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Old Jun 12, 2012, 12:45 AM
doo
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Help!
Need an airborn Tx for audio only.

Not sure if this is the correct forum, but I would bet someone here can help.

I'm looking for a transmitter to install in my sailplane. I only need the audio to transmitted from my variometer.

Have not had much luck finding a tx with an appropriate range for sailplane flying.

I was thinking that maybe one of the FPV transmitters might work, just using the audio channel?

What do you think?

Also I am curious about what receiver would be needed to pick up the audio channel. I have several all mode hand held scanners that go beyond 1.3 ghz.
Would this work for one of the 900mhz-1.3ghz transmitters? If so, what mode would i need the rx to be set to? AM, FM, WFM, USB, LSB, ect?

Thanks for the help.
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Old Jun 12, 2012, 01:08 AM
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There are tons of FM and UHF spy transmitters offered on ebay,
if your RC link is UHF LRS then use FM (76-108) band
the problem with ebay FM transmitters that they all non-PLL free running oscillators only usable with analog radios.

If you fly non-UHF then it is safe to use UHF spy bug, ebay transmitters normally limited to few milliwatts and fixed at 433.920MHz that is heavily used by car alarms. Ultimate audio link would be using my RF beacon set to continues transmission inputting your audio, then you can set RF power level up to 80mWt, any frequency to use whatever walkie-talkie.

If more than 3-4 pilots in this forum want FM version of UHF RF beacon I'll prep. new device in a day or two. All the same functions like fading tones, user set frequencies 76-110MHz and even Hi-Fi stereo. Many cellphones and MP3 players have extended 76-108 FM (Japan band) , tune your channel outside of commercial band (76-86) for 2-3km range withonly 20mW. Downside of FM TX is long antenna (same sa 72MHz RC)
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Old Jun 12, 2012, 01:29 AM
doo
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[QUOTE=fmkit;21872808]There are tons of FM and UHF spy transmitters offered on ebay,

Do you have any guess of a typical range for the UHF transmitters on ebay?

at this point, I will only be flying with in visual sight of my 3m sailplanes.

Thanks.
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Old Jun 12, 2012, 01:41 AM
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I just read item description of few UHF xmtrs, seem they all claim 300-350meters (could be much better if airborne) and they ask 180% of what normal RF beacon cost.
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Old Jun 12, 2012, 01:51 AM
doo
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just curious if the advertised range was typical or over estimated.

Ok, i am intrigued now. What is the "normal RF beacon"?

Do you have a link that I could read about it?

Thanks.
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Old Jun 12, 2012, 01:58 AM
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http://www.rcgroups.com/forums/showt...beacon&page=41

http://fpv2.com/rf_beacon.html

the device is multifunctional and can input vario's audio
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Old Jun 12, 2012, 02:08 AM
doo
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Hey, if i can put the vario tone into it, and get a range of 1000+ feet then that sounds just like what I need.

Do you have any available now?

I don't need a special fm broadcast band one, the UHF would be fine.
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Old Jun 12, 2012, 02:21 AM
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yes, ship same day
I can solder 3.5mm or RCA plug if you want
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Old Jun 12, 2012, 02:25 AM
doo
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Are the tx power and frequency user adjustable?
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Old Jun 12, 2012, 02:30 AM
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yes, also the transmitter's input is VOX-like, if Varios puts out tone it is transmitted, no RF in between and your walkie-talkie is mute.
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Old Jun 12, 2012, 02:38 AM
doo
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Ok, just to make sure,
I can set the frequency from ~390-490mhz and ~780-980mhz
I can adjust the tx power up to 80mW
and i can have it behave as a beacon(beeps at varying tx power) or input my own audio source and it is vox activated.

This sounds like a really neat set up.

Anything special to order? Just follow the paypal link?

What do you estimate shipping time to USA?

Thanks for all the help.
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Old Jun 12, 2012, 02:47 AM
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all true except hack required if transmitting outside 390-480 band, have to bypass output filter so SiLab chip SI4432 is connected direct to antenna, the mod takes some SMT rework skill and tools, unless asked I never mod. the beacons., besides there are no walkie-talkies in 800MHz band.
registered airmail takes 2-4weeks
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Old Jun 12, 2012, 02:55 AM
doo
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I have sent you a private message.

Thanks.
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Old Jun 13, 2012, 02:39 AM
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yesterday our post office had short day so I was late
in the morning did some FW changes specific to vario
the beacon mode didn't change
microphone input still used for VOX but modulation is no longer analog
input audio or vario's tones heavily compressed and limited
you'll hear clean tones w/ your walkie-talkie regardless of input Vp-p,, input can vary from millivolts to 5v but volume never change and over-modulation not possible
you can swap audio sources without changing setting (gain,deviation).
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Old Jun 14, 2012, 12:44 PM
Quad Whisperer
Joined Jul 2008
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Hi fmkit.
I am also looking for an audio transmitter for my homemade Vario, see here for more info: http://www.rcgroups.com/forums/showthread.php?t=1635845

My vario also speaks, so the audio must be uncompressed.
Can I use your beacon for this? Or do you know of a another suitable transmitter?
I am planning to use a 433MHz walkie.

You seem do be the right man regarding radio stuff
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