Some years ago I gifted my then-employer with 150 feet of LMR-400 and replaced the RG-216 we had on our 10 meter OATS. As expected, we gained the ability to measure signals near 1 GHz that were formerly in the noise floor at the limit. But since they insisted on continuing to use an 8447D preamp. we had to add a 10 dB attenuator to get rid of receiver overload. Had they simply turned on the preamp in our preselector they could have had low noise AND gain. About a year later, the site was closed and I retrieved "my" coax. Sic transit Fountain Valley. Sigh. Cortland Richmond KA5S
----- Original Message ----- From: Kunde, Brian <mailto:[email protected]> To: Grace Lin <mailto:[email protected]> ;[email protected] Sent: 3/19/2008 5:30:00 AM Subject: RE: Internal Preamplifier Grace, The additional noise caused by the pre-amp is normal. All pre-amps add to the noise floor level and 5-10db is normal. If you are careful not to overload the input of your receiver, you can gain an additional 10db of noise floor by reducing the front end attenuation to 0db. The default attenuation is 10db. Installing a pre-amp near the antenna will help, but get a low-noise pre-amp. Using very good low-loss cable will help a lot. Use Heliax where you can. Keep you cable runs as short as possible. Hope this is helpful. The Other Brian _____ From: [email protected] [mailto:[email protected]] On Behalf Of Grace Lin Sent: Wednesday, March 19, 2008 7:13 AM To: [email protected] Subject: Internal Preamplifier Dear Members, The EMI receiver in my workplace comes with an internal preamplifier (20dB) up to 3.6GHz. I thought if I turned on this preamplifier, I should lower the noise floor 20 dB. Without the preamplifier on, my noise floor at 30 MHz read about 20 dBuV. With the preamplifier on, the noise floor read about 10 dBuV. There is only 10 dB difference between preamplifier on and off. Where did I miss? Is there any other adjustment (preselector, etc.) I should set as well? Thank you and look forward to your help. Best regards, Grace - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc _________________________ LECO Corporation Notice: This communication may contain confidential information intended for the named recipient(s) only. If you received this by mistake, please destroy it and notify us of the error. Thank you. - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
