145'09 is fine Why Move Frequency

1
145.09 is fineWhy Move Frequency?

• How your packet operating will improve after
  changing frequency.
• (Or Why I dont want to wait for some guy
  halfway across the state to stop transmitting
  before I can get a reasonably good packet
  connection!)

2
The Present Situation

• Nearly everyone is on 145.09 throughout the state
• Works fine sometimes but boggs down now and then.
• Cannot get reliable connections to distant nodes.
• Sometimes even my local node doesnt hear me well.

3
When it works 1 user

• Craig N8KMY connects to the KAL node 15 miles
  away.
• He hears KAL and KAL hears N8KMY.
• Its a beautiful thing, no retries, good and fast
  responses and data throughput.

4
Add 1 distant user

• Lyle AB8CB gets on from the Soo and connects to
  the WA8OOH-10 Telpac node.
• Neither N8KMY nor KAL can hear AB8CB directly,
  but KAL can hear WA8OOH-10 marginally.
• The converse is true as WA8OOH can hear KAL, but
  not N8KMY.
• (NOTE Coverage regions shown may be exaggerated
  mildly to account for variations in station
  performance.)

5
Some facts to remember

• A packet station will not transmit if it hears
  another station currently transmitting on the
  frequency, even if its too weak to copy.
• Any data errors received will cause the incoming
  packet to be ignored.
• When two stations double the resulting audio
  often has audio products called a heterodyne
  that are of varying levels depending on the
  comparative signal strengths of the stations
  doubling.

6
Life in Slow Motion..

• N8KMY is connected to KAL and sends the command
  to read a message.
• AB8CB is connected to WA8OOH-10 and sends the
  command to read a message
• KAL receives N8KMYs command just fine, as does
  WA8OOH-10 receives AB8CBs command.

7
The Slow Response

• KAL starts transmitting the packet with the
  message information to N8KMY
• WA8OOH-10 has to wait until KAL is finished
  sending the packet before it sends its
  information to AB8CB
• AB8CB thinks WA8OOH-10 is a bit slow today, but
  doesnt realize WA8OOH-10 is waiting for the
  large packet from KAL to finish being transmitted.

8
Dropped Packet 1

• KAL finishes transmitting and now WA8OOH-10 is
  sending its long packet to AB8CB.
• N8KMY, hearing the KAL packet, sends the ACK
  acknowledgement packet to KAL. N8KMY cannot hear
  WA8OOH-10 and thinks its transmitting in the
  clear.
• KAL does not decode the ACK from N8KMY because
  N8KMY doubled with WA8OOH-10 and there was
  enough heterodyne noise in the decoded audio for
  even a single bit of error in the data.

9
Repeated Packet 1

• Since KAL did not get the ACK acknowledgement
  packet from N8KMY it resends the long information
  packet again.
• WA8OOH-10 has to wait again while KAL transmits
  the retry packet.
• Possibly, while KAL is transmitting the retry
  packet, AB8CB is having no luck getting through
  to WA8OOH-10 because he is now doubling with
  the KAL signal as heard by WA8OOH-10.

10
N8KMY is lucky

• Lucky for N8KMY that WA8OOH-10 was not
  transmitting when his station sent the ACK
  acknowledgement to KAL on receipt of the first
  part of the message information.
• KAL now sends the second information packet of
  the message N8KMY is reading.

11
AB8CB Reads His Mail

• AB8CB commands WA8OOH-10 to send him his first
  mail message and lucky for him, KAL was not
  transmitting at the time.
• WA8OOH-10 has the information packet ready to
  send but waits for KAL to finish transmitting
  its packet to N8KMY.

12
KB8TAS Joins in

• Jerry, KB8TAS makes a connection to the W8COL
  COLBBS Tnc-bbs to check for mail.
• COLBBS hears KB8TAS, WA8OOH-10, KAL and N8KMY
• KB8TAS hears KAL and COLBBS but not N8KMY, AB8CB,
  nor WA8OOH-10

13
COLBBS Lists the mail

• When WA8OOH-10 finishes sending its info to
  AB8CB, COLBBS jumps on and quickly sends its
  information to KB8TAS while KAL waits to send the
  next packet to N8KMY.
• AB8CB sends an ACK acknowledgement to WA8OOH-10
  to acknowledge the last packet heard, but doubles
  with COLBBS and the ACK packet is lost, WA8OOH-10
  will have to resend/retry the previous packet.

14
N8KMY wonders what happened

• N8KMY hasnt gotten any more text of his message
  in a while, it is as if KAL doesnt hear him well
  any more.
• Lots of packets are flying, but they are all
  retries with the same data.(on the right, a
  young KF8KK holds a bit of data)

15
KB8TAS wonders what gives

• KB8TAS manages to get the mail listing from
  COLBBS but wonders why it was so slow in
  coming.(on the right, WA5ZAI has had enough
  with retries!)

16
Is the Internet down

• AB8CB thinks that perhaps theres a problem with
  the internet gateway at WA8OOH-10 as the mail
  took forever to come in.(on the right is
  where dropped packets go into a place one best
  not venture!)

17
Want to add one more

• WZ8N from Manistee attempts to connect to DX
  cluster K8MV-2 via digipeater GRTR00 and get a DX
  listing
• Use your imagination as to what happens
  next(well not quite as bad as hurricane
  katrina.)

18
What Was Happening

• Packet works using Carrier Sense Multiple
  Access (CSMA) and expects only one transmitter
  to be active at any given moment.
• CSMA works great when everyone can hear everyone
  else even faintly.
• CSMA fails when there are stations not heard by
  everyone else--- these are called hidden
  transmitters.

19
The Hidden Transmitter Dilemma

• When you have hidden transmitters there is
  doubling on the packet network which often
  results in dropped packets and retries.
• Doubling on packet is worse than on FM voice as
  all you need is one erroneous data bit for the
  entire packet to get dropped.

20
Dismal Future Outlook?

• If everyone stayed on the same 145.09 channel
• For every new station that activates the entire
  system slows down a bit more.(just like 6 gas
  would slow the economy!)

21
The Solution

• Move local areas onto isolated frequencies and
  use network gateways to link these together.

22
The Benefits

• Reliable performance
• Faster response
• Greater functionality (N8KMY would now be able to
  reliably converse keyboard-to-keyboard with
  AB8CB, or even WB8TKL waaay downstate.)(some of
  the best networks look like a haywired mess at
  times well, sort-of)

23
How Can I Help?

• Smile when you change the frequency of your
  packet transceiver.
• Rejoice at the smaller number of retries.
• Encourage more hams to explore the packet mode.

24
Final Thoughts

• Packet networks are much like living entities
  that evolve and change.
• As usage increases there may be another frequency
  move recommended.
• Were all in this together, with a common goal,
  smile and be happy!
• 73 de KF8KK (kf8kk_at_iook.org) 1/2006