Author Topic: Fy6800 vs Fy6900  (Read 19117 times)

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Offline Johnny B Good

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Re: Fy6800 vs Fy6900
« Reply #100 on: July 19, 2019, 06:43:40 pm »
So the output is "known" by the microcontroller , nothing new ,  but a Siglent or a similar generator is actually measuring the output in some way if you load it down ?
About this you don't find anything in manuals .

 Well, the microcontroller will certainly 'know' what the output voltage is supposed to be. All that is required is an additional input from a current sensor to be able to calculate the load impedance and the resulting voltage. If it isn't mentioned in the Siglent manuals (the same cannot be said for the Feeltech manuals[1]), then it isn't a feature of the generator.

 I only mentioned these possible features on the basis of hypothesis from the feeling that radiolistener (and many others) may have been spoilt by such features actually being implemented in the more expensive models, particularly Keysight products, otherwise why the complaint about this halving of the set Vpp when connected to a matching load?

 I honestly don't know of any signal generators that do calculate the load impedance for display to the operator (or, optionally, compensate for its effect on the output voltage in order to keep it at the set p-p voltage - given enough system resources in the generator, anything is possible when backed by a generous R&D budget).

[1] In the manuals for the FY6600 and 6800 models, they both mention a non-existent 10Vpp limit in the 10 to 20MHz range when, in fact, the 20Vpp limit (on sine and square waves at least) actually runs all the way from zero to 20MHz inclusive before dropping straight down to the 5Vpp limit of the opamp which drives the THS3002i which is bypassed by a relay in the frequency range beyond the 20MHz limit. Getting "back on topic", It's quite possible that the same error has been duplicated in the FY6900's manual.

JBG


 

Offline Johnny B Good

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Re: Fy6800 vs Fy6900
« Reply #101 on: July 19, 2019, 06:54:57 pm »
I've (hopefully this time!) attached higher definition movie files of the traces I posted in my previous two postings mainly to reduce the pain of having to watch the effect at such an execrable resolution of just 320x240. Please enjoy!  ;)
Previous files was in common .mkv format, easily playable.
What should I do with these new files in unknown format ?!

 Hi Jacon,

 You had me worried for a moment. I think you may have skipped a step this time round. I'd zipped each one individually using Ark. The files are mkv type as before and, just for good measure, I downloaded them to make sure that they hadn't been got at in any way. I got back exactly what I'd uploaded. They should play just fine once they've been extracted. :)

 The only difference this time round being that I couldn't figure out how to access the pkzip option menu to choose "store", so there's a modicum of compression used this time round. Possibly the reason the others played ok as zip files is because there hadn't been any compression allowing your media player to recognise them as mkvs and play them without you actually extracting them.

JBG
« Last Edit: July 19, 2019, 07:01:08 pm by Johnny B Good »
 

Offline Jacon

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Re: Fy6800 vs Fy6900
« Reply #102 on: July 19, 2019, 07:05:52 pm »
OK - done  ;)
 

Offline radiolistener

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Re: Fy6800 vs Fy6900
« Reply #103 on: July 19, 2019, 09:39:35 pm »
It has an output resistance of 50 ohms.
And the amplitude is set without load.

In reality "without load" condition is impossible. Amplitude with no load doesn't have sense, you cannot create such condition for high frequency. As you know, even open BNC connector has some impedance. In order to measure amplitude, you're always needs to apply some load. Any measurement equipment has impedance and when you connect it to generator, it will make load.

The standard impedance for high frequency measurements is 50 Ohm. Almost all high frequency measurement equipment has 50 Ohm impedance. So, if signal generator shows amplitude for random high resistance load (this is what HiZ exactly means), you're needs to always recalculate these random "volts" to standard volts. Because "HiZ" voltage is completely useless and don't have sense for real measurements.

