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| Banggood 50 ohm BNC feed-through terminator - a quick review |
| << < (6/15) > >> |
| stj:
i actually thought if anything, the T-piece would be the problem by causing reflections. |
| alm:
Not if the terminator has terrible VSWR above 50 MHz (I have not verified it, but 10baseT does not require it, and I trust TheSteve's assertion). The short stub from the terminator (assuming you connect it directly to a high-impedance input) will not become an issue until much higher frequencies. Has anyone observed a difference between the cheap 10base2 tees and proper RF ones? I would expect the construction to be quite similar, but I have never used the 10base2 ones for critical work. |
| edpalmer42:
I've bought various terminators over the years. Most of my work is at 10 MHz or less so just about anything will work. But I've measured some terminators that are likely 10base2 at higher frequencies so I'd know which ones to grab if I needed to. At 100 MHz, they all had a return loss > 30 dB (VSWR < 1.06). At 1 GHz, they varied from < 8 dB (>2.3) to > 18 dB (< 1.3). I've also measured various unmarked SMA terminators. They all measured > 28 dB @ 1 GHz. To make the measurements, I used a signal generator, directional coupler, and RF power meter. Calibration is questionable so take the actual numbers with a grain of salt. I suspect that if you tore apart a name-brand multi-GHz rated terminator, you'd find a very special style of resistor. Maybe a circular resistor that would be comparable to an infinite number of resistors in parallel instead of two or three resistors. Continuous soldered ground around the outside, no discontinuities anywhere, etc. Bottom line, if you can measure your terminators, or you work at low frequencies, 10Base2 might be all you need. Ed |
| TheSteve:
This is a standard low cost BNC 50 ohm terminator - nothing special, it likely represents what you can expect from one. Good enough to use to 200 MHz + |
| CJay:
--- Quote from: TheSteve on July 08, 2017, 06:53:05 am ---This is a standard low cost BNC 50 ohm terminator - nothing special, it likely represents what you can expect from one. Good enough to use to 200 MHz + --- End quote --- That's nice to see, it's satisfying to see my simplistic measurement was on the money. Have you a 10B2 T-Piece and would you mind throwing it into the mix to see how that performs? |
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