And of course 122.305 is same as 122.300 so if you use a 25k radio nobody can tell
Not true.
I flew to Dunsfold the other day and due to a misunderstanding with my student, I initially dialled up 119.100 on a 25kHz box. They called back saying “Readability 2; are you calling on 119.100? The correct frequency is 119.105.”
I redialled 119.105 and everything was fine.
So they clearly can tell.
Are you telling me that what happened at Dunsfold didn’t happen?
Timothy wrote:
I flew to Dunsfold the other day and due to a misunderstanding with my student, I initially dialled up 119.100 on a 25kHz box. They called back saying “Readability 2; are you calling on 119.100? The correct frequency is 119.105.”
The requirements for transmitter frequency accuracy on a 25 kHz box are wide enough that your transmitter could be within specs and still sufficiently off to make reception difficult with a receiver having the 8.33 spec bandwidth.
But is seems to be the accepted truth in this forum that modern 25 kHz boxes are in practise accurate enough to be within 8.33 kHz specs anyway. In that case there is absolutely no way the ground station could tell.
Hold old is your 25 kHz radio?
The key aspect here is that the 005 add-on doesn’t change the transmit frequency.
119.100 is not a 005 add-on so can’t be used with a 25k radio.
Most UK airfields have gone to 833 using the 005 add-on.
Peter wrote:
119.100 is not a 005 add-on so can’t be used with a 25k radio.
Do you mean 119.010?
Timothy wrote:
Not true.I flew to Dunsfold the other day and due to a misunderstanding with my student, I initially dialled up 119.100 on a 25kHz box. They called back saying “Readability 2; are you calling on 119.100? The correct frequency is 119.105.”
I redialled 119.105 and everything was fine.
So they clearly can tell.
If the 25kHz radio is in spec, it might not be because you dialled it up on a 25kHz radio – it could be due to antenna placement for that radio, the feedline to the antenna, the efficiency of the antenna and how well matched it is. Unless the 25kHz radio centre frequency is well off it’s unlikely they can tell “because it’s a 25kHz radio”. There’s a good chance if you swapped the feedlines for the two radios behind the instrument panel, they’d give you “readability 2” if you called them on 119.105 on the 8.33 radio and readability 5 if you called them on 119.100 on the 25kHz box. All things being equal and modern radios in good condition, no one can tell if you’re calling on 119.100 or 119.105 because they are the same frequency.
I accept all of that, and the theory, but Peter said that no-one on the ground will know if you are using a 25kHz radio.
That is demonstrably not true, in a real life scenario, as I have explained.
Was this the same box you used for .105 and .100?
No. Firstly on a 25kHz box on 119.100 then a 8.33kHz box on 119.105. That was exactly the scenario Peter described.
