<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 14 (filtered medium)"><style><!--
/* Font Definitions */
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
@font-face
{font-family:Tahoma;
panose-1:2 11 6 4 3 5 4 4 2 4;}
@font-face
{font-family:"Comic Sans MS";
panose-1:3 15 7 2 3 3 2 2 2 4;}
@font-face
{font-family:Consolas;
panose-1:2 11 6 9 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:12.0pt;
font-family:"Times New Roman","serif";
color:black;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:blue;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:purple;
text-decoration:underline;}
pre
{mso-style-priority:99;
mso-style-link:"HTML Preformatted Char";
margin:0in;
margin-bottom:.0001pt;
font-size:10.0pt;
font-family:"Courier New";
color:black;}
span.HTMLPreformattedChar
{mso-style-name:"HTML Preformatted Char";
mso-style-priority:99;
mso-style-link:"HTML Preformatted";
font-family:Consolas;
color:black;}
span.EmailStyle19
{mso-style-type:personal-reply;
font-family:"Comic Sans MS";
color:windowtext;
font-weight:normal;
font-style:normal;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-family:"Comic Sans MS";color:windowtext'>An RF attenuator is not the same as an RF gain control. RF Gain is actually IF gain (or even more appropriately, IF attenuation!), and is inside the AGC control loop. An RF attenuator is outside that loop, at the same place as the bandpass filters (or preselector) and any RF preamps, i.e. close to the antenna. It’s useful to attenuate strong signals before they get into the radio.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Comic Sans MS";color:windowtext'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Comic Sans MS";color:windowtext'>It IS, however, pretty obvious that something was amiss. I also have the ’71 catalog, and it clearly shows “NOISE BLANKER” text carefully scratched out so as not to be all that noticeable. Very cool! A mystery! Having designed a noise blanker, I can attest to how hard it is to get the dang things to work the way you want them to. And of course there is the popular misconception that they reduce broadband noise. They only reduce impulse noise, such as from electric fences or car ignition. True NR is a DSP thing.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Comic Sans MS";color:windowtext'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-family:"Comic Sans MS";color:windowtext'>Brian, W0DZ<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Comic Sans MS";color:windowtext'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext'> Heath [mailto:heath-bounces@puck.nether.net] <b>On Behalf Of </b>Guy Giacopuzzi<br><b>Sent:</b> Saturday, March 15, 2014 9:07 PM<br><b>To:</b> pbrickey@verizon.net; heath@puck.nether.net<br><b>Subject:</b> Re: [Heath] SB-303 Noise Blanker Schematic<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal style='margin-bottom:12.0pt'>Coool....now, does anyone have an SB-104 schematic handy so that a comparison could be made? I'm betting that Pete's 303 blanker is unique to the 303'...and now the big question remains, why didn't they develop this on the 303'? I know the answer to one question though....The question, is why does a 303' have an rf attenuator in the first place? It's kind of stupid, and it doesn't do anything that an rf gain control can't already do. Soooo, I bet this "rf attenuator' was the cheap answer to "What do we fill that spot with?" that the engineers had to answer when they couldn't get the noise blanker to work. At least, that's my theory...<br><br>Guy, <br>WA6OQQ<o:p></o:p></p><div><p class=MsoNormal>On 3/15/2014 2:30 PM, <a href="mailto:pbrickey@verizon.net">pbrickey@verizon.net</a> wrote:<o:p></o:p></p></div><blockquote style='margin-top:5.0pt;margin-bottom:5.0pt'><pre>Hi,<o:p></o:p></pre><pre> I have had quite a few questions about this, so I thought I would send out the schematic that is in my SB-303 manual.<o:p></o:p></pre><pre>It is attached.<o:p></o:p></pre><pre> 73's,<o:p></o:p></pre><pre> Peter<o:p></o:p></pre><p class=MsoNormal style='mso-margin-top-alt:0in;margin-right:.5in;margin-bottom:0in;margin-left:.5in;margin-bottom:.0001pt'><br><br><o:p></o:p></p></blockquote></div></body></html>