This is why "HiZ" amplitude is completely useless indication. Frankly speaking, this is complete bullshit. These "HiZ" random volts for random impedance can be used just for marketing purposes in order to misleading those peoples who don't have knowledge and don't know Ohms law.  :bullshit:


« Last Edit: July 19, 2019, 10:30:57 pm by radiolistener »
 

Offline radiolistener

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Re: Fy6800 vs Fy6900
« Reply #104 on: July 19, 2019, 09:58:17 pm »
For instance you can use a generator with an impedance of 75 ohm to drive a 50 ohm line, allowing for the additional 1.94dB drop (a 60% drop versus the matched case of a 50% drop).

If you're using non standard load, you can easily recalculate amplitude when you know 50 Ohm load based amplitude. With HiZ you will stuck, because there is no actual HiZ in reality. There is always some impedance on the output connector. Even if you BNC is open it still have some impedance, which depends on the frequency. HiZ doesn't exists in reality, so this "HiZ" amplitude is not "HiZ", it is acutally amplitude for some high random impedance. And this is why these "HiZ" volts are random.

The fancy and more expensive signal generators may well offer such a feature. Considering your question, they probably do and possibly by monitoring the current versus voltage output to calculate the actual impedance it is connected to so as to leave the operator a hand free to scratch their balls.

All that is required is an additional input from a current sensor to be able to calculate the load impedance and the resulting voltage.

There is no need to "monitor the current versus voltage output". No need for sensors. If signal generator has 50 Ohm output impedance, it will automatically keep "current versus voltage". The same as simple resistor doesn't need any kind of sensors and "monitor the current versus voltage" in order to keep it's resistance properly. This is simple Ohms law!

I = U/R

There is no need to monitor for current and voltage, the current will be automatically adjusted to the voltage, according to the Ohm's law. And you can simply add your load impedance and get current correction. Since almost all RF equipment has 50 Ohm connectors, you're don't needs to think about it, just use standard 50-ohm impedance voltage.

You can easy calculate dBm power value from 50 Ohm voltage. For HiZ it even doesn't have sense, just because you cannot measure power on random HiZ impedance.

This will turns into problem if you're using so called "HiZ amplitude". In such case it will turns into:

I = U / [random high impedance]

If you will try to convert it to dBm power, it leads to:

P = U^2 / [random high impedance] = [random power value dBm]

This is why HiZ amplitude in context of signal generator for MHz frequencies is complete bullshit:horse:


Personally speaking, I'm rather glad that the Chinese designers of cheap affordable T&M kit have avoided this insult to the intelligence of their hobbyist target market demographic by not adding such unnecessary "Bells and Whistles"

Actually these Chinese guys added "Bells and Whistles", such as useless "HiZ amplitude". It makes hard to use this signal generator, because you're always needs to recalculate real amplitude to these random volts and it needs to re-check real amplitude with measurement equipment in order to avoid confuse.

But you didn't answer on my question - is it possible to recalibrate FY6600 in such way? To show standard 50 Ohm amplitude. It will make life more easy. I hear that there is possible amplitude calibration. So, may be it can be done with proper amplitude calibration for standard 50 Ohm load?

Just think about some special multimeter which show non standard voltage for "spherical horse in the vacuum" model. And you're needs to multiply it's result by sqrt(35) in order to get standard voltage. It's just awful. The same thing with this "HiZ amplitude". This is how this "feature" looks like from the user's point of view.  :-//

I remember that some people mention that there is some attenuator in the FY6600 frontend, which unfortunately didn't properly matched to 50 Ohm due to poor design, so it may leads to issues with 50 Ohm voltage calibration. Is this true?

Why developers of FY6600 are trying to make life difficult by inventing this random "HiZ amplitude" instead of using standard 50 Ohm voltage which is used everywhere? Is this just attempt to hide some critical fail in hardware design?

