RF Switch for a 100 yards

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K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
I am no stranger to RF switching. I have one for one of my basement lights. The remote is at the top of the stairwell. Today I will be working on a 433 remote for testing air brakes and one of the things I will have to do is change the antenna on the receiver because it sucks. It's just a coil of wire about and inch and a half long. I am going to try to make a 1/4 wave vertical using the metal piping in the valve set as a counterpoise.

One issue I have to circumvent is polarization. If the receiver is vertically polarized, it will be at nearly a null if the hand held transmitter is horizontally polarized. The techs that will be using the device are diesel mechanics and just want the thing to work. They don't know anything about polarization, and don't care.

I have real world experience with 433 RF, and I am telling you there is no legal set up that will work for the OP.

Insteon uses the electrical conductors as a path for the signal to switches. As I posted earlier, it seems to work up to 400' with no problems.
 
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K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
I know the answer to this, I am just curious if others here know how to figure it out.

I want a piece of copper wire to be a 1/4 wave resonant at 433 MHz for this ground plane configuration. How long should the wire be? In inches. To the nearest 32nd, or 3rd decimal place.

I have no way to check the SWR, so starting long and cutting back until I get a match isn't an option. In this case I have to use math and just go with it.
 

FionaZuppa

Senior Member
Location
AZ
Occupation
Part Time Electrician (semi retired, old) - EE retired.
I know the answer to this, I am just curious if others here know how to figure it out.

I want a piece of copper wire to be a 1/4 wave resonant at 433 MHz for this ground plane configuration. How long should the wire be? In inches. To the nearest 32nd, or 3rd decimal place.

I have no way to check the SWR, so starting long and cutting back until I get a match isn't an option. In this case I have to use math and just go with it.

what do you mean "no legal setup that will work" ?? 2.4GHz wifi band (unlicensed) with yagi's on each side can go many miles.

many types of antenna at "1/4 wave". my ARRL Antenna book has many different types that can be effectively 1/4 wave, so your question is kinda vague and has no one answer.

but why even try to "figure it out", just buy +3dbi
https://www.amazon.com/dp/B0107ODQ4...t=&hvlocphy=1013442&hvtargid=pla-348384096656
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
what do you mean "no legal setup that will work" ?? 2.4GHz wifi band (unlicensed) with yagi's on each side can go many miles.

many types of antenna at "1/4 wave". my ARRL Antenna book has many different types that can be effectively 1/4 wave, so your question is kinda vague and has no one answer.

but why even try to "figure it out", just buy +3dbi
https://www.amazon.com/dp/B0107ODQ4...t=&hvlocphy=1013442&hvtargid=pla-348384096656

My question has a definite answer. I told you what type of 1/4 wave antenna I was using, a ground plane.

The advertised gain of any antenna is dependent on the assumption of a take off angle relative to the horizon. It means nothing for a take off angle that is above or below the horizon. The gain at a desired angle other than 0 degrees has to be either measured or modeled using modeling software.

I don't need to buy an antenna, and I don't want to. I don't want or need to install a BNC connector, and that rubber duck is nearly a dummy load compared to a real 1/4 wave antenna. True measured gain from duck antennas like that are more in the 0 dbi category. Advertisers lie. Especially with antennas. I own dozens of antennas of all sorts of configurations, some I bought, others I made. All I need is to replace the wire that's on the board with one that will be resonant at 433 MHz. A 10 minute job, if that. With my design, I can make the take off angle higher than the horizon which is what I may need because the receiver will be at ground level and the transmitter will be a couple feet above that.
 

FionaZuppa

Senior Member
Location
AZ
Occupation
Part Time Electrician (semi retired, old) - EE retired.
My question has a definite answer. I told you what type of 1/4 wave antenna I was using, a ground plane.

6.4783328180975075" @exactly 433MHz. what wire dia and material are you using for the antenna?
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
6.4783328180975075" @exactly 433MHz. what wire dia and material are you using for the antenna?

