Message-ID: <D75656363EA44A8FBBF84DE15C475A45@AGB>
From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <1541636554.20151013163425@chriswilson.tv> <43464DACBFAA49C08A73FB93FFF52105@gnat> <603371935.20151014123307@chriswilson.tv> <9E19F2EA072B4AE3A7A112534A29B460@gnat> <323462263.20151015234436@chriswilson.tv> <57405F26C6A94F04B25E124CC1F9814B@gnat> <867200100.20151016094832@chriswilson.tv> <10FBC32E57324835BDD4008B3133BC11@AGB>
In-Reply-To: <10FBC32E57324835BDD4008B3133BC11@AGB>
Date: Fri, 16 Oct 2015 16:28:55 +0100
MIME-Version: 1.0
Importance: Normal
Subject: Re: LF: Re: Should I be aiming for a better match than this?
Content-Type: text/plain;
	format=flowed;
	charset="iso-8859-1";
	reply-type=response
Content-Transfer-Encoding: 8bit
Sender: owner-rsgb_lf_group@blacksheep.org
Precedence: bulk
Reply-To: rsgb_lf_group@blacksheep.org
Status: O

Ok  -3 dB at  241 Km range .... back to  normal  !

73-G,


Rx at Fri, 16 Oct 2015 15:00:14 GMT
>From 2E0ILY by DF2JP Loc JO31HH
Frequency: 0.136 MHz (2200m), OPERA, -17dB
Distance: 655 km bearing 101°


Rx at Fri, 16 Oct 2015 15:00:13 GMT
>From 2E0ILY by G3XKR Loc IO70UX
Frequency: 0.136 MHz (2200m), OPERA, -3dB
Distance: 241 km bearing 208°

--------------------------------------------------
From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
Sent: Friday, October 16, 2015 3:20 PM
To: <rsgb_lf_group@blacksheep.org>
Subject: Re: LF: Re: Should I be aiming for a better match than this?

> 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?
>
> Sorry to read that  Chris ,
>
> I often  thought  wspr  would  of  been  better  named  'ICARUS' , you 
> where  +10 dB  and more in hand on your  OP32  spots , I did  see  G3XKR 
> showing  -4 dB  on  the  first  day , but only the  one time, later spots 
> where  lower ,  [the  s/n is  the  average  over the  tx cycle and  quite 
> accurate],
>
> Could problems  of struck  after this ?
>
> The  reflected power, is  most likely  to be  the  return of  harmonic 
> energy from the  ATU, caused by  waveform distortion, your class e/d amp 
> is based on producing  a  pulse train,  fo is recovered by the  filter / 
> ATU ,
>
> One of the  Ł5 usb dongles in ds with  sharp-sdr  , will  give  you a 
> usable  spectrum  plot of the  relative  levels , f0,f1,f2 f3  etc
>
> 73-Graham..
>
> --------------------------------------------------
> From: "Chris Wilson" <chris@chriswilson.tv>
> Sent: Friday, October 16, 2015 9:48 AM
> To: "Alan Melia" <rsgb_lf_group@blacksheep.org>
> Subject: Re: LF: Re: Should I be aiming for a better match than this?
>
>> 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
>>
>>
>