FeelElec FY6900 Function Generator Review and making use of the VCO function -
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- Опубликовано: 18 янв 2021
- #047
FeelElec FY6900 Function Generator
A long term review and detailed explanation of using the VCO (Voltage Controlled Oscillator) function.
Other videos featuring this instrument here:-
SDG Electronics Review
• SDG #096 Feeltech FY69...
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I like you didn’t replicate the same information capably presented by other reviewers. Your impressions of the usefulness and operational characteristics from your chair are most valuable to me. As a hobbyist, and new one at that, I don’t have much of a budget for “nice to have” but not essential kit. I appreciate your frank comments as what to expect from this unit.
I enjoy your video work and find them interesting and educational. Thanks for taking your time to produce.
"Bode plots" are mentioned a few times in this video, pronounced with a silent 'e'. However, the correct pronunciation is the way their inventor, Hendrik Bode, said his name, as "boh-dee".
I found using the VCO with a cable from Ch 2 was messy and not accurate. From what I've seen, the response of the VCO isn't quite linear and mine had to be pushed slightly over 5 volts with the ramp to reach the end frequency. The offset was also slightly off.
The best way was to use the FM modulation function, using Ch 2 as the modulating signal. I used it with a slow five step ramp and a frequency meter to check it worked, and it was pretty much spot on. There's also far less messing about. The falling edge of the ramp can be used as a trigger for a scope or you could use the ramp to drive the X axis in X-Y mode on the scope.
They produced a very sophisticated sweep feature with all sorts of options, but didn't add a sync pulse. At least I've not found any way of picking up a sync pulse in sweep mode. It's a bit like making a fantastic car, but not including a steering wheel.
I’ve had mine for around a year now, it’s pretty great other than the lack of a power switch on the front panel. I’m not a fan of devices that “sleep” as does this, being used to older stuff that might decide to burst into flames in the middle of the night. I mainly use it as an RF generator for aligning AM radios, and it accomplishes that task very well.
Yes I only use the front panel power switch if I want to keep the settings during the day. I always switch off at the back for overnight.
thank you. I power up my fy6900 almost ever over the usb port - that works perfect. The ratio between price and usability ist very, very good and i think for hobby and educational purposes it is a nice product.
To reach the same functionality you can use the modulation of the fy6900. Only the freqence setup is slightly different. It can be set the middle freqency und a span. Its useful to find the center frequency of filters. The sweep rate configuration is simular to your setup, means CH2 ist set to ramp of 5V.
The benefit of this methode you need no Connection between CH2 and the VCO input.
Greetings
Thank you for the tip. Would you explain how the middle frequency and the span are related to the settings (CH1 Freq) and (BIAS Freq) in the MOD mode? I set (CH1 Freq) to 3kHz and (BIAS Freq) to 2kHz. The sweeping appears to start at 2kHz and stop at 3kHz. According to this observation, the sweep frequency appears to start at (CH1 Freq)-(BIAS Freq)/2 and stop at (CH1 Freq). Does this sound right? The offset of CH2 does not change the sweeping range.
do you recommend for a student and hobbyist man? Thank you good video.
I’m thinking of purchasing one of these, but can I ask it is capable of outputting a 455khz tone mod at say 30%. So you can align IF stages of a transistor radio ie Roberts rambler ?
Yes, page 27 of the manual says:
AM
Source Internal (CH2) / External (VCO IN Port)
Modulating Waveform Sine, Square, Triangle, Ramp, Arbitrary waveform
Depth 0% to 120%
Modulating Frequency Internal : 1μHz~1MHz; External: 1μHz~2KHz;
Another great video Bill.
Is it possible to get a 455KHz signal modulated with say 400Hz or 2500 Hz out of this unit?
If I set Channel 1 to 455KHz and then press mod, the modulation is fixed to channel 2
I’m confused.
I sat down and had a play. These are the steps I took:
Ensured both channels were active; set channel 1 to 455 KHz and outputting a sine wave; set channel 2 to an audible frequency - I chose 600Hz; selected the MOD button and chose AM modulation ensuring the modulation source was set to Channel 2; used the BNC to alligator clip leads to connect from Channel 1 to the grid of the converter tube in the tube radio I wanted to check. The 600Hz audio signal was heard from the radio and I could tune the IFTs to peak them.
I haven't purchased one of these FY6900 units yet, but I am VERY close. Some interesting ideas for doing frequency sweeps for filter and Bode plot measurements. The FM modulation idea from fredsmith5473 looks promising. I was wondering about another idea...
