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AUDIO FILTER
Ramsey Electronics Model No.
Here's a quick and easy way to eliminate interfering CW
signals! This filter uses a digital bandpass filter to knock out
those unwanted signals. The adjustable center frequency and
switchable bandwidth add some versatility to this hard working
kit!
•
Utilizes "state of the art" switched capacitor bandpass filter IC's !
•
Four selectable bandwidths - 750 Hz, 500 Hz, 250 Hz, and 100 Hz -
all with digital accuracy.
•
Adjustable filter center frequency for convenient listening.
•
Overload protected input accepts headphone or speaker level
audio.
•
"Smart" power input allows for AC or DC operation.
•
Audio bypass when unit is switched off - no need to disconnect
unit when not in use.
•
Speaker and headphone level outputs with adjustable volume. No
need for an external audio amp.
E - Z CW
AF1 • 1
AF1
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Summary of Contents for Ramsey Electronics AF1 CW AUDIO FILTER
- Page 1 E - Z CW AUDIO FILTER Ramsey Electronics Model No. Here’s a quick and easy way to eliminate interfering CW signals! This filter uses a digital bandpass filter to knock out those unwanted signals. The adjustable center frequency and switchable bandwidth add some versatility to this hard working kit! •...
- Page 2 RAMSEY MINI-KITS Many other kits are available for hobby, school, Scouts and just plain FUN. New kits are always under development. Write or call for our free Ramsey catalog. KIT NAME KIT INSTRUCTION MANUAL Ramsey Electronics publication No. MAF1 Revision 1.1 First printing: October, 1994 ...
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Page 3: Kit Assembly
AF1 Assembly instructions .... 8 Schematic diagram ..... 10 Parts Layout diagram ....11 Hook-up configurations ....13 Troubleshooting ......14 Ramsey kit warranty ....15 RAMSEY ELECTRONICS, INC. 590 Fishers Station Drive Victor, New York 14564 Phone (585) 924-4560 Fax (585) 924-4555 www.ramseykits.com... - Page 4 In an attempt to limit the number of carriers heard through the receiver one of the easiest solutions is to filter the received audio to only allow a single CW tone to be heard. That's where the Ramsey AF1 filter comes in to help. AMPLITUDE...
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Page 5: Theory Of Operation
THEORY OF OPERATION Let’s have a look at what makes our audio filter so special. Have a look at the schematic diagram and follow along. First, having a look at the power supply section of the AF1 notice that diodes D3, 6, 7,and 8 form a full wave bridge rectifier. - Page 6 AF1 PARTS LIST Please check the boxes after the components have been identified, and now is a good time to “sort” the like components into groups or bins (an egg carton does nicely) to avoid using the wrong component during assembly. RESISTORS AND POTENTIOMETERS Please note that the kit contains some “special”...
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Page 7: Miscellaneous Parts
DPDT pushbutton switch (S1, 2, 3) 1/4” stereo headphone jack (J2) AF1 printed circuit board RAMSEY Learn-As-You-Build KIT ASSEMBLY There are numerous solder connections on the AF1 printed circuit board. Therefore, PLEASE take us seriously when we say that good soldering is essential to the proper operation of your transmitter! •... - Page 8 Now, let's get building! Since you may appreciate some “warm-up” soldering practice as well as a chance to put some “landmarks” on the PC board, we’ll first install some “hardware” components. This will also help us to get acquainted with the up - down, left - right orientation of the circuit board.
- Page 9 polarity. See the parts diagram for proper placement. The capacitor should fit snugly down to the PC board. When installing the components be sure to save some of the longer clipped leads to use later as “jumper” wires. 12. Install C11, another 1000 uF electrolytic capacitor. Be sure to observe the proper polarity.
- Page 10 23. Install R22 and R21, both 100 ohm [brown-black-brown]. They are also mounted standing up. 24. Install stand up resistor R20, 1K ohm [brown-black-red]. 25. Form and install diode D1, a 1N4148 type small signal diode [small glass case with black band]. Be sure to orient the part as shown in the parts placement diagram.
- Page 11 AF1 PARTS LAYOUT DIAGRAM AF1 • 11...
- Page 12 31. Using a scrap component lead, form and install JMP11. 32. Install C13, .1 uF disc [marked .1 or 104]. 33. Install C2, .001 uF disc capacitor [marked 102 or .001]. 34. Install R1, 47K ohm [yellow-violet-orange]. I’ll bet you didn’t forget to stand it up.
- Page 13 “poke through” the front panel. CONGRATULATIONS You have just completed your AF1 CW audio filter unit. Take a well deserved break now. Give your eyes a rest. When you return, be sure to check over your work on the entire circuit board.
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Page 14: Troubleshooting Instructions
We sincerely hope that you have enjoyed the construction and use of this Ramsey Kit. As always, we have tried to compose our manual in the easiest, most “user friendly” format that is possible. As our customers, we value your opinions, comments, and additions that you would like to see in future publications. - Page 15 But on rare occasions a sour component can slip through. All our kit parts carry the Ramsey Electronics Warranty that they are free from defects for a full ninety (90) days from the date of purchase.
- Page 16 AF1 CW AUDIO FILTER Quick Reference Page Guide Introduction to the AF1 ....4 How it works ........5 Parts list ......... 6 AF1 Assembly instructions .... 8 Schematic diagram ...... 10 Parts Layout diagram ....11 Hook-up configurations ....13 Troubleshooting ......14...
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