[aprssig] Digipeating with TM-D700A

[Wes Johnston]

If the cross band repeat function of the radio _is_ allowing you to decode
packets from an HT inside, then I would say that the local digipeater's TXdelay
is too long.  What this means is that the local digi is still sending the sync
flags in the beginning of the packet after all the time it takes the cross band
repeater to realize there is a signal there, plus the txdelay of the cross band
transmitter.... this (in relative terms) is an enormous amount of time.

That may be very convienant for you, but let's look at the consequences....

The local digipeater is the busiest packet station in your town.  Let's say that
it transmits every 10 seconds.  Since the kpc3 tncs come with a default txdelay
of 350ms, and most radios will accept a 100ms setting, you are wasting 250ms
with _every_ transmission.  One TX / 10 seconds is 6 a minute, 360 / hour. 
That's 90seconds of lost time!

Let's look at it another way.... if a mic-e packet takes .35 of a second to TX,
and your digipeater is adding to that .25, that's nearly a 50% loss on that
type of packet!  If you shorten the TXdelay you can fit more trackers into a
given area.

It might be that when you wish to run the cross band digi trick, you can log
into your local digi and increase it's TXdelay temporarily during your event. 
But the rest of the time, your digi's TXd needs to be much lower.  When
learning about the lowest setting, do NOT experiment remotely!! it will surely
cost you a trip to the digi site if you get it too low.

I wrote a power point on this about 18 months ago...
http://www.kd4rdb.com/kd4rdb/APRS%20Network%20Optimization.ppt

Wes
--



Quoting Chris Rose <kb8uih at sbcglobal.net>:

> I use that configuration when I attend monthly club
> meetings and take my hand held inside and leave my
> mobile on in the parking lot.  I am not sure why it
> doesn't work for you.  Is the structure of the
> building interfering with transmission?
> I may have my UIDIGI set to Relay, Wide.
> If you don't have any locals responding to Realy then
> that may be the problem?
>
> 73,
> Chris
> KB8UIH
>
> --- Ken Kinyon <w7ts at comcast.net> wrote:
>
> > I have agreed to demonstrate some APRS software at a
> > ham fest.  I will
> > however be inside a building.  I will be using a
> > Laptop and TH-D7A.  I
> > thought I could configure the TM-D700A in my truck
> > in the parking lot to
> > digipeat so I could receive some signals inside. To
> > test it I set the UIDIGI
> > parameter in the D700 to relay and turned digipeat
> > on.  T set the path in
> > the TH-D7 to relay, wide.  The D700  digipeats the
> > TH-7's signal and it
> > shows up on Find-U.  However the D700 will not
> > digipeat any one else's
> > signal so I can pick it up on the hand held and
> > display it on the computer.
> > I imagine this is because I am not directly
> > receiving anyone who has relay
> > in their path.  Is there a way that I could set the
> > D700 to digipeat some of
> > the relay or wide stations in the area (Loveland
> > Colorado) so something
> > besides the hand held and my truck will show up on
> > the computer?.  I am
> > aware that this is going to add to the traffic, but
> > it will be a short
> > duration demo.
> > Thanks,
> > Ken W7TS
> >
> >
> > -------------------
> > Kenneth E.  Kinyon
> > 34 Princeton Circle
> > Longmont, CO 80503-2106
> > -----------------------
> > E-mail: W7TS at comcast.net
> > ------------------
> >
> >
> >
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