Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id vBTCAXGd009472 for ; Fri, 29 Dec 2017 13:10:36 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1eUtQT-0006x5-J3 for rs_out_1@blacksheep.org; Fri, 29 Dec 2017 12:06:13 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1eUtQS-0006ww-TJ for rsgb_lf_group@blacksheep.org; Fri, 29 Dec 2017 12:06:12 +0000 Received: from mail-wm0-x235.google.com ([2a00:1450:400c:c09::235]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89) (envelope-from ) id 1eUtQP-0001wf-TN for rsgb_lf_group@blacksheep.org; Fri, 29 Dec 2017 12:06:11 +0000 Received: by mail-wm0-x235.google.com with SMTP id t8so47994862wmc.3 for ; Fri, 29 Dec 2017 04:06:09 -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=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to; bh=D2kV69Tu74YaC3OiOa2BXA7ZObeO8Ls4qeSCJbwKlXI=; b=L7yCsAwQn1RbQSdl+qaPYGgYAZT/TXMjZjgzr2fatXYE42j9UDUnm0zcr6OqDfn10A fmCEyl9EI+/X2oNt+6R7QvCev/hRIZ+ZZpKPa6lkzKYVAyrdujB6T1PHiQWEtc0k0qKl HVn6ys4r4CZ92CLiON4AQJwbqinS/BBJwHrInj+eujBYlLy6S87qZSDU6CPY6BnfuvJk IchhIRd1iT3oLfS0Ix3FLTclmbbUQNy004XDf/5scHOTv2fCA80Uip7L2wiCsBhdv2pj u5yyX0o9a08fjI1rKk/hu4fBAtqDkAkrnfRsIAEL1oXKqk6YqwAK9zGOgjfUocEGoXIW POvQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=D2kV69Tu74YaC3OiOa2BXA7ZObeO8Ls4qeSCJbwKlXI=; b=nOrt0KgKEs3JAqkqgzIiudFcALIoAFTJBytyuJ8fsx+a5rbSi0kyoy7X4wZeBX06Pa 8i9VOHg03XQs6EmIzpFSCQ67PskmySSSGMcan7LTyAGdZHWbkCtvFJNylLGrkfs1GUQ7 DYc3GiEc/ua3ZDlZ/rCrrHfbMi7F7H6//ps8O1rmfyFnTomfJBKk5HqCwSXNtGB8cIvL G4p9QvML0f8pujuS5DfRE03FM9tAySJvabzykb8LBaNU7ujdhT3s14cEq8HTV1xkj5YW 3cfy8InpCy6TYYArZdHbzbI+rdyw67RWj6u28FE0RKVCM6g+w56GafZ8U4/0mqyYmSi9 3Wyg== X-Gm-Message-State: AKGB3mKwTRHNAORp0a4ucVOmVipwiu497f7Co4Qow9ZOt0qeeoTtbYl3 ytDlcTSFT0//KnKRI8wCmUI1RC/m5JiyQ/v1zSw= X-Google-Smtp-Source: ACJfBosKPlRi8NI+Dz/YvbdjwF2Gwqu03WGOZUAHvgf5V/SE8z32OeFK5AlFtl4O17Yfh58kz77GFZoKhlNe6E3zGxY= X-Received: by 10.80.170.87 with SMTP id p23mr45935631edc.289.1514549168321; Fri, 29 Dec 2017 04:06:08 -0800 (PST) MIME-Version: 1.0 Received: by 10.80.177.54 with HTTP; Fri, 29 Dec 2017 04:06:07 -0800 (PST) In-Reply-To: References: <1608d073056.marcocadeddu@tin.it> <4556666E6F7849679451F95BD8C43FAA@Clemens0811> <9dbb1de2-0d17-b64f-3051-fd63f1f29cc4@n1bug.com> <51D7E4AF62D34F388A618D1DEA4942D2@Clemens0811> <5ea52d97-4678-1781-e3b5-6f0d12c6a5fb@n1bug.com> <1071712789.20171229112605@gmail.com> From: Andy Talbot Date: Fri, 29 Dec 2017 12:06:07 +0000 Message-ID: To: rsgb_lf_group@blacksheep.org X-Spam-Score: 0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Sounds more like feedback. RF feeding back into the driver stages. The LF component you see is, perhaps, a beat between generated RF and oscillatory RF due to feedback. Or feedback itself oscillating at LF. Or something like that [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (andy.g4jnt[at]gmail.com) 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: c1dcf088149efa0360827745859da381 Subject: Re: R: Re: LF: TXing 2200m WSPR Content-Type: multipart/alternative; boundary="94eb2c0df40e2c3af8056179753d" 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 --94eb2c0df40e2c3af8056179753d Content-Type: text/plain; charset="UTF-8" Sounds more like feedback. RF feeding back into the driver stages. The LF component you see is, perhaps, a beat between generated RF and oscillatory RF due to feedback. Or feedback itself oscillating at LF. Or something like that Vaguely recall something similar happening here in the dim and distant past. Perhaps a couple of times even In fact, I think it explains why my 475kHz 400W Class-E PA which is built open-style has an aluminium screen above the input circuitry (Of course, I may have added that due to an earlier poor-screening experience - it's all too long ago to remember). 'jnt On 29 December 2017 at 11:56, N1BUG wrote: > Hi Chris, > > At PS side of the choke, no RF behaving or misbehaving. > > At output transformer side of the choke, mainly negative-going pulses > which become distorted similarly to the output when misbehaving. > > Drain waveform is like a sine wave with regular shaped positive half, > negative half is double peak. When misbehaving, same basic shape but blurry > just as the RF output is... looks as if amplitude constantly changes from > cycle to cycle, as though modulated by a lower frequency. > > Gate waveform almost a pure sine wave (remember this is a class AB/B/C > amp), develops amplitude blur or modulation when misbehaving. > > My "gut" tells me this amp is oscillating at a frequency well below the > band (maybe at VLF) but only when feeding the antenna. Perhaps the fact the > antenna is a very reactive load at VLF sets it off? I don't know why it > would happen at different RF power levels with 13V / 19V PSU unless it is > proportional to current somewhere... > > I'm about ready to take this amp down to the train track and strap it on a > rail... might be rather satisfying. ;-) > > Paul N1BUG > > > > On 12/29/2017 06:26 AM, Chris Wilson wrote: > >> >> >> Hello N1BUG, >> >> >> What does the scope show if you look at each side of the choke in the >> PA? I did some tests ages ago using the stacked chip caps on the PA >> side of the choke compared to conventional leaded caps and the >> difference was marked. I would certainly try a proper dust iron core >> for the choke, ferrite can't be right... I don't use a LPF after the >> U3S but my amp is "Class D" and is happy with being driven with square >> waves. >> >> Friday, December 29, 2017, 11:13:03 AM, you wrote: >> >> One final thing. >>> >> >> Thought maybe something in the antenna was breaking down (arcing or >>> corona), so made another check: >>> >> >> I now have the capability to run the PA on 13V or 19V. At 19V I can >>> make more power into the antenna before the signal goes dirty, >>> compared to 13V. RF power is RF power. If it was something failing >>> in the antenna system I think it should happen at the same RF power, >>> no matter what DC supply voltage I use on the PA... >>> >> >> Paul >>> >> > --94eb2c0df40e2c3af8056179753d Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Sounds more like feedback.=C2=A0 =C2=A0 RF feeding back in= to the driver stages.=C2=A0 =C2=A0The LF component you see is, perhaps, a b= eat between generated RF and oscillatory RF due to feedback. Or feedback it= self oscillating at LF.=C2=A0 Or something like that

