HotSpot internal RF connector - trying to add external antenna ? - Page 1
Forum section: electronics / rf-microwave

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: April 13, 2022, 02:56:52 am
content: Just switched to a Alcatel Linkzone 2 hotspot , T-Mobile service .And want to try to add external antenna , no access or ports for connection .I did find - while searching the web , a post from someone that opened up the case and showed pictures of surface mount RF connectors that I see on all kinds of devices laptops , cell phones etc. - these are typically internal connectors --- some labels to call them I have found are 1-PEX MNF2 , Hirose U.FL & UMCX ?The main issue is like many consumer WiFi products - these seem to be RP = Reverse Polarity connector - and that is the issue so far - cannot find RP connectors of this style ?Looking for a - right angle 1-PEX cable to SMA ?So I can add an external antenna ?Will get some extras for other projects and for test gear .In the search there was a diagram showing the RP pin - when plugged in , it does 2 things makes the RF connection - but also the pin moves a contact away from the internal trace / disconnects , there is 2 of these on the board .Which brings up another question - in lots other stuff - ham radio etc. , many times something like this would have a 50 Ohm termination on the connector - it is not open in normal sense = shield & center connector open = because the center has the circuit completed by the lever action - that when the RP connector is connected [ guessing for testing at factory ] the pin pushes on the lever - disconnecting the connection & now the added cable takes over --- from internal antenna - to what I want - to cable for external antenna ?

author: El Rubio
author_rank: Regular Contributor
timestamp: April 13, 2022, 01:00:45 pm
content: There are companies that will make a custom adapter or pigtail cable that would allow you to connect an external antenna. If you can get something and adapt to an SMA, there are SMA reverse polarity adapters. You mention more than one connector in the hotspot. One or more are for the cellular bands, and one or more are for the WiFi side. Both of these MiMo technology and may implement multiple antennas. The most important thing would be to identify which are WiFi and which are cellular and you can get wideband antennas for each of those. It’s also possible that some of these connectors are not antenna connectors also.

author: cdev
author_rank: Super Contributor
timestamp: April 13, 2022, 02:23:14 pm
content: Hirose connector footprints are often present within commercial routers, sometimes the connector is already there, sometimes, just the footprintWhen they are present its best to use them. The other alternative is to cut a trace and use that to attach a coax connector, and then attach an antenna appropriate to the frequency. This works and sometimes it works well. Often the results are mixed, It works the best if you can get a good ground connection for the coax shield. With vias around it so your ground is to both sides. The wire you add must be very short, almost nothing, to the center part outside the coax, or your SWR will be too high. (If you have a VNA to test this connection, its a good idea to do so. Ive used pigtails made from tiny teflon coated coax and had it work well. Dont add too much coax, either, as coax loss at 2.4 or 5 GHz is very high. Ay discontinuities will imact your signal a lot. Go slow and you'll get the hang of it.A small bowtie antenna works for both bands. Keep in mind that these u.fl etc connectors are not designed to be used frequently, so whatever you connect should be left on except when youre permanently switching to another antenna. If you anticipate more frequent use, use a u.fl to female sma. Then mount the SMA female jack somewhare on the box so it can be used normally.Quote from: KD0CAC John on April 13, 2022, 02:56:52 am

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: April 13, 2022, 05:42:09 pm
content: Still looking for info on the original question - access to RP connector - and coax to SMA standard ?Only looking to get better cell service , not WiFi - so only need to connect external cell antenna .

author: Bud
author_rank: Super Contributor
timestamp: April 13, 2022, 06:44:00 pm
content: I do not think it is trivial. For cell service you need to transmit as well as receive, so a matching circuit for the external antenna will be needed.

