Eagle Electronics Z-9500

ASE Correction

Loran signals are affected by the terrain

they

travel over. Plains, lakes,

mountains, and cities

affect the signal and

they

each affect it in different

ways. This effect is called the additional secondary phase factor, or

ASF. It's usually factored in when a loran chart is made. However,

ASF's vary

from

place

to place, so there can be differences between the

chad and the real world.

There can also be a difference in your actual position and the one

displayed by the

bran,

due to ASF. In this case, the loran signals are

distorted from their theoretical

position. Since the

measured ID's are

shifted, the loran shows a ID or latitude/longitude that is not the actual

position.

The Z-9500

has an correction feature that lets you change the ASF.

This forces the loran to use a new ASF instead of the one that resides in

its memory. You can shift the ASF by changing the TD offset or by

entering your actual

latitude/longitude position.

The

Z-9500 also has automatic ASF selection. TD's and latitude/longi-

tude are automatically corrected when the Automatic ASF feature is on.

However, not all areas in all GAl's are covered

by the Automatic ASF

feature, If you enable this feature and the ASF's aren't available in your

area, a

warning message appears in the

message box. You will have to

manually enter an ASF.

To change

the ASF, first press the MENU key. Next, press

the key

adjacent to the "Change Setup" label. Now

press

the

key

next to the

"More" label. Finally, press the

key next to the "ASF Correction" label.

The screen shown at the

top

of the next

page appears. This menu lets

you change the ASF using TD offsets or latitude/longitude correction,

TURN AUTOMATIC/DIGITAL SONAR ON/OFF

Your Z-9500 is actually two sonar units in one housing. The graph

portion graphically displays all echoes from the underwater world on

the screen. The

digital sonar displays numbers on the screen to show

the depth of the bottom. It is an extremely complex and accurate

device using

the latest in software technology to elimihate false echoes

and show

only

the true bottom

depth.

However, any digital sonar can be. fooled. This

typically

occurs in very

shallow water. The reason this happens

is shown on the two charts

below. First look at the chart on the left. The sonar

signal penetrates

the surface clutter, hits the bottom and returns. There's a clear differ-

ence between the surface clutter and the bottom. The digital has no

problem with these conditions.

Problems occur when the surface clutter extends to the bottom as

shown on the right. The digital sonar cannot distinguish between

surface clutter and the bottom and so it becomes "lost." It may

flash

the last known bottom depth or it may lock onto an unrealistic depth

such as 900 feet in a lake that only gets 60 feet deep at its deepest

point. If the unit is in automatic, the

auto-ranging feature may change

the range to an extremely deep depth, such as 0 to 600 feet. This

compresses the information on the display, making it difficult to read.

The Z-9500 is versatile

enough

to handle these situations. If it shows

these

symptoms in shallow water, press

the MENU key. Next, press

the key next to the "More" label 2 times. Now

press the

key adjacent to

the Digital Sonar label. Now press the key adjacent to the "Digital

Sonar" label. Now

press

the

key adjacent to the "Dig. Sonar Off" label.

The screen will clear and the Z-9500 will display sonar information

again. You may

need to change the

range

to 0-10

0-20 feet. If there

is a lot of "clutter" or random echoes on the

screen, turn the sensitivity

down until a definite bottom echo is seen. Use the unit in this manner

until you move into deeper

water. Once you're in deeper water, the

digital and automatic features can be turned back on by simply press-

ing the AUTO key.

IMPORTANT!

ASF corrections entered by the user are

good only

for the stations in

use at the time and

location

being corrected. If

you travel

away from

the

area, the ASF correction may

not be

valid. ASF corrections

may

not be usable if you change stations, or if the unit automatically

changes stations. This especially holds true if you enter a latitude/

longitude position

to change ASF. The Z-9500 will only apply

the

ASF correction to the stations in use - not all of

them. Remember, if

you change stations, especially if you change GAl's, the ASF will

have to be re-entered.

94 43

PDF compression, OCR, web-optimization with CVISION's PdfCompressor