Hello Jim, and Readers:
Recently I was looking for a way to record some long distance sounds, and thought of a solution for Listening post observation posts. I discovered an old Dish Network or Direct TV dish will work fine with a microphone mounted to it.
Using a UHF or N type bulkhead RF connector mounted to the point where the old antenna LNB was mounted I drilled a hole large enough on the front of the antenna mount with a step drill for the base of the RF connector, and 1/8th holes for the flange mount of the connector, and mounted it with 4-40 hardware. Using a standard PA system microphone mount, and screwing it on to the RF connector and then placing the microphone to the dish focal point. allows for a bit more forward gain, and a bit more directional capability.
I found a small audio mixer for a single or multiple microphone setup works fine, Musicians Friend.com has these small mixers for as little as about seventy five dollars. They can be connected to a set of earphones, and or a recording device like a cassette tape recorder, or MP3 recorder. There are several brands that are low cost, I bought a Baringer model for my setup. I prefer microphones with standard XLR PA system connectors and standard microphone cables to keep things simple and standardized.
I must caution there are laws protecting your neighbors privacy and those laws should be obeyed. I do believe in a situation where there may be threatening times and being able to hear threats sooner than later would be very beneficial.
The mount for the dish can be a simple pipe on a stand, or rig it up to some kind of portable tripod. Most of the available mixers use and 18 volt AC power supply so a small AC inverter would be required to run the device. I have modified a few units to work on 12 VDC as long as I don’t need the phantom power for a microphone the unit works fine. But for those who don’t know how to make this modification it is best to use a small DC to AC inverter. Using one of those battery booster boxes so prevalent in auto parts stores or box stores will work fine, they usually incorporate an AC inverter, light, and cigar lighter socket for 12 volt accessories. I found that recording the sounds I was looking to record were able to be heard very well through the mixer amplifier, in the headphones. So much so that my old shoulder held artillery ears could actually distinguish what was going on.
If you were limited in personnel resources and needed to force multiply, think about obtaining several dishes and placing them in strategic places run all the microphones into a multi-channel mixer and listen to everything with enhanced hearing, if a sound of interest is heard, simply fade out one mike at a time until only the one of interest is heard. Low impedance microphones like the ones with XLR three pin connectors will work to about 200 feet or more, Just think about how far the lines are run at large concerts from a stage to the sound booth.
I am fortunate I have several dishes that have been left after discharging the television companies from getting too greedy. The dishes are generally left when the receiving equipment is returned to the companies. I have several friends who have offered them to me also. They can frequently be found at yard sales too.
I might also mention that these units can be adapted to make small microwave video and audio sender, receiver units, It takes four dishes and two sets of video sender/ receiver units to make a full duplex system. They generally have 4 channels each. The 5 GHz units would have the most gain for the dish sizes, and by making one set with the antennas horizontal and one full set vertical polarization the units can give you a couple of miles of line of site full duplex audio and video. Usually the video sender receiver units have two audio sub channels. providing two separate telephone circuits, The video can be connected to a video camera and used for remote surveillance or a video data link. Unless you run some kind of encrypted audio through a computer audio sound card, these units are in the clear.
Being microwave and highly directional the probability of intercept is much lower and at 5 GHz the chances of someone having a scanner or spectrum analyzer to look for your signals is reduced. These video units usually also work on 12 volts. They are consumer products as purchased. Modified they then become a device that no longer meets Part 15 rules. Please take this into consideration if you plan to construct these units.
Running simple audio video lines from the sets to a monitoring position can be done up to about 50 feet or so.
This piece is over-simplified but to keep this in mind for future reference, a good radio tech or engineer can accomplish these projects fairly easily. the 5 GHz, or even 2.5 GHz units can be used, but the antenna systems for the units must be modified and takes someone familiar with antenna systems to accomplish this easily. Blessings, – Dave in Oregon