How to modify offset in FT 817

Hello all

I made some test in AO-07 satellite with gpredict hamlib and my FT-817 everything going very well but I noticed that people call me 2 KHz bellow the frequency shown in the downlink vfo , as an example :

Today I was listening in 145.935 with radio engaged and track too, L mode turned on. A station called me and I hear him calling on 145933 +/- … How I can modify this parameters, seems that I have a frequency shift or offset that in other programs like satpc32 could be modified… any thought???


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If the RX and TX frequencies are not linked together in the radio controller (the button with “L”) you should be able to change the downlink frequency without affecting the uplink frequency.



When I have L button selected and the forward and return frequencies get linked, I receive a station and as soon as I release the L button, I always get responded by that station 2-3KHz below the frequency I was receiving that station on.

I don’t know whether this is due to doppler effect or a wrong parameter configuration.


I’m not sure I understand you, but this is what I do:

Start pass with “Lock” enabled. Spin the Rx dial until you get a a strong CQ, and then fine tune the Rx so that the voice sounds correct.

Then I “unlock” the frequencies and start Tx’ing, responding to the CQ. As I do that, I fine tune the Tx frequency until my voice sounds correct. The pre-programmed frequencies are never 100% correct (the chinese sats are close, though) - so I essentially have to do this every time.


I can’t hear my voice because I work semi duplex. I know that pre programmed frequencies may vary from a sat to another but I’m wondering if there is a feature to add a frequency shift to correct this , it could be very useful to people like me working in semiduplex. I know that satpc32 cand modify the frequencies with a shift to correct that issue but I couldn’t find it in Gpredict. I love the program and the way that with hamlib manages the transceiver…

Thnaks a lot

The only way I know of is to go into the satellite file (each satellite is listed by it’s NORAD number) and offset the range of either the uplink or the downlink to match the offset you want. I did this with a few satellites but later found that since they drift frequently, you would have to constantly adjust the offset.

Working half duplex is a big issue in this regard, you essentially have to CQ only, and let other people find their way to your downlink. Have you ever thought of using a cheap dongle for a Rx only radio? I exclusively use one for my SSB (and sometimes FM) contacts with few issues. It doesn’t work well with SO-50, though - as I don’t have enough filtering to prevent the 2m uplink from killing the 70cm downlink…

Yes I bought a RTL from noolec and it works fine, but I use to work in portable and it is very uncomfortable. I know that semiduplex is weird to work sats, I’m planning to buy another FT817 but , you know money comes sloooooow!!!
I guess that the file containing sat by list is located into Gpredict directory? Or it has a different container… I will check it , I noticed a 2 Khz offset at downlink, let see what happens… Thanks a lot fer Info and help

73 de Rick EA4ZK

I noticed this too but I just use the RIT control on my IC-9100. It’s labeled CLAR for clarifier on the FT-817. I have on as well.
73 Bob vk2byf

Thanks Bob,

I dont have enough fingers!!! :slight_smile: :smile:

But yes you are right , I’m going to use it is the best solution

73’s de Rick EA4ZK

But if you are already using a computer (for cat control of the 817), how is having the dongle for receive any less “portable”? It’s literally the size of a pack of gum, no?

Yes, but my computer is very old, Acer aspire one, it works very slow, I’m pretty new in Linux and didn’t look for a program to use the SDR dongle … Need more time but I’m working on it…

Gqrx works for me on Linux Mint. There is also QubicSDR but I don’t like the UI.

As a point of reference, I’m running GQRX + Gpredict + Hamlib on a laptop from 2012. Works no problem. Might want to give it a whirl… might just work for you.