Hello, I’m trying to make a simple VHF transmitter/beacon with ideally ~1km range (at a minimum 500m) and as small as possible. It will be incorporated into an instrument housing mounted on a wildlife GPS collar which will drop off at a programmed time. The VHF transmitter will be used with a simple receiver/headphones to locate the dropped instrument. It will be powered from a 3.3V power switch. It does not need to transmit any data, only a locatable signal, and needs to begin transmitting signal immediately upon receiving power. I’m thinking ~150MHz (for increased range), but could also be 433MHz. I plan to integrate 1/4 wave antenna. Ideally I’m looking for a solution that does not require a microcontroller for operation (fine if needed for initial programming). I was considering a RMF69 unit with a 10k resistor (for continuous tone transmission) or a 555 timer (for pulsed transmission). Would this solution work for the application? Would a pulsed transmission using a 555 timer significantly more power efficient? Is there a simpler/better solution? If there’s an OTS option that is inexpensive that would work as well. Let me know if any more details would be useful. I have some RF experience, but not much so the more explanation the better. Thanks!
One of these might work?
Thanks for the suggestion! Yes I was looking into that part. I’m trying to set it up without the need for a microcontroller. I think I could transmit continuous transmission by connecting data pin to ground or Vin, would that work? It would be even better to have periodic transmission for power efficiency. To accomplish this at ~1Hz, I was considering using a 100kOhm resistor and a 2uF capacitor, connecting the resistor between Vin pin and data, and the capacitor between the data pin and ground. Would this work? Would there be a simpler/better way to accomplish this?
A 555 sending out a string of pulses at 2KHz is what I’d use, but give the resistor capacitor oscillator a try, it might work. I haven’t verified this but I believe it should give you a 2000 Hz tone when tuned to the transmitter frequency.
I think you’re underestimating how difficult it will be to locate the RF beacon, whatever it winds up being. The receiver(s) system is by far the more difficult challenge.
You can start experimenting with receiver/transmitter pairs more readily available like walkie talkies or one of those headphone-FM radio transmitters or remote LED Christmas lights.
If you can narrow the search within a kilometer or less, I’d consider a noisemaker with a periodic and loud homing tone to use your wetware stereo audio receiver. An old smoke detector will make this sort of sound for weeks when the battery gets low.
Similarly, if you can search for the beacon at night and in wilderness, an infrared light source and some entry level NV equipment, possibly even existing photographic equipment and cell/cams, might do the trick.
In the ham radio world we have all sorts of direction finding tools, including the Kraken, which is likely a bit of overkill for you. 
Question: Why not a microcontroller? One way or the other, you will have to precisely define what you want the system to do. Another option might be the programmable logic chips from Dialog. They are VERY low cost to develop with, come on convenient prototyping boards, and can do surprisingly complex things. I designed a transmit only avalanche beacon (rather similar to your system I think) which implemented controllable transmit on time, and time between pulses, plus logic to blink an LED once a second at first, then switch to every other second to save power, plus generating the precise 457kHz carrier (in your case a kHz tone to modulate the transmitter), plus a wakeup to the main system after 12 hours in transmit. It’s been a few years and I’m likely leaving some things out… All this on a small inexpensive chip plus a crystal and two caps (because I needed an accurate transmit frequency, you could use one of the on-chip oscillators. In the end, a one-chip-wonder, and probably <$2
IMHO Sparkfun should carry the Dialog line, it is VERY hobbyist friendly,
Here’s a link to one of the parts in the line, they can be a bit tricky to find since Renesas aquired them. “GreenPak” is a good search term.
SLG46826