That is the answer for the question "What is the length of a 433MHz radio wave in free space?".

18 AWG CU insulated stranded for the material and size, which has no effect on the math. You missed one factor, and that has nothing to do with size and material of the wire, but all to do with the antenna configuration.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
what do you mean "no legal setup that will work" ?? 2.4GHz wifi band (unlicensed) with yagi's on each side can go many miles.

You better read up on what is legal in the 2.4 gig band without a license.

https://www.air802.com/files/FCC-Rules-and-Regulations.pdf

You are allowed a max of 1 watt into a 6 dBi antenna, or 160mW into a 30 dBi antenna.

Also, 2.4 gig has much MORE path loss than 433 MHz. If 433 is below the noise in a real live application, 2.4 will be nearly invisible.

Now, the ultimate way to prove me wrong is to make such a device that will turn on a floodlight 300' away from inside a house using totally legal gear. I would love to see it, actually.

For the record, I am so persnickety about being legal because I have been a ham radio operator since 1994 and I am not fond of interlopers.
 

GMc

Senior Member
I am no stranger to RF switching. I have one for one of my basement lights. The remote is at the top of the stairwell. Today I will be working on a 433 remote for testing air brakes and one of the things I will have to do is change the antenna on the receiver because it sucks. It's just a coil of wire about and inch and a half long. I am going to try to make a 1/4 wave vertical using the metal piping in the valve set as a counterpoise.

One issue I have to circumvent is polarization. If the receiver is vertically polarized, it will be at nearly a null if the hand held transmitter is horizontally polarized. The techs that will be using the device are diesel mechanics and just want the thing to work. They don't know anything about polarization, and don't care.

I have real world experience with 433 RF, and I am telling you there is no legal set up that will work for the OP.

Insteon uses the electrical conductors as a path for the signal to switches. As I posted earlier, it seems to work up to 400' with no problems.

K8MHZ,

Don't know how these would be for a test box but I've read from others that they work great;

https://pcbs.io/share/rJ36o

There is a link near the bottom of the page for more information.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
K8MHZ,

Don't know how these would be for a test box but I've read from others that they work great;

https://pcbs.io/share/rJ36o

There is a link near the bottom of the page for more information.

Thanks, but I don't need a dipole. The vertical I am going to use costs less than a penny and has about the same gain.

Dipoles are not suited well for vertical polarization. They shine when they are used horizontally. Since the transmitter will be vertical most of the time, the receiver also needs to be vertical.
 

GMc

Senior Member
Thanks, but I don't need a dipole. The vertical I am going to use costs less than a penny and has about the same gain.

Dipoles are not suited well for vertical polarization. They shine when they are used horizontally. Since the transmitter will be vertical most of the time, the receiver also needs to be vertical.

Interesting. Been playing around with some RF, 915Mhz, for some home automation. It's fun and interesting to say the least. You have any blogs or video's of the stuff your working on?

Thanks for the information!
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Interesting. Been playing around with some RF, 915Mhz, for some home automation. It's fun and interesting to say the least. You have any blogs or video's of the stuff your working on?

Thanks for the information!

Thanks for the thanks!

No blogs or videos. I really don't want anyone copying my work, or even seeing what I use for parts. Just finding parts for my particular applications took hours.

I build test devices all the time. All my own design. I build stuff that there is no viable commercial alternative to. I stated back in the 80's by making test equipment for the new computer controlled fuel systems in cars.

The series I am working on right now enables one person to do a DOT certification on semi-trailers. The tech can be anywhere around or under the trailer and operate and test all the lights and both the service and parking air brakes by activating them with a hand held remote control the size of a cell phone. No more two person teams where one person operates the brakes and lights while the other walks the trailer and does the check out.

