Return-Path: X-Spam-DCC: paranoid 1290; 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=-1.0 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_10_20,HTML_MESSAGE 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 t9G9E7Fd016913 for ; Fri, 16 Oct 2015 11:14:07 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Zn126-0003By-IR for rs_out_1@blacksheep.org; Fri, 16 Oct 2015 10:10:38 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Zn126-0003Bp-3V for rsgb_lf_group@blacksheep.org; Fri, 16 Oct 2015 10:10:38 +0100 Received: from mail-wi0-f181.google.com ([209.85.212.181]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.86) (envelope-from ) id 1Zn110-0005Bg-To for rsgb_lf_group@blacksheep.org; Fri, 16 Oct 2015 10:10:36 +0100 Received: by wicll6 with SMTP id ll6so671769wic.1 for ; Fri, 16 Oct 2015 02:09:18 -0700 (PDT) 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=BS8Mh8gazfI9nNWDUqlE4F3gQX3j1Gr+Sj+iqBfWHzg=; b=Shlr/Zwb8RLVZbK+6qzgNVoT6+8MdALPJ/V0fyQCmefFiaZz8lmLpI9w9siF3We0Sj GUdUZQ0TohhH7KFgl8cKkh83F+NBGpjloaLtRQzUvbTcUdEnhLppaf6hRSdQtbFA1tOW E1PunJ+yC8CH6eFNis/TZyxFo5BSTyR2iM3c+lbnSDBgPJ0DL+8CuOHrlJfySD3kGXQy wr22+vNNfsRPuUTOkUeI8GM95Plu/i0259EoSGGM5MlqemAFES+Y06K5K6EZRPKJ4qVj EXn9+z4Ztc4tOGf85F3/kPeADqGYuGsoXVovaUcH8Qksz0g03RKYVJmWnsn8LoV1aR2u lirQ== MIME-Version: 1.0 X-Received: by 10.180.198.12 with SMTP id iy12mr3451218wic.72.1444986558771; Fri, 16 Oct 2015 02:09:18 -0700 (PDT) Received: by 10.28.47.212 with HTTP; Fri, 16 Oct 2015 02:09:18 -0700 (PDT) In-Reply-To: <867200100.20151016094832@chriswilson.tv> References: <1541636554.20151013163425@chriswilson.tv> <43464DACBFAA49C08A73FB93FFF52105@gnat> <603371935.20151014123307@chriswilson.tv> <9E19F2EA072B4AE3A7A112534A29B460@gnat> <323462263.20151015234436@chriswilson.tv> <57405F26C6A94F04B25E124CC1F9814B@gnat> <867200100.20151016094832@chriswilson.tv> Date: Fri, 16 Oct 2015 10:09:18 +0100 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org X-Scan-Signature: ffe713a28f995f248841b38a647a96f7 Subject: Re: LF: Re: Should I be aiming for a better match than this? Content-Type: multipart/alternative; boundary=047d7b6247f48a7b6f052235263c 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: 4404 --047d7b6247f48a7b6f052235263c Content-Type: text/plain; charset=UTF-8 I have always intensely disliked tapped 'loading' coils such as that, for precisely the reason you mention - a tap at one turn. This is the sort of thing you'd expect with a high Q system. Tapped coils, mutual coupling is always a hit and miss affair you have to set up by trail and error. A complete bodge - just because its simple Much better is to measure your antenna's total input resistance when resonant, then make a ferrite cored matching transformer to transform that resistance to the 50R (or whatever) your Tx is designed to drive. Ferrite cored transformers are near enough perfect at this (but remember V = 4.44 F.N.A.B for the minimum turns needed) and a few taps there will allow for variation in antenna resistance changing with weather conditions. At 700 Watts I use an old ETD49 core with Ae = 200mm^2, ferrite type something like EC90 if memory serves. Standard SMPSU type anyway. At the 700 Watt level it barely gets warm My 7m high Tee antenna at 137kHz when resonant varies from 90 ohms in dry summer conditions to as much as 130 or 140 ohms in wet soggy weather. The transformer is incorporated into the Tx and serves dual purpose as matching and isolation for teh direct-from-mains switcher PA. It has switchable output taps for a number of impedance including 50R and a range from 80 to 150R. A 10m run of UR43 coax is quite happy at the 3:1 ish SWR resulting http://www.g4jnt.com/137tx.pdf Andy G4JNT On 16 October 2015 at 09:48, Chris Wilson wrote: > Hello Alan, > > Friday, October 16, 2015 > > > Things took a sorry turn late last night, when making a final TX I > noticed the meter in the G3YXM amp that switches between FWD / REF and > measuring DC volts was reading low. Waveform voltages from the > Scopematch looked much as always, but when changing the switch between > forward and reflected