I just don't understand - why?  :-\
« Last Edit: July 19, 2019, 10:55:16 pm by radiolistener »
 

Offline radiolistener

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Re: Fy6800 vs Fy6900
« Reply #105 on: July 19, 2019, 11:54:25 pm »
Calibrating the voltage setting for the unloaded condition is the most logical choice (it's very easy to check this well defined unloaded voltage output).

This is not logical and completely useless. Even more, such calibration is completely incorrect. Just because it requires to connect voltage meter to the output connector. Your voltmeter will change this impedance. And your voltage measurement will be actual for specific impedance which is a combination of output generator impedance and your voltmeter input impedance. You will lost your calibration just when you detach your voltmeter from output connector. It will leads to significant change of impedance on the output connector and as result voltage will be changed.

So, this so called "calibration" for "HiZ amplitude" will be lost just when you disconnect your voltmeter from the output connector of your generator.  :-DD

The other issue is that when you use voltmeter with input impedance different than 50 Ohm with 50 ohm coax cable, or just with a piece of wire, it will leads to impedance mismatch and wave reflections. As result your voltmeter will give you incorrect voltage.

In order to avoid such issues with voltage variation due to impedance changes, you're needs to calibrate it with voltmeter which has 50 Ohm imput. It means that all voltage measurements will be 50-ohm impedace based and cannot be applied for so called "HiZ amplitude".  :popcorn:

I can say more. If you're using "HiZ amplitude", there is no way to get known RF power level for calibration. Because HiZ means high resistance (infinite resistance in ideal case), so it will leads to infinite power for any voltage  :-DD
« Last Edit: July 20, 2019, 12:05:22 am by radiolistener »
 

Online bdunham7

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Re: Fy6800 vs Fy6900
« Reply #106 on: July 20, 2019, 12:02:08 am »
It has an output resistance of 50 ohms.
And the amplitude is set without load.

In reality "without load" condition is impossible. Amplitude with no load doesn't have sense, you cannot create such condition for high frequency. As you know, even open BNC connector has some impedance. In order to measure amplitude, you're always needs to apply some load. Any measurement equipment has impedance and when you connect it to generator, it will make load.

The standard impedance for high frequency measurements is 50 Ohm. Almost all high frequency measurement equipment has 50 Ohm impedance. So, if signal generator shows amplitude for random high resistance load (this is what HiZ exactly means), you're needs to always recalculate these random "volts" to standard volts. Because "HiZ" voltage is completely useless and don't have sense for real measurements.

This is why "HiZ" amplitude is completely useless indication. Frankly speaking, this is complete bullshit. These "HiZ" random volts for random impedance can be used just for marketing purposes in order to misleading those peoples who don't have knowledge and don't know Ohms law.  :bullshit:

While it's true that 50R is a common impedance used in HF, it isn't completely universal and is only conventional for a limited range of conventional instruments dealing with RF.  Common, yes.  Universal, no.  What you don't seem to understand is that the threshold where transmission lines and 50R impedance become necessary is in the 50-200MHz range.  Below that, depending on line length and input capacitances, it is entirely practical and common to use higher impedance setups.  At 1 MHz you can use banana plugs if you like.

There are many things that you might connect your sig-gen to, and in the case of the FY6x00 series, I'm going to guess that most of them are what you call Hi-Z.  Since the output impedance is 50R, the errors caused by varying between 1M, 10M, or even the common 10K and 47K input impedances of audio equipment, are quite small.  If you have something with say 600R or significant capacitance for your selected frequency, well you'll have to do the math.
 
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Offline radiolistener

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Re: Fy6800 vs Fy6900
« Reply #107 on: July 20, 2019, 12:14:29 am »
What you don't seem to understand is that the threshold where transmission lines and 50R impedance become necessary is in the 50-200MHz range.

I'm understand it pretty good. Because I was seen how a small impedance mismatch on a 10 cm wire leads to SWR > 1.5. and it happens at 3-5 MHz!

