If you have followed any of my magazine columns in the pages of Monitoring Times over the last 25 years, you might have seen me use the term -- "Spectrum Hole."In August 2006, I introduced the concept of Spectrum Holes to my readers here on the Milcom Monitoring Post blog. In just over the course of a year, I mapped out and posted to the pages of this blog, all of the spectrum holes I had in my personal data base for the 225-400 MHz military air band.
Since then the readership here on the Milcom MP blog has increased over five fold in size so it is time for another round of updates. Starting with this posting I will compile and post a new list of UHF Milair spectrum hole frequencies.
So what are frequency Spectrum Holes?
A spectrum hole is a term that I coined many years ago for a lack of activity on a frequency within a portion of the radio spectrum. When you have valid frequency assignment in a spectrum bandplan that has no reported/monitored activity or known allocation assigned to that frequency by the controlling agency, you have a spectrum hole.
It has always been well worth the memory space in my scanners to have spectrum holes from the 225-400 MHz military aeronautical band programmed in. What makes the spectrum holes in the 225-400 MHz range so fascinating to me is that what was finally heard some of my former spectrum hole frequencies has been very interesting.
For instance, several years ago, a few of my then spectrum hole frequencies in the 225-400 MHz band turned out to be AFSATCOM downlinks from DoD military communications satellites in high Molniya polar orbits.
So if you want to do some cutting edge exploration of the UHF Milair band and be the first to monitor comms on a spectrum hole freq, grab an extra scanner or a few spare memory locations, and plug in the frequencies from my spectrum hole list posted here on this blog and let me know what you hear.
Mr. MT, down in FLA, did just that and recently passed along a couple of his spectrum hole discoveries.
"252.300 - I received a signal that seemed to be digital. (I have no digital receiver at this time.)
326.250 - I had one side of a voice conversation that seemed to be from a ground based transmitter. I now have a radio looking at that frequency only."
When reporting activity on any of the spectrum hole frequencies in my list, be sure to pass along any info that can help identify the user and frequency usage. Also let me know if you want your catch listed here and how you want to be identified.
Please note that my spectrum hole list is valid for ITU Region 2 only (North/Central/South America). Other areas of the world have their own bandplans so this list would not be valid in say Europe, where the UHF Milair band is extremely packed with activity.
So folks, let's get cracking and let me know if you hear any activity on any of my mystery frequencies presented below in this posting.
Will you be the first radio monitor to hear any activity on the spectrum hole frequencies listed in this posting? Who will be the first person to intercept and report a true radio mystery?
Spectrum Hole List Part 1 (225.000-259.975 MHz)
Note: Any frequency below that is bolded are the highest priority monitoring targets and should be monitored very closely. Any freqs marked with an asterisk should also be high on your target list.
225.0750 226.0750 226.9250 226.9750 227.2250 227.3250 227.3750 227.4250 227.4750 227.5250 227.5750 228.0250 228.0750 228.6750 228.7750 228.8250 228.8750 229.0250 230.2500* 233.9250 234.6250 234.6750 234.7250 234.7500* 235.0750 235.3750 235.4250 235.5250 235.5750 235.8750 236.1250 236.1750 236.5750 236.6250 236.6750 236.8750 236.9250 237.4750 237.5250 237.6250 237.7250 238.0750 238.4500* 238.4750 238.5250 238.7750 238.8750 238.9250 239.0750 239.1250 239.1750 239.2250 239.3750 239.4250 239.5250 239.5750 239.7750 239.9250 240.0750 240.1750 240.2500* 240.3250 240.3750 240.5250 240.5500* 240.5750 241.8750 241.9500* 242.0250 242.0500* 242.0750 242.2500* 242.3250 242.3750 242.4750 242.5250 242.6250 242.6750 242.7750 243.2500* 243.3250 243.3500* 243.3750 243.4250 243.4500* 243.5250 243.5500* 243.5750 243.6250 244.3250 244.3750 244.4250 244.5250 244.6250 244.6750 244.8250 244.9250 245.0250 245.0750 245.1250 245.4250 245.4500* 245.4750 245.5250 245.6250 245.6750 247.0250 247.0750 247.1250 248.3750 248.4750 248.5250 248.6250 248.6750 248.7750 249.9750 250.1750 250.2750 250.3750 250.4750 250.5750 250.6750 250.7250 250.8250 250.8750 250.9750 251.3750 251.5750 251.6250 251.6750 252.2250 252.2750 252.3250 252.3750 252.4500* 252.4750 252.6750 252.8750 253.1750 253.2250 253.2750 253.4250 253.4750 254.6250 254.6500* 254.7750 254.8750 254.9250 255.0250 255.0750 255.2750 255.3250 255.4250 255.4750 255.5250 255.6250 255.6500* 255.6750 255.8250 255.9250 255.9750 256.0750 256.1250 256.1750 256.4250 256.7250 256.9750 257.0250 258.0250 258.0500* 258.0750 258.1750 258.2250 258.2750 258.3250 258.4750 258.5250 258.8750 258.9250 258.9750 259.0500* 259.0750 259.2250 259.2500* 259.2750 259.5250 259.6250 259.7750 259.8500* 259.8750 259.9250 259.9750