Author Topic: Another Warning of Cheapo China (Just a Terminator)  (Read 5575 times)

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Offline Mechatrommer

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Another Warning of Cheapo China (Just a Terminator)
« on: May 11, 2011, 10:48:38 am »
not so genius though. just a 50 ohm terminator which measured as shorted 0 ohm. this is a "free" replacement from previous wrongly (broken?) sent terminator. the real joke is, there is etching saying its a 50 ohm terminator. dissapointed and dont want for another wait (esp with hongkong post overloaded), i rip it apart, luckily i didnt break anything. turned out the cheapo resistor inside got its both leads shorted. DIY and now its fixed. the only good thing is, the seller is honest and did send the replacement for free. ebay seller id: chinarf...
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline Kiriakos-GR

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Re: Another Warning of Cheapo China (Just a Terminator)
« Reply #1 on: May 11, 2011, 11:00:27 am »
This story just ring a bell to me , about the Cheap female BNC to dual banana (adapter) .

Looks identical with the branded, but the positive connector point in the center,
has wrong diameter (larger), and causes problems.

I got two used ones made by Pomona , and this solved my problem for good.    ;)
 

Offline david77

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Re: Another Warning of Cheapo China (Just a Terminator)
« Reply #2 on: May 11, 2011, 11:23:03 am »
Oh yes, that rings a bell.

Back in the days of 10Base2 LAN I made my experience with cheap china BNC plugs, terminators and T's.
Hours of fun!

Btw. I still have some 10Base2 LAN working at home & at the office. They're both long runs that I have no intention of updating as long as they work. Involves much pulling and crawling through dusty dirty spaces...
 

Offline Mechatrommer

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Re: Another Warning of Cheapo China (Just a Terminator)
« Reply #3 on: May 11, 2011, 12:27:35 pm »
Looks identical with the branded, but the positive connector point in the center,
has wrong diameter (larger), and causes problems.
i will be really pissed off if this kind of problem is not fixable with diy. wrong... very wrong.

Back in the days of 10Base2 LAN I made my experience with cheap china BNC plugs, terminators and T's.
i got "shorted" T as well from earlier package after several use. DIY rip apart fixed it (took out the culprit, a long thin metal wire like inside), had fun and at least i know how the cheapo T is constructed. i just dont have any idea how crappy they did their job in the factory.
« Last Edit: May 11, 2011, 12:29:48 pm by Mechatrommer »
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline vk6zgo

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Re: Another Warning of Cheapo China (Just a Terminator)
« Reply #4 on: May 12, 2011, 06:48:54 am »
Even the Tektronix through terminations aren't that brilliant when you open them up.

Just a leaded resistor,no special pcb or SMD device.

The new ones may be better, though.

They do work,until the top & bottom bits separate after many years of use.

VK6ZGO
 

Offline scrat

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Re: Another Warning of Cheapo China (Just a Terminator)
« Reply #5 on: May 12, 2011, 10:00:18 am »
In my ingenuousness, I always thought 50 Ohm terminators were peculiarly made to ensure real (in the mathematical sense, i.e. resistive) 50 Ohm impedance over a specified frequency range...
One machine can do the work of fifty ordinary men. No machine can do the work of one extraordinary man. - Elbert Hubbard
 

Offline Mechatrommer

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Re: Another Warning of Cheapo China (Just a Terminator)
« Reply #6 on: May 12, 2011, 11:13:08 am »
In my ingenuousness, I always thought 50 Ohm terminators were peculiarly made to ensure real (in the mathematical sense, i.e. resistive) 50 Ohm impedance over a specified frequency range...
lol. i guess the normal resistor type will be good (flat impedance) up to several hundreds MHz, and make sure its metal encased to avoid EM leak. where in GHz range, parasitics (inductance and capacitance) start to play their role. and there is no "real resistive only" impedance on earth, there will be only R,L,C together, but not separated. at least the agilent app note said that.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline saturation

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Re: Another Warning of Cheapo China (Just a Terminator)
« Reply #7 on: May 12, 2011, 11:55:17 am »
If you have a chance to read up on resistors, SMD film types give the best response to the limits of BNC, ~> 1GHz or more.  Putting a through hole resistor as pictured in mecha's terminator, can give parasitics mainly due to the leads and other things in the construction of that type of resistor.

When I'm in a pinch, I use resistors to terminate too, just keep the leads as straight as possible, and its likely good only to ~< 500 MHz; but well within the Rigol 1052e capabilities.



In my ingenuousness, I always thought 50 Ohm terminators were peculiarly made to ensure real (in the mathematical sense, i.e. resistive) 50 Ohm impedance over a specified frequency range...
lol. i guess the normal resistor type will be good (flat impedance) up to several hundreds MHz, and make sure its metal encased to avoid EM leak. where in GHz range, parasitics (inductance and capacitance) start to play their role. and there is no "real resistive only" impedance on earth, there will be only R,L,C together, but not separated. at least the agilent app note said that.