At 50-100 MHz it will become even much more sensitive. With 50-100 MHz even wire shift for 0.01 mm will leads to significant change.

Impedance mismatch is a not big deal at very low frequencies, such as 50 Hz or 1000 Hz. But when you're working with frequencies above 100 kHz it become significant. For 1 MHz and more it is very significant.

This is 60 MHz signal generator and impedance match is very and very critical at such frequencies.

You can do these "HiZ" measurements for sound wave generator, when your output is below 10-20 kHz. But when you're working with 100 kHz and above, such approach is not accepted at all.

No take into account impedance for measurements at 1 MHz and above is complete bullshit.
« Last Edit: July 20, 2019, 12:23:07 am by radiolistener »
 

Offline radiolistener

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Re: Fy6800 vs Fy6900
« Reply #108 on: July 20, 2019, 12:29:35 am »
the errors caused by varying between 1M, 10M, or even the common 10K and 47K input impedances of audio equipment, are quite small.

This is not audio generator. It works with MHz range signal for which impedance plays very important role.

There is no excuse for "HiZ measurements" for RF signals. This is complete bullshit and even don't try to say the opposite.

First try to find 10 MHz calibration source with 0 dBm power level for your "HiZ" RF voltmeter  :-DD


Since the output impedance is 50R

I have suspicion that there is a serious hardware issue with 50 Ohm impedance. Because I don't see reason to show non-existing voltage for non-existing impedance. If it has 50 Ohm, then just show voltage for 50 Ohm to not ruin Ohm's law! It will be correct measurement and all will be ok.

But for some reason it shows non-existing voltage for non-existing so-called "HiZ" impedance. What is the reason for that?   :-\
« Last Edit: July 20, 2019, 12:54:25 am by radiolistener »
 

Online bdunham7

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Re: Fy6800 vs Fy6900
« Reply #109 on: July 20, 2019, 03:52:20 am »
You seem to have a lot of criticism of a sub-$100 amateur-grade piece of equipment that you've apparently never seen or touched!  And some interesting ideas about impedance that seem like the ham-radio equivalent of audiophoolery to me--but I'll leave all that alone. 

The FY6x00 series are low-cost AWGs, not serious RF-generators.  The fact that some can stretch all the way to 60MHz doesn't make them suitable for any serious RF work, IMO.  I have other tools for this with better frequency accuracy and lower phase noise--I wouldn't even think of using this tool as serious RF generator and mine only goes to 15Mhz anyway.  I would guess, as I said before, that the vast majority of these are being used with high-impedance loads.  I suspect a lot of them are connected to oscilloscopes and drawing pictures.

Some--and only some--of your comments may make some sense if you are working on RF power systems, but as for low-level signals, it is very common to have an intentional impedance mismatch where a low impedance output drives a higher impedance input.  This is how you keep distortion low, for example. Circuits are commonly designed this way going into the many-MHz and beyond.  Impedance matching has its place, but that place isn't everywhere.
 
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Offline CDaniel

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Re: Fy6800 vs Fy6900
« Reply #110 on: July 20, 2019, 05:41:26 am »
Bellow 5Vpp the 50 ohm is an output series resistor that limit the current for the op amplifier when you short it ... you can calculate the real voltage for a load .

For a "classic " generator with an output  attenuator you don't even know the series resistor and is variable for every output range ... ok could be calibrated to show correctly for 50ohm load and that's about all . But anyway not so high frequency generators are calibrated the same as FY6600 , for infinite load .
« Last Edit: July 20, 2019, 05:44:35 am by CDaniel »
 
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Offline radiolistener

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Re: Fy6800 vs Fy6900
« Reply #111 on: July 20, 2019, 07:53:58 am »
You seem to have a lot of criticism of a sub-$100 amateur-grade piece of equipment

this is not criticism of device, this is criticism of wrong way to measure AC voltage for frequencies above 1 MHz.

