Offsets

[xflyerwdavis]

I have a Kenwood TH-F6A that I would like to use to contact the ISS if possible.
I understand that the offset is-1.31, my radio will only go -1.31 or -1.35; what do I do?
Walter KD4OMR

 

[Captain Kilowatt]

If the offset is -1.31 and your radio will do
-1.31 what is the problem? If you are trying toaccount for Doppler shift then change the tuning step to 5 KHz or program separate TX and RX frequencies into memory channels. You can make any offset that way.

 

[xflyerwdavis]

My mistake. My radio will do -1.30 then it goes to -1.35. I cannot get it to program -1.31.
73
Walter KD4OMR

 

[Captain Kilowatt]

Same answer as above. Change the tuning steps to 5 khz or program separate odd split. frequencies

 

[exces3]

what are we talking about here?

ISS transmits on 145.800mhz
ISS wants to receive on 144.490
or not, is that where 1.31 comes from?

who corrects for doppler, the person receiving?

 

[Captain Kilowatt]

what are we talking about here?

ISS transmits on 145.800mhz
ISS wants to receive on 144.490
or not, is that where 1.31 comes from?

who corrects for doppler, the person receiving?

Correct. You as a ground based user would RX on 145.800 and TX on 144.490 which is 1.31 MHz lower hence the offset. The receive end compensates for Doppler shift usually however this is low in frequency and it is not that much and most don't bother. On 70 cm however Doppler can be significant and must be accounted for on the receive end.Sometimes it can be 5-10 KHz of shift.