HFU HF Underground
Loggings => VHF/UHF Logs, including satellites and radiosondes => Topic started by: ChrisSmolinski on October 17, 2019, 1916 UTC
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Tuning around the VHF aviation band, I found a station on 117.900 MHz AM, synth OM with non stop weather. Somewhat weak, so difficult to pick out more details than it's weather. Some quick web searches failed to turn up anything.
Any ideas? Josh? You're the VHF/UHF guru, any guess who/what this is?
Update:
OK, now I am not sure this is weather. He's mentioning states, several from this area like NY, CT, NJ, MD, VA, "and coastal waters", then flight level something or other. Some sort of warning/advisory?
OK solved... I think! The Westminster VORTAC transmitter.
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"The VHF airband uses the frequencies between 108 and 137 MHz. The lowest 10 MHz of the band, from 108–117.95 MHz, is split into 200 narrow-band channels of 50 kHz. These are reserved for navigational aids such as VOR beacons, and precision approach systems such as ILS localizers."
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That is Westminster VORTAC and should be sending MCW of EMI. The weather is the HIWAS (https://www.faa.gov/air_traffic/publications/atpubs/fs_html/chap2_section_4.html) service.
See if you can get better reception with a horizontally polarized antenna.
And the FAA is considering discontinuing the HIWAS service.
https://www.federalregister.gov/documents/2018/07/23/2018-15632/notice-of-proposal-to-discontinue-hazardous-inflight-weather-advisory-service-hiwas
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I now believe this was not weather, but just a short repeated message about general aviation rules in the area. Apparently some VORs send this kind of message, from some brief web searches.
Westminster sends weather on 121.250, it is one of my "tough to hear beacons" that I use to gauge VHF antenna performance. The Frederick airport is even harder for me to hear.
One problem is I am using a "satellite" 900-2500 MHz LNA out at the discone, which likely has very low gain or perhaps even some loss down in the VHF band. Eventually I would like to get a better remote LNA.
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If you go to this site
https://skyvector.com/
type in KDMW,
then in the tabs at the top click on Washington,
and them zoom in, you should see the VFR chart for Washington area.
121.25 is the automated weather for the KDMW airport and the EMI VORTAC is no co-located as you can see in the chart.
You can see in the picture, the 117.9 EMI VORTAC has a little H in the box, standing for HIWAS. Usually that is just weather, but I imagine since it's the DC area, that is why you are hearing other messages about airspace. That site has the capability to listen on 122.1 for aircraft and transmit voice on 117.9.
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Thanks for the map link!