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RE: Mode-B vs Mode-J



> The link between a typical dual-band mobile rig with an OMNI 
> antenna and a
> typical mode J satellite transponder has almost a 22 dB link inbalance
> between uplink and downlink.  (no wonder the first-timer 
> doesn't hear it!)

Actually, the imbalance is likely to be _worse_ than this, because your
typical mobile antenna (and base omni that the first timer will try the
birds out with) has a flatter radiation pattern on 70cm than on 2m.
> 
> The link between the same dual-band mobile rig and a mode B satellite
> transponder is just about balanced.  (everyone hears it!)

Again, radiation patterns for typical newbie stations favour Mode B even
more.

> Mode-B is really quite a nice way to go.

There's only one fly in the ointment down here, and that's the paging
systems on 148 MHz, which cause some grief to 2m (I don't use 2m mobile
around town a lot as a result).  However, a decent (read: one with good
strong signal performance), and a low, skward pointing antenna (even a
diople!) solves all of these issues.
> 
> Also, the original reason for Mode-J (Japan) was because it 
> was impossible
> to hear the 2m Mode-B downlink in Japan because all the truckers and
> CB'ers in Japan were using 2 meter rigs for lots of illegal 
> operations,
> making the 145.8 to 145.9 band useless for downlnks.  But that was 20
> years ago.  Now they have all migrated to Cellphones and other bands.

Now, the problem is illegal equipment getting into the uplink on 145 MHz.
:-(
> 
> But these are just long term design issues.  I fully support ANY
> transonder (Mode-J or B) that AMSAT choses to build..

Agreed, though I have a strong preference for B over J, for the reasons
stated.

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