author: LaserSteve
author_rank: Super Contributor
timestamp: April 13, 2022, 08:50:42 pm
content: I've tried this with a modern Hotspot and some well optimized antennas. Far better antennas then the ceramic patch antennas in the Hotspot. I was in a somewhat marginal location, but was still getting reasonable data transfer rates with modest errors. I purchased proper low loss adapters, did everything I could to minimize cable and path loss. Net result, the cell site lowered the transmitter power on both ends, minimizing the net link budget back to where it was before. I'd get a few minutes of a hotter, faster, lower BER link, then it dropped right back to where it was before. This was verified using the system's own diagnostics.I then gave the antennas to a friend who had the same system but a much longer path. The system did the same thing. Dropped the TX powers back considerably and established the same data transfer parameters.These antennas were not YAGI but 5/8ths wave.In other words, sometimes the system does not want to accommodate your better antennas, for what you view as your benefit.Steve

author: cdev
author_rank: Super Contributor
timestamp: April 13, 2022, 09:26:17 pm
content: The system probably determines that you 'don't need' the improved signal strength, since your signal sounds stronger to it. So it rations itself.They are trying to reduce the RF range to generaly increase the number of connections possible in a given area by various kinds of diversity including spread spectrum, of various forms.As far as doing surgery on 2.4 GHz and 5 GHz radios. Its not impossible and a little bit of skill at it is useful. I recently got an inexpensive nanovna2 and that had dramatically improved my RF pigtail making skills, since I can now check anything of that kind fairly easily, within limits. (now what I'm looking for are the right clips to use at the "calibration plane" to make the connection.Be aware that this (modification of a wifi antenna) is an area where a countries domestic regulation may limit the use of external antennas on wifi equipment. However, I would suspect that the rules would mostly apply to manufacturers, to gain type acceptance, and that as long as one was not modifying output power, and instead were increasing directionality, which lets not forget, reduces the signal to non-desired directions, making communications easier for them..In short its quite possibly a more efficient use of the airwaves on a pointto point connection. At least thats what I think is the intent of the laws. Manufacturers sell two different kinds of APS, omni and directional. Suppose you have an omni ap without any means of changing the antenna. You shouldnt be forced to buy an expensive point to point high gain AP if you can easily build one yourself by connecting a gain antenna wich might let youcommunicate with a client or AP a longer distance away - with specificity (and reducing the RF spread all around everywhere)for an individual home user attempting to get more range, they might be unlikely to care in most situations, Dont mess with anything other than that, however.I dont know. I know that its not only impolite, its probably ilegal to spatter signal of any kind around any more than necesary. Just like you dont shout indoors.It would be smart to check the local rules. Personally, Ive been building and using my own wifi antennas for as long as wifi has been available. Usually to attempt to improve signal within my own apartment or home and confine as much of that signal as possible to "where the laptop needs to be used" Its a lot of fun and Ive been able to extend my range for my home wifi substantially in the past, for example, from a window that overlooked a street with several cafes on it, several hundred meters away.But I have never used any kind of amplifier. Mostly this was for fun when I lived within range of a nice cafe. Where I live now there are no cafes within range that I know of.Just neighbors whose own wifi I would not want to interfere with.

author: cdev
author_rank: Super Contributor
timestamp: April 13, 2022, 09:29:58 pm
content: 5/8 wave is renowned for excellent gain on many bands as an omni antenna. Not many people know about it.If you need a single band omni vertical ham antenna for HF, especially 15 meters and above (because the height is manageable) 5/8 wave does very well for DX.Quote from: LaserSteve on April 13, 2022, 08:50:42 pm

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: April 13, 2022, 10:06:10 pm
content: Some backround , I live in a Airstream trailer - basically a faraday cage with windows - so I hang the hotspot by USB in window .That's aside from being in a area with low to bad connection ---- to cell network for HOTSPOT , so the desire for external antenna .Being into ham radio , I also like to learn more about making RF do well for either ham radio , or cell service = hotspot .I have some test gear , oscilloscope , spectrum analyzer , VNA , Bird meter , etc.But this is mostly as a hobbyist / not an RF engineer - I wishSo have some of the basics .So again looking for connector RP connector , cable to SMA [ I figure non available as short as a couple inches to SMA to case of hotspot , so then high quality coax to external antenna ?Info is always a good thing .

author: El Rubio
author_rank: Regular Contributor
timestamp: April 13, 2022, 11:46:56 pm
content: You need to identify the connector type on the board, then you can probably find a pigtail jumper to something common like and SMA. You can then get a small SMA reverse polarity adapter from Amazon or ebay. Depending on the connector type on your board, you may find that on ebay as well. There are lots of places that will make a cable for you- google.Another suggestion recently discussed here is you could get a cellphone booster amp. This would improve your hotspot performance and your cellphone inside the Airstream. Just don’t get the one on Amazon with a rubber “bag phone” style whip antenna on it.