The FY6x00 series are low-cost AWGs, not serious RF-generators. 

it doesn't matter if it RF or audio grade. If it allows to select voltage, this is should be real voltage!

When you use so-called "HiZ" voltage for 10 MHz signal, this is something like voltage applied to "spherical horse in the vaccuum" which doesn't exists in reality  :-DD

you can replace the horse with a cow if you wish


What Z do you mean when you talking about HiZ? Infinite? 100 MOhm? 1 MOhm? 10 kOhm? 100 Ohm? or may be 1 Ohm?

100 pF capacitor has about 159 Ohm impedance at 10 MHz. 159 Ohm is HiZ or LowZ?

« Last Edit: July 20, 2019, 08:27:44 am by radiolistener »
 

Offline pantelei4

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Re: Fy6800 vs Fy6900
« Reply #112 on: July 20, 2019, 10:01:23 am »
this is not criticism of device, this is criticism of wrong way to measure AC voltage for frequencies above 1 MHz.
The device does not measure the output voltage.
 
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Offline CDaniel

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Re: Fy6800 vs Fy6900
« Reply #113 on: July 20, 2019, 01:41:46 pm »
He doesn't seem to understand that no usual generator is measuring the output , so even if it's calibrated for 50 ohm or whatever you may choose , you must be certain that the load impedance  is exactly that , and not containing stupid capacitors  :(  and inductors that form complex impedance variable with the frequency  :-DD

Sorry , but for measurements you must have a good radio frequency voltmeter ... and not relly on the "magic" numbers a generator is giving to you .
« Last Edit: July 20, 2019, 02:44:38 pm by CDaniel »
 
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Offline radiolistener

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Re: Fy6800 vs Fy6900
« Reply #114 on: July 20, 2019, 03:14:21 pm »
The device does not measure the output voltage.

it doesn't measure voltage, but it should provide voltage which is selected on the control panel, if you selected 2 Vpp it should put 2 Vpp on the output. And RF power meter connected to the output should display 10 dBm power level. If it's true, then all works as expected. This is expected behavior.

But I think you will get 3.9 dBm or something like that, it will depends on how FY6600 analog frontend is close to 50 Ohm. That is fail.

Also, there is a problem to calibrate signal generator for these HiZ voltage. This is incorrect way to use 2x of real voltage. Because 2x amplitude will be expected for infinite impedance, which is not the case for FY6600. It doesn't has inifinite impedance, so your calibration will be wrong.
 

Offline Johnny B Good

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Re: Fy6800 vs Fy6900
« Reply #115 on: July 20, 2019, 04:52:30 pm »
For instance you can use a generator with an impedance of 75 ohm to drive a 50 ohm line, allowing for the additional 1.94dB drop (a 60% drop versus the matched case of a 50% drop).


But you didn't answer on my question - is it possible to recalibrate FY6600 in such way? To show standard 50 Ohm amplitude. It will make life more easy. I hear that there is possible amplitude calibration. So, may be it can be done with proper amplitude calibration for standard 50 Ohm load?


 You've obviously "Read the Book" but seem to have developed some oddball ideas. Considering that English is not your native tongue and most of the technical literature tends to be published in English, you may have had more of a struggle than native English speakers who, quite frankly will find it difficult enough to comprehend the subtleties of such technical texts despite of the lack of any such "Language Barrier".

 Anyway, all I can advise is that you go through the literature again and take another look whilst keeping in mind what you've learnt here. I'm not going to waste time arguing all the points you've raised here since that would lead to arguments in the vein of "How many Angels can dance on the head of a pin?"

 As for your claim that I didn't answer your question, you are somewhat in error. It's true the short snappy answer you were seeking was buried near the end of my effusive (some might say long winded) reply #94 (fourth paragraph from the bottom) but answer it I did, as you can see from the following extract taken from that reply:-

[QUOTE/]

 In answer to your question... what was it again? Oh yes, the business of the unloaded voltage being a "Chinese Thing"(tm) and the possibility of having the voltage setting expressed as that which a matched load would produce (i.e. display 1Vpp instead of 2Vpp to account for the loading effect of a termination matching the output impedance of the generator).