Best Wishes,

 Saturation
 

Offline scrat

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Re: Another Warning of Cheapo China (Just a Terminator)
« Reply #8 on: May 12, 2011, 01:08:28 pm »
In my ingenuousness, I always thought 50 Ohm terminators were peculiarly made to ensure real (in the mathematical sense, i.e. resistive) 50 Ohm impedance over a specified frequency range...
lol. i guess the normal resistor type will be good (flat impedance) up to several hundreds MHz, and make sure its metal encased to avoid EM leak. where in GHz range, parasitics (inductance and capacitance) start to play their role. and there is no "real resistive only" impedance on earth, there will be only R,L,C together, but not separated. at least the agilent app note said that.


That's right, of course, rigorous specs for a termination load will say how much it will deviate from resistive 50 Ohm).
The fact that even Tektronix used through hole resistors made me think of the fact that one expects the specialized manufacturers to make things radically different from what anyone of us could make, just to see that in the end diy is the best option for simple things like these.
Another example could be the test leads supplied with a cheap (but maybe with decent, too) multimeters: they're usually made to last for a couple of measurements, but usually anyone with a little ability and simple tools can fix them to last at least some months.
One machine can do the work of fifty ordinary men. No machine can do the work of one extraordinary man. - Elbert Hubbard
 

Offline vk6zgo

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Re: Another Warning of Cheapo China (Just a Terminator)
« Reply #9 on: May 13, 2011, 08:51:45 am »
In all fairness to Tektronix,the terminations I have had occasion to see "torn down"were of uncertain age.
Normally,they are very reliable,so you may find terminations in the average workshop which date back to the age of
the 545B,with matching characteristics.
If you aren't a Tek part No. guru,they all look pretty much alike.

The ones I've seen look as if they were hand made,where leaded resistors would be the easiest type to use.
Maybe the newer ones use SMD components.

It is fun to check terminations with a Spectrum Analyser,Tracking Generator,& a Directional coupler.
Out of one 50 ohm term that looked like the OPs one,another with a fluted grey plastic body,several 50 ohm 1kW
Test Loads,& two 20dB attenuators in cascade,the latter gave the best result (80dB return loss),with the big Test
Loads next,& the two so-called  50 ohm terminations the worst.
No, I don't have the figures to hand,it was done several years ago at work.

I'm not sure if the Attenuators were Agilent or Bird,the Test Loads were Bird and a generic Chinese one,the terminations were generic also,possibly from RS Components.
From memory,the tests were over about a 300MHz range,centred on 480 MHz.

VK6ZGO


« Last Edit: May 13, 2011, 08:58:14 am by vk6zgo »
 

Offline saturation

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Re: Another Warning of Cheapo China (Just a Terminator)
« Reply #10 on: May 13, 2011, 11:43:56 am »
Over the past year I've noticed that local US sellers have prices =< China prices, believe it or not.  I rarely buy direct from China for the entire year and continue to do so.

Another side bit of news that matches that, my friends in middle management for manufacturing say they are moving out of China, and looking to other Asian countries and back to America and leaving their China operations for the Chinese market.
Best Wishes,

 Saturation
 

Offline scrat

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Re: Another Warning of Cheapo China (Just a Terminator)
« Reply #11 on: May 13, 2011, 11:56:55 am »
Over the past year I've noticed that local US sellers have prices =< China prices, believe it or not.  I rarely buy direct from China for the entire year and continue to do so.

Another side bit of news that matches that, my friends in middle management for manufacturing say they are moving out of China, and looking to other Asian countries and back to America and leaving their China operations for the Chinese market.

Isn't China manufacturing quality rising? Are they only increasing their labour costs?
If it will be as you say, maybe it's good news, the economy is rebalancing a little (with its natural negative feedback!).
One machine can do the work of fifty ordinary men. No machine can do the work of one extraordinary man. - Elbert Hubbard
 

Offline saturation

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Re: Another Warning of Cheapo China (Just a Terminator)
« Reply #12 on: May 13, 2011, 02:55:28 pm »
Yes, very much so, so is their cost of living, regulation and cost of doing business.  

For example, look at the Rigol 1052E, the price difference between most any US seller and direct from China is almost nil for over a year now.

Over the past 2 years, eBay Chinese vendors for cellphone accessories, laptop PSU replacements etc., have gradually disappeared and local US sellers [ likely of ~ Chinese products] are =< in price for the direct from China vendors.  It currently, looks more like shipping costs are killers.  

However, you can still find Chinese stuff that beat the US hands down, like battery cases, I bought a few > 1 year ago for $1 for 10 pieces, while its sold here for $1 each, shipping included.  I'm not sure why they are still so cheap, but get it while you can.








Isn't China manufacturing quality rising? Are they only increasing their labour costs?
If it will be as you say, maybe it's good news, the economy is rebalancing a little (with its natural negative feedback!).
Best Wishes,

 Saturation
 

Offline Kiriakos-GR

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Re: Another Warning of Cheapo China (Just a Terminator)
« Reply #13 on: May 13, 2011, 07:15:10 pm »
Well I have long time to say the words : I do favor UNI-T ...  ( among others)   ;D

And the reason is, that  they are products with acceptable quality level,
and additionally have one pricing policy , that is almost the same worldwide. ( I prefer few more $ and local warranty )

Also I have take an personal oath, to never ever buy again, anonymous products.
From China or elsewhere.


     
 


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