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Hearing Weak DX on 80 & 160

Bill Tippett W4ZV

October 1, 2005

SEDCO – Ten-Tec Hamfest

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Introduction

“You can’t work ‘em if you can’t hear ‘em!” ~The Old Timer

K4RID – QRV 80m 1960 W0ZV – QRV 80m ‘80, 160m ‘84 80m DXCC 339 (need 4 more) 160m DXCC 317 (need 22 more)

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Weak Signals in Noise

“Since you can’t increase the weak signal, reduce the noise!” ~The OT

1. Noise reduction (S/N issues) 2. Signal strength (propagation

issues) 3. Other (experience, practice)

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Noise Reduction

Different types of noise:

Atmospheric (lightning-induced) Man-made (power lines, electric

fencers, FCC part 15 devices) Precipitation static (rain, snow,

dust)

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Antenna Metrics

Beamwidth – included angle for 3 db gain reduction (azimuth or elevation)

RDF – W8JI definition based on Eznec calculations of max forward gain versus 3D gain at all azimuths and elevations

DMF – ON4UN calculation based on forward gain versus averaged F/R in rear 180 degrees (best F/R metric)

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Azimuth Example

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Elevation Example

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Where ’s the noise coming from?

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Lightning Strikes

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Noise Reduction – Forward Direction If the noise is from the same direction as

the signal, minimize forward beam width to “slice through” the noise

BSEF 8 el / 4el BS vert = ~25 deg. (but not practical to cover 360 degrees)

Parallel 2wl Bev = 44 deg. W8JI 8-circle vert = 55 deg. Single 2wl Bev = 62 deg. Single 1wl Bev = 78 deg. 4-square vert = 86 deg.

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…but, Optimize S/N

If noise not exactly same direction, use knowledge of geography and antenna patterns.

Example: FT5XO’s bearing SE and thunderstorm noise South.

Solution: ESE Beverage includes FT5XO but attenuates noise.

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Noise Reduction – Rear

Most wintertime DX not the same direction as storm QRN…don’t need narrow forward beamwidth.

Winter storms from Texas to Caribbean are very common...thus need maximum F/R performance toward EU (JA normally not an issue).

ON4UN’s DMF is the most useful metric for F/R performance.

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Directivity Merit Factor

2X 2wl Beverages EF – 33.8 dB 2X 1wl Beverages EF – 30.1 dB 4-square – 24 dB W8JI 8-circle – 22.6 dB

Conclusion: 1wl Beverage EF pair extremely effective for Middle East, Europe and Africa…not much more space than single Beverage

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For City Dwellers…

Acreage matters! So don’t set unrealistic expectations.

K9AY/Flag/Pennant/EWE arrays quite effective but cannot compare to phased Beverages or large vertical arrays.

K2UO has ~225 DXCC on 160 from a city lot so you can still have lots of fun!

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High-angle Antennas

Sometimes high-angle antennas are optimum. Most common at your sunrise and sunset.

Beverages and vertical arrays are all low-angle antennas, so consider an inverted-V or dipole as a complement. In this case use the same antenna for both transmit and receive.

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Inv-V vs 3el Vertical TOA

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Man-made Noise

Noise audit (home, neighborhood, power lines) and remove at the source (or move!)

SWL RX and whip or loop antenna MFJ-852 (for power lines) Tune 1710 kHz on your car radio RX noise blankers work well for modern

electric fencers (but RX overload) MFJ-1025 for local single-point noise

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Precipitation Static

Verticals are bad Beverages are good Noise blankers sometimes work Sometimes nothing works

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About That Weak Signal

You can’t make it stronger but Mother Nature can! Remember the 3 P’s --- Propagation, Patience and Persistence.

Propagation – Know when the DX signal may peak and watch azimuth changes.

Patience – Propagation may move toward you. Don’t call if you can’t hear!

Persistence – Keep trying! JT1CO and UK8DAN literally took seasons to work!

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Other Issues

Practice listening to weak signals. N2XE’s Beacon starts in October; YR2TOP on 1810.5.

Modern receiver sensitivity (MDS) not a factor, but learn which settings work best for your ears (i.e. Pitch, Bandwidth, AGC, RF Gain, NR, NB, Diversity, etc).

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Need more info?

ON4UN’s Low-Band DXing 4th edition (the only book you need)

W8JI.com (many pages of info) Topband reflector archives

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Conclusion

Low Bands are challenging but fun! Great conditions are just ahead. Good RX antennas are a must. Nobody said it would be easy! Get in there and have some fun!

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Beverage Kits - $10 Transformer (50 or 75 ohm coax),

non-inductive termination & instructions

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