Return-Path: Received: from rly-me01.mx.aol.com (rly-me01.mail.aol.com [172.20.83.34]) by air-me05.mail.aol.com (v125.7) with ESMTP id MAILINME054-9954a9b8bff34d; Mon, 31 Aug 2009 04:38:42 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-me01.mx.aol.com (v125.7) with ESMTP id MAILRELAYINME011-9954a9b8bff34d; Mon, 31 Aug 2009 04:38:24 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Mi2OC-0003NM-6y for rs_out_1@blacksheep.org; Mon, 31 Aug 2009 09:37:24 +0100 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Mi2OA-0003ND-No for rsgb_lf_group@blacksheep.org; Mon, 31 Aug 2009 09:37:22 +0100 Received: from smtp2.citigroup.com ([192.193.221.103] helo=mail.citigroup.com) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Mi2Ny-0004sJ-Mn for rsgb_lf_group@blacksheep.org; Mon, 31 Aug 2009 09:37:17 +0100 Received: from imbhub-mw02.nam.nsroot.net ([159.17.94.189]) by imbaspam-ss01.namdmz.dmzroot.net (8.13.8/8.13.8/SSMB_EXT/ev: 24741 $) with ESMTP id n7V8b2Q7027772 for ; Mon, 31 Aug 2009 08:37:04 GMT Received: from exuksm06.eur.nsroot.net (Exuksm06.eur.nsroot.net [169.183.26.36]) by imbhub-mw02.nam.nsroot.net (Switch-3.4.0/Switch-3.4.0) with ESMTP id n7V8b1O3006194 for ; Mon, 31 Aug 2009 08:37:02 GMT Received: from exukmb49.eur.nsroot.net ([169.183.32.64]) by exuksm06.eur.nsroot.net with Microsoft SMTPSVC(5.0.2195.6713); Mon, 31 Aug 2009 09:36:52 +0100 X-MimeOLE: Produced By Microsoft Exchange V6.0.6619.12 content-class: urn:content-classes:message MIME-Version: 1.0 Date: Mon, 31 Aug 2009 09:36:52 +0100 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: LF: Re: FT-817 at LF/MF Thread-Index: AcoqEyCmCMkGooOZQOizPIbZQWb7QAAAoQ2A References: <92C6FA2037874B9888C28DDBF9096246@JimPC> <9afca2640908300531w1393b476y7a06b102a9db9076@mail.gmail.com> <9afca2640908310111g1dd602bete769fd68a7aed6f8@mail.gmail.com> From: "Scholz, Marco " To: X-OriginalArrivalTime: 31 Aug 2009 08:36:52.0989 (UTC) FILETIME=[30CD52D0:01CA2A16] X-Scanned-By: MIMEDefang 2.52 on 169.175.16.180 X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01CA2A16.30AAE074" Subject: RE: LF: Re: FT-817 at LF/MF X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.6 required=5.0 tests=HTML_20_30,HTML_FONTCOLOR_BLUE, 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-IP: 193.82.116.20 X-Mailer: Unknown (No Version) ------_=_NextPart_001_01CA2A16.30AAE074 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Hello Roger, i use a FT857 and like your experience it works fine with a PA0DRT Miniwhip antenna on 500KHz and poor on 137KHz. Since i use for 137KHz the G0MRF Preamp (http://g0mrf.com/preamp.htm) receiption is much, much better on 137KHz and i'm happy so far with it. =20 thanks regards Marco DD7PC _____ =20 From: owner-rsgb_lf_group@blacksheep.org [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Roger Lapthorn Sent: Montag, 31. August 2009 10:12 To: rsgb_lf_group@blacksheep.org Subject: Re: LF: Re: FT-817 at LF/MF Thanks for these figures Jim. They back up my practical experience. Yes, on 500kHz the FT817 works surprisingly well with the lash-up untuned antenna but clearly matching what antenna I have would help further. =20 On 137 kHz the FT817 RX is unusable and I've been trying with a simple SBL1 up-converter with some post mixer gain. If I'm going to take a more serious interest in 137/500kHz I'll have to work on the antenna and a better receive system, especially on 137kHz. My real interest is 10m but at the moment the LF bands are far more interesting, HI.=20 Thanks again for this helpful data. 73s Roger G3XBM 2009/8/30 James Moritz Dear Roger, LF Group, =20 Re: using the FT-817 and long wire for receiving the WSPR beacons - I have an FT-817 also, which I mostly use with a converter for VLF - MF reception due to its poor sensitivity at low frequencies. I just did a quick sensitivity check on mine - the following figures are for 10dB SNR using the 500Hz CW filter: =20 4.5MHz (the output frequency of my converter): "IPO on" (ie. preamp off) -117dBm "IPO off" (preamp on) -125dBm =20 Sensitivity is much the same over the HF range. =20 502kHz: IPO on -105dBm IPO off -108dBm =20 137kHz: IPO on -89dBm IPO off -80dBm =20 So sensitivity is about 20dB down on 500k, which is more or less passable, but a bit disastrous at 137k where it is around 30 - 40dB down depending on whether the preamp is selected or not. =20 The un-tuned wire will also be a contributing factor - at low frequencies, it will have a high capacitive impedance with a huge mismatch to the low impedance RX input. You can expect to lose a further 20dB or more at 500k, and 30dB or more at 137k, compared to having some sort of antenna tuner. =20 These figures are not unusual for the situation of using a "random" wire with typical amateur HF rigs with general coverage RX, so it is not surprising people often get reasonable results at 500k using this sort of setup for receive, but 137k usually needs a bit more sorting to get useful reception =20 Cheers, Jim Moritz 73 de M0BMU =20 =20 =20 =20 =20 --=20 ------------------------------------------------------------- http://g3xbm-qrp.blogspot.com/ http://www.g3xbm.co.uk G3XBM GQRP 1678 ISWL G11088 ------_=_NextPart_001_01CA2A16.30AAE074 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable
Hello Roger,
i use a FT857 and like your experienc= e it works fine=20 with a PA0DRT Miniwhip antenna on 500KHz and poor on 137KHz. Since i use= for=20 137KHz the G0MRF Preamp (http://g= 0mrf.com/preamp.htm) receiption=20 is much, much better on 137KHz and i'm happy so far with=20 it.
 
