July 2007 - Eagle (INACTIVE) - mailman.amsat.org

70 cm Frequency Stability Tests Results
by Juan Rivera 04 Jul '07

04 Jul '07

All, I should have gone to work today but I ended up working on the 70 cm Receiver all day instead. Today marks a milestone for me -- my first use of audio files. You'll find two in my write up if you click HERE <http://www.juanr.com/pages/hobbies/ham_radio/Eagle/Stability.htm> . I think they work much better than descriptions and graphs. Now you can hear what I'm talking about... Have a great 4th! I plan to do a temperature run on the receiver tomorrow to celebrate! Let's see what that internal oscillator does when it's not at room temperature! P.S. to OSCAR guys... If you have time come on over and help me run this test. I'll probably start early to beat the heat. If you've never been gassed by CO2 before, now is your chance! 73, Juan - WA6HTP

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TeamSpeak conference for Tuesday 10 July 2007
by Jim Sanford 04 Jul '07

04 Jul '07

All: For whatever reason, I'm unable to update EaglePedia (it ignores my changes), so here's the agenda as I see it. Feell free to suggest additons to me, I'll keep a running total and publish just prior to the meeting. Topics: 1. Symposium 2. Requirements documentation ' 3. WBS and schedule development 4. Status reports UHF RX S2 Rx 5, EMI Please add topics. Thanks & 73, Jim wb4gcs(a)amsat.org

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70 cm Receiver Frequency Stability and One More Glitch
by Juan Rivera 03 Jul '07

03 Jul '07

All, Here's a plot of frequency drift in the 70 cm Receiver - first on internal reference, then on external reference: The first part of the plot is with the receiver and the signal generator set to 435.500000 MHz on internal reference. You can see the slow steady drift upwards of about 15 Hz over a period of about 5 minutes. Then I reinitialized the receiver for the external reference. It locked right up and the output was exactly 10.700000 MHz where it stayed. The most important thing I noticed is not on this graph. With internal reference selected, but while feeding 10 MHz into the external reference input, (as it might be configured in flight) the two reference signals are beating together. It wasn't until I started listening to the output of the receiver by patching it into a distribution amplifier so I can feed my counter, the SDR-IQ, the TS-2000, and the HP 8566B all at once that I noticed it. The result is that the input signal is FM modulated by the beat between the two reference oscillators. I also noticed some unexplained jumps in frequency that I have not yet been able to capture. I'll dig into this again when I have more time. 73, Juan

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CAN-Do Causing RF Frequency Jumps in 70 cm Receiver
by Juan Rivera 03 Jul '07

03 Jul '07

John and CAN-Do Team, I was in the process of checking some configuration files in preparation for my hunt for the 10.7 MHz spur. I initialized the receiver on 435.500, internal reference, and set up the SDR-IQ to display the IF output signal. Then I clicked the heartbeat button on the Can-Do Net Controller and was about to load the initialization file for external reference. As soon as I clicked the heartbeat button the IF output started jumping. I think it's the three second jumps that I have seen before, but I thought those were caused by a momentary loss of DC input power. In this case the receiver power is coming directly from the bench supply. I killed the CAN-Do module power and the IF jumping stopped. As soon as I applied power to the CAN-Do module again, the jumping returned. The duration of the jumps is very short and I am unable to capture a carrier - either with the SDR-IQ or using my TS-2000. They sound like clicks over a wide frequency range. Since the next revision of the receiver will be autonomous, perhaps this won't be an issue for us, but it will for others so it should be understood and documented in my opinion. 73, Juan

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10.7 MHz Spur
by Juan Rivera 02 Jul '07

02 Jul '07

John, I found the source of the 10.7 MHz spur. It's being generated inside the receiver itself. This is the first spur I have found that is not caused by switching power supplies. The origin appears to be in the 10 MHz reference area. I turned off and unplugged the SDR-IQ and fed the IF output from the 70 cm Receiver to my TS-2000. The spur is still there. Next I connected the RF input to my sniffer loop and moved it around the PCB surface. I get the strongest signal near the long trace between the two Freq inputs to U4 and U9, the two phased-locked loops. 73, Juan

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