Envelope-to: dave@picks.force9.co.uk Delivery-date: Mon, 16 Jan 2006 16:23:19 +0000 Received: by ptb-mxcore02.plus.net with spam-scanned (PlusNet MXCore v2.00) id 1EyX8W-00082B-QQ for dave@picks.force9.co.uk; Mon, 16 Jan 2006 16:23:19 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore02.plus.net with esmtp (PlusNet MXCore v2.00) id 1EyX8W-00080K-CF for dave@picks.force9.co.uk; Mon, 16 Jan 2006 16:23:16 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1EyX7N-0006tp-AS for rs_out_1@blacksheep.org; Mon, 16 Jan 2006 16:22:05 +0000 Received: from [193.82.59.130] (helo=relay2.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1EyX7M-0006tg-Hb for rsgb_lf_group@blacksheep.org; Mon, 16 Jan 2006 16:22:04 +0000 Received: from smtpout0165.sc1.cp.net ([64.97.136.165] helo=n082.sc1.cp.net) by relay2.thorcom.net with esmtp (Exim 4.51) id 1EyXhQ-0001Pj-Ac for rsgb_lf_group@blacksheep.org; Mon, 16 Jan 2006 16:59:21 +0000 Received: from l8p8y6 (62.252.208.130) by n082.sc1.cp.net (7.2.069.1) id 43C554450007D60A for rsgb_lf_group@blacksheep.org; Mon, 16 Jan 2006 16:21:50 +0000 Message-ID: <000601c61ab8$e82855e0$82d0fc3e@l8p8y6> From: "hamilton mal" To: rsgb_lf_group@blacksheep.org References: <000c01c61955$de2ddce0$6401a8c0@JAYTERMINAL> <000b01c61969$5f7b1480$86327ad5@w4o8m9> <001101c619ae$436c1b00$ef497ad5@w4o8m9> <000f01c619ec$264266e0$0be9fc3e@l8p8y6> <004d01c61a34$af113580$0201a8c0@private.network> Date: Mon, 16 Jan 2006 16:16:19 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4807.1700 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4807.1700 Subject: LF: Re: Re: Re: Re: TA Content-Type: text/html; charset=windows-1252 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-PN-SpamFiltered: by PlusNet MXCore (v2.00) Content-transfer-encoding: 8bit
 
----- Original Message -----
From: Scott Tilley
To: rsgb_lf_group@blacksheep.org
Sent: Monday, January 16, 2006 12:35 AM
Subject: LF: Re: Re: Re: TA

Quoting Mal...
 
"This QRS business is severe on PA fets and some psu's, especially the slower crawls. Anything beyond QRS 3 - 10 could be fatal over long periods for most rigs. Any sudden antenna instability, windy condx, showers then sunshine ie SWR variations are tricky at the vy slow speeds, even the Decca Jeeps have been know to blow smoke in amateur applications."
 
I don't buy that at all.
 
My station has run 24/7 for extended periods at max power
 
What is max power, ie a 100 w or so or 1kw ? You can get away with a lot at low power but at higher levels it is a different story, also the protection circuit used plays a critical part, if it works properly and closes the PA down at the slighest breeze then you will not have a problem. Most amateur FET rigs do not have a lot of protection and are therefore vunerable.
 
 
with a floppy vertical to deal with the 'Pacific breeze' and rarely if ever have I lost a FET and never a power supply... All my FET failures can be classed as operator error not environmental factors... My only FET death this year was caused by arcing to my nearby 80m dipole.  It arced for a good 30minutes by the look of the grab I was sent and then one of the FETs in the TX shorted...
 
Some operators around the UK are running the DECCA amp at 1.2 kw, had you been using this power you would probably have burnt the housed down instead of just one FET.
I will keep an eye out for SMOKE in your direction, I am more likely to see this than hear you on cw.
 
 
The trick is ensuring good cooling and sizing of the parts, particularly ferrites.  If there is a danger to the FETs its when you're doing that old switched carrier mode rather rapidly and only if you haven't taken good care of the transients on the FET drains ;-)
 
Sorry Mal but my observations during prolonged and rapid weather changes don't indicate that amateur transmitters are so delicate that they can't handle long QRSS dot modes...  I've run my sinewave (QRSS near-infinity) for weeks on end without trouble during all kinds of weather events...
 
I have data if you want to see it...
 
I believe you but let me know what happens when you get some real POWER into that wobbly antenna.
 
Scott