[hfsig] HF performance under 1000 miles?

Robert Bruninga bruninga at usna.edu
Tue Oct 11 13:29:49 CDT 2016


The tradeoff I’m working with here is position resolution for an APRS
mobile.  Right now Grid squares are worldwide unique.  This requires a lot
of bits that never change unless the DX is huge.  I took another look at it
and if we organize the same grids into groups that are 9x9, instead of the
current 180x180, then we can get a position down to about 0.2x0.3 miles
instead of the current 7x10 mile resolution in the same number of bits.



But the positions are not unique worldwide but repeat every 1800 miles in
latitude and every 2500 miles in longitude.  But this pretty well covers a
continent.  SO, we can use this if we chose a band that hardly ever goes
beyond 1800 miles…



What do you think about 30 meters?  I guess it can still do that far?  OK,
then what about 40m?



And again, I am only talking about the transmitter end being a mobile with
a vertical antenna.

I appreciate your input.



Bob

WB4aPR



*From:* hfsig [mailto:hfsig-bounces at tapr.org] *On Behalf Of *Mitch Winkle
*Sent:* Tuesday, October 11, 2016 9:21 AM
*To:* TAPR HF Modes SIG Mailing List
*Subject:* Re: [hfsig] HF performance under 200 miles?



DX is hardly evil as long as the results are achieved.  Your project, your
decision...my 2 cents.

Mitch



On Oct 10, 2016 9:37 PM, "Robert Bruninga" <bruninga at usna.edu> wrote:

But I dont want DX ever in this app..  I want HF that works out to 250
miles during the day and not much beyond 500 miles at night.  Then, just
like WIDE1-1 on VHF, we can keep things HF local, re-use the freuqncy and
also gain 100 to one precision by not having to transmit worl-wide unique
posits, but just say 1000 mile unique.  That's the idea anyway.

I climbed up the roof to inspect my multi-band dipole and to my amazement,
all 8 legs were intact, and just drooping down in the shrubery on all
sides, so it looks like aI can gt back on HF by just a lot of rock throwing
and string...

bob, WB4APR



On Mon, Oct 10, 2016 at 11:36 AM, Mitch Winkle <mitchwinkle at gmail.com>
wrote:

That's not always valid reasoning when it comes to HF actually, and here's
why.



Just because the "nearest" HF gate is 200 - 300 miles away doesn't mean
that's the best one to use all the time.  NVIS communications make sense if
you are networking around that model (such as MARS does in regional
comms).  If you are involving alternate connectivity such as internet, RF
distance is rather inconsequential.



Case in point:  Using WINMOR for Winlink connectivity for the recent
Virginia ARES SET, it was necessary for me to use a station in North Miami,
FL, over 1000 miles away in order to gain access to the network reliably on
HF.  Now the same could be said for HF APRS as well.  Why worry about the
distance at all?  Designate a frequency on each band and be happy.
Scanning is commonplace for many types of networking tools such as packet,
ALE and Winlink systems.



To try to provide a direct answer to your question though, an overall high
availability data only band like 30m (which is already the target for many
using APRS) makes a lot of sense.  It's long-regional flavor spans not only
NVIS on it's edge days of propagation, but good sky wave as well, and solid
overnight performance for many hundreds of miles.  It is common to have
trans-Atlantic QSO's in the dark also.



"What frequency should I use on HF?" is one of the most asked questions in
all of Amateur Radio.  The answer is almost always the same.  "The one that
works today."


--
Mitch Winkle
http://ewamjlu.blogspot.com
...How long will you go limping between two different opinions? If the LORD
is God, follow him...
1 Kings 18 ESV



On Mon, Oct 10, 2016 at 9:44 AM, Robert Bruninga <bruninga at usna.edu> wrote:

For under say 200 miles, what is the best band round the clock?

Given that a 1 Watt WSPR transmitter performs as if it was 1000W due to
processing gain, couldn't it punch through the day time noise?

And APRS only has to go say 200 miles to the nearest HFgate to provide
almost total coverage of the USA because every where is within 200 miles of
a city where maybe a ham will be running an HF gate?

So that is the question.  Forget the high noise levels... WSPR can work
through that.  what band will provide the connectivity 24/7/364 over that
200 to 300 mile range?

Bob


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