Author Topic: Oscilloscope questions.  (Read 2325 times)

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Offline wade7575

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Oscilloscope questions.
« on: September 29, 2016, 06:25:23 am »
My son is wanting to a few projects with me and one happens to be an Elenco AM FM Radio kit and I want to use an oscilloscope during the build like they suggest to help him get the most out of building the kit,I have a bit of an understanding of how an oscilloscope works and plan on watching a few videos that I found on youtube.

What I'm woundering is they say in the manual when you are tuning it you need to be able to see a clipped wave in the display and I was looking at getting a JYE Tech DSO138 DIY Kit but I'm not sure if it will display that kind of signal,I was also that the JYE Tech DSO138 kit is not very good past 100mhz is this true,these are the 2 I was thinking of getting can anyone tell me if either will work,I also choose these as they are small and compact witch would be great for me as I do not have a lot of storage room.

http://www.banggood.com/DSO138-DIY-Digital-Oscilloscope-Kit-Electronic-Learning-Kit-p-969762.html

http://www.banggood.com/DSO068-DIY-Oscilloscope-Kit-With-Digital-Storage-Frequency-Meter-ATmega64-AVR-Microcontrol-p-981017.html

Also if you look at this link and go to page 14 you can see the picture of the wave I'm wanting to know about.

https://www.manualslib.com/manual/235858/Elenco-Electronics-Am-Fm-108tk.html
 

Offline MosherIV

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Re: Oscilloscope questions.
« Reply #1 on: September 29, 2016, 06:41:17 am »
Do not waste your time or money on crap like that.
There is no way some cheap digitizer can be any good as a oscilloscope.

They normally just use the on board ADC at max capture rate and then display it. Most of them can only aceive 50M samples per sec which means they only have effectively 25MHz bandwidth.

They have pretty much no input protection, so any signal above 5 to 10V will destroy the ADC / processor.

If you want cheap, look on ebay, there are some going for around £50 for an analogue.
For around £120 you can get new low end digital scopes that knock the spots off that crappy thing you are looking at.
 

Offline MK14

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Re: Oscilloscope questions.
« Reply #2 on: September 29, 2016, 06:43:30 am »
I'd suggest building the kit, without an oscilloscope. If you have not already got one.
The instructions, seem to give directions on how to build the radio, with or without an oscilloscope.

The scope you linked to, would need to be built (it is a kit as well). Also it is not very good as regards scopes go. E.g. Its frequency range is very poor. You might be better off, getting a very cheap second hand, REAL scope. If you have room for it. Or delaying getting a scope until, the beginners electronics experience picks up.
 

Offline tautech

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Re: Oscilloscope questions.
« Reply #3 on: September 29, 2016, 06:44:43 am »
Welcome to the forum.

A reasonable scope along with a DMM are 2 of the tools that you can think of as an investment for gaining knowledge and "tuning" projects. There'll be lots of advice as to what's best for you but so often it comes down to "needs" and budget.
There's commonly 2 schools of thinking: a 2nd hand CRO or a new DSO.
If you can afford new it's the best way to go as older CRO's are problematic for the novice to repair should they fail.
Something like this can do most basic needs.
http://www.siglentamerica.com/pdxx.aspx?id=26&T=2&tid=1
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Offline wade7575

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Re: Oscilloscope questions.
« Reply #4 on: September 29, 2016, 07:10:40 am »
I may look into getting a cheap used scope,I'm not worried about building anything however as I can do threw hole or SMD without any problems what so ever as I have built a lot kits for myself and other people I just haven't had the need to get a scope for any project until now although I know it is not a must have item for this project and just thought it would be fun to play with one so I could do some learning my son.
 

Offline MK14

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Re: Oscilloscope questions.
« Reply #5 on: September 29, 2016, 07:16:23 am »
I may look into getting a cheap used scope,I'm not worried about building anything however as I can do threw hole or SMD without any problems what so ever as I have built a lot kits for myself and other people I just haven't had the need to get a scope for any project until now although I know it is not a must have item for this project and just thought it would be fun to play with one so I could do some learning my son.

If you ask/look around, you might be able to get one for free. E.g. Universities/Businesses may be getting rid of old ones. Some of the free lists (Craigs etc), may have them as well.

