So lately I observed one of my student's practical tests with their DPE (private pilot oral), and he got asked a question that made me wonder... Before I say what it is, please note that the question asked was not intended to be honestly answered by my student, the DPE just wanted to show him something new and didn't expect the student to really know this...
Anyway, he asked the student why any FSS would split up their frequencies (using one to receive while transmitting on the VOR). I've always known how to utilize the whole 122.1R frequency, but I myself honestly never understood the purpose of this. Here at Redding (KRDD) we have a frequency to contact FSS on 122.1R and receive on RDD VOR/DME on 108.4. However, just 20 miles away at Red Bluff (KRBL) is a normal FSS frequency on which you can receive and transmit.
I didn't have enough time to stop and talk to the DPE afterwards about this, but it sparked my curiosity none the less. Why does this type of setup even exist? From what I understood based on the very short explanation the DPE provided, is that the actual FSS or RCO is located pretty far from this location, so transmitting on 122.1 actually transmits to the co-located VOR, where the signal is then diverted to FSS via a landline. And therefore that is why FSS communicates on that same VOR frequency... So is this true? The other thing I don't understand is that I overheard another instructor here state that you could actually still receive FSS on 122.1 if you are airborne high enough to reach the RCO/FSS directly. Is this true as well? I've never tried it.
Would love to know this one! (My student passed the checkride, by the way).
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