power the forward power was perhaps less than a > third on full power, and the reflected power was the converse and up a > lot. I tried into the dummy load, which uses a different co-ax and it > was the same. It was still putting a signal out into Germany, although > the WSPR reporter networks seemed to show a big drop in received > signal level. > > > I am wondering if this feedback or whatever sometimes happens has > damaged a FET, can one or more of the 4 fail and still leave it > operational, but with reduced power and more reflected power? The > failure I had with the output stage in the early stages of working > with this was spectacular, noisy, smoky and terminal, leaving no > output at all. For convenience the circuit is at: > > http://www.chriswilson.tv/amp.doc > > > With regard to your advice below, I don't have a clamp on current > meter, but did pick up a suitable little meter movement at the Newbury > Rally to build one, so I will get one knocked together. I am > suspecting my toroidal auto transforming matching transformer, it > seems to need a bizarre feed tap, just one turn from the earthy end, > and get pretty warm. I may build a galvanically isolated one like John > Rabson has suggested. But first I need to find out what mischief I > have done to the amp! > > I have now experienced the transmissions tripping the main house > distribution RCD several times, and have realised that the recent > random going off of the workshop alarm (panel shows a window knock > sensor has set it off, but I am sure it's RF) coincides with > transmission when the signal shows odd on the Scopematch. Thanks Alan. > > > > Hi Chris Im glad the tap idea helped. It is quite difficult at a > distance to > > think of things that might cause the effects but it looks like we nailed > > one. > > > Your suggestion of RF getting into the system is a good one. It is always > > difficult with a short antenna because you have a lot of radiation near > the > > equipment.When I started using a 130ft end fed wire on HF with an FT-101 > and > > its low-Z dynamic mic I got terrible problems not seen when I used a > > Heathkit HW100 with a crystal mic. The latter was a lot easier to by-pass > > for RF. Eventually a trial with a ferrite rod (ex MW aerial ferrite) > pushed > > into the coils of the curly lead completely stopped the problem. I had no > > trouble on CW....only when the mic was in. > > > What you need to find is where the RF is affecting, then how its getting > in. > > It may well be that some of the chassis' is going live to RF ....if that > is > > the case you may even feel it :-(( > > > Try to make sure that the RF stays outside the shack if you can. Ground > the > > antenna end of the coax......try to run the coax at right angles to the > > aerial as it leaves the coil. Possibly put some beads on the the remote > end > > of the coax or a couple of turns through a torroid. I think you have a > > ferrite coupled current meter?? put it over the coax when you are using > the > > dummy load. You shoud see very little current indicated, do the same with > > the aerial/tuner connected and I guess you will see a lot more. That (if > it > > is the case) will give you something to aim at. Get the readings > similar to > > those on the dummy load. I think the RF is probably comming back on the > coax > > braid. > > > That's my best guess at the moment.....my, you are learning a lot of > > practical radio in a short time :-)) I may be totally off target but it > a > > good place to start. > > > Best of Luck > > Alan > > G3NYK > > > > > > > > > > > -- > Best regards, > Chris mailto:chris@chriswilson.tv > > > --047d7b6247f48a7b6f052235263c Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
I have always intensely disliked tapped 'loading' = coils such as that, for precisely the reason you mention - a tap at one tur= n. =C2=A0 =C2=A0This is the sort of thing you'd expect with a high Q sy= stem.=C2=A0 Tapped coils, mutual coupling is always a hit and miss affair y= ou have to set up by trail and error.=C2=A0 A complete bodge - just because= its simple

