[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: re: QRM 2m, question for sat builders



>- Bigest reason is that with MODE-J you have no
>problem with the 3rd harmonics of
>  the transmitter. This makes your receiver overloaded
>and less sensitive without
>  any good filter at the TX side. Its a real serious
>problem.

Understood, but somehow SO-35 and AO-7 overcame it, and my mobile rig is content to transmit 50 watts into the same antenna it listens on 435 with, with no ill effect given the right choice of frequencies. Isn't it better to deal with this problem once in the satellite and not at every ground station?

>- Then on 70cm there is much more bandwidth available
>than on 2m. An downlink on
>  70cm makes the change smaller of having downlink
>interference of 2 satellites.

Conversely, Mode J leaves you with conflicting uplinks, with seems to be a bigger problem (listen to FO-29 during a mutual pass with AO-51). If we had enough 2 way LEOs to fill up 2 meters I wouldn't be upset if they sometimes overlapped.

>- For the groundstation you also need to have more ERP
>on 70cm compared with 2m.
>  This is because of more path losses. More power on
>70cm is more complicated than
>  on 2m because of more cable losses, more expensive
>amplifiers etc...

When I worked AO-7 and SO-35 with 5 watts, amplifier expense did not seem to be a big issue....


>Just wait for P3e, it will have MODE-UV (the old
>MODE-B) :o)

I can not wait my friend, I am in need of a HEO in a bad way...but I was specifically discussing mode choices at LEO.

Thanks for the reply.

73, Drew KO4MA
----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home