need help on getting/making a 433.9 MHZ antenna

[stanlam]

I purchased a garage door monitor. Basically, the sending module attaches my garage door and the receiving monitor is inside my house. The monitor tells you if the garage door is open or close. The company I purchased it from advertises it has an 800 feet maximum range. I'm getting about 50 feet. I know the unit works on 433.9 MHZ because I checked the FCC website. The included antenna is only a short wire. Does anybody know if I can attach some type of real antenna to this wire to extend the range? I've tried several different ways of making an antenna, but I'm not coming from the engineer aspect. I'm just creating any type of antenna that I can imagine with my mind. So far all the antennas I've created hasn't helped much. Can somebody please help me and tell me how to extend the range of this projects.
What type of antenna should I make or buy?
Thanks.

 

[Beetle]

433.9 MHz is right in the middle of the 70cm amateur band! Who made this door opener?

You can add more wire to the receiver antenna; just strip the ends and twist another few feet of just about any kind of copper wire. This might work. I wouldn't try modifying the transmitter, though.

 

[stanlam]

433.9 MHz is right in the middle of the 70cm amateur band! Who made this door opener?

You can add more wire to the receiver antenna; just strip the ends and twist another few feet of just about any kind of copper wire. This might work. I wouldn't try modifying the transmitter, though.

It's a Skylink GM-434RTL Long Range Garage Alert Kit......

Amazon.com: Skylink GM-434RTL Long Range Garage Alert Kit: Home Improvement

I'm sort of confused about extending the wire. I found this other website...

RF Module External Antenna Design

and it says the antenna length for 433.9 MHZ is suppose to be 6.81 inches. So if I extend the antenna wire to 10 feet, does it make it worst then a 6.81 inches antenna wire?

 

[HomerBB]

Put a parabolic dish behind it.
A metal bowl, colander, wok, etc will give it directionality and increase its range.
I did this with a wifi receiver and my signal on a distant router went from 1 bar to five.

 

[stanlam]

Put a parabolic dish behind it.
A metal bowl, colander, wok, etc will give it directionality and increase its range.
I did this with a wifi receiver and my signal on a distant router went from 1 bar to five.

I might need to do that. However, as of now, is there another way because my wife isn't going to be happy seeing that type of funcky antenna in my living room?

 

[Robb]

What Beetle said is still unanswered - concerning the use of 433mhz.

".....433.00-435.00 AUXILIARY/REPEATER LINKS....."
U.S.A. VHF/UHF BAND PLAN
I have no idea how a commercial business can violate FCC regs when choosing a freq like that and be allowed to sell it. Wonder if it was registered in the US? At least, one would have to wonder.

As far as the antenna length goes, that is directly related to the frequency in use. As freq changes; so does the resonant length of ANY antenna. Basic radio rule. At that freq on question, the length is short - as mentioned above. Using a 10 ft piece of wire would DEFINITELY be the wrong move.

Our resident antenna Guru - HomerBB - said that a parabolic reflector might be considered. I think is is worth the trial-and-error too. Shouldn't be too much error, and the first try may well work. Use the 6.81 in length for the radiator in the parabolic reflector.

 

[stanlam]

What Beetle said is still unanswered - concerning the use of 433mhz.

".....433.00-435.00 AUXILIARY/REPEATER LINKS....."
U.S.A. VHF/UHF BAND PLAN
I have no idea how a commercial business can violate FCC regs when choosing a freq like that and be allowed to sell it. Wonder if it was registered in the US? At least, one would have to wonder.

As far as the antenna length goes, that is directly related to the frequency in use. As freq changes; so does the resonant length of ANY antenna. Basic radio rule. At that freq on question, the length is short - as mentioned above. Using a 10 ft piece of wire would DEFINITELY be the wrong move.

Our resident antenna Guru - HomerBB - said that a parabolic reflector might be considered. I think is is worth the trial-and-error too. Shouldn't be too much error, and the first try may well work. Use the 6.81 in length for the radiator in the parabolic reflector.

So am I suppose to put this parabolic reflector on the transmitter and the receiver? Also, is it okay for me to extend the current wire antenna to a length so I can put it in the parabolic reflector?


FYI.....

Just in case somebody is wondering how I got the frequency, I went to the website.....

OET -- FCC ID Search

Then I looked for a sticker on the garage sensor transmitter that stated FCC and...

KUT GUS101

Once you type it in it shows all the information including the instructions that came with the garage door monitor. I never even knew about this until I read it somewhere else.

 

[Captain Kilowatt]

There are lots of imported devices operating on the 70 cm band. Some are legal and some are not. Remember, amateurs are allocated 70 cm on a SECONDARY user basis. That mean we must NOT cause interference to other licensed users and must accept interference from other licensed primary users of the band.

 

[Beetle]

6.81 inches is right around 1/4 wavelength at 400 MHz. This is important for a transmitter but not so much for a receiver. A longer antenna will, in most cases, provide the receiver with a stronger signal.

I don't think the parabolic reflector will be of much use. WiFi frequencies are up in the 2.4 GHz range, and higher. At 400 MHz, a quarter wavelength is about half a foot. At 2.4 GHz (2400 MHz) it's less than 0.1 foot. Makes a big difference.

Recommendation is still to extend the receive antenna. And by the way, if there are hams in your area who use 70cm, your garage door monitor/opener might behave differently than you'd expect.

 

[Beetle]

So am I suppose to put this parabolic reflector on the transmitter and the receiver? Also, is it okay for me to extend the current wire antenna to a length so I can put it in the parabolic reflector?