Much better is to measure your antenna's= total input resistance when resonant, then make a ferrite cored matching t= ransformer to transform that resistance to the 50R (or whatever) your Tx is= designed to drive.

Ferrite cored transformers are= near enough perfect at this (but remember V =3D 4.44 F.N.A.B for the minim= um turns needed) =C2=A0and a few taps there will allow for variation in ant= enna resistance changing with weather conditions. =C2=A0=C2=A0
At= 700 Watts I use an old ETD49 core with Ae =3D 200mm^2, ferrite type someth= ing like EC90 if memory serves. =C2=A0 Standard SMPSU type anyway. =C2=A0 = =C2=A0At the 700 Watt level it barely gets warm

My= 7m high Tee antenna at 137kHz when resonant varies from 90 ohms in dry sum= mer conditions to as much as 130 or 140 ohms in wet soggy weather.=C2=A0 Th= e transformer is incorporated into the Tx and serves dual purpose as matchi= ng and isolation for teh direct-from-mains switcher PA. =C2=A0 It has switc= hable output taps for a number of impedance including 50R and a range from = 80 to 150R. =C2=A0 A 10m =C2=A0run of UR43 coax is quite happy at the 3:1 i= sh SWR resulting


A= ndy =C2=A0G4JNT


On 16 October 2015 at 09:48, Chris Wilson <chris@chri= swilson.tv> wrote:
Hello Al= an,

Friday, October 16, 2015


Things took a sorry turn late last night, when making a final TX I
noticed the meter in the G3YXM amp that switches between FWD / REF and
measuring DC volts was reading low. Waveform voltages from the
Scopematch looked much as always, but when changing the switch between
forward and reflected power the forward power was perhaps less than a
third on full power, and the reflected power was the converse and up a
lot. I tried into the dummy load, which uses a different co-ax and it
was the same. It was still putting a signal out into Germany, although
the WSPR reporter networks seemed to show a big drop in received
signal level.


I am wondering if this feedback or whatever sometimes happens has
damaged a FET, can one or more of the 4 fail and still leave it
operational, but with reduced power and more reflected power? The
failure I had with the output stage in the early stages of working
with this was spectacular, noisy, smoky and terminal, leaving no
output at all. For convenience the circuit is at:

http://www.chriswilson.tv/amp.doc


With regard to your advice below, I don't have a clamp on current
meter, but did pick up a suitable little meter movement at the Newbury
Rally to build one, so I will get one knocked together. I am
suspecting my toroidal auto transforming matching transformer, it
seems to need a bizarre feed tap, just one turn from the earthy end,
and get pretty warm. I may build a galvanically isolated one like John
Rabson has suggested. But first I need to find out what mischief I
have done to the amp!

I have now experienced the transmissions tripping the main house
distribution RCD several times, and have realised that the recent
random going off of the workshop alarm (panel shows a window knock
sensor has set it off, but I am sure it's RF) coincides with
transmission when the signal shows odd on the Scopematch. Thanks Alan.


> Hi Chris Im glad the tap idea helped. It is quite difficult at a dista= nce to
> think of things that might cause the effects but it looks like we nail= ed
> one.

> Your suggestion of RF getting into the system is a good one. It is alw= ays
> difficult with a short antenna because you have a lot of radiation nea= r the
> equipment.When I started using a 130ft end fed wire on HF with an FT-1= 01 and
> its low-Z dynamic mic I got terrible problems not seen when I used a > Heathkit HW100 with a crystal mic. The latter was a lot easier to by-p= ass
> for RF. Eventually a trial with a ferrite rod (ex MW aerial ferrite) p= ushed
> into the coils of the curly lead completely stopped the problem. I had= no
> trouble on CW....only when the mic was in.

> What you need to find is where the RF is affecting, then how its getti= ng in.
> It may well be that some of the chassis' is going live to RF ....i= f that is
> the case you may even feel it :-((

> Try to make sure that the RF stays outside the shack if you can. Groun= d the
> antenna end of the coax......try to run the coax at right angles to th= e
> aerial as it leaves the coil. Possibly put some beads on the the remot= e end
> of the coax or a couple of turns through a torroid. I think you have a=
> ferrite coupled current meter?? put it over the coax when you are usin= g the
> dummy load. You shoud see very little current indicated, do the same w= ith
> the aerial/tuner connected and I guess you will see a lot more. That (= if it
> is the case) will give you something to aim at. Get the readings=C2=A0= similar to
> those on the dummy load. I think the RF is probably comming back on th= e coax
> braid.

> That's my best guess at the moment.....my, you are learning a lot = of
> practical radio in a short time :-))=C2=A0 I may be totally off target= but it a
> good place to start.

> Best of Luck
> Alan
> G3NYK










--
Best regards,
=C2=A0Chris=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 mailto:chris@chriswilson.tv



--047d7b6247f48a7b6f052235263c--