Let's say you set up a sweep on channel 1, for 10kHz to 100kHz, with a sweep rate of once per second. Then, on channel 2, you set up a square wave, with 1 Hz frequency. If you display both on a scope (triggering on the square wave), how will they appear relative to each each other? Will they drift relative to one another? Will they stay locked? Will the edges of the square wave be at some arbitrary position relative to the channel 1 frequency-sweep? If they drift, could you very slightly adjust the 1Hz square wave frequency so that the two waveforms stay in more-or-less sync? (Kind of like manually adjusting the time base on an old scope with no trigger. :-) )
The 1 Hz sweep rate and the 1Hz square wave are never the same coming out of ch1 and ch2. But you can adjust the frequency of ch2 in the 1/1000 of a Hz, so after an hour of tedious setting and resetting you could get an image that 'sort of' locks.
The most important problem I encountered sweeping with the internal sweep + a ramp signal from ch2 connected to the scope in X-Y mode (I tried a day's work to test, haven't tried the VCO yet) is that the frequency is not raised analogue, but in about 10-20 steps from low to high. On fast sweep speeds, say more than 1/20 of a second, a filter that is swept will show a stair case pattern, and only a very few steps. Unusable. You could sweep slower, then there are more steps per curve, but since I have an analogue scope it gets very hard to judge what I see. With a digital storage scope you are better off. You can look at his other video to see an example of that: ruclips.net/video/yrS-1KXppmw/видео.html&lc=UgwPSD-weP_YRG4OJRp4AaABAg.A4MDxKwW9rtA4UAaIDZlLD
Next test I will try the VCO with the ramp from CH2, but I assume that that will make no difference, otherwise it would be a feature already.
Update: I just setup a sweep through the VCO input with a ramp from CH2, and had succes. No more bulky steps like from the internal sweep function, but a smooth path, and fast enough that my analoge scope shows a workable image of a pass through filter, so no digital storage scope needed. Just follow the instructions in that other video.
Internal sweep, according to the manual, the frequency steps used when sweeping lineair are defined by:
Step value =（End value - Start value）/（Sweep time*100)
So if you want a nice image, and need for that 20 images/sec on your (analoge) scope screen, and you sweep an IF filter from 535kHz - 575kHz, the steps the sweeper uses are (575 - 535) / (0.05*100) = 8kHz steps..... That is what I meant by unusable.
Thanks for this interesting video. I too have a FY6900.
I have a question about impedance matching. If I'm not mistaken, the FY6900 has an output impedance of 50 Ohms. Did you set the input impedance of your Hantek scope to 50 Ohms too? Because I'm not seeing 50 Ohms terminators in your setup. Or are the frequencies you are using so low that impedance matching is not an issue?
Thanks for the videos! I'm subscribed :-)
Yes it's 50ohm output. I do normally use a terminator, but managed to forget on this occasion!
I have been doing a bit more work with the FY6900, another video to follow. ..
I am on a steep learning curve!
@@LockdownElectronics Thanks for your quick reply. I'm on a steep learning curve too :-)
BTW, I have a handheld Hantek too, like yours, and I just checked the channel menu: I can't set the impedance, so it might be that your bench Hantek scope is missing that feature too.
I had my one going for calibration and I had it at Hz and now it’s at MHz and I don’t know how to change the frequency to go back to hertz damn. Anyone can help?
I guess you figured it out by now: select frequency, and press OK to toggle through from µHz to MHz.
Can this generator output an AM modulated signal, say 600Khz w/ 1Khz Mod?
Yes it can
@@LockdownElectronics At age 65, and with an electronics background, I have just started a project to re-furbish a 1930's RCA 9K-1 tube-type (valve) AM broadcast/shortwave Radio, (IF is 460 KHz). I am thinking this might be a good device to align this radio, at the required alignment frequencies of 400 KHz, 1700 KHz, 6 MHz, and 18 MHz? Would it be good for this purpose?
@@RonS387 I would say yes, and I would use something like a 10n 600V capacitor to isolate the generator from the radio.
On your way to 1k, huh?
Ha ha! Not even half way....
@@LockdownElectronics but you started your channel a few months ago. That's a nice progress.
Yes I guess it is, thank you!
@@LockdownElectronicslooking forward to watch another long term review on your function gen and your oscilloscope after 6 months.
73
@@DoctorThe113 I need video suggestions, so I will add that to my 'ideas' list, thank you!
Why do you need so many different devices? Are you a collector?
Мой FY6900 photos.app.goo.gl/K54bcLK8t3VFTxiR8
Can you have too many devices?
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