FYI.....

Just in case somebody is wondering how I got the frequency, I went to the website.....

OET -- FCC ID Search

Then I looked for a sticker on the garage sensor transmitter that stated FCC and...

KUT GUS101

Once you type it in it shows all the information including the instructions that came with the garage door monitor. I never even knew about this until I read it somewhere else.

You can do whatever you like to a receiving antenna (I'm going on the assumption - I know - that the floppy wire antenna is receive-only). Don't do anything with the transmitting antenna.

 

[HomerBB]

Beetle may be right about the dish not being so useful at this wavelength, however i thought it worth a try. it is correct that you should only attempt changes on the receiving antenna, so the dish is only necessary for the receiving end.

It was only a suggestion based on improved receive I had experienced on a signal I believe to be about 1/8 mile away from me. My increased bandwidth went from 12 Mbps to 50 Mbps by aiming the dish at the source.

Maybe just a longer receiving antenna will do . . . This evening I had to out a piece of wire on the little extendable antenna on a radio in order to hear the Razorbacks game over a commercial FM station. We've all done that, I would think, so I'd give the suggestion a try.

 

[stanlam]

Beetle may be right about the dish not being so useful at this wavelength, however i thought it worth a try. it is correct that you should only attempt changes on the receiving antenna, so the dish is only necessary for the receiving end.

It was only a suggestion based on improved receive I had experienced on a signal I believe to be about 1/8 mile away from me. My increased bandwidth went from 12 Mbps to 50 Mbps by aiming the dish at the source.

Maybe just a longer receiving antenna will do . . . This evening I had to out a piece of wire on the little extendable antenna on a radio in order to hear the Razorbacks game over a commercial FM station. We've all done that, I would think, so I'd give the suggestion a try.

I spent about an hour trying different ways of modifying the receiving antenna without any success. The telescoping antenna I used was removed from an old boom box radio. The length of the antenna is about 3 feet when extended. I tried connecting the telescoping antenna directly to the receiver's built-in wire antenna so it was right next to the receiver. I also tried connecting the wire antenna to a wire that was made for a CB radio and I put the telescoping antenna outside closer to sending unit and it still didn't help.

Any other suggestions on modifying the antenna on the receiving unit?

 

[stanlam]

Put a parabolic dish behind it.
A metal bowl, colander, wok, etc will give it directionality and increase its range.
I did this with a wifi receiver and my signal on a distant router went from 1 bar to five.

I think my next attempt will be to try this parabolic dish on the sending unit's built in wire-antenna. Will report back the results soon....

 

[Dave_W6DPS]

You can do whatever you like to a receiving antenna (I'm going on the assumption - I know - that the floppy wire antenna is receive-only). Don't do anything with the transmitting antenna.

But a lot of things done to a receiving antenna simply don't make sense. Just extending it will not neccesarily increase signal strength.

First, make sre that both antennas are in the same plane. If one is vertical and the other is horizontal you lose about half the signal strength.

A parabolic dish for 434 MHz would need to be about 4 feet in diameter to really boost gain, and that is with a half-wave antenna at the focal point. A bowl or something similar might act as a primitive reflector, but you would need to experiment with the spacing to get the most out of it. try a small pizza plate about 2.75 inches behind the antenna, and adjsut to see if you get any increase in performance.

One thing that might actually help is providing a counterpoise for the quarter-wave antennas. You are much better off with an actual half-wave antenna, but adding a grond wire about the same length as the existing antenna wire, and tied to the ground for the unit near the antenna connection, would likely help.

If you have an old "bow tie" type table-top UHF television antenna it might help if you can get the twinlead to the antenna connection in the unit's case. The "rabbit ears" that had the dual loop UHF antenna might work, but not as well.

UHF Outline Bow-Tie Antenna : Indoor Antennas | RadioShack.com

The connection to the receiver's antenna connections on the circuit board might be a bit tricky, depending on your soldering skills...

Dave_W6DPS

 

[stanlam]

SUCCESS, IT WORKS!!!!

But a lot of things done to a receiving antenna simply don't make sense. Just extending it will not neccesarily increase signal strength.

First, make sre that both antennas are in the same plane. If one is vertical and the other is horizontal you lose about half the signal strength.

A parabolic dish for 434 MHz would need to be about 4 feet in diameter to really boost gain, and that is with a half-wave antenna at the focal point. A bowl or something similar might act as a primitive reflector, but you would need to experiment with the spacing to get the most out of it. try a small pizza plate about 2.75 inches behind the antenna, and adjsut to see if you get any increase in performance.

One thing that might actually help is providing a counterpoise for the quarter-wave antennas. You are much better off with an actual half-wave antenna, but adding a grond wire about the same length as the existing antenna wire, and tied to the ground for the unit near the antenna connection, would likely help.

If you have an old "bow tie" type table-top UHF television antenna it might help if you can get the twinlead to the antenna connection in the unit's case. The "rabbit ears" that had the dual loop UHF antenna might work, but not as well.

UHF Outline Bow-Tie Antenna : Indoor Antennas | RadioShack.com

The connection to the receiver's antenna connections on the circuit board might be a bit tricky, depending on your soldering skills...

Dave_W6DPS

Dave,

IT WORKS!!!!! That was awesome advice. I used an old UHF antenna that was in my garage for some 10 years. The UHF antenna doesn't look like the link you showed, but it was an antenna that was made exclusively for UHF. I still can't believe I got it to work. The telescoping antenna made no difference, but this UHF antenna makes a world of difference when hooked up to the receiver. Thanks a million,
Stan