 The answer in the case of these Feeltech generators is no (at least for the moment - if development of an OSS front panel firmware package ever resumes (seems rather unlikely though) you may well get the opportunity to add this feature to your "Wish List").

[/quote]

 To lend extra clarity, I've rendered the relevant words in bold typeface. The original did not have any parts in bold, I use bold and italics rather sparingly in these posts lest they lose their impact through overuse. In this case, my use of bold text seemed rather appropriate to the occasion ;)

 You've also had several responses to this question along much briefer lines with pantelei4 giving the most concise answer of all (short and to the point  :-+).

 Whilst your assertions appear to be based on the theoretical limitations of generation and measurement of waveforms at high frequencies, such assertions would be more appropriate in a thread such as that linked to below where the facility to generate high enough frequencies to make what you're saying rather more relevant than here where a comparison of two very similar models of cheap ARB generators by Feeltech is being discussed.

https://www.eevblog.com/forum/testgear/siglent-ssg3000x-series-rf-signal-generators/msg1803173/#msg1803173

 The effects you speak of, are likely unmeasurable by most users of these Feeltech arbitrary wave/function generators so are of little significance here.

 The closest a proud owner of any of these generators will get to experiencing the effects you're describing is that of overlooking the need to properly terminate their BNC interconnecting cables. Anyone posting here about their FY6*** not meeting their frequency specification on sine waves will usually accept the friendly advice to terminate the cable with a 50R dummy load and try again, usually without further argument.

 As far as the topic of discussion in this thread goes, we seem to have speculated as much as the scant information on the actual device itself (the new FY6900) goes. It's now just a matter of time waiting for the reviews to appear. Until then, it rather looks like the discussion will remain in hiatus. BTW, having wandered 'back on topic', does anyone have any idea of the likely release date(s) of this latest and greatest from Feeltech (Feelelec)?

JBG
 

Offline Jacon

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Re: Fy6800 vs Fy6900
« Reply #116 on: July 20, 2019, 05:13:17 pm »
...
BTW, having wandered 'back on topic', does anyone have any idea of the likely release date(s) of this latest and greatest from Feeltech (Feelelec)?
JBG
According to Banggood FY6900 site, EU -60MHz versions are "in stock" today, shipping in 24h, while US versions
shipping are expected from 28th July  ;)
Overall 102 sold till now.
« Last Edit: July 20, 2019, 05:15:20 pm by Jacon »
 
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Offline radiolistener

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Re: Fy6800 vs Fy6900
« Reply #117 on: July 20, 2019, 05:47:57 pm »
Anyway, all I can advise is that you go through the literature again and take another look whilst keeping in mind what ou've learnt here.

There is no literature which can approve HiZ amplitude calibration for high frequency 50 Ohm output of signal generator.  :horse:
 

Offline radiolistener

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Re: Fy6800 vs Fy6900
« Reply #118 on: July 20, 2019, 05:58:19 pm »
The answer in the case of these Feeltech generators is no (at least for the moment - if development of an OSS front panel firmware package ever resumes (seems rather unlikely though) you may well get the opportunity to add this feature to your "Wish List").

Ok, thanks, this is what I'm asked for. I already know it shows incorrect voltage and you're needs to recalculate it each time when you need to setup amplitude. I don't need for explanation, I already know pitfalls due to this bug and know that you can still use it, but needs to take into account this behavior. It will leads to a lot of confusion and a lot of mistakes. The question was if it's possible to fix it. So, the answer is no. This is sad.  :-\
« Last Edit: July 20, 2019, 06:04:00 pm by radiolistener »
 

Offline Andreas

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Re: Fy6800 vs Fy6900
« Reply #119 on: July 20, 2019, 06:03:56 pm »
Why do you complain?

