[Pafgbt] Photos of shelf

[Brian Jeffs]

Bob,

Just to elaborate on what Junming mentioned:

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.

Thanks,

Brian


On Feb 1, 2013, at 10:15 AM, 刁俊铭 (Junming Diao) wrote:

Hi, Bob,

I have a question for you:
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.

Thanks,
Junming

On Mon, Jan 7, 2013 at 5:21 PM, 刁俊铭 (Junming Diao) <diaojunming at gmail.com<mailto:diaojunming at gmail.com>> wrote:
Thanks, Bob! This is very helpful!
Junming


On Mon, Jan 7, 2013 at 2:34 PM, Bob Simon <bsimon at nrao.edu<mailto:bsimon at nrao.edu>> wrote:
Hi,
     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.
     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
http://www.majr.com/
http://www.eastcoastshielding.com/
     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.
Hope this helps,
Bob..




On 1/7/2013 3:35 PM, 刁俊铭 (Junming Diao) wrote:
Thanks, Bob. Please tell me know the details of rack you buy from http://www.amcoenclosures.com/. I think this one is a good choice for us.
Junming

On Mon, Jan 7, 2013 at 6:23 AM, Bob Simon <bsimon at nrao.edu<mailto:bsimon at nrao.edu>> wrote:
variety to choose from




_______________________________________________
Pafgbt mailing list
Pafgbt at listmgr.cv.nrao.edu<mailto:Pafgbt at listmgr.cv.nrao.edu>
http://listmgr.cv.nrao.edu/mailman/listinfo/pafgbt

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listmgr.nrao.edu/pipermail/pafgbt/attachments/20130201/d624d485/attachment.html>