Note that there is simplex communications where the facility, usually 
flight service station (flight plans, weather conditions, and other info 
for safe  flight) transmit on the voice associated with a navigation 
frequency (typically a VOR (VHF omnirange station)) say 113.6 and the 
pilot transmits on a different frequency say 122.1 that has a receiver 
at that ground station.

Vitaliy wrote:
> Sean Breheny wrote:
>   
>> An Icom IC-R20. It can do simultaneous receive of two frequencies. I
>> initially noticed the apparent "duplex" by switching back and forth
>> between the two freqs but then confirmed it using the simultaneous
>> receive.
>>     
>
> Do you have the unblocked version? How much did you pay for it? Would you 
> recommend it? :-)
>
> Sorry for asking so many questions.
>
> Vitaliy 
>
>   
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