Return-Path: Received: (qmail 95190 invoked from network); 23 Feb 2005 16:57:26 -0000 Received: from unknown (HELO ptb-spamcore02.plus.net) (192.168.71.3) by ptb-mailstore04.plus.net with SMTP; 23 Feb 2005 16:57:26 -0000 Received: from mailnull by ptb-spamcore02.plus.net with spamcore-l-b (Exim 4.32; FreeBSD) id 1D3zq1-0009kd-08 for dave@picks.force9.co.uk; Wed, 23 Feb 2005 16:58:16 +0000 Received: from [192.168.67.2] (helo=ptb-mxcore02.plus.net) by ptb-spamcore02.plus.net with esmtp (Exim 4.32; FreeBSD) id 1D3zpx-0009il-KY for dave@picks.force9.co.uk; Wed, 23 Feb 2005 16:58:09 +0000 Received: from post.thorcom.com ([193.82.116.20]) by ptb-mxcore02.plus.net with esmtp (Exim) id 1D3zp6-0008dY-6U for dave@picks.force9.co.uk; Wed, 23 Feb 2005 16:57:16 +0000 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1D3zlJ-0000zs-3W for rs_out_1@blacksheep.org; Wed, 23 Feb 2005 16:53:21 +0000 Received: from [193.82.116.30] (helo=relay.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1D3zlI-0000zj-Mv for rsgb_lf_group@blacksheep.org; Wed, 23 Feb 2005 16:53:20 +0000 Received: from one.surfree.co.uk ([195.80.0.234]) by relay.thorcom.net with esmtp (Exim 4.43) id 1D3zlG-00017t-95 for rsgb_lf_group@blacksheep.org; Wed, 23 Feb 2005 16:53:20 +0000 Received: from standalone ([212.248.140.34]) by one.surfree.co.uk (8.9.3/8.9.3) with SMTP id RAA23146 for ; Wed, 23 Feb 2005 17:54:09 GMT Received: by localhost with Microsoft MAPI; Wed, 23 Feb 2005 16:51:47 -0000 Message-ID: <01C519C7.F67A6590.actalbot@southsurf.com> From: Andy To: "'rsgb_lf_group@blacksheep.org'" Date: Wed, 23 Feb 2005 16:51:45 -0000 Importance: high X-Priority: 1 (Highest) Organization: UKNWN(UK) X-Mailer: Microsoft Internet E-mail/MAPI - 8.0.0.4211 MIME-Version: 1.0 X-SPF-Result: relay.thorcom.net: 195.80.0.234 is neither permitted nor denied by domain of southsurf.com X-Spam-Score: 0.1 (/) X-Spam-Report: autolearn=failed,X_PRIORITY_HIGH=0.093 Subject: LF: RE: Re: Off Topic Ft101zd Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Status: No, hits=0.5 required=5.0 tests=X_PRIORITY_HIGH 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 X-Spam-Filtered: by PlusNet SpamCORE (v3.00) Off the shelf A/D converters (mostly single chip) have come on in leaps and bounds in recent years, thanks to (dictated by ?) the mobile phone industry. I think most cell phone base stations just downconvert and digitise the whole band in one go. So, with forward power control implemented, 14 bit (16 bit now) resolution is adequate. The GSM band is 25MHz wide so 65MHz sampling is adequate. This is just about suitable for entire HF band digitisation. At least, on a good day provided there are no mega-strong signals present such as on-board transmitters - there often will be! A/D converters got to this point over a very short period, a few years ago. In 1994, such 14 bit devices cost 10000 pounds each (from Analog Devices), now they cost a few tens of pounds. Now, I have heard of 100MHz devices - which are needed for 3G phones - but things seem to be moving more slowly now, so it looks as if technology is the limiting factor, or more likely the money that the mob. phone industry is prepared to throw at development of better A/D converters. However, the product I mentioned, was produced, by Hewlett Packard I believe, some time ago specifically for intercept equipment for communications and radar. It was in the HP catalogue at one time, but going back a few years. Don't have the exact hardware details to hand, but vaguely remember it was made up of discrete components, and was almost certainly a sigma delta type of A/D ( one or two bit sampling very, very fast, ie. several GHz, followed by processing, Same idea as in Codecs on soundcards) and cost an awful lot of money. I would have cost tens or hundreds of thousands of dollars for the complete system. While it may have been enhanced a bit by now , more likely its been forgotton. Contrasting the massive leap forward in technology in the commercial, and particularly mobile phone industries, with the slow down / stagnating of purely military research since the end of the Cold War, I guess much comint (and software defined radio) hardware just uses off the shelf devices now. On a totally different matter : Have just read that the Zepp antenna is so named as it was once used as the antenna towed behind Zeppelin airships. Does anyone know if this is so? I've certainly never come across any other derivation of its name. Andy G4JNT for [the modern day equivalent equivalent of WW2 monitoring > >stations] that digitises the entire HF spectrum in one go. > > > Do really exist A/D converters capable of 24-bit resolution at 30 MHz > bandwidth ? > If the answer is yes, then recently I haven't paid too much attention to > what was > happening in the technology field... > > 73 Alberto I2PHD >