The idea is to use VERY sensitive (-120db) FRS/GMRS UHF transceivers found on Ebay or Walmart for $10-$25 to pick fading signals transmitted by low power long lasting(weeks !) RF beacon,
I fly my planes above corn fields that now has grown 2.5meter high and so dense it will stop 0.5W 2.4GHz video transmission completly past 40meter so low freq. beacon was built to replace spotters and fly comfortable anytime, today it tested 800meter of corn field using Yaesu VX2 radio and 550meter using $10 UnidenGMR325 radio!
The circuit is built around CC1070 chip, designed specifically to transmit Narrow FM such as 6kHz wide FRS channels.
Series of up to four beeps transmitted at user set interval. 1st beep at 15mW, 2nd at 3mW,3rd at 0.1mW and last beep at 0.01mW
Using any available police scanner, UHF HAM radio, FRS/GMRS 2-way radio one can locate target without any special skill.
Just listen how many beeps you're getting and how noisy are the last two beeps to estimate if you're getting closer. When you pointing antenna in transmitter direction or blocking RF path with your body the beeps become noisier /weak.
In order to hear 4th beep clearly (microwatt power!)beep you must be very close, some 50ft at most while 1st beep can be hear mile away (in open space).
While in standby the transmitter draws microamperes and while transmitting average current draw is 45mA. With carefuly set duty cycle the beacon can run few weeks using tiny single cell LiPo .
Delayed start (up to 8hours user set) helps to save battery even more.
RF output 12-15mw
Tuning range is about 390 to 490MHz and from 780 to 980MHz, 1kHz step
Period from 1s to 99m
transmitted beeps 1-5
weight 4g
[
attachment=84]
[
attachment=85]
[
attachment=86]
[
attachment=87]
Hi!
Cool article fmkit
Simple but cool idea! You can use a normal PMR 433MHz radio to find your model right? Did you have some links to these product? How long can I run the circuit with lipo?
Thanks for the info!
Best wishes
Heiko
(06-20-2009 11:44 PM)Grandcaravan Wrote: [ -> ]Hi!
Cool article fmkit
Simple but cool idea! You can use a normal PMR 433MHz radio to find your model right? Did you have some links to these product? How long can I run the circuit with lipo?
Thanks for the info!
Best wishes
Heiko
thanks,
the transmitter tuned to any PMR/GMRS/FRS.. WHATEVER license free ISM frequency in UHF or 900MHz
lets calculate how long it will transmit using 500mAh 1S Lipo:
assume duty cycle 55s off / 5s transmitting at 45mA
this makes average current 45/(55/5)=4.09mA
500/4.09=122.2 hours or 5 days and couple hours
I have one beacon transmitter sitting here in my room sending signals for 3 days, from inside the room 4th floor I can ride bycycle 1 mile and still hear the signals. Such low transmission would be not enough for voice comm mile away but in this case nose is meaningful, it's desirable that atleast one beep breaks up and "clean" beeps are simply counted.
Broken beep breaks even more when signal path blocked with your chest so you know which way to go.
HI!
Since i lost my fully equipped ES last weekend i am really down and about to give up FPV.
The frustrating part is that it was not that far away anywhere in a forest but impossible to find.
I will not do FPV again without such a device!
But i have some questions:
Is such a device legal in the EU? I dont know much about this but i think 433Mhz is legal?
Do other 433 MHz devices such as wireless weather stations interference?
How can the beacon be tuned to a desired(legal) frequency?
What scanner do i need exactly?
Do i need a radio licence to by- use such a scanner?
When do u expect to sell this units?price?
Walter
Hi Walter
Welcome here!
Very sad that you lost your Easy-Star.
But now some good news:
Yes, you can use this device in Europe if you are using 433MHz or other legal frequencies. And you don´t need any radio license for running this locator.
Did you know these pmr radios? You can buy these 433MHz radios for low money in supermarket and they have a range of 5km.
Best wishes and have fun here!
Heiko
Hello Heiko,
May i ask u to have a look at this link?
http://www.hofer.at/at/html/offers/2827_8020.htm
Would such a radio be appropriate?
It says 446 Mhz
If so there is one question left:
How can the beacon be tuned to a desired(legal) frequency?
I would be happy to buy, test or whatever u can offer, your device.
Thanks for the info in advance!
Walter
Hi Walter!
Yes, this is exactly what I mean. There are some EU legal frequencies between 433MHz and 446MHz. You can also use the Citizen Band.
But your last question, only fmkit can answer
I need such a locator, too
What can you offer fmkit?
Thanks and Greetings
Heiko
(06-21-2009 10:32 AM)Grandcaravan Wrote: [ -> ]Hi Walter!
Yes, this is exactly what I mean. There are some EU legal frequencies between 433MHz and 446MHz. You can also use the Citizen Band.
But your last question, only fmkit can answer
I need such a locator, too
What can you offer fmkit?
Thanks and Greetings
Heiko
I looked at UHF radio linked in last post - yes it will work ! 8km spec. is no joke, these radios all have dual convesion RX with CRYSTAL filters.
To put it short ANY radio described as "UHF" can be used.
I almost completed the
RF beacon webpage and need your input to fill drop down presets options to include transmitted frequencies and duty cycle. I know well american channels and not sure what license free channels used in Europe.
Those able can solder two buttons and molex pins to standard LCD (HD44780) can set any channel, those wanting plug-n-play device get the beacon preprogrammed.
After searching the internet I found frequency table of license free (Europe) channels:
F1 = 446,00625 MHz.
F2 = 446,01875 MHz.
F3 = 446,03125 MHz.
F4 = 446,04375 MHz.
F5 = 446,05625 MHz.
F6 = 446,06875 MHz.
F7 = 446,08125 MHz.
F8 = 446,09375 MHz.
Hello again,
Thats good news!
I will buy the radio next week from the link i mentioned above. I hope its still available.
I am interested in a preprogrammed one.
Changing frequency should be still possible later if necessary.
So we need a confirmation for the listed channels to be legal in frequency and output power in the EU?
I hope someone can help here?
Walter
(06-21-2009 01:54 PM)FlyingBee Wrote: [ -> ]Hello again,
Thats good news!
I will buy the radio next week from the link i mentioned above. I hope its still available.
I am interested in a preprogrammed one.
Changing frequency should be still possible later if necessary.
So we need a confirmation for the listed channels to be legal in frequency and output power in the EU?
I hope someone can help here?
Walter
if you google CC1070 chip datasheet it says:"
Fully on-chip VCO Programmable frequency makes crystal temperature drift compensation possible without TCXO Suitable for frequency hopping systems Suited for systems targeting compliance with EN 300 220, FCC CFR47 part 15 and ARIB STD T-67 "
the chip puts out clean RF, free of spurs or harmonics, more than that: it's output almost 50 times lower than permitted 0.5w (PMR/FRS channels).
options added,
page updated
I can also program delayed start (30minutes or 1 hour)
(those w/LCD can do it themselves)