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Date: Mon, 31 Aug 2009 09:36:52 +0100
Message-ID: <BEA259931570B948B5DF6825FA3F2D6417D15A26@EXUKMB49.eur.nsroot.net>
Thread-Topic: LF: Re: FT-817 at LF/MF
Thread-Index: AcoqEyCmCMkGooOZQOizPIbZQWb7QAAAoQ2A
References: <92C6FA2037874B9888C28DDBF9096246@JimPC> <9afca2640908300531w1393b476y7a06b102a9db9076@mail.gmail.com> <AC8257E889D74628857985598FC9B96D@JimPC> <9afca2640908310111g1dd602bete769fd68a7aed6f8@mail.gmail.com>
From: "Scholz, Marco " <marco.scholz@citi.com>
To: <rsgb_lf_group@blacksheep.org>
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Subject: RE: LF: Re: FT-817 at LF/MF
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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 <james.moritz@btopenworld.com>


    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

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<META http-equiv=3DContent-Type content=3D"text/html; charset=3Dus-ascii">
<META content=3D"MSHTML 6.00.2900.5848" name=3DGENERATOR></HEAD>
<BODY>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D305583208-31082009><FONT face=3D=
Arial  color=3D#0000ff size=3D2>Hello Roger,</FONT></SPAN></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D305583208-31082009><FONT face=3D=
Arial  color=3D#0000ff size=3D2>i use a FT857 and&nbsp;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 (<A  href=3D"http://g0mrf.com/preamp.htm">http://g=
0mrf.com/preamp.htm</A>) receiption=20
is&nbsp;much, much better&nbsp;on 137KHz and i'm happy so far with=20
it.</FONT></SPAN></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D305583208-31082009><FONT face=3D=
Arial  color=3D#0000ff size=3D2></FONT></SPAN>&nbsp;</DIV>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D305583208-31082009><FONT face=3D=
Arial  color=3D#0000ff size=3D2>thanks</FONT></SPAN></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D305583208-31082009><FONT face=3D=
Arial  color=3D#0000ff size=3D2>regards</FONT></SPAN></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D305583208-31082009><FONT face=3D=
Arial  color=3D#0000ff size=3D2>Marco</FONT></SPAN></DIV>
<DIV dir=3Dltr align=3Dleft><SPAN class=3D305583208-31082009><FONT face=3D=
Arial  color=3D#0000ff size=3D2>DD7PC</FONT></SPAN></DIV>
<DIV dir=3Dltr align=3Dleft>
<HR tabIndex=3D-1>
<FONT face=3DTahoma size=3D2><B>From:</B> owner-rsgb_lf_group@blacksheep.o=
rg=20
[mailto:owner-rsgb_lf_group@blacksheep.org] <B>On Behalf Of </B>Roger=20
Lapthorn<BR><B>Sent:</B> Montag, 31. August 2009 10:12<BR><B>To:</B>=20
rsgb_lf_group@blacksheep.org<BR><B>Subject:</B> Re: LF: Re: FT-817 at=20
LF/MF<BR></FONT><BR></DIV>
<DIV></DIV>Thanks for these figures Jim. They back up my practical=20
experience.<BR><BR>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.&nbsp; <BR><BR>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. <BR><BR>Thanks again for=
 this=20
helpful data.<BR><BR>73s<BR>Roger G3XBM<BR><BR><BR><BR>
<DIV class=3Dgmail_quote>2009/8/30 James Moritz <SPAN dir=3Dltr>&lt;<A  hr=
ef=3D"mailto:james.moritz@btopenworld.com">james.moritz@btopenworld.com</A=
>&gt;</SPAN><BR>
<BLOCKQUOTE class=3Dgmail_quote  style=3D"PADDING-LEFT: 1ex; MARGIN: 0pt=
 0pt 0pt 0.8ex; BORDER-LEFT: rgb(204,204,204) 1px solid">Dear=20
  Roger, LF Group,<BR><BR>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:<BR><BR>4.5MHz (the output frequency of my=20
  converter):<BR>"IPO on" (ie. preamp off) -117dBm<BR>"IPO off" (preamp on=
)=20
  -125dBm<BR><BR>Sensitivity is much the same over the HF=20
  range.<BR><BR>502kHz:<BR>IPO on -105dBm<BR>IPO off=20
  -108dBm<BR><BR>137kHz:<BR>IPO on -89dBm<BR>IPO off -80dBm<BR><BR>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.<BR><BR>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.<BR><BR>These figures are not unusual=
=20
  &nbsp;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<BR><BR>Cheers, Jim Moritz<BR>73=
 de=20
  M0BMU<BR><BR><BR><BR><BR></BLOCKQUOTE></DIV><BR><BR clear=3Dall><BR>--=
=20
<BR>-------------------------------------------------------------<BR><A =
 href=3D"http://g3xbm-qrp.blogspot.com/">http://g3xbm-qrp.blogspot.com/</A=
><BR><A  href=3D"http://www.g3xbm.co.uk">http://www.g3xbm.co.uk</A><BR>G3X=
BM &nbsp;=20
&nbsp;GQRP 1678 &nbsp; &nbsp; &nbsp;ISWL G11088<BR></BODY></HTML>

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