I am doing this for a friend of mine that owns a semi truck repair facility.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Right now, I am off to the store. I just started my van using an RF signal from a key FOB. I will turn off the downstairs lights using an RF remote. My foyer, garage and patio lights are all on motion sensors, which will be part of the gadget line up that will be used just to make it out of the yard. I also have, but don't use, an RF transmitter that plugs into any earphone of any device and plays what it 'hears' on my FM radio.

I like this stuff.
 

GMc

Senior Member
Thanks for the thanks!

No blogs or videos. I really don't want anyone copying my work, or even seeing what I use for parts. Just finding parts for my particular applications took hours.

I build test devices all the time. All my own design. I build stuff that there is no viable commercial alternative to. I stated back in the 80's by making test equipment for the new computer controlled fuel systems in cars.

The series I am working on right now enables one person to do a DOT certification on semi-trailers. The tech can be anywhere around or under the trailer and operate and test all the lights and both the service and parking air brakes by activating them with a hand held remote control the size of a cell phone. No more two person teams where one person operates the brakes and lights while the other walks the trailer and does the check out.

I am doing this for a friend of mine that owns a semi truck repair facility.

I understand. Sounds very interesting. Love playing with this stuff, I'm struggling with the programming though. I've done a lot with PLC's but this stuff makes no logical sense to me.

If you get a ham radio license, you can use up to 1500 watts PEP on 915MHz. No ERP limit, you can use as much antenna gain as you like.

Interesting

Right now, I am off to the store. I just started my van using an RF signal from a key FOB. I will turn off the downstairs lights using an RF remote. My foyer, garage and patio lights are all on motion sensors, which will be part of the gadget line up that will be used just to make it out of the yard. I also have, but don't use, an RF transmitter that plugs into any earphone of any device and plays what it 'hears' on my FM radio..

Sweet. I don't have any fobs yet so I control everything thru my phone.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Sweet. I don't have any fobs yet so I control everything thru my phone.

That's the direction everything is going right now. I predict that soon proprietary remote control transmitters will be replaced by a mobile computer platform app. It will be cheaper and allow for more flexibility.

I have an ODBII 'scanner' that cost less than $20. It is for Android, I use a tablet computer to communicate with it via Bluetooth. It does everything a $1500 scanner from 10 years ago would do, plus more, and there are no wires or cables. I got the tablet computer for free, all I had to do was drive to pick it up. It was a promotion by the manufacturer.

I paid $30 for an adapter and around $10 for an app to look at the computer systems on semi-trucks.

What is really cool is not being tethered to the vehicle like you are with Snap-On type ODBII scanners.
 

FionaZuppa

Senior Member
Location
AZ
Occupation
Part Time Electrician (semi retired, old) - EE retired.
You better read up on what is legal in the 2.4 gig band without a license.

https://www.air802.com/files/FCC-Rules-and-Regulations.pdf

You are allowed a max of 1 watt into a 6 dBi antenna, or 160mW into a 30 dBi antenna.

Also, 2.4 gig has much MORE path loss than 433 MHz. If 433 is below the noise in a real live application, 2.4 will be nearly invisible.

Now, the ultimate way to prove me wrong is to make such a device that will turn on a floodlight 300' away from inside a house using totally legal gear. I would love to see it, actually.

For the record, I am so persnickety about being legal because I have been a ham radio operator since 1994 and I am not fond of interlopers.
yeah, i know about power densities.
you do not need to be anywhere near 4w EIRP in 2.4GHz to go 300ft.
 

FionaZuppa

Senior Member
Location
AZ
Occupation
Part Time Electrician (semi retired, old) - EE retired.
That is the answer for the question "What is the length of a 433MHz radio wave in free space?".

18 AWG CU insulated stranded for the material and size, which has no effect on the math. You missed one factor, and that has nothing to do with size and material of the wire, but all to do with the antenna configuration.
the length gave is not the answer for "free space", its for Earth at STP.
and i do adjust sizes of antenna elements based on material and diameters.
configuration? sure, but you asked for 1/4 wave length so i assumed a omni stick and not anything else that is 1/4 wave.


check out LoRa Arduino shield
 
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