1. Soundcard Digital Modes for Dxing
Or Dxing on a Budget by
Jim Sears
WA3MEJ
10 August 2012

2. Typical Questions Newbies Ask
Why use digital modes for Dxing?
What hardware is necessary?
What software is necessary?
How much power is needed?
Who is using digital modes?
When and where should I look for stations?
Copyright J.L.Sears WA3MEJ

3. Why Use Digital for Dxing?
Don't need high power
Lots of Dx stations use Digital
You can gain 25 or more Db over SSB
Some modes copy signals 20+ db below noise
Great for hearing impared operators
Copyright J.L.Sears WA3MEJ

4. What hardware is necessary?
In addition to the normal station equipment a computer with a soundcard installed and an interface are all that are required.
Copyright J.L.Sears WA3MEJ

5. Copyright J.L.Sears WA3MEJ
Typical Interface
Copyright J.L.Sears WA3MEJ

6. Where to get an Interface
An interface can be homebuilt or can be purchased from one of the normal suppliers
Tigertronics
MFJ
Rigblaster
Buxcom
Copyright J.L.Sears WA3MEJ

7. What software is necessary?
Special software is necessary for soundcard digital modes. Some of the authors have written packages that support many modes.
Copyright J.L.Sears WA3MEJ

8. Copyright J.L.Sears WA3MEJ
Software
JT65hf
Mixw
Digipan
Fldigi
Multipsk
TrueTTY
Winpsk
Winwarbler
And many more
Copyright J.L.Sears WA3MEJ

9. How much power is needed?
Typically less than 25 watts is used on all bands, many stations use 10 watts or less
Copyright J.L.Sears WA3MEJ

10. Copyright J.L.Sears WA3MEJ
The Digital Advantage
Tests between WA3MEJ and W3JW in Deltaville, Va. Show 100% communications was possible with 1 watt on PSK31 when communications with watts on SSB was just barely possible on 160m in during the summer.
10 log (1500/1)=
10 log (1500)=
10 * 3.176= 31.76db
Copyright J.L.Sears WA3MEJ

11. Compare Spectrum CW & PSK31
Copyright J.L.Sears WA3MEJ

12. Common Soundcard Digital Modes
BPSK
QPSK
Olivia
RTTY
MT63
MFSK16
JT65hf
WSJT
Wolf
Argo
WSPR CW
Copyright J.L.Sears WA3MEJ

13. Who is using digital modes?
JY5FX 17m
CO8LY 40M
HB9ARI 40M
ZS2ACP 40M
ZL3NB 40M
5H3ME 20M
SA6OA 80M
UA9MA 20M
TO3X 20M
A61BK 40M
SU9VB 30M
TF3IG 20M
J73WA 20M
UU9JQ 40M
VP2MFF 17M
SV1EQA 17M
6D0LM 20M
FG4NO 17M
KG4SS 40M
KF3AK 10M
C31CK 20M
J38RF 17M
JQ1TIV 30M
VK3LD 30M
Copyright J.L.Sears WA3MEJ

14. Copyright J.L.Sears WA3MEJ
What Goes Wrong
Hardware
Software
Improper Adjustment
Operator error
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15. Example of Good Signals
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16. Examples of Bad Signals
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17. Copyright J.L.Sears WA3MEJ
Bad BPSK
Railroad tracks Transmitter probably drawing ALC and probably running too much power.
Notice AGC action
This is bad thing! It robs All the other stations because he hogs receiver gain
Railroad
Copyright J.L.Sears WA3MEJ

18. Copyright J.L.Sears WA3MEJ
AGC Action
Overdriven?
Notice about half way
Down. The change in
color is due To AGC
action
This is bad thing! It robs
All the other stations
because he hogs receiver
gain
Copyright J.L.Sears WA3MEJ

19. How to Correctly Tune Transceiver
Tune up as you do for CW/SSB
Set mode to USB
Leave Power set to Maximum output
Adjust sound card "Out" to set power out & make sure xcvr does not draw ALC at all
Adjust sound card "In" for just enough audio to get a good reliable trace on the waterfall
Copyright J.L.Sears WA3MEJ

20. Copyright J.L.Sears WA3MEJ
Weak Signals WORK
You dont need a lot of power. This station
is probably running Less than 30w and yet
his signal is quite copyable
Copyright J.L.Sears WA3MEJ

21. Copyright J.L.Sears WA3MEJ
JT65 DX is Plentiful
Copyright J.L.Sears WA3MEJ

22. Copyright J.L.Sears WA3MEJ
Things NOT to DO
Turn RF down after tuneup
Run any ALC
Run excessive power
Copyright J.L.Sears WA3MEJ

23. Things You Will Want to Do
Keep power low (25-30w or less)
Listen before transmitting
Adjust power out by adjusting audio from computer
Have someone check your signal occasionally
Don't be afraid to try operating above the listed MUF
Check frequency do not interfere with others
Have fun
Copyright J.L.Sears WA3MEJ

24. Copyright J.L.Sears WA3MEJ

25. Copyright J.L.Sears WA3MEJ

26. Copyright J.L.Sears WA3MEJ
15M Contact
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27. Copyright J.L.Sears WA3MEJ
Real Time Map 8/31/12
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28. Copyright J.L.Sears WA3MEJ
Paul N0NBH Predictions
Paul N0NBH predicted MHz for Z
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29. Copyright J.L.Sears WA3MEJ
MUF Definition
The MUF is the highest frequency for which an ionospheric communications path is predicted on 50% of the days of the month.
On a given day, communications may or may not succeed at the MUF. Commonly, the optimal operating frequency for a given path is estimated at 80 to 90% of the MUF.
Copyright J.L.Sears WA3MEJ

30. Copyright J.L.Sears WA3MEJ
MUF
Is a predicted number
Varies acording to the takeoff angle
Implies signal quality
Highly path dependent
Copyright J.L.Sears WA3MEJ

31. Copyright J.L.Sears WA3MEJ
Calculating MUF
Fcrit
MUF =
Cos θ <--- Incident Angle OR
Sin θ <--- Take Off Angle
Copyright J.L.Sears WA3MEJ

32. Critical Frequency (Fcrit)
That frequency at which a signal will pass through the ionosphere and not be reflected back to earth
Ref:
Copyright J.L.Sears WA3MEJ

33. Copyright J.L.Sears WA3MEJ
VI Sounder Geometry
Copyright J.L.Sears WA3MEJ

34. HF Signals - Angle of Arrival
20 Meters
17 Meters
15 Meters
12 Meters
10 Meters
Europe
1-21
1-12
2-12
2-11
Far East
1-16
2-15
1-17
3-13
S. America
1-13
Oceana
2-10
S. Africa
3-12
S. Asia
2-14
3-14
4-11
Copyright J.L.Sears WA3MEJ

35. MUF based on Critical Angle
Fcrit
MUF-using cosine 1
6.5
6.50 10
6.60 15
6.73 20
6.92 25
7.17 30
7.51 35
7.94 40
8.49 45
9.19 50
10.11 55
11.33 60
13.00 65
15.38 70
19.00 75
25.11 80
37.43 85
74.58
Copyright J.L.Sears WA3MEJ

36. Copyright J.L.Sears WA3MEJ

37. Copyright J.L.Sears WA3MEJ
VI Boulder, CO
Fcrit = 6 .0MHz
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38. Copyright J.L.Sears WA3MEJ
To Calculate MUF
Must Know:
Fcrit – critical frequency
Take Off Angle or Incident Angle
Minimum % time circuit must be present
Implies:
Circuit quality or signal to noise ratio
Copyright J.L.Sears WA3MEJ