What is this RF part. - Page 1
Forum section: electronics / beginners

author: NPG
author_rank: Contributor
timestamp: March 14, 2025, 08:40:53 pm
content: I recently bought a large lot of assorted RF connectors on ebay.I am trying to identify the part pictured below.My guess is that they are either attenuators or inline terminators.PN engraved on them is "TEI 14949 TNA3-1000"I've google that.So they are Trompeter parts, yet I have not been able to find anything about them online. I have found different items that start with "TEI 14949" but end in different numbers, so am guessing that there was a complete product line from them designated by 14949.I tested them with a multimeter.The center pin has ~ 1M.No continuity between center and ground.So I'm leaning toward attenuator, as when testing a known 50inline terminator, the center pin was 0with 50between center and ground.I further tested with a function gen & scope, with the part in line and not.No real difference in PtP voltage on the low end of the RF spectrum.At ~ 3Mhz the PtP started dropping, and continued to drop further up.Baseline ~ 13Mhz PtP = ~9.25VTesting ~13 Mhz PtP = ~ 6.25VI am guessing the "A-3-1000" in the part number might mean Attenuation from 3Mhz - 1Ghz.Does anyone know where I can find some data on this animal?Thanks :-)

author: fzabkar
author_rank: Super Contributor
timestamp: March 14, 2025, 09:55:32 pm
content: See pages 38, 47 and maybe others:https://web.archive.org/web/20220326041437/https://web.archive.org/web/20140325105500/http://www.connecticc.com/pdfs/trompeter_catalog-3.pdfhttps://web.archive.org/web/20140325105500/http://www.connecticc.com/pdfs/trompeter_catalog-3.pdfEdit:The first link looks like an archive of an archive. :-?Edit #2:https://www.ebay.com/itm/391355674004(TNA3-75)

author: NPG
author_rank: Contributor
timestamp: March 15, 2025, 03:29:46 am
content: Quote from: fzabkar on March 14, 2025, 09:55:32 pmThank you!I think my animal is on page 38, bottom right side.The TNA3-R schematic matches my earlier multimeter measurement results.50to 75impedance matching pad.My guess is that the second number after "TNA3-" in the part number refers to the value in K \$\Omega\$s of the internal resistor.Quote from: fzabkar on March 14, 2025, 09:55:32 pmBet those have an internal resistance of 75K.Thanks. :-)

author: fzabkar
author_rank: Super Contributor
timestamp: March 15, 2025, 04:24:04 am
content: Quote from: NPG on March 15, 2025, 03:29:46 am50 ohms and 75 ohms are typical RF impedances. That's my understanding of the datasheet. Your part is an oddball.

author: CaptDon
author_rank: Super Contributor
timestamp: March 15, 2025, 01:27:06 pm
content: A 'real' 75 ohm BNC looks different than a 50 ohm BNC. If it were a 50 to 75 ohm transition it may possibly be visually verified. They do however look like simple attenuators.

author: NPG
author_rank: Contributor
timestamp: March 15, 2025, 05:37:11 pm
content: Quote from: CaptDon on March 15, 2025, 01:27:06 pmOk, so what is the visual difference between a 50 Ohm BNC and a "real" 75 Ohm BNC?This part has a standard BNC male on one end; and a standard BNC female on the other end.I actually have cables with 75 Ohm impedance with standard BNC male connectors on the ends.Thought I'd got a good deal on 50 Ohm cables until I realized that RG-59 does not and never will impede at 50 Ohms.Quote from: CaptDon on March 15, 2025, 01:27:06 pmThat is how it seems to behave electrically. With no indication to exactly what db value it attenuates to.As someone else stated, my part may be an oddball.Trying to figure out what this strange animal is.

author: tooki
author_rank: Super Contributor
timestamp: March 15, 2025, 05:51:18 pm
content: Quote from: NPG on March 15, 2025, 05:37:11 pmhttps://www.google.com/search?&q=50+75+ohm+bnc&udm=2Quote from: NPG on March 15, 2025, 05:37:11 pmBoth 50 and 75 ohm BNC are “standard”. They are just used in different applications: 75 ohms for video, 50 ohms for everything else.

author: NPG
author_rank: Contributor
timestamp: March 16, 2025, 12:45:19 am
content: OK, I see what you mean.50 Ohms, the dielectric comes out to the end of the center conductor.75 Ohm, the dielectric is recessed.Apparently, they can connect between types too.My 75 Ohm cables have 75 Ohm BNC's on them.I didn't know that was a thing.This part has 50 Ohm BNC's on the ends.

author: CaptDon
author_rank: Super Contributor
timestamp: March 16, 2025, 05:14:33 pm
content: Remember a 50 ohm rated attenuator will only perform to its specification when driving a 50 ohm load.

author: joeqsmith
author_rank: Super Contributor
timestamp: March 16, 2025, 05:25:51 pm
content: Quote from: NPG on March 14, 2025, 08:40:53 pmSo, both pins to case measure open. Pin to pin measure about a meg (*** does it measure the same in both directions?). Too low for a DC block and too high for an attenuator. Sure it is not a detector? Pull one apart and have a look.****The NanoVNA is dirt cheap. Plot S11, S22, S12 and S21.

author: Bud
author_rank: Super Contributor
timestamp: March 16, 2025, 09:46:28 pm
content: Connect the male end to a RF signal generator and check if the female end outputs DC voltage.

author: joeqsmith
author_rank: Super Contributor
timestamp: March 17, 2025, 12:25:35 pm
content: Quote from: joeqsmith on March 16, 2025, 05:25:51 pmShown is an old detector using N connectors. Both pins to case measure an open. Pin to pin measures about 15M in one direction, open in the other, using my BM869s in autorange. The BM869s diode check does not have a high enough voltage to measure the drop. You meter could very well measure different values on this same part. For this part, the RF is injected into the male port. Female is the rectified signal. Female pin to case is about 0.03nF.