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Jay,
When everything is installed correctly, the SA44B should use the FTDI D2xx driver, not the FTDI virtual com port. It should show up under USB devices, but not under your list of COM ports. Hopefully this helps.I would recommend an active GPS antenna. As long as it has >20 dB of gain, you probably won’t benefit much from an additional amplifier. But these will be low level signals, and might be difficult to measure directly. More accurate measurements could be made by capturing I/Q and processing it using GPS algorithms.
Into a 50 ohm load, +10 dBm is about 1 V(peak), or 2Vpp. You would probably want a 1-2 watt amplifier with >20 dB of gain if you need 10 V(peak). You would probably also want to filter out harmonics before and maybe after amplifying to make it a good sinusoid.
Thank you for your recommendation. We’ll add this to our customer feature request list!
We also added a preselector to the BB60D. It is a sub-octave preselector designed to greatly reduce any second-order nonlinearities (IP2) above 130 MHz by rejecting out-of-band energy.
Below 130 MHz, we have a direct conversion band to 30 MHz, and above that a band that uses a push-pull amplifier to improve IP2 (but to a lesser extent than the preselector).Phil,
The BB60D uses the same ADC as the BB60C. It’s a very good 14 bit ADC. The dynamic range improvements came from using high IP3 amplifiers and mixers, and carefully balancing gain through the entire signal chain (too much or too little gain anywhere in the signal chain and either your noise floor or linearity pay a price).Distortion free dynamic range is 2/3 (IP3-DANL). With a -10 dBm reference level, IP3 at 1 GHz (on the most recent unit calibrated) is +15 dBm, and DANL at the same settings is -142 dBm for a 1 Hz bandwidth, so dynamic range would be about 104.7 dB at 1 GHz, normalized to a 1 Hz RBW. It would be lower at 6 GHz than 1 GHz, and obviously lower at higher RBWs as well.
We do not spec dynamic range, but we do specify worst case DANL and IP3. Hopefully this helps.
Both devices have an Arb mode, but the VSG25 is limited to 2k symbols (very small buffer). It looks like these chirps are often clustered together in a sequence, and never wider than about a MHz, so the VSG60A would be the right choice, since its buffer is on the PC/laptop and can be very large if needed.
Glad you found it. +/- 1 ppm initial, +/- 1 ppm/year. A typical unit will be quite a bit tighter than this.
Kaiser,
Unfortunately we have several switching regulators in our power supply that have a maximum operating input voltage of 16 volts. We could have added an additional DC-DC conversion in front to extend this, but this would have reduced efficiency and added heat for all customers.
There are quite a few 24V – 12V DC-DC converters on the market. I realize it’s not an ideal solution, but hopefully it will work for you.You should be able to export your good trace, offset by some amount (e.g. 2 dB) in spreadsheet software, and then import it as a limit line. This might be another approach to consider.
I know Matlab has some tools for GPS signal generation. You could also just use one of our receivers, a bias tee, and a good GPS antenna + preamp to capture a GPS signal and then play it back with the VSG60A.
Thank you for bringing this to our attention. I will alert our software team to this issue, and see if they can duplicate it.
You will notice in the specifications that the DANL (noise floor) specification is 4 dB higher below 700 MHz vs. above 700 MHz. A 4-5 dB step in the noise floor is normal. This is due to a design decision to optimize for noise figure in the 700 MHz – 2700 MHz communications band, and to push for better linearity at low frequencies.
I’m not sure what signal you’re looking at there, but it is possible that level of noise is actually on your signal. You can turn the preselector on and off below 640 MHz, and change your reference level by 10 dB. If the noise level changes considerably, it may be partially from intermodulation inside the SM200C. Otherwise, it is likely part of your input signal.
One thing to watch out for is noise from the USB cable ends can mass with weak GPS signals, so it is best to have some distance between the GPS antenna and any USB 3.0 cable. A couple of meters is usually sufficient.
We ran a fresh batch of tests, with the API as it currently stands. I was a little surprised. A 2 GHz span (roughly 2 ms of actual sweep time), took from start to finish (not queued), on average:
SM200B = 4.4 ms
SM200C = 4.8 ms
There were no significant peaks in the 1000-sweep test. From this, it looks like the SM200C has a bit higher latency across the board (something like 2.8 ms vs 2.4 ms).
Obviously these numbers will vary from computer to computer and sweep to sweep, and peak numbers will vary based on CPU load, but it’s a starting point.Kaiser,
Good news and bad news. In Windows, even though the median latency for the SM200C is a bit lower than the SM200B, the peak latency can be high (I have seen 80 ms delays when opening a PDF for example).
I do not believe the same problem exists on the Linux side.Mneuman,
ThinkRF has some upconverters. Or if you’re on a budget, you could get the ADMV1013 eval board and cobble something together. Maybe even use an LO from Windfreak if you don’t have a generatorWe have a software suite for instrument calibration. See https://signalhound.com/software/signal-hound-field-calibration-software/ for more information. A typical calibration lab will have most or all of the equipment required.
GSingh,
Yes, those IMD3 products appear to be from the generator, at typical values. Typically you will see -50 dBc below -10 dBm, but it will get worse as you increase amplitude.
If you need two-tone better than -50 dBc, you would probably want 2 generators and a directional combiner. There are digital techniques as well, but they will be less stable over temperature and frequency.