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 w9E9Og3X020123 for ; Sun, 14 Oct 2018 11:24:44 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1gBcY4-00063T-S0 for rs_out_1@blacksheep.org; Sun, 14 Oct 2018 10:18:56 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1gBcXa-00063E-3r for rsgb_lf_group@blacksheep.org; Sun, 14 Oct 2018 10:18:26 +0100 Received: from smtp2web.tin.it ([212.216.176.236]) by relay1.thorcom.net with esmtp (Exim 4.91_59-0488984) (envelope-from ) id 1gBcXY-0007Pq-Cr for rsgb_lf_group@blacksheep.org; Sun, 14 Oct 2018 10:18:24 +0100 Received: from feu5 (10.192.64.15) by smtp2web.tin.it (8.6.060.43) id 5B27C17303298544 for rsgb_lf_group@blacksheep.org; Sun, 14 Oct 2018 11:18:23 +0200 Received: from (95.251.143.73) by webmailtin.pc.tim.it; Sun, 14 Oct 2018 11:18:23 +0200 Message-ID: <16671de907b.marcocadeddu@tin.it> Date: Sun, 14 Oct 2018 11:18:23 +0200 (CEST) From: "marcocadeddu@tin.it" To: Mime-Version: 1.0 X-Originating-IP: 95.251.143.73:1712 X-Spam-Score: 1.0 (+) 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 @@CONTACT_ADDRESS@@ for details. Content preview: Hi Chris & LF fellows, I have also a similar problem to your Chris, but I haven't still found the origin: at the end of WSPR transmission, in the 2 seconds pause before the ptt switches to rx, I see a high peak in the return loss (very high SWR if you prefere) with lower associated froward power. This should mean a short transmission outside the matching of the antenna I guess.. maybe an audio tone few kHz away or a sort of regeneration through the driver.. It happens both in the LFTX which is an half bridge Decca style and in the MFTX which is a class E amplifier. No worries of course for the LFTX which is very sturdy ;-) but I guess this could be one of the problems I encountered testing the MFTX. [...] Content analysis details: (1.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [212.216.176.236 listed in list.dnswl.org] -0.0 RCVD_IN_MSPIKE_H3 RBL: Good reputation (+3) [212.216.176.236 listed in wl.mailspike.net] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (marcocadeddu[at]tin.it) -0.0 SPF_PASS SPF: sender matches SPF record -0.0 T_RP_MATCHES_RCVD Envelope sender domain matches handover relay domain 0.0 HTML_MESSAGE BODY: HTML included in message -0.0 RCVD_IN_MSPIKE_WL Mailspike good senders 1.0 FREEMAIL_REPLYTO Reply-To/From or Reply-To/body contain different freemails X-Scan-Signature: 567a11ac6cfe1e88f3054745c06178fe Subject: R: Re: VLF: Class E PA Content-Type: multipart/alternative; boundary="----=_Part_3371_1427881.1539508703361" 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 ------=_Part_3371_1427881.1539508703361 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Hi Chris & LF fellows, I have also a similar problem to your Chris, but I haven't still found the = origin: at the end of WSPR transmission, in the 2 seconds pause before the ptt swit= ches to rx, I see a high peak in the return loss (very high SWR if you pref= ere) with lower associated froward power. This should mean a short transmission outside the matching of the antenna I= guess.. maybe an audio tone few kHz away or a sort of regeneration through= the driver.. It happens both in the LFTX which is an half bridge Decca style and in the = MFTX which is a class E amplifier. No worries of course for the LFTX which is very sturdy ;-) but I guess this= could be one of the problems I encountered testing the MFTX. 73, Marco IK1HSS ----Messaggio originale---- Da: dead.fets@gmail.com Data: 14-ott-2018 11.00 A: "DK7FC" Ogg: Re: VLF: Class E PA Hello DK7FC, The biggest voltage and current spikes in my W1VD Class d amp are when a WSPR or OPERA transmission ceases, from back EMF I presume. I am curious as tvo whether a "soft voltage start" circuit could be devi= sed and added to other power supplies similar to the one discussed earlier? Sunday, October 14, 2018, 9:30:20 AM, you wrote: > =20 > Hi Tom,=20 > =20 > Good luck with your PA. > Tell us the component values when you're finished, as well as the > actual efficiency. From my LF PA i remember the coil, which was > quite large already ('air-cored'). > =20 > Regarding current peaks at the first switching: I would simply > ignore the problem and see if the FET will survive (and how old it > becomes). If it's lifetime is actually to short, then i would start > thinking about a solution for the problem. One of them just costs 2 > EUR or so, so it is worth to try... > =20 > 73, Stefan > =20 > =20 > =20 > Am 14.10.2018 00:16, schrieb DK1IS:=20 > =20 > Hello group, > Just to close this thread: > Concerning the problem of the first drive pulse with DC power > already on: Bob, W1XP, made an important contribution in a private > mail. He pointed out that the current spike I was worried about > would be limited by the FETs output characteristic anyway. Looking > to the data sheet of my intended IRFB 4227 this seems to be true > although there could persist a certain limitation by the save > operation area. Perhaps I was a little bit too naive estimating the > peak current as Vdc / Rdson ... Be that as it may, using the newly > discovered DC soft start feature of my power supply should overcome > this challenge. Controlled by a logic level input it runs up the > output voltage with a time constant of about 100 ms. This will > protect the FET, avoid any key clicks and won=C2=B4t affect the > readability of the long lasting vlf signals. To keep the signal > phase constant (essential on vlf) oscillator and gate drive of the FET wo= n=C2=B4t be keyed at all. > I=C2=B4ve just modified the antenna / loading coil system to resonate at > 8270 Hz without transformers, - 3dB band width now being 168 Hz. > Including 25 m RG213U from the arbour to the shack (being later on > part of the matching network) the feeding impedance is now 480 Ohms > pure resistive which will be matched to the rest of the class E PA > by its output network. Thus I`m able to omit the two matching > transformers being used up to now, see www.qrz.com/db/dk1is.=20 > Now I=C2=B4m waiting for the driver ICs coming from China - in Germany > up to now without additional tax ;-) ! > Thanks for all the feedback, 73, > Tom, DK1IS=20 > =20 --=20 Best regards, Chris mailto:dead.fets@gmail.com ------=_Part_3371_1427881.1539508703361 Content-Type: text/html;charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi Chris & LF fellows,

