Improve the range of your remote detonator!

[The ALL-MIGHTY]

If anyone has a remote detonator that's range you'd like to improve, then I’ve found something for you! I found these two IC's that will increase the range of any RF, and I think IF, device. They amplify the frequencies 10mhz-3ghz! And on top of that the IC's are about as big as a 555 timer circuit and are extremely simple to hook up (the thing has 5 ground terminals, one vcc terminal, and RF in/out terminals). I don't know exactly how far this will increase your range but it will probably amplify the signal around 18-20db.

There are two different IC's, one will amp your signal from your transmitter and the other will provide a power boost to signals coming into your receiver. I would recommend only using the transmitter amp one because it amplifies the signal going out, not in, like in the receiver booster one. With the receiver one, too much power going in can damage your receiver, so be careful. The things are about 15$ a piece off Digi-Key, I’ll get mine as soon as I get around to ordering it.

Here are some links:


Product page:
http://www.linxtechnologies.com/ldocs/modules/m_bba.shtml

PDF specs page:
http://www.linxtechnologies.com/ldocs/pdfs/bbamanual.pdf

Digi-Key purchase page:
http://www.digikey.com/scripts/us/dksus.dll?Criteria?Ref=47584&Cat=31392740



Hope this helps some people...! (i've been trying to find stuff like this forever)

[Tuatara]

Nice find! Note that the spec says max 50mW output on the high power version, so if you're already at the legal limit for a small tx (about 10mW) you will see a range increase of about 2x.

Amplifying at the receiving end wont always produce the desired result, as the receiver's noise figure will degrade, by about 4dB in this case. The only time this is a real advantage is when you have a long antenna cable to drive, so putting an amplifier just after the antenna can improve the SNR of the system.

$15 is pretty good for a hybrid device, especially from Digikey.

[The ALL-MIGHTY]

I found another RF amp that provides a greater db output power but has a 28v input requirement. If your willing to carry a 28v batter around, about 3 9v's, you should get greater range from your transmitter, oh yes its frequency range is 1-200mhz. what do you think Tuatara? worth it or not? and i can't find a price on it yet.


http://www.remec.com/products/part_results.cfm?part_number=qbh-2832

http://www.remec.com/pdfs/qbh2832%208_05_03.pdf

[Tuatara]

That one looks pricey. Notice it not only needs 28V, it sucks half an amp too. Thats 14W, most of which is going to wind up as heat - hence the fat metal mounting block. This thing would only be useful for VHF or CB frequencies. Most of the "door chime" type OTC transmitters will be using the unlicensed bands around 305MHz or 433MHz, so this one wont help much.

For ISM band (800-1000MHz) look at Maxim (http://para.maxim-ic.com/compare.asp?Fam=rf_pwr_amp&Tree=Wireless&HP=Wireless.cfm&ln=)

[stanfield]

I'm wiring my own radio transmitter and I will use the PLA05W from Aurel... sounds damn good but damn expensive : about 40$ !

Anyway ! security has no price :)

see ya...

[The ALL-MIGHTY]

Tuatara: you said that with a normal tx you should see a range increase if 2x. But in the pdf under "typical application" it says that with a low cost narrow band tx you should see a range increase of 6-7x. That being said is a 10mW tx the same as a low cost narrow band tx? And: what category would an r/c car tx fall under?

[Tuatara]

The range increase I suggested was based on radio propagation being roughly an inverse square law : double the range, signal drops to 1/4. So going from 10mW to 50mW is a bit over 4x power, ergo range is doubled. The suggestion of 6x to 7x range may be based on a lower input power - its not quoted in the text, but given the 18dB of gain available, you could get 50mW out from less than 1mW input.

[john_smith]

While we're at it...how much wattage would it take to achieve an about 2 mile range in urban area? Say the transmitter operates on commercial FM band and has a 1/4 wavelength telescoping antenna, and the receiver is a cheapo OTC FM radio.

[Tuatara]

That is a surprisingly difficult question to answer. Urban situations really throw a spanner in the works when it comes to radio propagation, due to multipath interference. You can get a reflection from a building that will completely flatten your signal at one point, yet 1 metre further out you get perfect reception. FM also works better if you have line-of-sight from TX to RX. Buildings and hills wont do you any favours.

I'd go for about 100mW and experiment to see if you get the range you want. That should be plenty for 2 miles. Check your local radio licensing laws to see how much you can transmit without bringing the FCC or whatever down on your head. They WILL find you - they have the technology and they are watching. (been there, done that, bought the T-shirt:D )

[The ALL-MIGHTY]

I found this schematic for a 1-watt class c amplifier a long time ago. Ever since I’ve been playing around with the idea that it could be used for my rc detonator to increase range a lot. I already did the math for the capacitor and inductor values a while ago but never purchased parts because I didn't know if it would work. http://www.wenzel.com/pdffiles/class_c.pdf is the page I got the schematic from. Tuatara, you think this would or could be adapted for a 49mhz TX? It can be used with frequencies from 30-200mhz but I thought I’d ask just to be sure. Thanks

[Tuatara]

Should work just fine for 49MHz, provided you've got enough drive power. Looks like its calling for 13dBm input, which is 20mW. The parts shouldn't cost much - go ahead and have a play!