There are more quirks on these cheap hobby generators like
- 80% AM is in reality only 65% and the amplitude is too low.
- when changeing the frequency over USB interface the AM modulation is switched off.

https://www.eevblog.com/forum/testgear/fy6800-dds-signal-generator-questions/msg2502990/#msg2502990

So for the price you will have to arrange with the "features"

with best regards

Andreas
 
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Offline radiolistener

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Re: Fy6800 vs Fy6900
« Reply #120 on: July 20, 2019, 06:07:32 pm »
Why do you complain?

May be manufacturer will find all these issues and it will be fixed. If you don't complain, then manufacturer even will not know that there is something wrong with their device.   :-//

I just thought to buy this sig-gen, but this "HiZ amplitude" is a real stopper. I'm thinking how I will convert real amplitude to these "HiZ" and will get a lot of mistakes due to that, this HiZ is real head pain.
« Last Edit: July 20, 2019, 06:18:06 pm by radiolistener »
 

Offline Johnny B Good

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Re: Fy6800 vs Fy6900
« Reply #121 on: July 20, 2019, 06:55:02 pm »
You seem to have a lot of criticism of a sub-$100 amateur-grade piece of equipment that you've apparently never seen or touched!  And some interesting ideas about impedance that seem like the ham-radio equivalent of audiophoolery to me--but I'll leave all that alone. 

The FY6x00 series are low-cost AWGs, not serious RF-generators.  The fact that some can stretch all the way to 60MHz doesn't make them suitable for any serious RF work, IMO.  I have other tools for this with better frequency accuracy and lower phase noise--I wouldn't even think of using this tool as serious RF generator and mine only goes to 15Mhz anyway.  I would guess, as I said before, that the vast majority of these are being used with high-impedance loads.  I suspect a lot of them are connected to oscilloscopes and drawing pictures.

Some--and only some--of your comments may make some sense if you are working on RF power systems, but as for low-level signals, it is very common to have an intentional impedance mismatch where a low impedance output drives a higher impedance input.  This is how you keep distortion low, for example. Circuits are commonly designed this way going into the many-MHz and beyond.  Impedance matching has its place, but that place isn't everywhere.

 Are you thinking what I'm thinking?  >:D

 Those comments are pretty close to my own thoughts on the matter of radiolistener's contributions to this thread.

 radiolistener appears to have a very tenuous grasp of the subject. One give away being his error in referring to a 1Vpp in 50 ohms as 0dBm50 when in fact it's actually very close to +4dBm50. 0dBm50 is represented by a p-p voltage of 634mV (224mV rms).

 The 0dBm600 figure of rms voltage in common use within the audio industry is burned into my mind as 775mV, surprisingly close to a 2Vpp value at 2.191919 Vpp.

 Aside from that goof, he lost all credibility by claiming a VSWR of 1.3 from the effect of a few centimetres of wire (15cm, istr) on a 3.5MHz test signal (or was it 3 to 5MHz? ICBA to go back and check - whichever it was, it makes very little difference).

 My best guess from these clues, is that radiolistener is a shortwave listener with ambitions of becoming a licensed "Radioham", using an HF transceiver as his shortwave radio come signal generator. How often do we see measured VSWR mentioned in the context of signal generators (especially the low end variety we're currently discussing)? The only other kit where I see mention of directional couplers and VSWR as a matter of course, are Vector Network Analysers (VNA).

 The suspicion that he's been experimenting at the bottom end of the 80 metre ham band leads me to put two and two together and get four (five, if they're large values of two). I may be well off the mark but that's my best guess for what it's worth. >:D

JBG
 
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Offline CDaniel

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Re: Fy6800 vs Fy6900
« Reply #122 on: July 20, 2019, 07:29:55 pm »
Why do you complain?

