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I'm looking for test equipment suggestions. I have an oscilloscope, DVM, LCR meter but need enough equipment to at least finish this T-41...doubt I will live long enough to build anything more complicated ;-)
In the DSP and SDR book they mention an audio signal generator with quadrature and a spectrum analyzer. Any suggestions on models that won't break the bank but are sufficient for building, testing and tuning the T-41?
Anyone advice on this signal generator, not sure if it can generate quadrature? https://www.amazon.com/Professional-Generator-Seesii-Precision-Dual-Channel/dp/B08T9H9FBY/ref=asc_df_B08T9H9FBY?mcid=b9e572b8f8e63e6fbdcf4c21c805b61f&hvocijid=15043490532578762466-B08T9H9FBY-&hvexpln=73&tag=hyprod-20&linkCode=df0&hvadid=721245378154&hvpos=&hvnetw=g&hvrand=15043490532578762466&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9002666&hvtargid=pla-2281435177858&th=1

I have that signal generator and it isn't great. It's very noisy for low amplitude (<100mV) signals. It is useful for some quick tests, but you can't trust it at low signal levels. I've not tried to generate quadrature signals with it, not sure if its capable.

I've had some success using my computer's sound card as a quadrature signal generator for audio frequencies, but the DAC is not fast enough for fully testing the T41.

I have a similar signal generator, but the brand is "FeelElec" and the model is FY6800.? ?I have used it extensively for SSB transmitter testing.? It also functions as a pretty good frequency counter.
It's not a laboratory grade instrument.? But for general purpose use on the bench, it's quite a bargain.? I don't see the same problem as Oliver, as the amplitude can go down without noticing significant noise or distortion,

at least for basic SSB testing.? And it does generate quadrature tones at audio frequencies, so you can drive a QSE.? This generator will be very useful for T41 transmitter tests if it performs like mine.

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Strongly recommended is a TinySA Ultra spectrum analyzer.? You need to get the Ultra, because the regular TinySA does not have enough resolution to distinguish SSB tones.

But even with that, the scan is extremely slow.? You should also get a 50 watt rated attenuator of 30 to 40 dB, and a collection of smaller attenuators.? 10 watts is +40 dBm, so

you need at least 40 dB of attenuation to keep from blowing up the spectrum analyzer during transmitter testing.? An alternative is a directional coupler and attenuator.

A collection of SMA cables of various lengths is helpful.

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I believe the TinySA Ultra was upgraded recently, however, the scan speed is still very slow.? My TinySA Ultra includes an RF signal generator.? Very useful!

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I tried using an SDRPlay as a spectrum analzyer.? It works, but it was a hassle to use.? The TinySA Ultra was much easier to deal with on the bench, and it doesn't require a computer.

In my opinion a spectrum analyzer is a bare minimum needed to tune up a phasing type SSB transmitter.? Ultimately I purchased a Siglent spectrum analyzer VNA combo which is a really amazing instrument.

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For tuning filters, a NanoVNA is extremely helpful.? Another bare minimum, but in my case the Siglent VNA has proved to be far superior.? But you will pay $$$ to get that.

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73 Greg KF5N

If you want to purchase several instruments, consider .? At about 4"x4"x1", it's great if you don't have a lot of space.? It includes the following instruments:

Oscilloscope Waveform Generator Power Supplies Voltmeter Data Logger Logic Analyzer Pattern Generator

Static I/O Spectrum Analyzer Network Analyzer Impedance Analyzer Curve Tracer Protocol Analyzer Script Editor

I recommend the Pro pack which includes probes and a BNC adapter which increases the bandwidth.

On Sat, May 17, 2025 at 11:09 AM, jerry-KF6VB wrote:

I have created a file for it that turns it into a two-tone oscillator for testing SSB transmitters.

You can import signal files into Digilent instruments as well.? You can also create custom functions directly in the tool.? Here's my first attempt at creating quadrature two-tone signals.?

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I still have a lot to learn with this little thing!

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I've just started playing with two-tone signals with the T41.? V66-9 can already create the two-tone signals internally from the two-tone calibration routine.? I want to see if I can create some useful screens using the receiver side (with the CAL relay on).? The receiver would need to be calibrated first for it to be of much use on the transmission side.? Probably a crazy idea, but things like that interest me.

On Sun, May 18, 2025 at 04:50 PM, Terrance Robertson, KN6ZDE wrote:

Thanks Terrance. When you say (see below) that the two-tone signals are created internally now with the V66-9 cal routine, does that mean I don't need the audio generator?

V66-9 can already create the two-tone signals internally from the two-tone calibration routine.?

John - A signal generator has many uses.? I use one often.? But if you're goal is just finishing the T41, I would focus on the , mainly the Transmit IQ Calibration where some external equipment is needed.

Hi John,

I use a two-channel Siglent SDG 2122x generator that can synchronize the channels and phase shift one by 90 deg - hence quadrature signals.

The Spectrum analyze is not entirely necessary and I would suggest trying to borrow one. Also, many of the recent digital Oscilloscopes have a built-in frequency analysis capability that should suffice.

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If you really want a decent SA, i use the Siglent SSA3021x with TG source. Pricey, but very capable.

Al

AC8GY

I have a full range of Siglent equipment however for recent Electronics merit badge I used one of these:

FNIRSI? 2C53P 3-IN-1 50MHz 250MS/s Dual Channel Tablet Touchable Oscilloscope Multimeter DDS Generator

Hi Tim, is the Fnirsi scope-multimeter the one that costs about $90?? I've been interested in that one.? I have not seen the tablet.

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The Fnirsi RLC tweezers are great!? I was using them recently to measure variable capacitors.

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73 Greg KF5N

Yes I think I paid $120ish for it.

Just ordered the 350mhz one with SA functions.

Looks to have tracking generator function because is shows Bode plot on web.

Tim

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This is from the manual on the one with SA functions?

①The amplitude gain scale value of the output signal relative to the
input signal, which is linearly distributed.
②The amplitude gain curve of the output signal relative to the input
signal.
③The phase shift curve of the output signal relative to the input signal.
④Cursor measurement data, the three data of C1/C2 respectively
represent the frequency corresponding to the C1/C2 cursor line, the
gain value at the intersection of the cursor line and the gain curve,
and the phase shift value at the intersection of the cursor line and
the phase shift curve. The three parameters of DC respectively
represent the absolute value of the difference in the frequency
corresponding to the C1/C2 cursor line, the absolute value of the
gain value difference, and the absolute value of the phase shift value
difference.
⑤Excitation signal amplitude setting column, range 0~5V.
⑥Excitation signal offset setting column, range -2.5V~+2.5V.
⑦Excitation signal start frequency setting column, range
100Hz~50MHz.
⑧Excitation signal end frequency setting column, range
100Hz~50MHz.