<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
</head>
<body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">
Bob,
<div><br>
</div>
<div>Just to elaborate on what Junming mentioned:</div>
<div><br>
</div>
<div>In past operations with the 20 meter telescope and the Arecibo telescope we have only had about 30-40 dB of LNA gain ahead of our receiver boards. This matched the signal levels pretty well at the ADCs. Since you now have much more gain ahead of the
receiver cards (I assume this is in order to put the signal above the noise floor in the fiber link) we will need to attenuate by 40-50 dB at the output of your fiber receiver before going into our receiver boards. At least that is our current thinking so
that we do not overdrive our receivers. Before we buy attenuators (in-line MiniCircuits sma type) we want to confirm the level calculations, and see if you had any other ideas.</div>
<div><br>
</div>
<div>Thanks,</div>
<div><br>
</div>
<div>Brian</div>
<div><br>
</div>
<div><br>
<div>
<div>On Feb 1, 2013, at 10:15 AM, µó¿¡Ãú (Junming Diao) wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">Hi, Bob,
<div><br>
</div>
<div>I have a question for you:</div>
<div>Our receiver board has 60 dB gain, which leads to too much power (10 W) to ADC (ROACH). Can you tell me whether there is some methods to fix this problem. </div>
<div><br>
</div>
<div>Thanks,</div>
<div>Junming<br>
<br>
<div class="gmail_quote">On Mon, Jan 7, 2013 at 5:21 PM, µó¿¡Ãú (Junming Diao) <span dir="ltr">
<<a href="mailto:diaojunming@gmail.com" target="_blank">diaojunming@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Thanks, Bob! This is very helpful!
<div>Junming
<div>
<div class="h5"><br>
<br>
<div class="gmail_quote">On Mon, Jan 7, 2013 at 2:34 PM, Bob Simon <span dir="ltr">
<<a href="mailto:bsimon@nrao.edu" target="_blank">bsimon@nrao.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">Hi,<br>
Attached is the original order I did for the rack purchase. I told you incorrectly; it was not Amco, but instead it was IMS engineered products. I don't know your exact application, but be aware that shielded racks are very expensive compared to the
non-shielded type. <br>
Our racks are positioned over a forced air plenum. So, you may need honeycomb RFI air filters for both intake and exhaust air. Depending on heat generated, you may need additional fans on the exhaust side to pull air out of the rack. We purchase RFI
air filters form either MAJR or East coast shielding<br>
<a href="http://www.majr.com/" target="_blank">http://www.majr.com/</a><br>
<a href="http://www.eastcoastshielding.com/" target="_blank">http://www.eastcoastshielding.com/</a><br>
You'll need to size the filters according your requirements. Installation of these filters requires machine shop work to insure proper fitting for RFI shielding.<br>
Hope this helps,<br>
Bob.. <br>
<div>
<div><br>
<br>
<br>
<br>
On 1/7/2013 3:35 PM, µó¿¡Ãú (Junming Diao) wrote:
<blockquote type="cite">Thanks, Bob. Please tell me know the details of rack you buy from <a href="http://www.amcoenclosures.com/" style="color:rgb(17,85,204);font-size:12.666666984558105px;font-family:arial,sans-serif" target="_blank">http://www.amcoenclosures.com/</a>.
I think this one is a good choice for us.
<div>Junming<br>
<br>
<div class="gmail_quote">On Mon, Jan 7, 2013 at 6:23 AM, Bob Simon <span dir="ltr">
<<a href="mailto:bsimon@nrao.edu" target="_blank">bsimon@nrao.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
variety to choose from</blockquote>
</div>
<br>
</div>
</blockquote>
<br>
</div>
</div>
</div>
</blockquote>
</div>
<br>
</div>
</div>
</div>
</blockquote>
</div>
<br>
</div>
_______________________________________________<br>
Pafgbt mailing list<br>
<a href="mailto:Pafgbt@listmgr.cv.nrao.edu">Pafgbt@listmgr.cv.nrao.edu</a><br>
http://listmgr.cv.nrao.edu/mailman/listinfo/pafgbt<br>
</blockquote>
</div>
<br>
</div>
</body>
</html>