I need a cheap miniature through hole HF RF PCB to cable connector recommendatio - Page 1
Forum section: electronics / projects

author: Fflint
author_rank: Frequent Contributor
timestamp: January 12, 2025, 08:47:29 pm
content: I recently opened an old Kenwood HF radio and I saw a bunch of these great Taiko Denki TMP K01X-A1 RF connectors. For anyone that doesn't know what I'm talking about they are these:Here is one unplugged.They are not made anymore as far as I can tell so they are only sold one by one on ebay and are used to repair old equipment .I'd love to have something like this for <30MHz stuff. Some modern miniature connections are either not through hole. So they don't benefit from a stronger anchor point. They are quite expensive and the cables require specialised tooling to make beyond a simple crimper. Mhf for example are both too small and require made cables to be bought.Mmcx looks like it would be good ,but that on the other hand is quite expensive . I don't need Multi GHz frequency support. I'm doing few tens of MHz and ability to unplug from a board without having to unsolder would be great. I need a simple way to attach a coax cable to a pcb (ideally detachable) .Smb would be great if it didn't cost that much. Someone may think $2 is not a lit, but if you need 20 in a device that would otherwise cost $20 altogether plus another $20 for a cast metal enclosure.... It just makes no sense. The Taiko Denki was so great because it was really just a piece of pressed metal. No casting , no machining so it probably cost few cents each.So, does anyone know some alternatives ?

author: Konkedout
author_rank: Frequent Contributor
timestamp: January 12, 2025, 10:45:28 pm
content: I assume you have looked into RCA phono connectors? They are for audio but much smaller than BNC and ought to be cheap. I do not know how the RF impedance will compare with your example.

author: phansel
author_rank: Contributor
timestamp: January 13, 2025, 06:39:53 pm
content: MMCX is usually through-hole. Looks super similar.u.FL or MHF is surface mount and a bit delicate.

author: Fflint
author_rank: Frequent Contributor
timestamp: January 14, 2025, 12:55:10 am
content: Quote from: Konkedout on January 12, 2025, 10:45:28 pmThey are huge in comparison . Maybe it is not apparent in the photo, but these are 3mm diameter coax cables. A tire connector is 4mm in diameter.Quote from: phansel on January 13, 2025, 06:39:53 pmMMCX would be good if they could be bought for pennies as these were back in the day. Sadly the cheapest mmcx I can get is $2.

author: thm_w
author_rank: Super Contributor
timestamp: January 14, 2025, 01:22:46 am
content: SMA is going to be the most common larger size and probably cheapest <16c each:https://www.lcsc.com/product-detail/Coaxial-Connectors-RF_HOAUC-HYCW19-SMAW6509-1350B_C5301856.htmlMCX a bit more 50c each:https://www.lcsc.com/product-detail/Coaxial-Connectors-RF_Shenzhen-Kinghelm-Elec-KH-MCX-KE-STM_C7542041.html?s_z=n_mcx

author: squadchannel
author_rank: Frequent Contributor
timestamp: January 14, 2025, 01:33:07 am
content: Similar to Tek Peltola connector.I too would suggest MMCX or SMB.40$ is not a big price. If it's not broken, you don't need to replace it, coax connectors are not cheap.cheapest ones are made in China, but I don't know about the quality.

author: mtwieg
author_rank: Frequent Contributor
timestamp: January 14, 2025, 01:38:47 pm
content: Quote from: Fflint on January 12, 2025, 08:47:29 pmIf you want to be able to make cable assemblies yourself, then SMA/MCX/MMCX/SMB are basically the cheapest option. Especially if you need the cables/connectors to be rugged.To get lower cost you have to go for true micro connectors (u.fl, ipex, mhf, etc). Yes, you'll probably have to buy pre-made cable assemblies, but these are generally pretty cheap too. If these cables don't need to be cycles often, then their fragility isn't an issue.If neither of those are good enough, then forget about coax altogether. Maybe consider using FFC cables, which can be very cheap and support many signals (robustness is maybe still an issue). Or repurpose a media cable like HDMI, SATA, network cable, etc (especially convenient for differential signalling). Hard to give specific recommendations without knowing more about your application.

author: Fflint
author_rank: Frequent Contributor
timestamp: January 15, 2025, 12:52:43 am
content: Quote from: mtwieg on January 14, 2025, 01:38:47 pmIt has to be coax. Shielding is a must.Sadly, that's another area of technological regres we have in our field. We used to have coax pcb connectors that cost pennies. Now the cheapest option is at least 10x more. But hey, you get to use it with GHz frequencies (you may not even need like myself).Anyway ,thanks for the replies. I guess soldering and unsoldering will be the only way. Sma is way to bulky to put 10 of them on a small.Ordering cable assblies is too much of a hassle for the single devices I make.I'll check the costs of the SMB, but I doubt it will make sense. Having a detachable connector is great for these times when you just want to add/replace one component . Realistically that will happen maybe few times during the entire device life. Spending 2x on building it to accommodate it makes zero sense.Maybe if I could figure out a way to make my own mmcx that could be an option. They are the only price equivalent I saw so far for the old connector.

author: Someone
author_rank: Super Contributor
timestamp: January 15, 2025, 01:19:15 am
content: Quote from: Fflint on January 15, 2025, 12:52:43 amPennies in what era? How is that connector assembled ? crimp pin and crimp outer? or soldered pin? What cables is it compatible with?Quote from: Fflint on January 15, 2025, 12:52:43 amFlat-flex comes in shielded versions. If you want cheap then you have to move with the volume markets and they are using flat flex for space or price constrained interconnect... and analog signalling can end up more expensive than the same performance from digital.

author: mtwieg
author_rank: Frequent Contributor
timestamp: January 15, 2025, 01:11:56 pm
content: Quote from: Fflint on January 15, 2025, 12:52:43 amAll of the options I suggested offer shielding, including FFC.Quote from: Fflint on January 15, 2025, 12:52:43 amThe act of ordering premade cables is more of a hassle than making your own by hand...?Do your connectors actually have to be on the PCB itself? Would it be enough to solder coax pigtails to the board with free-hanging SMA/SMB connectors?Quote from: Someone on January 15, 2025, 01:19:15 amFrom what I can tell from scattered images, you have to separate the shield braid into two parts, twist and fold those back, and they sit in the two bulges in the connector. The tool then crimps the connector to the braid.For the center conductor it seems to be soldered in a very novel way, shown here (also shows the shield being soldered instead of crimped, maybe they didn't have the crimp tool?)https://shop.technofix.uk/tmp-male-plug-taiko-denki-tmp-k01x-a1Anyways I can see why these would be convenient for light-duty hobbyists. I can also see why they are no longer manufactured (the assembly method doesn't appeal to anybody besides hobbyists). I couldn't find any info on mating cycles, but they don't look any more robust than u.fl or similar micro connectors.

author: smashedProton
author_rank: Frequent Contributor
timestamp: January 15, 2025, 01:59:58 pm
content: Consider direct soldering FFC cable to board and using CPW or microstrip over hatched plane for the RF.