I have also a similar problem to your Chr= is, but I haven't still found the origin:
at the end of WSPR transmissio= n, in the 2 seconds pause before the ptt switches to rx, I see a high peak = in the return loss (very high SWR if you prefere) with lower associated fro= ward power.
This should mean a short transmission outside the matching o= f the antenna I guess.. maybe an audio tone few kHz away or a sort of regen= eration through the driver..
It happens both in the LFTX which is an hal= f bridge Decca style and in the MFTX which is a class E amplifier.
No wo= rries of course for the LFTX which is very sturdy ;-) but I guess this coul= d be one of the problems I encountered testing the MFTX.

73, Marco I= K1HSS

----Messaggio originale----
Da: dead.fets@gmail.com
Data: 14-ott-2018= 11.00
A: "DK7FC"<rsgb_lf_group@blacksheep.org>
Ogg: Re: VLF: C= lass E PA



Hello DK7FC,

The biggest voltage and curren= t spikes in my W1VD Class d amp are when
a WSPR or OPERA transmission ce= ases, from back EMF I presume.

I  am  curious  as tvo= whether a "soft voltage start" circuit could be devised
and  added=   to  other  power  supplies  similar  to&nbs= p; the one discussed
earlier?

Sunday, October 14, 2018, 9:30:20 A= M, you wrote:

>   
>  Hi Tom,
>=  
>  Good luck with your PA.
>  Tell us the com= ponent values when you're finished, as well as the
> actual efficienc= y. From my LF PA i remember the coil, which was
> quite large already= ('air-cored').
> 
>  Regarding current peaks at the= first switching: I would simply
> ignore the problem and see if the = FET will survive (and how old it
> becomes). If it's lifetime is actu= ally to short, then i would start
> thinking about a solution for the= problem. One of them just costs 2
> EUR or so, so it is worth to try= ...
> 
>  73, Stefan
> 
>  > 
>  Am 14.10.2018 00:16, schrieb DK1IS:
>&nb= sp; 
> Hello group,
> Just to close this thread:

&= gt; Concerning the problem of the first drive pulse with DC power
> a= lready on: Bob, W1XP, made an important contribution in a private
> m= ail. He pointed out that the current spike I was worried about
> woul= d be limited by the FETs output characteristic anyway. Looking
> to t= he data sheet of my intended IRFB 4227 this seems to be true
> althou= gh there could persist a certain limitation by the save
> operation a= rea. Perhaps I was a little bit too naive estimating the
> peak curre= nt as Vdc / Rdson ... Be that as it may, using the newly
> discovered= DC soft start feature of my power supply should overcome
> this chal= lenge. Controlled by a logic level input it runs up the
> output volt= age with a time constant of about 100 ms. This will
> protect the FET= , avoid any key clicks and won=C2=B4t affect the
> readability of the= long lasting vlf signals. To keep the signal
> phase constant (essen= tial on vlf) oscillator and gate drive of the FET won=C2=B4t be keyed at al= l.

> I=C2=B4ve just modified the antenna / loading coil system to= resonate at
> 8270 Hz without transformers, - 3dB band width now bei= ng 168 Hz.
> Including 25 m RG213U from the arbour to the shack (bein= g later on
> part of the matching network) the feeding impedance is n= ow 480 Ohms
> pure resistive which will be matched to the rest of the= class E PA
> by its output network. Thus I`m able to omit the two ma= tching
> transformers being used up to now, see www.qrz.com/db/dk1is.=

> Now I=C2=B4m waiting for the driver ICs coming from China - i= n Germany
> up to now without additional tax ;-) !

> Thanks= for all the feedback, 73,
> Tom, DK1IS
>   

--
Best regards,
Chris      = ;            &n= bsp;         mailto:dead.fets@gmail= .com




------=_Part_3371_1427881.1539508703361--