Message-ID: <A3A23A09BD1D4741A8223A3CE5B66FB7@gnat>
From: "Alan Melia" <alan.melia@btinternet.com>
To: <rsgb_lf_group@blacksheep.org>
References: <CAHAQVWMs_556+qzyTJWOqDmgrPGzX62J2FfBH3ceRZ3fbfTfDg@mail.gmail.com> <001a01d394ff$8f3f54a0$adbdfde0$@go2.pl> <CAHAQVWPYMZEHGzQ0aQX_rPKUUkDLuLk3T=x6WmqjA5uckCsGuQ@mail.gmail.com> <00c801d3960f$4ce1ab10$e6a50130$@go2.pl> <CAHAQVWMMKM2ZoyyKty6v97K00RNeSxmpk6KmdePx0Nod4UYJcw@mail.gmail.com> <2B993CD1387E48D689FB9EF68B409ABB@Mike2PC>
Date: Thu, 25 Jan 2018 21:53:20 -0000
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Subject: LF: Re: Re: 136kHz WSPR experiment
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Michael, there is no 'Admin' on this list server. It is a very old s/w =
and the lack of acceptance may have something to do with the maximum =
message size (inc attachments) which I think is about 500kB. It is also =
basically a text server so there is always the possibility of it =
objecting to something in your HTML. We have no control, it is totally =
unmanned, we cant even check the logs to determine the problem. It does =
handle most things in a kindly way. :-))

Alan
G3NYK
  ----- Original Message -----=20
  From: Michael Sapp=20
  To: rsgb_lf_group@blacksheep.org=20
  Sent: Thursday, January 25, 2018 8:31 PM
  Subject: LF: Re: 136kHz WSPR experiment


  Roger: I tried to post a reply to the group prior but it did =
apparently did not make it past the admin monitor or it exceeded message =
size limit.

  I found the key to getting the FT-817 to receive well on LF and MF is =
to use a low pass filter with good in-band return loss characteristics =
between the antenna (e-probe, EWE, etc.) and the=20
  FT-817.  If you have ever tried listening to an AM broadcast station =
with the FT-817 and it's VHF rubber duck antenna, you know it is =
stone-cold deaf that way.  But if you use an antenna with a reasonable =
50 ohm match at lower HF, the FT-817 hears AM band stations (530 ~ 1600 =
kHz) very well. The same principle applies to LF/MF in the 100kHz to 500 =
kHz range.  The FT-817 receiver front end needs to see something close =
to 50 ohms to receive signals efficiently.  But it also needs most of =
the AM band energy rejected so it will not overload.  Using an LPF with =
a good pass band match seems to solve the problem when using an e-probe =
antenna at LF/MF with the FT-817.  Also do not use the preamp in the =
FT-817. Turn off the AGC and NB.

  There is a VE7BPO NDB filter with build information online that is =
easy to construct with commonly available parts if you do not have an =
LF/MF LPF filter available. I'm sure if you try it or another good LF/MF =
LPF with your FT-817 you will see an immediate order-of-magnitude =
improvement in receive performance at LF/MF.  I use a variation of the =
VE7BPO filter for 630m and a 9th order 300 kHz Butterworth LPF for LF.  =
The Butterworth LPFs have very good pass-band return loss and the FT-817 =
responds very well to having the filter between the antenna and the =
radio at LF.

  For even better performance I run a broadband LF/MF 2N3904 preamp =
after my LPF and either a 3dB pad or a 50 ohm universal diplexer for the =
frequency of interest after the preamp and into the FT-817.  I built the =
2N3904 preamp last night to try it out based on your recent FT-817 LF =
postings...

  Last night I was able to decode WH2XXP in AZ from PA with the FT-817 =
at some 3000 km distant 55 times with the FT-817 on the 2200m band. I =
was just able to occasionally decode WH2XXP with only the LPF and no =
post filter preamp.  With the 2N3904 preamp into a 3 dB pad and then =
into the FT-817 I was able to obtain a best overnight SNR of -18 on =
WH2XXP at 3000 km distant. I did need to use the attenuator in the =
FT-817 to adjust the rx level.

  Quick sketch of preamp and FT-817 rx layout...

  https://www.dropbox.com/s/tmszk33xuyjjtnc/2N3904P.JPG?dl=3D0

  Pix of filter-preamp setup but with 137 kHz diplexer on preamp  output =
instead of 3 dB pad...

  https://www.dropbox.com/s/tms4gruu2x8azz4/flpredp.jpg?dl=3D0

  73 Mike wa3tts
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<BODY dir=3Dltr bgColor=3D#ffffff>
<DIV><FONT size=3D2 face=3DArial>Michael, there is no 'Admin' on this =
list server.=20
It is a very old s/w and the lack of acceptance may have something to do =
with=20
the maximum message size (inc attachments)&nbsp;which I think is about =
500kB. It=20
is also basically a text server so there is always the possibility of it =

