Harmonic operation


#41

Might be …

As far as stable … iv seen the signal stay some what stable … it does not drift 100Khz but more like 20khz over time.

There would be no Doppler shift … antenna and HB100 were stationary.

HB100 antennas are pair of dipoles (radiating squares?) with no reflector … the signal did drop some, just not as much as i thought it should – as you too – but i think there is also reflections from around the room being picked up. — with that comment, i really, really really need to modulate the signal with SOMETHING to know for sure the source …

I threw away a walkman couple of days ago (been cleaning out the garage as you can see in the video) … need to dig it out and use that with a pot and place a resistor in series with the 5V source …


#42

No … seems stable as long as hte temp stays constant and you dont bump/vibrate the HB-100 !!!
Big note on “DONT BUMP/VIBRATE” … you’ll see …

I had problems at first … dead car battery, pulse noise from the battery charger , vibration from the CD spinning around making the HB-100 jump around 15Khz …


#43

I did a bit more testing today. I separated the signal source from the LimeSDR by 20’.

Using just a WR-90 transition in to the Lime, I can see a signal about 20 dB out of the noise. At this level, I’m just starting to see the phase noise on the edges. The CW does sound OK.

I then changed out the transition for a 25 dBi 10 GHz Flat Panel. MTI MT-9010. Signal level jumped about 20 dB, but so did the phase noise to the point that the CW was no longer clean. Raspy. I was able to clean it up by reducing LNA gain on the Lime. No way this would survive on a Mountaintop during a contest.

By comparison, I used my $7.95 Avenger PLL321S and was able to see a clean signal over 70 dB louder easily. I used the LimeSDR as an IF.

Using the LimeSDR for receive on 10 GHz is an interesting experiment, but I don’t see me using it for 10 GHZ receive. It would be better utilized as an IF at 618 MHz on the output of an Avenger or real 10 GHz rig.

MP4 of the test here:

---- https://www.dropbox.com/s/87036rekv8f8ayo/20160630_125559.mp4?dl=0 ----

I did put pads inline and saw input levels drop very close to the pad value. I was using HSDR with the ExtIO_LimeSDR dll for the tests.


#44

Is the I/Q balance good with your setup @ 10Ghz …?

I still need to see if there is a way to manually set I/Q calibration … at about 1.5Ghz the I/Q starts to show that it needs better adjustment and DC hump is no longer removed.

I wonder if the noise floor and phase noise would be cleaned up any too.


#45

Sure … the gain will be 12db lower than max possible due to the 3rd harmonic (of Lo) power level.

I wonder if using the LNB’s LNA with some padding – like 30db – with no down conversion into the lime would improve performance.

With out knowing the LimeSDR-USB LNA’s performance curves (on paper – does it have a part ## or PDF?) its hard to know what its gain is on 10Ghz.


#46

Oh … wait …

Your getting a signal from noise floor (i assume its -100db) to -30db??

I don’t think i get a signal above -40db — i feel i need to double check my memory.

Isn’t the theoretical dynamic range of a 12bit ADC 72.2 dB ?


#47

Maybe this doc is useful in this discussion. I’m just following along as a casual observer hoping I learn a little here and there.

https://wiki.myriadrf.org/LimeMicro:LMS7002M_Datasheet


#48

Lots of information in it … but nothing about the internal parts/schematic. nothing of what value the DC blocking cap to the LNA is thats reducing the overall 100Khz performance nor the equal part ## used in the LNA or its S parameters (not that i can deduce anything from “S” parameters anyways)

I think i asked those questions awhile ago and were un-answered (i think)


#49

The internal parts of the LMS7002M?

I think some of these answers are here, possibly spread around a little. I recall seeing a discussion of S parameters for certain.


#50

yep …


#51

N1JZE Double check that LPA …
I have 4 now … im not saying its junk … but the take off angle seems to be at ~25deg … so putting the waveguide to coax transition directly inline will not get you anything …

I built a ltc5508 power detector and took me a while to figure out the PLA pattern is NOT pointed off of the front of it …


#52

Had an idea … , i can still detect 10ghz signal with no antenna … my lime is not shielded

Thought I might play around with this little bit again now that I’ve settled down after my wife telling me she wanted a divorce … that’s probably going to happen in about 12 days . I’m praying that my marriage be reconciled with my wife but she is still saying that her friend that she stays with every weekend is just a friend. I guess when you start lying to your spouse you just can’t stop doing it.

If you pray to God, believe in Jesus Christ … please pray for my marriage.


#53

It also helps to keep the low pass filter at max … 130mhz.


#54

Qusetion …

Does undersampling aka beyound the nyquist… cause a 180 degree phase shift in calculations like 3rd harmonic does in a I/Q system?


#55

Still trying to figure this out off and on it’s clearly being picked up by the lime but the signal is affected when you cover the patch antennae but it seems that it is picking up signal elsewhere. I need to get my lime shielded and get a better idea of exactly how the signals getting into the limeSDR