbot andy.g4jnt@gmail.com [rsgb_lf_group] < > rsgb_lf_group@yahoogroups.co.uk> > To: rsgb_lf_group ; rsgb_lf_group < > rsgb_lf_group@yahoogroups.co.uk> > Sent: Fri, 8 Jan 2016 21:51 > Subject: [rsgb_lf_group] Linear Amp for LF > > Are there any proven reliably designed LF amplifier designs power > amplifiers for 137 / 475? Wideband, covering both ideally Rated for > at least 300 Watts output, and ideally a lot more. > > I saw G3YXM's low-HF design, and it looks promising for low frequency use= , > but he appears to have not gone that way and went for a switchmode versio= n > at LF/MF > > Of course, I could just redesign that, or something similar, using > suitable ferrite and a bit of feedback ,but it would be nice to avoid > reinventing too many wheels. > > Using switching MOSFETs as linear amps still doesn't feel quite right, bu= t > enough people seem have managed it now (including my own design for a low > power one) that it looks a sound-enough route to follow up. The one > thing that does bother me about the technique is bias compensation with > temperature. It is really asking for active bias control, but in a > class-B or -AB design, where bias just affects standing current, that get= s > more-than a bit tricky as a concept. > > Andy G4JNT > > __._,_.___ > ------------------------------ > Posted by: David G0MRF > ------------------------------ > Reply via web post > > =E2=80=A2 Reply to sender > > =E2=80=A2 Reply to group > > =E2=80=A2 Start a new topic > > =E2=80=A2 Messages in this topic > > (4) > Visit Your Group > > > - New Members > > 2 > - New Photos > > 3 > > [image: Yahoo! Groups] > > =E2=80=A2 Privacy =E2=80=A2 > Unsubscribe > =E2= =80=A2 Terms > of Use > > . > > __,_._,___ > --001a114432ae2a630a0528e39805 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
With the re-interest there appears to be in WOLF, and= the gradual moving on with processing and data comms technology, it might = be time to revisit modes that require a bit of linearity.=C2=A0=C2=A0

Its well known that=C2=A0idPSK and coherent modes in g= eneral will offer an immediate 3dB advantage over non-coherent modes.=C2=A0= However, in many practical situatins they are let down by the non linear p= rocessing needed to recoder carrier coherency and symbol timing.=C2=A0=C2= =A0 So non-coherent - FOR PRACTICAL PURPOSES wins.

Recent tests using EBnaut show just what can be done if the need for carri= er / clock recovery are removed (by using ultra stable sources) , so there = may be some mileage to be gained by looking again.

The magic point to reach is to make sure the advantages gained by coherenc= y, in terms of S/N and hence transmitted power for any given path, offset t= he reduced efficiency of a linear PA stage.=C2=A0 Typically =C2=A085% (clas= s-E) down to =C2=A0to 45% (Class AB).=C2=A0=C2=A0 So we really need to make= sure our new data modes give us that extra 2 to 3dB.=C2=A0 Which, judging = by EBnaut with its simple BPSK mayty be possible.

= Once linear amps are in use, then the route to faster data in a given narro= w bandwidth opens up - and more scope for espreimentation.

As an aside - I am wondering if a speeded up version of WOLF might= work for the higher microwavbe bands.=C2=A0 Say 1000B/s or even faster BPS= K with all the processing overhead of WOLF.

Andy= =C2=A0 G4JNT
=C2=A0

On 9 January 2016 at 09:14, David G0MRF g0mrf@aol.com [rsgb_lf_group] <rsgb_lf_g= roup@yahoogroups.co.uk> wrote:
=20
=C2=A0
=20 =20

