Return-Path: Received: from mtain-mb12.r1000.mx.aol.com (mtain-mb12.r1000.mx.aol.com [172.29.96.32]) by air-di01.mail.aol.com (v127_r1.1) with ESMTP id MAILINDI013-eab84b99378f11f; Thu, 11 Mar 2010 13:33:51 -0500 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-mb12.r1000.mx.aol.com (Internet Inbound) with ESMTP id 2B90738000181; Thu, 11 Mar 2010 13:33:49 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1NpnBn-0000bK-AI for rs_out_1@blacksheep.org; Thu, 11 Mar 2010 18:32:55 +0000 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1NpnBm-0000bB-PI for rsgb_lf_group@blacksheep.org; Thu, 11 Mar 2010 18:32:54 +0000 Received: from out1.ip06ir2.opaltelecom.net ([62.24.128.242]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1NpnBj-0005ur-Gg for rsgb_lf_group@blacksheep.org; Thu, 11 Mar 2010 18:32:54 +0000 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AhQFALPFmEtOkzPM/2dsb2JhbACMRAOOGnO9N4R7BA X-IronPort-AV: E=Sophos;i="4.49,621,1262563200"; d="scan'208,217";a="453166510" Received: from unknown (HELO xphd97xgq27nyf) ([78.147.51.204]) by out1.ip06ir2.opaltelecom.net with SMTP; 11 Mar 2010 18:32:44 +0000 Message-ID: <002a01cac149$3a573e90$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: References: <000a01cac139$b9d5e5a0$0401a8c0@xphd97xgq27nyf> <9afca2641003111003j73c81acdl454ca28e6dc9909b@mail.gmail.com> Date: Thu, 11 Mar 2010 18:32:04 -0000 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: DREAM 9 ANTENNA Content-Type: multipart/alternative; boundary="----=_NextPart_000_0027_01CAC149.261F2870" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,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 x-aol-global-disposition: G x-aol-sid: 3039ac1d60204b99378d5e86 X-AOL-IP: 193.82.116.20 ------=_NextPart_000_0027_01CAC149.261F2870 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable With no effort as described previously, I can copy tha Alpha sigs abou= t S6 on the 1/4 wave 500 inv L not resonated. RX is Hagenuk/Eddystone= EE430 on its low range 10 - 55kcs 73 de mal/g3kev ----- Original Message -----=20 From: Roger Lapthorn=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Thursday, March 11, 2010 6:03 PM Subject: Re: LF: DREAM 9 ANTENNA Thanks for the good advice Mal. I do hope you can find some time to= give 9kHz a go as you'd be such a valuable contributor to any experim= ents.=20 As a more general question, at what S/N should one expect to receive= the ~11kHz Alpha beacon on a well optimised RX? 73s Roger G3XBM On 11 March 2010 16:41, mal hamilton wrote: Probably an inv L or T antenna as high as possible for TX is the= best solution for 9 kcs. Base load the antenna with the necessary ind= uctance for resonance and if necessary add another small inductor in= series to ground and adjust with taps up from ground to get a 1 : 1= match with the coax feed from the TX, readjust the main inductor to= maintain resonance if necessary. This system has never failed me on 73, 137 and 500 kcs and this wo= uld be my approach on 9 kcs. RX is a different matter and there are a variety of antennas suita= ble.=20 I can RX the Alpha signals around 12 kcs at good strength using my= 500 kcs 1/4 wave inv L and weaker on the 40m loop both antennas not= resonated for 9 kcs. Obviously if resonated the signals would be very strong with these= antennas.=20 9 kcs is a lot easier to get going than the other LF/MF bands beca= use there is an abundance of LF generators and high power audio amplif= iers about, I would suggest modifying a audio amp output to 50 ohms with a sui= table transformer then use existing station equipment for monitoring= and measuring. Suggested approach for making a large inductor to resonate antenna= . Get several slotted laundry baskets size diam 600mm, height about= the same, stiff plastic material. Wind some wire on a few and connect= in series with antenna and check for resonance, then add baskets as= necessary to resonate at desired frequency These baskets fit into one= another and look tidy.=20 Use the largest diam wire possible to achieve the desired inductan= ce. If using a vy small inv L with lots of Henries required then go fo= r the water butt coil former. Do not forget some earth radials and rods. I could probably manage about 4 inv L antennas in parallel, 500 kc= s size, loaded against ground and would hope the signal would travel= some hundreds of miles. If only I had the time. de mal/g3kev --=20 http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk http://www.youtube.com/user/G3XBM G3XBM GQRP 1678 ISWL G11088 ------=_NextPart_000_0027_01CAC149.261F2870 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
With no effort as described previousl= y, I can copy=20 tha Alpha sigs about S6 on the 1/4 wave 500 inv L not resonated. RX is= =20 Hagenuk/Eddystone EE430 on its low range 10 - 55kcs
73 de mal/g3kev
----- Original Message -----
Sent: Thursday, March 11, 201= 0 6:03=20 PM
Subject: Re: LF: DREAM 9 ANTE= NNA

Thanks for the good advice Mal.  I do hope you= can find=20 some time to give 9kHz a go as you'd be such a valuable contributor= to any=20 experiments.

As a more general question, at what S/N should= one expect=20 to receive the ~11kHz Alpha beacon on a well optimised RX?

73= s
Roger=20 G3XBM


On 11 March 2010 16:41, mal hamilton <g3kevm= al@talktalk.net>=20 wrote:
Probably an inv L or T antenna as= high as=20 possible for TX  is the best solution for 9 kcs. Base load th= e antenna=20 with the necessary inductance for resonance and if necessary= add=20 another small inductor in series to ground and adjust with ta= ps up from=20 ground to get a 1 : 1 match with the coax feed from the TX, = readjust=20 the main inductor to maintain resonance if necessary.
This system has never failed me= on 73, 137 and=20 500 kcs and this would be my approach on 9 kcs.
RX is a different matter and ther= e are a=20 variety of antennas suitable.
I can RX the Alpha signals around= 12 kcs at=20 good strength using my 500 kcs 1/4 wave inv L and weaker on the 40= m loop=20 both antennas not resonated for 9 kcs.
Obviously if resonated the signal= s would be=20 very strong with these antennas.
9 kcs is a lot easier to get goin= g than the=20 other LF/MF bands because there is an abundance of LF generat= ors and=20 high power audio amplifiers about,
I would suggest modifying a audio= amp output to=20 50 ohms with a suitable transformer then use existing station equi= pment for=20 monitoring and measuring.
Suggested approach for making a= large inductor=20 to resonate antenna.
Get several slotted laundry baske= ts size diam=20 600mm, height about the same, stiff plastic material. Wind some wi= re on a=20 few and connect in series with antenna and check for resonance, th= en add=20 baskets as necessary to resonate at desired frequency These basket= s fit into=20 one another and look tidy.
Use the largest diam wire po= ssible to=20 achieve the desired inductance. If using a vy small inv L with lot= s of=20 Henries required then go for the water butt coil former.
Do not forget some earth radials= and=20 rods.
I could probably manage about 4= inv L antennas=20 in parallel, 500 kcs size, loaded against ground and would hope&nb= sp;the=20 signal would travel some hundreds of miles.
If only I had the time.
de mal/g3kev
 
 
 
 
 



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