[Jacks Complete]

Just a suggestion, but surely you would do better to build a small-ish directional aerial/antenna? Do a search on "Pringle can antenna" on google. You get a lot of derectionality, but it should be fine for anything approaching line of sight, which I suspect most... single use... devices would be. A basic sight would make it simple.

Something less directional could be used instead, there are plenty of designs about. Even a 3dB gain will double your range, and ten dB would make it ten times further. IIRC Pringle ones go up to something daft like 18dB!

This way, you don't need to carry a device that could get you into trouble with the FCC or whoever, until you assemble it. And that's a good thing. You would be less likely to get caught if you were broadcasting directionally, too.

If you knew where you were going to stand to detonate, you could even have gain on the reciever, but that might be risky!

[Tuatara]

Directional antennas are just a wee bit tricky at 49MHz (translation: very big) but at UHF and higher are very practical, and as Jack said, an easy way to get more range (not quite for free, but pretty close to it).

Small correction: 3dB gain = double the power = 1.4 times the range (far field)
10dB gain = 10x power = 3x range

Edit: Just had a look at the Pringle can antenna. Nice! Note that it runs at 2.4GHz (thats microwave), thats how they got so much gain into such a small space. Not exactly inconspicuous though - even the most credulous cop is going to wonder about the N connector hanging out the side :D

[postalwarrior]

o well i cant even figure out how 2 make a remote detonator

[Jacks Complete]

Wow, postal posted, and then gets banned. I wonder if he went postal?

Anyway...

Tutara,

Thanks for the correction. I should probably have checked up on that. I was, as you rightly said, thinking of power alone, rather than range.:o

[HVD]

I realy wouldn't want to be using any 49 mhz equipment for ... shall we say 'sensitive' ... switching applications. It may be cheap to pull it out of an old remote controlled car etc but it really isn't worth the risk or minor cost savings. It's realitively easy to build a UHF system (418 or 433 Mhz or higher if you wish) that uses an 8 bit code to identify itself to the reciever and pre-aligned Tx Rx modules.

Stick an external antenna with gain on the Tx as well (ie even a 1/4 wave whip. To keep it 'legal' in the UK you should only have an internal antenna on the Tx) and you can get over the quoted 200 m range with the legal 10 mW RF out. Line of site i can get about 350m - possibly more - with 1/4 wave antenna's.

Stick one of those monolithic IC rf amplifiers on the Tx and you can increase the range yet again.

Of course the advantage is that because it's an 8 bit code the chances of getting interference is minimised and hopefully only you can activate the reciever. A step up is to use a rolling code IC but that's a little more advanced.

Anyway check out google for cheap Rx Tx modules and check out HT12E, HT12D & HT12F Remote Control Encoder/Decoders at maplin.co.uk for starters. You can just literaly wire the encoders straight into the input of the transmitter and the decoder straight from the output of the reciever. Stick in a transistor and a relay and you'r home free to switch whatever you want :-)

Hope this was useful and can steer some people away from 49 mhz equipment and missing limbs whenever some kid switches on his Toys R Us walkie talkies :-)

HVD

[The ALL-MIGHTY]

Ok, it seems everyone is like "don't go with 49mhz TX’s, think about some little kid playing with his car and accidentally setting off whatever your trying to light!". Now in a sense this is true but come on, with some common sense your CAN avoid all this! For starters I don't live in a crowed area, the closest house is about 400-500 ft away, and they don't have kids, nor do any live on my road, so that kind of eliminates any problems at my house. Second, usually I don't set off anything AT my house to avoid suspicion, the place I do set most of my stuff off is about a 3/4 of a mile from ANY houses what so ever, and no one with a r/c would ever go back there (no good terrain for small cars) and it takes about 15 min to get to (walking) so why would a little kit walk all that distance to play w/ his car for 20min on shity ground? And third: even though I use a remote det system I still use fuse (give me time to cover ears, put down TX, whatever) which means if for some remote reason if it did get set off prematurely you would see the fuse burning and have time to get at least 20ft away and hide behind a tree or duck or something. So with a little common sense you can make a 49 or ever 27mhz system work and not worry about blowing yourself sky high. But then again, as someone on this forum has for their signature, “common sense isn’t always common” (I think I got that one right), as long as I observe my own safety regs, I’m happy…

[Tuatara]

The comments that apply to CB or RC channels, also apply to any radio channel. Interference comes in many forms, from many sources, so this must be taken into account by using an encoding system which will provide robustness in a noisey (radio noisey!) environment. No system will ever be perfect, but you can make the chances of a false trigger very, very small. Combined with all the usual precautions, you and those around you will get to keep their limbs;)

[rayman]

as long as I observe my own safety regs, I’m happy…

And that was his second to last post, His last post was ummm 12 days later

Not trying to dig up an old thread, But safty is not something to shrug at