Ev Tupis wrote:
> ----- Original Message ----
> From: Nate Duehr <nate@natetech.com>
>
> I interpreted the rules restricting no more than one transmitter active per
> band to mean that if the APRS is on VHF, the VHF SSB must be off, or
> vice-versa.
>
> Wouldn't you agree?
> ---------------------------
>
> Ah yes! You're right, of course. Here's how that is addressed...
>
> TNC's use an anti-collision method called CSMA. Carrier Sense Multiple
> Access. They use their RXing to assure that there is no signal on the
> channel prior to TXing.
>
> Even at 147.585 MHz, there is significant QRM from SSB operation on 144.2
> MHz. As a result is (often, but not always) that the packet HamIM system
> will not TX until your SSB station stops TXing.
I was using a D-700, no TNC. My experience with this was that the QRM
from the 144.X SSB radio would overload the D700 enough that it thought
the channel was CLEAR, not busy, and it would transmit. (I noticed this
a few days before the 'test.)
> Lastly, if it no combination of settings works, use a contacts on the 2m SSB
> station to activate a relay that makes/breaks the TNC's PTT control.
Again, in this case I wasn't running a TNC, but it wouldn't matter --
the radio thought the channel was clear. Even a real TNC interfaced to
that radio in my particular setup would think that, although your idea
of physically pulling the PTT connection would work... but it's
something else to break during the contest, and something else to be
wired up and tested... and if you switch to a backup VHF radio for any
reason, you'd still have to deal with turning the data radio off, etc.
> The advantage of HamIM is significant where home-based stations know to
> employ the strategy. Even Rover-to-Rover communications is enhanced since
> they often operate from hilltops (LOS) and get noticed more easily. I've
> completed QSO's with HamIM equipped rovers because of HamIM that I would have
> missed otherwise.
Yeah, I'm meaning to try the HamIM thing out with at least one other
rover out here if we can figure it all out -- but it's secondary or
tiertiary to actually operating in the contest, so it'll either get
installed and tested... or it won't. The number of points any HamIM
contacts would add on a single band, don't outweigh simply getting on
the air, finding the other rover, and working them. Maybe HamIM belongs
on another band other than VHF, but that would make us "captive
HamIM'ers" or some other silly crap, and defeat the purpose of using it
to "find" other rovers... as if there were any out there that would have
enough gear, time, and effort to have another complete VHF station, TNC,
computer dedicated to HamIM, etc. (No, I will *NOT* put HamIM on the
logging computer... sorry... logging is sacred. GRIN.)
It's in the "maybe next year" category right now, and we'll see if it
even makes the short list of things that need to be done to put the
rover on the road next year. I'm changing vehicles (going to use a
Suburban... the folks that think building a big contesting station at
home is expensive, I'll send you my fuel bill and we can compare!
GRIN...), so there's a lot of prep work to "re-build" the rover setup
for next year...
Plus if I had to choose between using HamIM and maybe dragging the video
camera along for some documentation and fun later making up some video
of the great time we have in the middle of nowhere... the video camera
would win hands down. And operating when the bands are open wins over
*everything* else. (GRIN)
Nate WY0X
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