Here are my measurements over the weekend on a Flex 5000A as far as the affect of the AGC-T setting. The AGC-T is AGC threshold. There was no difference between 100 and 120 on my unit. Below 100 there is a normal progression of a higher threshold. Reading Threshold for 3 dB audio drop from -33 dBm (5 mV) or S9 + 40 dB, with the Preamp OFF 120 2.7 uV 110 2.7 uV 100 2.7 uV 95 3.2 uV 90 5.6 uV 85 10.1 uV 80 17.9 uV
Preamp ON 100 0.55 uV 95 0.65 uV 90 1.13 uV 85 2.1 uV 80 3.6 uV An Icom 756 Pro III has the following AGC thresholds: No preamp: 2.3 uV Pre 1: 0.7 uV Pre 2: 0.3 uV K3 No Preamp 2.1 uV Preamp 0.6 uV R-4C 0.7 uV (obviously it in effect always has the preamp (RF tube) enabled. 75S-3C 1.3 uV IC-781 No Preamp 2.5 uV Preamp: 0.7 uV IC-7800 with 6 kHz roofing filter No Preamp 4.5 uV Pre 1: 1.2 uV Pre 2: 0.6 uV 73, Rob, NC0B >>> Gary Carter <[email protected]> 7/11/2009 11:07 AM >>> Thanks for all the pointers guys! I took the AGC-T down to 92 (the default at 90 was just a tad too low for me) and everything is working well. I notice a considerable difference when I go from the ARR preamp, no preamp and the Power SDR preamp. The ARR P50VDG really pulls weak signals out of the noise for me. I need all the help I can get considering I have a Cushcraft short boom 5 element beam that's only 14 feet off the ground on the back deck of the house! 73, Gary - WA4IAM Clay W7CE wrote: > Gary, > Unless your local noise floor is very high, you should see the > displayed noise floor drop a lot when you enable the preamp. That's > because you're lowering the total receiver noise figure from about 22 > dB to about 2 dB. You can really see it if you connect a 50 ohm load > to the antenna port and then turn the preamp on and off. That takes > your local QRN out of the picture and lets you see the improvement in > RX noise figure. > > 73, > Clay W7CE > > ----- Original Message ----- From: "Gary Carter" <[email protected]> > To: "Flexradio" <[email protected]> > Sent: Friday, July 10, 2009 1:05 PM > Subject: [Flexradio] 6 Meter Preamp Settings > > >> Purchased an Advanced Receiver Research model P50VDG preamp for my >> Flex 5000A and just installed it today. Using two 3' RG59 75 ohm >> patch cables to connect the preamp in the RX1 loop. I read the KB >> article on the antenna setup for using the RX1 loop and have that >> setup per the instructions, but I want to pass this by the group to >> make sure I have all my other settings correct. Of course I have the >> RX1 loop enabled, but I also have the preamp controls for 6 meters >> enabled and the preamp (Power SDR) turned off. Since the gain of the >> P50VDG is listed as 24 dB I have the gain box in the antenna >> selection window set at 24 dB, and the AGC-T I left set at 110. Does >> this appear to be correct? The external preamp is working fine, I'm >> just a little concerned seeing the noise floor on the panadapter drop >> so significantly. I want to make sure my receiver S meter readings >> continue to be accurate. >> >> 73, Gary - WA4IAM >> >> _______________________________________________ >> FlexRadio Systems Mailing List >> [email protected] >> http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz >> Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ >> Knowledge Base: http://kc.flex-radio.com/ Homepage: >> http://www.flex-radio.com/ >> Message delivered to [email protected] > > _______________________________________________ FlexRadio Systems Mailing List [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ Message delivered to [email protected] -- If this email is spam, report it here: http://www.onlymyemail.com/view/?action=reportSpam&Id=ODExMjI6OTI4MTA0NDg0OnJvYkBuYzBiLmNvbQ%3D%3D _______________________________________________ FlexRadio Systems Mailing List [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kc.flex-radio.com/ Homepage: http://www.flex-radio.com/ Message delivered to [email protected]
