Review: Multicomp Pro BNC Terminator 50 Ohm 0.5W SPC15280 - Page 1
Forum section: electronics / general

author: killingtime
author_rank: Regular Contributor
timestamp: May 15, 2023, 01:18:38 pm
content: Multicomp Pro BNC Terminator 50 OhmModel: SPC15280Bought two of these from CPC to terminate my scope inputs at 50 Ohms. Scope inputs are 1M in parallel with 14pF. I was going to buy some Amphenol terminators which are much more expensive but after doing some calculations and factoring in the scope capacitance, it's a pointless exercise beyond about 300MHz as the capacitance dominates regardless of how accurate your 50 Ohm terminator is.LTSpiceIV sim attached. At 300MHz the voltage is down almost 17%, and that's assuming a perfect 50 Ohm terminator. I think expensive terminators make more sense if you have a scope with very low capacitive inputs, or you need to run higher power. The only downside is the power rating, which limits you to 5V RMS. OK for the purpose.Specification:Multicomp is a CPC/Farnell own brand.Impedance: 50 OhmsPower: 0.5WBody : Brass, Nickel-PlatedInsulator : DelrinPin : Brass, Gold-PlatedCost 1.30 GBP Inc TaxesSWR Frequency (MHz)1.1 4201.2 7201.3 9301.4 11101.5 12301.6 13501.7 14701.8 15901.9 16802.0 17702.23 20002.85 25003.70 3000

author: Texmisure
author_rank: Newbie
timestamp: July 17, 2023, 06:57:48 am
content: 0.5w or 5w? You see a stamped 5w(farnell site) on the picture, the dot is not evident!Regards

author: CosteC
author_rank: Regular Contributor
timestamp: July 18, 2023, 06:05:42 am
content: Well, lets say it is rather cheap thingIt does not have any sensible datasheet, so use over, give or take 100-300 MHz is questionable.If your SWR graph comes from NANO-VNA or similar then you can get well better terminators - with SWR below 1.1 @ 3 GHz easilly. Not for 2 GBP however.Oscilloscopes loading are quite normal and unavoidable. 14 pF is not bad.I think first terminator with datasheet is POMONA Model 3840. Even AMPHENOL 000-46650-51RFX does not state SWR or max frequencyhttps://www.amphenolrf.com/000-46650-51rfx.html(shame Amphenol!)

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: July 27, 2023, 12:14:30 am
content: I have a bunch of Amphenol 50 ohm BNC loads. Brand New. As far as I remember, they are only good for HF. Nowhere near 1 GHz.I also have a bunch of SMA Shuner loads, which are quite good.I do not know why they are calling this thing a terminator. It is a load. A terminator has input and output. At least that is my understanding. It seems that loads and "terminators" both get called "terminators" by various manufacturers. Maybe I am not correct, but I think that thing is a LOAD.Another thought is that whatever else you are using to connect the load as a "terminator" is causing the poor freq response. However, Like I said, in my experience BNC loads are not very good at higher freq. Maybe there are some that are, but I have not seen one.

author: bdunham7
author_rank: Super Contributor
timestamp: July 27, 2023, 12:36:29 am
content: Quote from: killingtime on May 15, 2023, 01:18:38 pmYou should check your actual scope BW performance with the terminator, it may be much better than your sim predicts. The sim doesn't take into account that the capacitance of the oscilloscope may have some resistance in series with it nor does it know what inductances of the input parts are. I recently tested some 350-400MHz scopes with a NanoVNA as part of another discussion and I tried a cheap-ish 50R inline terminator as well--the results were not so terrible.

author: tooki
author_rank: Super Contributor
timestamp: July 27, 2023, 09:41:39 am
content: Quote from: Wallace Gasiewicz on July 27, 2023, 12:14:30 amNah, you’ve made up a weirdly narrow definition in your mind. Everyone calls them terminators because they’re used to terminate cables.Take a look at, for example, old 10Base-2 (BNC) Ethernet: you’d run the bus using tees to branch off to each device (including the last devices on the bus!), and then at each end of the bus, you’d stick on a terminator onto the unused jack of the tee.Old-school SCSI was similar: it needed a terminator at each end of the bus.Passthrough terminators exist, too. That doesn’t make non-passthrough ones any less of a terminator.