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: April 14, 2022, 09:09:36 pm
content: I think I mentioned I have a ham radio lic. - so I know about most of the rules .I do have VNA , spectrum analyzer , oscilloscope , antenna analyzers , I do micro soldering with stereo microscope .I am not interested in getting cafe etc. from other places , no intent in amplifying ect.The hotspot drops out a lot , so just bad reception , and inside aluminum trailer .Not sure , I guess another question --- seems like for some yrs. now when I [ watching many forums ] there is many responses THAT NEVER ANSWER THE QUESTION = the 2nd question ?The added info , rules etc. I think are a good thing , either I do not know , or for general knowledge for anyone / everyone reading a post of interest .So with 7 replies [ not as many as some posts I've seen without answers ] but still ?For those looking to be offended - no need to reply--- this is not ment to offend --- it's now just a 2 part question finding a RP connector , and just seeing if others ever notice / wonder why no answers

author: cdev
author_rank: Super Contributor
timestamp: April 15, 2022, 01:59:48 am
content: Quote from: KD0CAC John on April 14, 2022, 09:09:36 pmWell, reverse polarity coax connectors are around, Ive bought them many times. I recently bought a Reverse SMA to N-female. This was to allow the use of a tiny USB NIC with a better antenna, when needed.I have dealt with a company c called The RF Connection and been very satisfied with the cables they made me. They are in Gaitherburg, MDhttp://www.therfc.comThey use high quality parts and the cables they make last, and dont show lots of loss.

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: April 15, 2022, 02:04:37 am
content: I am not saying they do not exist , I've also bought a number of RP connectors / adapters .My point - the question is these surface mount connectors , I can find standard - but have been on a number of suppliers sites - AND CAN NOT FIND - I looking for help to find

author: cdev
author_rank: Super Contributor
timestamp: April 15, 2022, 02:09:26 am
content: I bought a stick of u.fl connectors for PCB mount on ebay, also I got a bunch of pigtails there. With the male already connected to the micro coax already. I am able to solder them to a PCB but I could never put male hirose connectors on that ultra tiny coax.I doubt if many of us here would be successful with that. Might as well let others do that bit of it. That leaves me with the easy fun part, build an antenna myself..

author: Bud
author_rank: Super Contributor
timestamp: April 15, 2022, 04:55:04 am
content: Quote from: KD0CAC John on April 15, 2022, 02:04:37 amAre you looking for this type of connector ?https://www.digikey.ca/en/products/detail/te-connectivity-amp-connectors/2337019-1/9974052

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: April 15, 2022, 03:19:20 pm
content: That is the type , but it is not RP - the pin is in the pigtail .

author: Bud
author_rank: Super Contributor
timestamp: April 16, 2022, 08:06:14 pm
content: I would not sweat and would just replace the connector on the board and buy a suitable length microcoax with a SMA on the other end (straight or RP depending on the antenna connector)

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: April 17, 2022, 02:24:58 am
content: 1st off , reverse polarity on the pigtail connecting to the board SMD , not the SMA , have a number of SMA RP .This is not the 1st time I've seen these , want to be able TO WORK WITH THESE , besides the fact they serve a disconnect issue .

author: Bud
author_rank: Super Contributor
timestamp: April 17, 2022, 06:07:54 pm
content: That is what i am saying, I'd replace the SMD u.fl connector with a male one, then use a pigtail with whatever connector on the antenna end i want.

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: April 17, 2022, 06:46:52 pm
content: OK , I'm done , many non replies to my question , so I'm leaving thread for whatever future it may have .Thanks anyway

author: El Rubio
author_rank: Regular Contributor
timestamp: April 17, 2022, 10:56:29 pm
content: To be fair, you posted a question about adding external antennas to a hot spot. You got several suggestions, but not exactly what you were looking for. It took YOU 7 posts to finally point out that you had to use those existing connectors. You know, a pic or two might have helped get the point that you seem to think was obvious across. Good luck finding your connectors and even more so if you need help from others.

author: cdev
author_rank: Super Contributor
timestamp: April 21, 2022, 06:03:13 pm
content: Be aware that antenna changes may not be legal, within the letter of the law.So might be ill advised, perhaps its better to buy an access point for example, designed for long haul communications. They exist.