May be manufacturer will find all these issues and it will be fixed. If you don't complain, then manufacturer even will not know that there is something wrong with their device.   :-//

I just thought to buy this sig-gen, but this "HiZ amplitude" is a real stopper. I'm thinking how I will convert real amplitude to these "HiZ" and will get a lot of mistakes due to that, this HiZ is real head pain.

You better buy a proper HF voltmeter and stop complaining about this non sense ...
After all this talking nobody understand what do you want actually . Every generator has an output attenuator , so the series resistance will cause errors if the load is not exactly as expected .
 
The following users thanked this post: Jacon, Johnny B Good

Offline Johnny B Good

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Re: Fy6800 vs Fy6900
« Reply #123 on: July 20, 2019, 08:03:15 pm »
...
BTW, having wandered 'back on topic', does anyone have any idea of the likely release date(s) of this latest and greatest from Feeltech (Feelelec)?
JBG
According to Banggood FY6900 site, EU -60MHz versions are "in stock" today, shipping in 24h, while US versions
shipping are expected from 28th July  ;)
Overall 102 sold till now.

 Thank you for that information, Jacon.

 It looks like we might get some answers to our speculations very soon (Blogs, Youtube video reviews etc). I've just had a search for reviews and youtube videos but, as was the case a few hours earlier when I last checked, the only results were seller advertising and nothing on youtube. This thread is actually the third hit on the first page of a duckduckgo search! ::)

JBG
 

Offline radiolistener

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Re: Fy6800 vs Fy6900
« Reply #124 on: July 20, 2019, 08:10:40 pm »
radiolistener appears to have a very tenuous grasp of the subject. One give away being his error in referring to a 1Vpp in 50 ohms as 0dBm50 when in fact it's actually very close to +4dBm50. 0dBm50 is represented by a p-p voltage of 634mV (224mV rms).

This is LIE! I never referred 1 Vpp as 0 dBm. I referred 2 Vpp as 10 dBm. Also I indirectly mentioned 1 Vpp as 3.9 dBm.

So, YOU'RE LIAR!   >:(

Since you don't know exact dBm value for 1 Vpp at 50 Ohm, I can say: 1 Vpp = 3.9794 dBm at 50 Ohm

Also you're wrong, here is your mistake: 0 dBm is NOT 634 mV, actually it is 632.4555 mVpp or 316.2278 mVpk.

The 0dBm600 figure of rms voltage in common use within the audio industry is burned into my mind as 775mV, surprisingly close to a 2Vpp value at 2.191919 Vpp.

Here is also your mistake, 0 dBm at 600 Ohm load is not "2.191919 Vpp", actually it is 2.19089023002066 Vpp  :-//

My best guess from these clues, is that radiolistener is a shortwave listener with ambitions of becoming a licensed "Radioham"

here is again your mistake, I already have license and callsign for at least several years.

The suspicion that he's been experimenting at the bottom end of the 80 metre ham band leads me to put two and two together and get four (five, if they're large values of two). I may be well off the mark but that's my best guess for what it's worth.

This is again your mistake. Currently I'm experimenting with direct sampling SDR on FPGA which directly captures ether with 122.880 MHz ADC and performs digital down conversion. It allows to listen and transmit at any frequency from DC up to 61 MHz. Also I'm experimenting with 144 MHz band.

If you're thinking that you can hang noodles on my ears, you're also wrong. You can tell your tales that impedance doesn't matter for 60 MHz generator to someone other who don't know about it, but don't tell me that.

I just asked you if it's possible to fix this issue in the generator. I didn't asked you to explain if I need this or not. I already know what I need. And I expected simple answer from you, one of the following:
- "yes it is possible, here is how it can be done <...>"
- "no, it is not possible, but it will be available soon"

I already got your answer - "This is not possible. And nobody is working on this at the moment". So, please stop lie and manipulating.

Best regards
« Last Edit: July 20, 2019, 08:39:51 pm by radiolistener »
 


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