thanks
regards
Marco
DD7PC
From: owner-rsgb_lf_group@blacksheep.o= rg=20 [mailto:owner-rsgb_lf_group@blacksheep.org] On Behalf Of Roger=20 Lapthorn
Sent: Montag, 31. August 2009 10:12
To:=20 rsgb_lf_group@blacksheep.org
Subject: Re: LF: Re: FT-817 at=20 LF/MF

Thanks for these figures Jim. They back up my practical=20 experience.

Yes, on 500kHz the FT817 works surprisingly well with= the=20 lash-up untuned antenna but clearly matching what antenna I have would hel= p=20 further. 

On 137 kHz the FT817 RX is unusable and I've been= trying=20 with a simple SBL1 up-converter with some post mixer gain. If I'm going to= take=20 a more serious interest in 137/500kHz I'll have to work on the antenna and= a=20 better receive system, especially on 137kHz. My real interest is 10m but= at the=20 moment the LF bands are far more interesting, HI.

Thanks again for= this=20 helpful data.

73s
Roger G3XBM



2009/8/30 James Moritz <james.moritz@btopenworld.com>
Dear=20 Roger, LF Group,

Re: using the FT-817 and long wire for receiving= the=20 WSPR beacons - I have an FT-817 also, which I mostly use with a converte= r for=20 VLF - MF reception due to its poor sensitivity at low frequencies. I jus= t did=20 a quick sensitivity check on mine - the following figures are for 10dB= SNR=20 using the 500Hz CW filter:

4.5MHz (the output frequency of my=20 converter):
"IPO on" (ie. preamp off) -117dBm
"IPO off" (preamp on= )=20 -125dBm

Sensitivity is much the same over the HF=20 range.

502kHz:
IPO on -105dBm
IPO off=20 -108dBm

137kHz:
IPO on -89dBm
IPO off -80dBm

So=20 sensitivity is about 20dB down on 500k, which is more or less passable,= but a=20 bit disastrous at 137k where it is around 30 - 40dB down depending on wh= ether=20 the preamp is selected or not.

The un-tuned wire will also be a= =20 contributing factor - at low frequencies, it will have a high capacitive= =20 impedance with a huge mismatch to the low impedance RX input. You can ex= pect=20 to lose a further 20dB or more at 500k, and 30dB or more at 137k, compar= ed to=20 having some sort of antenna tuner.

These figures are not unusual= =20  for the situation of using a "random" wire with typical amateur HF= rigs=20 with general coverage RX, so it is not surprising people often get reaso= nable=20 results at 500k using this sort of setup for receive, but 137k usually= needs a=20 bit more sorting to get useful reception

Cheers, Jim Moritz
73= de=20 M0BMU







--= =20
-------------------------------------------------------------
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
G3X= BM  =20  GQRP 1678      ISWL G11088
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