objecting to something in your HTML. We have no control, it is totally =
unmanned,=20
we cant even check the logs to determine the problem. It does handle =
most things=20
in a kindly way. :-))</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial></FONT>&nbsp;</DIV>
<DIV><FONT size=3D2 face=3DArial>Alan</FONT></DIV>
<DIV><FONT size=3D2 face=3DArial>G3NYK</FONT></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; =
PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px"=20
dir=3Dltr>
  <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV=20
  style=3D"FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: =
black"><B>From:</B>=20
  <A title=3Dwa3tts@verizon.net =
href=3D"mailto:wa3tts@verizon.net">Michael Sapp</A>=20
  </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Drsgb_lf_group@blacksheep.org=20
  =
href=3D"mailto:rsgb_lf_group@blacksheep.org">rsgb_lf_group@blacksheep.org=
</A>=20
  </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Thursday, January 25, =
2018 8:31=20
  PM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> LF: Re: 136kHz WSPR=20
  experiment</DIV>
  <DIV><BR></DIV>
  <DIV dir=3Dltr>
  <DIV style=3D"FONT-FAMILY: 'Calibri'; COLOR: #000000; FONT-SIZE: =
12pt">
  <DIV>Roger: I tried to post a reply to the group prior but it did =
apparently=20
  did not make it past the admin monitor or it exceeded message size=20
limit.</DIV>
  <DIV>&nbsp;</DIV>
  <DIV>I found the key to getting the FT-817 to receive well on LF and =
MF is to=20
  use a low pass filter with good in-band return loss characteristics =
between=20
  the antenna (e-probe, EWE, etc.) and the </DIV>
  <DIV>FT-817.&nbsp; If you have ever tried listening to an AM broadcast =
station=20
  with the FT-817 and it's VHF rubber duck antenna, you know it is =
stone-cold=20
  deaf that way.&nbsp; But if you use an antenna with a reasonable 50 =
ohm match=20
  at lower HF, the FT-817 hears AM band stations (530 ~ 1600 kHz) very =
well. The=20
  same principle applies to LF/MF in the 100kHz to 500 kHz range.&nbsp; =
The=20
  FT-817 receiver front end needs to see something close to 50 ohms to =
receive=20
  signals efficiently.&nbsp; But it also needs most of the AM band =
energy=20
  rejected so it will not overload.&nbsp; Using an LPF with a good pass =
band=20
  match seems to solve the problem when using an e-probe antenna at =
LF/MF with=20
  the FT-817.&nbsp; Also do not use the preamp in the FT-817. Turn off =
the AGC=20
  and NB.</DIV>
  <DIV>&nbsp;</DIV>
  <DIV>There is a VE7BPO NDB filter with build information online that =
is easy=20
  to construct with commonly available parts if you do not have an LF/MF =
LPF=20
  filter available. I'm sure if you try it or another good LF/MF LPF =
with your=20
  FT-817 you will see an immediate order-of-magnitude improvement in =
receive=20
  performance at LF/MF.&nbsp; I use a variation of the VE7BPO filter for =
630m=20
  and a 9th order 300 kHz Butterworth LPF for LF.&nbsp; The Butterworth =
LPFs=20
  have very good pass-band return loss and the FT-817 responds very well =
to=20
  having the filter between the antenna and the radio at LF.</DIV>
  <DIV>&nbsp;</DIV>
  <DIV>For even better performance I run a broadband LF/MF 2N3904 preamp =
after=20
  my LPF and either a 3dB pad or a 50 ohm universal diplexer for the =
frequency=20
  of interest after the preamp and into the FT-817.&nbsp; I built the =
2N3904=20
  preamp last night to try it out based on your recent FT-817 LF=20
  postings...</DIV>
  <DIV>&nbsp;</DIV>
  <DIV>Last night I was able to decode WH2XXP in AZ from PA with the =
FT-817 at=20
  some 3000 km distant 55 times with the FT-817 on the 2200m band. I was =
just=20
  able to occasionally decode WH2XXP with only the LPF and no post =
filter=20
  preamp.&nbsp; With the 2N3904 preamp into a 3 dB pad and then into the =
FT-817=20
  I was able to obtain a best overnight SNR of -18 on WH2XXP at 3000 km =
distant.=20
  I did need to use the attenuator in the FT-817 to adjust the rx =
level.</DIV>
  <DIV>&nbsp;</DIV>
  <DIV>Quick sketch of preamp and FT-817 rx layout...</DIV>
  <DIV>&nbsp;</DIV>
  <DIV><A =
title=3Dhttps://www.dropbox.com/s/tmszk33xuyjjtnc/2N3904P.JPG?dl=3D0=20
  =
href=3D"https://www.dropbox.com/s/tmszk33xuyjjtnc/2N3904P.JPG?dl=3D0">htt=
ps://www.dropbox.com/s/tmszk33xuyjjtnc/2N3904P.JPG?dl=3D0</A></DIV>
  <DIV>&nbsp;</DIV>
  <DIV>Pix of filter-preamp setup but with 137 kHz diplexer on =
preamp&nbsp;=20
  output instead of 3 dB pad...</DIV>
  <DIV>&nbsp;</DIV>
  <DIV><A =
title=3Dhttps://www.dropbox.com/s/tms4gruu2x8azz4/flpredp.jpg?dl=3D0=20
  =
href=3D"https://www.dropbox.com/s/tms4gruu2x8azz4/flpredp.jpg?dl=3D0">htt=
ps://www.dropbox.com/s/tms4gruu2x8azz4/flpredp.jpg?dl=3D0</A></DIV>
  <DIV>&nbsp;</DIV>
  <DIV>73 Mike wa3tts</DIV></DIV></DIV></BLOCKQUOTE></BODY></HTML>

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