Products > Test Equipment
Banggood 50 ohm BNC feed-through terminator - a quick review
Someone:
--- Quote from: Pinkus on July 07, 2017, 09:17:42 am ---
--- Quote from: tggzzz on July 07, 2017, 07:37:59 am ---
--- Quote from: bjcuizon on July 07, 2017, 04:48:44 am ---I also wonder why tek/hp feedthru terminators can cost much. Are we paying for the name brand it has? Or does it have really really high quality parts used?
--- End quote ---
You are paying to avoid wasting your valuable time, by avoiding "surprises". The surprise in the first message is easy to spot, but you can waste a lot of time/effort with more subtle and/or intermittent faults.
"No DP manager lost their job because they bought IBM", and "no EE lost their job because they bought HP/Agilent/Keysight/Tek"
--- End quote ---
I wonder how a feed through terminator from a high brand will be constructed.
If you look at this picture
https://www.eevblog.com/forum/testgear/banggood-50-ohm-bnc-feed-through-terminator-a-quick-review/?action=dlattach;attach=329772;image
it is easy to see: you just have to accidentally drop it once (maybe it already was during shipping) and you can never be sure if each of the fragile resistors will have survived this, or if -due to the mechanical shock- there are micro cracks somewhere which will result in unpredictable results ... now or in a year from now.
Are Fluke, Tektronix or Keysight feed-through terminators using the same construction? Any volunteer with a jab saw? >:D
Though I remember that a Hameg (=Rohde & Schwarz) terminator was not much different (https://www.mikrocontroller.net/attachment/98198/HZ22.jpg)
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You could easily damage a brand name attenuator or terminator by dropping it, the extra cost is partly in the calibration/verification and partly the nice box!
CJay:
--- Quote from: stj on July 07, 2017, 10:40:06 am ---who would this compare to using a T-piece and a 50ohm terminator originally intended for networking??
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In the past I've found that arrangement OK up to around ~100MHz but that was the limit of what I could measure at the time, I've not checked them again since I got better gear but I'd expect the lead length to have some effect.
They're usually 'just' an axial leaded resistor crimped into a BNC centre pin and the trailing end is usually held in contact with the shell by a tight fitting plastic cap, there are some (DEC) which have a metal cap crimped over the end which may be better
djnz:
I have bought these from Aliexpress in the past. Same problem with mine - one was 50 ohm, the other was 100 ohm. I told the seller about this and they sent me two more 50 ohm ones, which turned out to actually be 50 ohm.
idpromnut:
I have built a couple of 50ohm terminators using 2 vertically mounted SMA connectors (of opposite gender): soldered the four posts back to back, and then bridge the conductor pins with 2 100ohm resistors. Shield the whole mess with some copper tape and you're done.
TheSteve:
--- Quote from: stj on July 07, 2017, 10:40:06 am ---how would this compare to using a T-piece and a 50ohm terminator originally intended for networking??
--- End quote ---
As was already mentioned those terminators generally perform pretty terrible over 50 MHz due to the internal design. If I have time this evening I'll plot the SWR on one.
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