Banggood 50 ohm BNC feed-through terminator - a quick review

[TheSteve]

Some time last year someone posted that Banggood had 50 ohm feed-through terminators for what is a reasonable price(6.66 USD shipped for a pair). I ordered a pair in December last year but they never arrived and a few months back Banggood issued me a refund. I was shocked yesterday when they arrived. It only took 7 months...

I did a quick check with a DMM and found one was near 50 ohms, the other though is 100 ohms - so quality control may be an issue.
Long story short the 50 ohm one actually works reasonably well.



Here is a picture showing SWR(return loss). I wouldn't really want to use these at 1 GHz but that shouldn't ever happen as any scope with such a high frequency will have a builtin 50 ohm terminator. For those with scopes up to 500 MHz without builtin 50 ohm terminators these will do the job though.


Resistor is close enough:

[BravoV]

For those with scopes up to 500 MHz without builtin 50 ohm terminators these will do the job though.

Steve, thank you, this is exactly what I'm expecting to hear. 

[alm]

The 100 Ohm one might be an open resistor if they used 2 100 Ohm chip resistors in parallel.

That seems very close to the specs of the Pomona 4119-50: VSWR < 1.1 up to 250 MHz and < 1.2 up to 500 MHz. That one uses a carbon film resistor. The Tek 011-0049-01 is better (VSWR < 1.2 DC-1 GHz). But still sounds like excellent value for the money.

[BravoV]

The 100 Ohm one might be an open resistor if they used 2 100 Ohm chip resistors in parallel.

That seems very close to the specs of the Pomona 4119-50: VSWR < 1.1 up to 250 MHz and < 1.2 up to 500 MHz. That one uses a carbon film resistor. The Tek 011-0049-01 is better (VSWR < 1.2 DC-1 GHz). But still sounds like excellent value for the money.

Yep, value for money for < 500 MHz works its very good.

As its full metal body, the physical built and mechanically is pretty decent imo, took a close up shot -> HERE (Beware of huge photo)

[TheSteve]

So far the 100 ohm one doesn't want to come apart. I haven't gone all crazy on it though.

[bjcuizon]

How about making one yourself, like mine..
https://www.eevblog.com/forum/projects/home-made-feed-through-terminator-for-bnc/msg1237711/#msg1237711

[bjcuizon]

By the way, can you give me a ballpark figure of what the VSWR is at 300MHz for this DIY Terminator I posted above? Given that I soldered the resistors on opposite sides to minimize stray capacitance. I cannot measure its performance because I do not have the right kit to do it. Thanks.

[TheSteve]

I can't really guess what it would be, but it is likely pretty decent. I know on my home brew SMA loads using three 0.1% 150 ohm 0603 resistors gives the best performance.

[BravoV]

So far the 100 ohm one doesn't want to come apart. I haven't gone all crazy on it though.

I tried too, looks like they glued the metal parts inside, still can't find way to open it up without destroying or at least chipping out the metal parts. 

[TheSteve]

So far the 100 ohm one doesn't want to come apart. I haven't gone all crazy on it though.

I tried too, looks like they glued the metal parts inside, still can't find way to open it up without destroying or at least chipping out the metal parts. 

OK, wrestled it open(they are threadlocked) - a pair of 100 ohm resistors.

[bjcuizon]

That's pretty neat though. What are the sizes/wattage of the resistors?

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?

[TheSteve]

They look to be 1206 resistors. I resoldered the resistors on the bad one and it is 49.75 ohms now. I am not convinced it will keep working though. While the resistors didn't fall off I can't help but think there is a crack in one of them.
The name brand ones are overpriced but I would think the internal construction is probably a decent amount nicer. I doubt they have hand soldered smt resistors going to the center conductor. Right now any stress on the center conductor can break the resistors.

[BravoV]

Steve, if you decided to fix it with the resistors like the ones you put in your home brew load as you mentioned above, please update us.

[lukier]

Thanks for testing. I just got 4 of these (I guess the same) few days ago:
https://www.aliexpress.com/item/P7001-2PCS-High-quality-BNC-to-BNC-Female-seat-50KY-50-ohm-matching-device-Q9-adapter/32661228102.html
and I wondered how good/bad these are. Thanks to your teardown now I see these are pretty much the same as the DIY ones I made a while ago

[BravoV]

Thanks to your teardown now I see these are pretty much the same as the DIY ones I made a while ago

As its clear it can be opened, I guess its time to mod it with better resistors or even construction to make it better at high freq ?

[lukier]

As its clear it can be opened, I guess its time to mod it with better resistors or even construction to make it better at high freq ?

Personally, I don't care as I only use such terminators on low end scopes that lack 50 Ohm input (Rigol DS1054Z, Micsig TO1074) and my higher performance scopes (LeCroy WaveRunner 6100A, Tektronix 2467) have 50 Ohm pathway, as IMHO every scope > 100-200 MHz should do.

If you are in the RF world then it might matter, but to be honest BNC connectors are not the best for higher frequencies anyway.

[tggzzz]

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?

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"

[Pinkus]

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?

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"

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?
Though I remember that a Hameg (=Rohde & Schwarz) terminator was not much different  (https://www.mikrocontroller.net/attachment/98198/HZ22.jpg)

[CJay]

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?
Though I remember that a Hameg (=Rohde & Schwarz) terminator was not much different  (https://www.mikrocontroller.net/attachment/98198/HZ22.jpg)

I reckon that as neat as the Banggood ones are, they will suffer from just being used let alone dropped, every time it's inserted into a 'scope or has a plug inserted it'll place mechanical stress on the solder joints unless it's potted somehow and I've no idea how that might affect the frequency response.

The Hameg one looks a better solution though I'd be surprised if the higher end, higher frequency ones from Fluke, Tek or Keysight are constructed that way, I'd suspect they're using something like the method used in the step attenuator here:

[stj]

how would this compare to using a T-piece and a 50ohm terminator originally intended for networking??

[Someone]

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?

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"

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?
Though I remember that a Hameg (=Rohde & Schwarz) terminator was not much different  (https://www.mikrocontroller.net/attachment/98198/HZ22.jpg)

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]

who would this compare to using a T-piece and a 50ohm terminator originally intended for networking??

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]

how would this compare to using a T-piece and a 50ohm terminator originally intended for networking??

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.