I thought it was your very first kit. If you have already made many kits, then it is kind of time to get a scope now.
 

Offline Gyro

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Re: Oscilloscope questions.
« Reply #6 on: September 29, 2016, 07:25:56 am »
Do not waste your time or money on crap like that.
There is no way some cheap digitizer can be any good as a oscilloscope.

They normally just use the on board ADC at max capture rate and then display it. Most of them can only aceive 50M samples per sec which means they only have effectively 25MHz bandwidth.

They have pretty much no input protection, so any signal above 5 to 10V will destroy the ADC / processor.

If you want cheap, look on ebay, there are some going for around £50 for an analogue.
For around £120 you can get new low end digital scopes that knock the spots off that crappy thing you are looking at.

Just to clarify, the DSO138 is a very cheap (sub $20), fun little kit for low frequency stuff. It is only 1Msps, so only good up to a couple of hundred kHz. It's not going to work at all for RF, audio frequency at best, 50V max.
Chris

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Offline rstofer

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Re: Oscilloscope questions.
« Reply #7 on: September 29, 2016, 09:09:10 am »
OK, I'm sold!  I just ordered two of the kits for my grandson and I to assemble/test.  I have never spent much time with radio circuits and my grandson is just starting EE school so he can use the practice.

You can get some decent scopes on eBay if you look for long time sellers offering a return policy.  Some will be just cleaned up, some will be tested and verified and the higher priced scopes will be calibrated.

I bought a Tektronix 485 about 12 years ago and it has worked perfect.  I paid about $200.  The only one I see on eBay that is worth postage is going for $650.  The rest are junk!
http://www.ebay.com/itm/Tektronix-485-Dual-Trace-350-MHz-Portable-Oscilloscope-/130682265274

Although I like analog scopes, I just bought a Rigol DS1054Z and the extra features make all these used scopes a waste of money.  Yes, if I needed more than 100 MHz, I might look again but too many people are buying used analog scopes and winding up with junk.  Look at all the descriptions that read "Sold for parts", "Powers up but...".  And I already have a fully functional 350 MHz scope (with no advanced features).

If your hobby is going to take you anywhere, you will need a decent scope.  I would think 100 MHz is about the lower limit on bandwidth and, personally, I want 4 channels more than any other feature.

That is a great project!  I am looking forward to my kits getting here next week.
 

Online Brumby

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Re: Oscilloscope questions.
« Reply #8 on: September 29, 2016, 01:39:47 pm »
the JYE Tech DSO138 kit is not very good past 100mhz is this true,

You are off by about 3 orders of magnitude.  100KHz is more like it, 200KHz tops.

Don't look at it as being useful for any much more than audio.  I have one and it's a bit of fun, but don't consider it as a serious scope. Please.
 

Offline wade7575

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Re: Oscilloscope questions.
« Reply #9 on: September 29, 2016, 02:03:57 pm »
I did not figure it to be a real serious peace of harware I myself have never used a scope and did not know what I would need for sure to use a scope to build the radio with,I know a scope is not a must have the radio kit I just figured if the DSO138 could do the job it would be another fun kit for me to build plus it's small and not to costly,but seeing that's out of the queston I'm not going to worry about unless I can find a used one for around 100 bucks.

the JYE Tech DSO138 kit is not very good past 100mhz is this true,

You are off by about 3 orders of magnitude.  100KHz is more like it, 200KHz tops.

Don't look at it as being useful for any much more than audio.  I have one and it's a bit of fun, but don't consider it as a serious scope. Please.
 

Offline Gyro

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Re: Oscilloscope questions.
« Reply #10 on: September 29, 2016, 07:06:23 pm »
By all means build one for fun (that little color display really is cute :D). It's even capable of useful work for visualising stuff when playing around with audio, opamps, timer circuits etc. It has a useful input senitivity range, it even has on-screen measurements.... Just don't try to use it for RF!

P.S. Make sure it's a genuine one! The Sainsmart and other fakes are nothing but trouble. http://www.jyetech.com/forum/viewforum.php?f=18&sid=f7b11da47f69d3b4c26a35306f5d1741
« Last Edit: September 29, 2016, 07:08:29 pm by Gyro »
Chris

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