Message-ID: <001f01cb121f$2b3d12a0$0301a8c0@your91hoehfy9g>
From: "mal hamilton" <g3kevmal@talktalk.net>
To: <rsgb_lf_group@blacksheep.org>
References: <000c01cb11dc$2b310020$0401a8c0@xphd97xgq27nyf> <3A2133327AFB454CAC336E25F96F4352@TonyLaptop>
Date: Tue, 22 Jun 2010 16:25:38 +0100
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Subject: LF: Re: Re: 137 Revival
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Tony
The G3YXM design some years back was reliable, two versions one for 12=
v and the other for 100v. My 137 kcs TX is similar but with several fa=
il safe features added.
The set up in my case is a IC706 on 13.7 Mcs, divider network down to=
 137 Kcs, driver tc4426 chip, 4 FET PA, matching transformer to 50 ohm=
s, LPF.
RF from TX fed via 50ohm cable to antenna some 100 yards away in a fie=
ld, loading coil at base of antenna approx 0.5 mH matched and resonate=
d to 50 ohm feed.=20
Monitor SWR and DC current to PA at all times during TX in case anythi=
ng goes wrong.=20
Fortunately in my case the system is reliable and stable. During storm=
y wx beware of SWR fluctuations and drawing excessive current that mig=
ht cause the PA FETS to expire, especially if using vy slow QRS MODE
I normally work CW normal speed and seldom go slower than QRS 3.=20
This is a class D pa

On 500 Kcs I use a different sort of TX, which is class E single ended=
 FET, which would also work on 137 Kcs with different values for L and=
 C.I built this TX in a few hours and it has proved totally reliable=
 after a number of years use, designed for 50 ohms and fed to a 1/4 wa=
ve inv L antenna at 100 ft high
There are plenty of designs about for class D and E transmitters suita=
ble for LF/MF on the web
De mal/g3kev
=20
.

  ----- Original Message -----=20
  From: Tony Baldwin=20
  To: rsgb_lf_group@blacksheep.org=20
  Sent: Tuesday, June 22, 2010 11:49 AM
  Subject: LF: Re: 137 Revival


  I fully intend to be QRV on 137 by the winter.
  On that note, can anyone recommend a reliable foolproof transmitter=
 that uses easily available components ?

  Tony, EI8JK.

    ----- Original Message -----=20
    From: mal hamilton=20
    To: rsgb=20
    Sent: Tuesday, June 22, 2010 8:26 AM
    Subject: LF: 137 Revival


    LF
    How about a 137 kcs Revival, much more interesting than 500, which=
 is more like 160 metres.
    CW, QRSCW, Invisible Ros etc
    G3KEV

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<META content=3D"MSHTML 6.00.2800.1141" name=3DGENERATOR>
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</HEAD>
<BODY bgColor=3D#ffffff>
<DIV><FONT face=3DArial size=3D2>Tony</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>The G3YXM design some years back was=
 reliable, two=20
versions one for 12v and the other for 100v. My 137 kcs TX is similar=
 but with=20
several fail safe features added.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>The set up in my case is a IC706&nbsp=
;on 13.7 Mcs,=20
divider network down to 137 Kcs, driver tc4426 chip,&nbsp;4 FET PA, ma=
tching=20
transformer to 50 ohms, LPF.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>RF from TX fed via 50ohm cable to ant=
enna some 100=20
yards away in a field, loading coil at base of antenna approx 0.5 mH=
=20
matched&nbsp;and resonated to 50 ohm feed. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Monitor SWR and DC current to PA at=
 all times=20
during TX in case anything goes wrong. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Fortunately in my case the system is=
 reliable and=20
stable. During stormy wx beware of SWR fluctuations and drawing excess=
ive=20
current that might cause the PA FETS to expire, especially if using vy=
 slow QRS=20
MODE</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>I normally work CW normal speed and=
 seldom go=20
slower than QRS 3. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2>This is a class D pa</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>On 500 Kcs I use a different sort of=
 TX, which is=20
class E single ended FET, which would also work on 137 Kcs with differ=
ent values=20
for&nbsp;L and C.</FONT><FONT face=3DArial size=3D2>I built this TX&nb=
sp;in a few=20
hours and it has proved totally reliable&nbsp;after a number of years=
 use,=20
designed for 50 ohms and fed to a 1/4 wave&nbsp;inv L antenna at 100=
 ft=20
high</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>There are plenty of designs about for=
 class D and E=20
transmitters suitable for LF/MF&nbsp;on the web</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>De mal/g3kev</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<BLOCKQUOTE dir=3Dltr   style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px=
; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"=
>
  <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV     style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color:=
 black"><B>From:</B>=20
  <A title=3Dei8jk@o2.ie href=3D"mailto:ei8jk@o2.ie">Tony Baldwin</A>=
 </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A title=3Drsgb_lf_group@=
blacksheep.org     href=3D"mailto:rsgb_lf_group@blacksheep.org">rsgb_l=
f_group@blacksheep.org</A>=20
  </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Tuesday, June 22, 2010=
 11:49=20
  AM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> LF: Re: 137 Revival<=
/DIV>
  <DIV><BR></DIV>
  <DIV><FONT face=3DArial size=3D2>I fully intend to be QRV on 137 by=
 the=20
  winter.</FONT></DIV>
  <DIV><FONT face=3DArial size=3D2>On that note, can anyone recommend=
 a reliable=20
  foolproof transmitter that uses easily available components ?</FONT>=
</DIV>
  <DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
  <DIV><FONT face=3DArial size=3D2>Tony, EI8JK.</FONT></DIV>
  <DIV>&nbsp;</DIV>
  <BLOCKQUOTE dir=3Dltr     style=3D"PADDING-RIGHT: 0px; PADDING-LEFT:=
 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT:=
 0px">
    <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV=
>
    <DIV       style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-co=
lor: black"><B>From:</B>=20
    <A title=3Dg3kevmal@talktalk.net href=3D"mailto:g3kevmal@talktalk.=
net">mal=20
    hamilton</A> </DIV>
    <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A       title=3Drsgb_l=
f_group@blacksheep.org       href=3D"mailto:rsgb_lf_group@blacksheep.o=
rg">rsgb</A> </DIV>
    <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Tuesday, June 22, 201=
0 8:26=20
    AM</DIV>
    <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> LF: 137 Revival</D=
IV>
    <DIV><BR></DIV>
    <DIV><FONT face=3DArial size=3D2>LF</FONT></DIV>
    <DIV><FONT face=3DArial size=3D2>How about a 137 kcs Revival, much=
 more=20
    interesting than 500, which is more like 160 metres.</FONT></DIV>
    <DIV><FONT face=3DArial size=3D2>CW, QRSCW, Invisible Ros etc</FON=
T></DIV>
    <DIV><FONT face=3DArial size=3D2>G3KEV</FONT></DIV>
    <DIV>&nbsp;</DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>

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