How to add this amplifier to these tx/rx pairs? - Page 1
Forum section: electronics / rf-microwave

author: Beamin
author_rank: Super Contributor
timestamp: November 03, 2017, 03:49:17 am
content: My questions to connect the tx modual to the amp do I need 50 ohm coax? Will wires work in its place? Should I find a ground on the TX and connect that up the outside of the amps SMA connector/will the amp not work if just one lead is connected to the center of the SMA connector?Since I cant find a decoder/encoder chip for this what kind of Arduino circuit will work in its place? The encoder chip had four switches that when pressed the decoder chip would chip on the RX would light up a corresponding LED. I am trying to emulate that with the Arduino. Some one mentioned Manchester encoding. What would I look for as far as an Arduino sketch that could do that? Is there a data protocol that makes two arduinos "talk to each other" using just one pin ( the radio has one input pin and receiver has one output that goes into the decoder. IF there is a chip that you know of that will work in its place that would be preferred. Seems like a lot of de/encoders would work over this I just have no idea where to look.FYI: This project is just for fun to test out low power long distance directional antennas. The focus will be learning the antennas so I want to make the hardware part reliable so that's not part of the variable or spend a whole bunch of time writing C code which I can't do much more then copy and paste.Lots of questions. If you know of links/videos where I can copy/learn that would always be helpful but for now I'm not even sure where to look. I got the idea from a youtube video I saw where he uses an encoder chip. I want to take his design then focus on improving range:So these are the TX/RXPair:QuoteAnd this is the amp (sorry I can't copy and paste the description) But basically This is the most info I can find off of it.1Mhz-2GHz amp12VDC input"20db""I=75ma"To be taken with a grain of salt . I see lots of these on ebay for 10 from china so they must have some sort of use in a product. What for I don't know.https://www.aliexpress.com/item/1MHz-to-3000MhZ-3GHz-2-4G-Broadband-Low-Noise-Amplifier-RF-LNA-Amp-Module-40DB-VHF/32813183120.html?src=google&albslr=221722480&isdl=y&aff_short_key=UneMJZVf&source=%7Bifdyn:dyn%7D%7Bifpla:pla%7D%7Bifdbm:DBM&albch=DID%7D&src=google&albch=shopping&acnt=708-803-3821&isdl=y&aff_short_key=UneMJZVf&albcp=653482935&albag=32646801963&slnk=&trgt=68416666751&plac=&crea=en32813183120&netw=g&device=c&mtctp=&gclid=EAIaIQobChMIq-Ptobmh1wIVhF6GCh08XwZqEAQYBCABEgKNJPD_BwE

author: Mjolinor
author_rank: Frequent Contributor
timestamp: November 03, 2017, 04:06:05 am
content: You will be breaking the law putting an amplifier on, If it is a learning exercise you will learn more by using them without.If you are sure you want an amplifier then buy a mini circuits one they will not bleed all over the spectrum and trash your (and your neighbours) TV.Most of the modules already put out the maximum permitted power and the specification of the antennas you are allowed to use is also laid down in law. Receiving antenna can be anything you like but the EIRP of the transmitter may not exceed the numbers stated in the standard.I do have a PIC assembler routine for NRZ removal, if you want a copy I can try to find it for you. I think I also have the other side of it for decoding that may be written in C. My dim memory suggests I may have used a Pi for that and for sure I would not have written that end in assembler so it is likely to be very crappily written C.

author: Beamin
author_rank: Super Contributor
timestamp: November 03, 2017, 05:12:29 am
content: Quote from: Mjolinor on November 03, 2017, 04:06:05 amYes that would be great. The PIC assemble routine feeds into the Arduino?I really just want to get the think working first and if I can get it working I can worry about all the bureaucracy latter. I appreciate your consideration for redtape but (not saying you re doing this) don't use that as excuse to with hold information: Most people are going to do it anyways but if they had access to all the info first the amount of potential damage is much lower then just having no idea what you are doing and blasting out power on the cell phone bands because some one withheld information that would have allowed you to be aware of what not to do.Since I have never made an amplifier circuit before and I want to try it out.

author: CJay
author_rank: Super Contributor
timestamp: November 03, 2017, 07:14:49 am
content: OK, obligatory 'don't do it, it's against the law' warning, not only might it land you in hot water, it would possibly upset a lot of people who suddenly find their doorbells, garage doors, baby alarms, thermostats, remote control plug sockets etc. stop working or do weird things.Now that's out of the way, you don't need the amplifiers to conduct your tests, in fact they may even be a hindrance as you need to implement TX/RX switching and walk a *long* way to make minor changes.Better antennae make more range than adding extra power into a poor antenna, plus they scale for line of sight, so experimenting with extreme low power to achieve best range over shorter distances is useful before you jump into higher power.There is a *lot* of information on antenna design out on the web, 434MHz is near as damn it a ham band so there will be lots of plans for 70CM antennae with gain, tuning one of those for use on your TX/RX pairs will make your life a lot simpler.PIC code, if in C should be pretty simple to port to Arduino, I've done it a few times the other way round so PIC examples are useful if they work, even if you only read the code to see where yours is going wrong, having said that, 433MHz modules have been around a *long* time so there should be many Arduino examples out there, again choose one, test it, choose another, test it, see how the range works out (those AM modules are crap and range is easily affected by bad code, there are, again, plenty of web resources which explain it nicely)...

author: Mjolinor
author_rank: Frequent Contributor
timestamp: November 03, 2017, 10:20:16 am
content: The PIC code is written in assembler. It would not fit in the PIC in anything else.I will see if I can find, it is at least five years since I did anything with it.

author: Mjolinor
author_rank: Frequent Contributor
timestamp: November 03, 2017, 10:32:00 am
content: OK. Here is the assembler listing.When compiled this is 6 bytes short of filling a 12F635 processor.This is in a device that you connect to a low voltage feeder in a substation for monitoring the voltage and current.What it does is:Find zero cross on voltage.Measure voltageFind zero cross on currentMeasure current (Rogowski coil)Measure phase angle between V and IMeasure frequency (voltage input only)Apply NRZ removalConvert the data to rs232 at 9600 baud (IIRC)Transmit data every 25 seconds (again I may not be remembering that time correctly)I will look for the Raspi bit some more, it is proving hard to find right now.

author: Mjolinor
author_rank: Frequent Contributor
timestamp: November 03, 2017, 11:03:02 am
content: OK. This is the RASPI bit I think. It may not be the full version.Warning: One should don ones Tena pants before reading my C coding as it may cause uncontrollable fits of laughter.This uses RRD database to make graphs over time for power state presented on a web page. It may not be the whole thing, I may have split it across different files, I just can't remember. If you can't find something then post back and I will look for it.

author: Mjolinor
author_rank: Frequent Contributor
timestamp: November 03, 2017, 11:10:55 am
content: Just so you know what the thing looks like here is a picture of the finished prototype.

author: Beamin
author_rank: Super Contributor
timestamp: November 03, 2017, 11:54:15 am
content: Quote from: Mjolinor on November 03, 2017, 11:10:55 amLooks like a brand new mouse and key board. So whats it do? Whats that red coil for the antenna? I think your explanation was a bit too technical.

author: Mjolinor
author_rank: Frequent Contributor
timestamp: November 03, 2017, 12:10:47 pm
content: It clips round an electricity cable to measure volts, amps, phase angle and frequency. You have maybe 30 of those in an LV substation and they all talk to one Raspi which then present the data from the sensors on a web page.The orange thing is a Rogowski coil for measuring the current.