Vag= uely recall something similar happening here in the dim and distant past.= =C2=A0 =C2=A0Perhaps a couple of times even=C2=A0 =C2=A0 In fact, I think i= t explains why my 475kHz 400W Class-E PA which is built open-style has an a= luminium screen above the input circuitry (Of course, I may have added that= due to an earlier poor-screening experience - it's all too long ago to= remember).

'jnt


On 29 December 2017 = at 11:56, N1BUG <paul@n1bug.com> wrote:
Hi Chris,

At PS side of the choke, no RF behaving or misbehaving.

At output transformer side of the choke, mainly negative-going pulses which= become distorted similarly to the output when misbehaving.

Drain waveform is like a sine wave with regular shaped positive half, negat= ive half is double peak. When misbehaving, same basic shape but blurry just= as the RF output is... looks as if amplitude constantly changes from cycle= to cycle, as though modulated by a lower frequency.

Gate waveform almost a pure sine wave (remember this is a class AB/B/C amp)= , develops amplitude blur or modulation when misbehaving.

My "gut" tells me this amp is oscillating at a frequency well bel= ow the band (maybe at VLF) but only when feeding the antenna. Perhaps the f= act the antenna is a very reactive load at VLF sets it off? I don't kno= w why it would happen at different RF power levels with 13V / 19V PSU unles= s it is proportional to current somewhere...

I'm about ready to take this amp down to the train track and strap it o= n a rail... might be rather satisfying. ;-)

Paul N1BUG



On 12/29/2017 06:26 AM, Chris Wilson wrote:


Hello N1BUG,


What=C2=A0 does the scope show if you look at each side of the choke in the=
PA?=C2=A0 I=C2=A0 did=C2=A0 some=C2=A0 tests ages ago using the stacked chi= p caps on the PA
side=C2=A0 of=C2=A0 the=C2=A0 choke=C2=A0 compared=C2=A0 to=C2=A0 conventio= nal=C2=A0 leaded=C2=A0 caps and the
difference=C2=A0 was=C2=A0 marked. I would certainly try a proper dust iron= core
for=C2=A0 the=C2=A0 choke, ferrite can't be right... I don't use a = LPF after the
U3S but my amp is "Class D" and is happy with being driven with s= quare
waves.

Friday, December 29, 2017, 11:13:03 AM, you wrote:

One final thing.

Thought maybe something in the antenna was breaking down (arcing or
corona), so made another check:

I now have the capability to run the PA on 13V or 19V. At 19V I can
make more power into the antenna before the signal goes dirty,
compared to 13V. RF power is RF power. If it was something failing
in the antenna system I think it should happen at the same RF power,
no matter what DC supply voltage I use on the PA...

Paul


--94eb2c0df40e2c3af8056179753d--