[VHFcontesting] Understanding HamIM

[Ev Tupis]

I'm chuckling as I write this because I'm spending so much time replying to 
individual messages from a recent posting to the VHFContesting list about the 
subleties of HamIM (very positive and encouraging e-mails...not disparaging in 
any way), I wonder why it seems like the "nay sayers" seem to post to the list 
while the others send direct. :)

Here's a quick FAQ, based on the emails I've most recently received.  By the 
way, don't confuse the thread about "Sports vs. Radiosports" with this.  They 
are two different things...

Q: What about the rule against two signals on a band?  What happens if I am in 
the middle of a contest contact on 2m SSB, and HamIM TX's?
A: You are in violation of the rules. :)  This is no different of an issue than 
what happens if you are on 146.55 FM making a voice contact, and you forget to 
turn off your voice or CW CQer on 144.200.  To avoid this, home stations set 
their HamIM TX interval to "9999" minutes.  That way, it will TX once 
automatically, but never automatically again.  Periodically, you manually TX. 
Rovers can either do the same thing, or (even better) use Packet Radio's ability 
to sense a channel that is in use and TX every 5 minutes.  Because your antennas 
are closer, your 144.2 MHz operation will probably QRM HamIM enough to have it 
not TX until you are done.  In all practicality...the rule exists to keep 
stations from monopolizing an entire band.  If the violation of this rule is 
incidental (as in: the 0.5-second HamIM transmission on a virtually unused 
147-MHz simplex frequency), I doubt you'll even have it brought to your 
attention. :)  Still, it is better to be safe, than sorry.

Q: Why FM?  Why Packet?  Why APRS?
A: FM is very tuning-insensitive and the equipment is cheap.  Just put as much 
RF output into your HamIM station as you can.  It's simplex FM, after all. 
Packet is cheap, too.  Even if you have to buy a KISS capable TNC.  This is 
built on APRS technology and APRS enjoys the following of thousands on a daily 
basis.  We talk a big talk about wanting to increase the VHF contesting 
ranks...here's a technology that not only helps us to squeeze out more QSO's, 
but it is something that may actually DRAW more mobiles into our niche (APRS is 
built around tracking mobiles...it's a natural!)

Q: Why vertical antennas?  Why not beams?
A: They are cheap. (see a theme emerging?)  They are omni.  You never know where 
a HamIM rover is going to show up from.  Home stations, and most rovers will 
want to use simple verticals.  "Competition grade" rovers may wish to use a 
small beam if they are at any significant distance from a population center. 
There's nothing wrong with setting up on a hilltop, 200km away from a population 
center, and pointing a 4-element vertical HamIM beam to where you know there are 
other operators to work.

Q: Why not just use an SSB liaison frequency to get noticed when Roving?
A: No reason not to.  HamIM has many advantages, though.  On HamIM...everyone 
uses 147.585 MHz as that "liaison" and it is automatically monitored for you. 
Imagine this:  You go to 144.260 (your published liaison frequency), you call CQ 
on SSB and are answered by a station who was waiting for you.  Off you go to 
"work the bands".  Several minutes later, someone else tunes to 144.260 to call 
you ('cause you said that is your liaison).  Hearing nothing, they assume you're 
not in range yet and go off to CQ more.  With HamIM, they know you're in range 
('cause you are now a symbol on their screen) and they send you a keyboard 
message.  That message will stay on your screen (it's a popup...like Internet's 
IM).  You can reply to it (making the QSO on 2m and logging it) and tell them 
what band you're on now, so they can join the QSO train as it works it's way 
through your available bands.  Rovers gotta LOVE this.  Imagine a handfull of 
small and medium size stations with HamIM and the impact that can have on a 
Rover's score!

'nuf for now.  Give it a try!
Ev, W2EV
more info: http://w2ev.rochesterny.org