Sea Pal Radio Co. Radio Compass Schematic

Sea Pal Radio Co. Radio Compass

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Product Information:
Model:Radio Compass
Manufacturer:Sea Pal Radio Co.

Schematic Pages

PNG: Page 1 Rider Manual Volume 12
PNG: Page 2 Rider Manual Volume 12

Schematics Content

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Page 2:


Volume control - Maximum all adjustments.
Connect generator ground to shell of antenna socket.
Connect dummy antenna value in series with generator output lead. Connect output meter across primary of output transformer.
Allow chassis and signal generator to " heat up " for several minutes.

The following equipment is required for aligning:
An all wave signal generator which will provide an accurately calibrated signal at the test frequencies as listed
Output indicating meter.
Non-metallic screwdriver
Dummy antennas - 1 Mfd., 50 Mmid.

NOTE "A" - The loop may be connected to the radio when making these adjustments. The ground of the signal generator is connected to the shell of the antenna socket and the other lead from the signal generator in series with the proper dummy to the grid of the 1A7GT tube. NOTE "B" - This adjustment should be made with the ground lead of the signal generator connected to the shell of the anterna socket. The other lead of the signal generator is connected in series with a 50 Mmf. dummy to the antenna terminal. NOTE " C - Trimmers C14 and C16 can be reached by removing the Sea Pal Nameplate on the side of the cabinet

When carefully used the instrument will indicate points within + 1 Degree.
A Rdio Beacon Broadcast Chart may be obtained from the United States Coast Guard at Washington, D.C. This chart contains instructions for its use The Sea Pal should not be installed too near your compass or the speaker magnet may affect the reading of the compass,
It is advisable to keep the unit away from metal as much as possible to eliminate excessive error in the readings.
Place the unit in line with the ship. that is, if you want the controls directly in front when you face the bow the back of the cabinet should point directly toward the bow. If the unit is used on one side of your cabin then it should be lined up so that it is parallel with a line drawn between the bow and the stern. The reason for keeping the unit in a parallel relation to the boat is that it will be easier to set the compass scale on top of the cabinet to conform to your compass settings when taking bearing

There is an index marker opposite the compass scale locking screw which aids you to set the scale in exact agreement with your compass when required.
In any radio compass there may be a deviation from a true reading due to the motor or other metal parts around the boat just as there is with a magnetic compass. The simplest method to determine the amount of deviation is to select a broadcast or beacon station which you can see from the ship Point your ship directly at the station and then tune the loop to the " Null " point. If there is no error the loop pointer should point to the station straight ahead, parallel with a line from bow to stern. If there is a deviation the pointer will not point exactly straight ahead. You can either note how many degrees the variation is and allow for it in future readings or you can turn the radio case so the loop pointer points straight ahead. This will correct for the error and you won't need to make any future allowance,

Check for deviation on several stations and also with the boat turned 180 Degrees from the stations,
To use your compass at a homing device Tune in the station near the harbor. Rotate the loop to the point where the signal is loudest. This point is quite broad and is therefore not accurate enough to follow. You must therefore find the " Null " point (the point at which the station is weakest).

The Null point will be where the flat side of the loop faces the station. The pointer on the Loop should then point to the station. Follow this " Null " point all the way in toward the station. When near the harbor of course you'll pick up the harbor lights and marker buoys.

Since the " Null'point can be obtained when the loop pointer points either to the station or directly away from it you should check with your magnetic compass just to be certain your direction is not away from the station.

To determine your position at Sea it is only necessary to take bearings on two broadcast stations and transfer these bearings to your chart (map). To find your position first loosen the locking screws on the compass scale on top of the Sea Pal. Rotate the scale so it reads the same as your ships compass. Make the same correction as you would for your compass and hold the ships course steady.
Now tune in a broadcast or beacon station the position of which you know. Rotate the loop to a point where the signal is loudest - Now turn the loop approximately 90 degrees to the " Null Point " (The point of weakest signal). You may have to adjust the volume either up or down to find the " Null Point ". Having found the Null the loop pointer should point directly at the station and on the loop scale you can now read in degrees the position of the station. Draw a line from this point on land with a parallel rule out to sea, on your chart.
Now repeat the same operation on another known station which is located farther along shore. When you draw your line from this station it will cross the first line at some point on the water - The point at which the lines cross is your position.