Hi Terry.
=C2=A0
Ask away...You have almost read my mind.......
=C2=A0
I've been looking at=C2=A0the class D=C2=A0circuit in detail over = the past few weeks....FETs obsolete....SWR detector not quite right etc.
I've even used it on its limits to make a nice QSO with SV on 630m= =C2=A0last weekend.=C2=A0 - Got so hot the snubber resistor on one of the= =C2=A0drains fell off
=C2=A0
I plan on producing around 50 boards=C2=A0if my Chinese manufacturer h= asn't gone bust in the stock market crash....=C2=A0
However, I'm not sure the linear board has much sales potential as= CW / WSPR / JT9 can all be done with non linear amplifiers.
=C2=A0
Also, the recently introduced power FETs are all optimised for rapid s= witching in power supply applications. That's very different from 15yrs= ago when the Vg and Id transfer characteristics were much more 'linear= ' in nature.
=C2=A0
What do you think??
=C2=A0
David
=C2=A0
=C2=A0
-----= Original Message-----
From: 'Terry GW0EZY' gw0ezy@sky.com [rsgb_lf_group] <rsgb_lf_group@yahoogroups.co.uk&= gt;
To: rsgb_lf_group <rsgb_lf_group@yahoogroups.co.uk>
Sent: Fri, 8 Jan 2016 23:51
Subject: RE: [rsgb_lf_group] Linear Amp for LF

=C2=A0
=20
=20
=20 =20 =20
Hi David
=C2=A0
I don=E2=80=99t suppose you would consider making some more PCBs for your= amplifier=E2=80=A6=E2=80=A6.?
=C2=A0
Sorry =E2=80=93 I couldn=E2=80=99t resist asking!
=C2=A0
73 Terry
=C2=A0
From:= rsgb_lf_group@yahoogroups.co.uk [mailto:rsgb_lf_gr= oup@yahoogroups.co.uk]
Sent: 08 January 2016 23:25
To: rsgb_lf_group@yahoogroups.co.uk
Subject: Re: [rsgb_lf_group] Linear Amp for LF
=C2=A0
=C2=A0
Hi Andy= .
=C2=A0<= /span>
If it h= elps, I found a series combination of a silicon diode and a schottky diode = has the correct characteristic to compensate for a FET in linear service. -= =C2=A0Avoiding components in the source.
I just = put them at the lower end of a potential divider chain that developed the b= ias voltage.
Worth a= try perhaps
=C2=A0<= /span>
73
=C2=A0<= /span>
David
=C2=A0<= /span>
=C2=A0<= /span>
-----Original Message-----
From: Andy Talbot andy.g4jnt@gmail.com [rsgb_lf_group] <rsgb_lf_group@yahoogroups.co.uk= >
To: rsgb_lf_group <rsgb_lf_group@blacksheep.org>; rsgb_lf_group <rsgb_lf_grou= p@yahoogroups.co.uk>
Sent: Fri, 8 Jan 2016 21:51
Subject: [rsgb_lf_group] Linear Amp for LF
=C2=A0
Are there any proven reliably designed LF amplifier des= igns power amplifiers=C2=A0=C2=A0for 137 / 475? =C2=A0 Wideband, covering b= oth ideally =C2=A0 =C2=A0Rated for at least 300 Watts output, and ideally a= lot more.
=C2=A0
I saw G3YXM's low-HF design, and it looks promising= for low frequency use, but he appears to have not gone that way and went f= or a switchmode version at LF/MF
=C2=A0
Of course, I could just redesign that, or something sim= ilar, using suitable ferrite and a bit of feedback ,but it would be nice to= avoid reinventing too many wheels.
=C2=A0
Using switching MOSFETs as linear amps still doesn'= t feel quite right, but enough people seem have managed it now (including m= y own design for a low power one) that it looks a sound-enough route to fol= low up. =C2=A0 =C2=A0The one thing that does bother me about the technique = is bias compensation with temperature. =C2=A0 It is really asking for activ= e bias control, but in a class-B or -AB design, where bias just affects sta= nding current, that gets more-than a bit tricky as a concept.
=C2=A0
Andy =C2=A0G4JNT
=20 =20 =20
=20

=20 =20
__._,_.___
=20 =20 =20 =20
Posted by: David G0MRF <g0mrf@aol.com>
Repl= y via web post =E2=80=A2 Reply to sender =E2=80=A2 Reply to group =E2=80=A2 Start a new topic =E2=80=A2 Messages in this topic (4)
=20 =20
3D"Yahoo!
=E2=80=A2 Privacy =E2=80=A2 Unsubscribe =E2=80=A2 Terms of Use

=20 =20 =20 =20
=20
.
=
= =20
__,_._,___
=20

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