I need to receive transmissions in this range. SparkFun has plenty of options for FM, up to 108, but I haven't found anything for the range I need.
Thanks!
Andy
Yes, I have Googled it and know about a lot of commercial full units at that frequency. The search returns 12 pages of results and every one of them is a full product or a discussion of use of full products. I don't know of an Arduino board for it and I am not an engineer; I can't just find parts and design one. I can wire one if it isn't very complex and I can code for it (that's my background).
I did not know for sure that it did not exist. I was hopeful that by posting here I might find out it did, or some simple mod to an existing item would work (like getting one of the SparkFun FM receivers to extend the range). I don't have the resources to design it, but I do have the resources to build it. I might use a slightly modded FM radio (there is a very short YouTube video from Make on how to do this) to tune the signal for the prototype. I am under an NDA and cannot disclose exactly what the Arduino will control. I have decades of software experience including a lot of firmware and drivers, so I understand what to do with chips as far as testing or setting pin states. Where I am weak is on resistors and capacitors and other support circuitry.
I was brought into the project to help create a prototype for proof of concept. It is hard to discuss openly without violating confidence, but the people I am working with have a manually controlled device of their own creation that addresses one market and could potentially address another if it had an autonomous operation mode.
If I am successful with this, it is likely to be well funded and a real engineer would integrate the components I am using for manufacturing. They have seed money now, but the budget I am working with is somewhat constrained. Spending hundreds to get the hardware for this is not a problem (as long as it it won't really cost that much in bulk), but thousands is, and I don't think I could bring in an engineer for less.
The Arduino concept is very cool - it allows guys like me who really mostly know software and the basics of building to put together some fairly sophisticated designs without any real engineering. But when you hit the wall, it is fairly solid...
121.5 Mhz is Civil Aircraft band, shouldn't be too difficult to connect an Arduno to the headphone socket of an Air band receiver........
121.5 is not only aircraft band, it's the emergency ("guard") frequency. Many 2m ham radios as well as most scanners will receive this frequency.
-j
121.5 Mhz is Civil Aircraft band, shouldn't be too difficult to connect an Arduno to the headphone socket of an Air band receiver........
That is likely what I will do for the prototype.
Since arbarnhart can't tell us anything, we're really just shooting in the dark here.
With all due respect, I don't think it is exactly dark. If I were asking about 100 MHz, someone would have whacked me with a noodle and pointed out that it is smack in middle of the FM range and sent me off to SparkFun. I need to monitor a different frequency and I was hoping there was an existing component built to drop in like there was for FM so there would be less work involved in incorporating it, less redundant parts drawing power, etc. You want to know why I want to monitor that frequency because we humans are curious. But I can't tell you without potentially incurring my client's wrath and possible legal recourse.
From researching some of them recently, I noted that their manufacturers (the OEM companies in China, not SparkFun) make some of those products in a way that they can be semi-customized for whatever frequency the customer needs. Including, I am quite certain, your frequency range.
Any particular one that I might look at and do further research on?
I did notice that the FM tuner has a crystal on board. Would replacing that change the range?
So are you saying that it is an aricraft related area? You are saying that it is AM (vs FM, etc.)? Again, you don't have to disclose it to US, but you must be sure of it yourself so that you know that it will work.
I don't know radio that well, I will readily admit. But on the Make video:
they use an FM radio with a minor mod to tune in air band traffic. I picked up a cheap radio and did that (I haven't verified yet, but I did get the effect in the video that tuning FM requires me to adjust much lower than the station's correct position) and when I get my "Company A" 
transmitter in a few days I will see if I can receive from it with that. Not a long term solution, even if it works, but will let me continue with a major part of it.
I find these kinds of threads aggravating. The original poster is extremely vague and is unaware of what they are asking and does not want to give further details.
My suggestion: find a local HAM operator and/or pilot. I just happen to be both.
FM Broadcast radios decode "FM" signals (clever how they named the radio)
121.5 is the Aircraft Emergency Frequency. All Aircraft radios are AM.
AM is not FM. A FM radio might detect the warbler if the ELT is activated but voices would be distorted.
At best, the arduino could detect audio and turn something on. However, any cheap Uniden scanner already does that and decodes the audio properly (via the record/aux connection).
Rural airports have automated light controls that can turn on the runway lights remotely by clicking the radio microphone a few times in the air (gives 5 minutes of runway lighting and then they turn off again). But that would be on the approach frequency, not the emergency frequency.
Try tuning your modified FM radio to the local airport frequency. Can you hear the tower? In a perfect world, 121.5 is NEVER used (only during a crash). The tower frequency is extremely busy and could be used by your RX circuit for testing.
OK, I talked to my client and convinced him that since lots of people make beacon finders, there is no harm in saying that a beacon finder is part of our product. I have a radio direction finder that indicates direction by lighting LEDs, so I just have to monitor the LED leads to get the direction it is indicating (figured that out all by myself without asking vague questions 
). The direction finder just needs to be wired to the antenna lead and the audio of a receiver tuned to the right frequency. For the prototype, for proof of concept, all I need is a receiver wired in to the finder, so no matter how bad the audio sounds, as long as the audio is controlled by the transmission, life is good. However, in the actual product, there does exist the possibility that there will be more than one beacon transmitting and I would have to decode a digital transmission to get the ID of the sending unit to decide whether or not to pay attention to the direction it came from. I would be trying to decode a block of information matching the last one on this page:
http://cospas-sarsat.org/index.php?option=com_content&view=article&catid=39:beacon-coding-guide&id=282:serial-user-protocol-examples&Itemid=118&lang=en
and there may be an option to use a different receiver to get the block second from the bottom from a different beacon.
I still cannot tell you what the product will do with the information about what direction a beacon is transmitting from, but hopefully there is enough "vagueness" removed for me to beg for someone to point me in a helpful direction.