MFJ-8100W_user.pdf

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1、MFJ-8100 World Band Receiver 1 MFJ-8100 World Band Receiver Table of Contents For Beginners Page 2 Just a Bit of History Page 2 Back to Today and the Future Page 3 A Simplified Explanation of How it Works Page 3 For Experienced Hams, Enthusiasts and Engineers Page 4 Receiver Controls and Connections

2、 Page 6 Understanding and Using the Regeneration Control Page 7 Tuning SSB Voice Signals Page 8 Using and Enjoying Your Receiver Page 9 Setting Up A Useful Shortwave Antenna Page 9 Your Receiver Audio Circuit Page 10 About the 5 Tuning Ranges of Your Receiver Page 11 Shortwave Listening in General P

3、age 12 In Case of Difficulty Page 12 Notes for Radio Hams the two jacks are wired in parallel to permit the use of two headphones. (NOTE: if a mono 1/8 plug is used for any reason, it must not be pushed all the way in, or it will short out the audio. ANTENNA CONNECTOR (J1) This binding post permits

4、easy hookup of any wire, or a banana plug may be inserted in its end. 10 to 20 feet of ordinary hookup wire (also called bell wire) provides good basic reception, even when installed indoors. See the section on Antennas in this book for more information. GROUND CONNECTION For casual operation, a gro

5、und connection is optional. However, a wire from this connector to a ground rod or cold water pipe will reduce unwanted noise and interference from nearby electrical devices or AC wiring and may boost receiver sensitivity. Attach the wire between the two washers, then tighten the wing nut. UNDERSTAN

6、DING & USING THE REGENERATION CONTROL In theory, your receivers Regeneration Control adjusts the level of feedback or self-oscillation of the FET detector section (Q1 and Q2). In PRACTICE, this control is like a joystick for managing and optimizing receiver performance. Your ability to handle this j

7、oystick saves you many dollars over todays cost of receivers which perform similar functions automatically. In fact, you might even get more control over receiver performance in varying situations than may be possible with more elaborate receivers. MFJ-8100 World Band Receiver 11 With the control tu

8、rned fully to the left (counter clockwise), the receiver is virtually silent. Regeneration begins at a certain point as you turn the control clockwise. The exact point varies not only from band to band but even as you tune within a given band. Regeneration begins as an audible increase in background

9、 noise followed by a soft hiss. The hiss, or any signals that may be on frequency, increases as you continue to turn clockwise. If you go too far, the signal becomes distorted, or the receiver begins to squeal (oscillate). Always use the LEAST amount of regeneration necessary for good reception of a

10、 given signal. As a rule, the best reception of AM shortwave broadcast signals occurs just BEFORE full regeneration. If you hear a whistle (carrier) along with an AM signal, turn the control back slightly until the carrier disappears. When there are a number of very strong shortwave AM broadcasts in

11、 a given band, such as is common in the early evening, you will find it possible to tune them in one after the other with the regeneration control set way back and requiring virtually no adjustment. In other words, you would tune from station to station just as if using any other type of shortwave s

12、et. When the receiver is adjusted for good AM reception, CW signals will sound like hisses. Advancing the regeneration control slightly will bring in the familiar beeping associated with CW, RTTY (radio teletype) or similar signals. The regeneration control can also serve as a fine tuning control, p

13、ermitting slight adjustments of CW pitch for the most pleasing sound, or best clarity in a SSB voice signal. After youve had some practice with using the regeneration control, it will become second nature, giving you a sense of real control over the performance of your receiver. TUNING SSB (Single S

14、ideband) VOICE SIGNALS SSB signals are all those voice signals which sound like Donald Duck unless they are tuned in very exactly. They have no background carrier as do AM broadcast signals. MFJ-8100 World Band Receiver 12 On modern ham radio transceivers, tuning SSB is made so easy by means of inte

15、rnal filters that many licensed ham operators are not aware of the basic technique for tuning in SSB signals on receivers without such filters. The first fact to know about any given group of SSB signals is whether they are Upper (USB) or Lower (LSB) Sideband. In ham radio communication, LSB is used

16、 on 1.8 through 7.3 MHz, and USB is used for all higher frequency bands (14, 18, 21, 28 MHz.) The best band to practice SSB tuning with your receiver is the 75 Meter band, 3.8 to 4.0 MHz, doing so in the evening when the signals are strong and plentiful. Notice that the band is spread out on the dia

17、l more than are the other amateur bands, which permits easier tuning. These are all LSB, lower sideband signals. Think to yourself: for LOWER sideband, tune DOWN. for UPPER sideband, tune UP. In practice, this means that you would approach the LSB signal by tuning from higher frequency (right) to lo

18、wer (left), from higher voice pitch to lower pitch. Heres how to do it step by step: 1. Pick out a strong, high-pitched Donald Duck voice. 2. Turn the tuning knob ever so slightly to the left. 3. If the pitch of the voice went DOWN slightly, youre heading in the right direction. 4. SLOWLY tune left

19、slightly more until the voice is clear. Reverse this process to tune to UP (to the right) to USB signals on the bands above 7 MHz. The Regeneration Control often can be used to do the last touch of fine tuning to bring the voice in clearly. If signals are exceptionally strong, it may be necessary to

20、 reduce the RF gain level (rear panel). SSB transmissions are used by embassies and agencies of various governments, so you might find interesting voice signals on other than ham frequencies. Check with a Shortwave Listener (SWL) or listings in Popular Communications Magazine for more details. MFJ-8

21、100 World Band Receiver 13 USING & ENJOYING YOUR RECEIVER To get maximum satisfaction from your new shortwave receiver, we encourage you to develop good familiarity with these sections of this manual: _ Antenna Considerations _ Regeneration Control _ Band Switch and Tuning Ranges _ Audio Notes Howev

22、er, lets say it all as briefly as possible: 1. The better the antenna, the better the reception. In general, 20 to 30 feet of wire will give good results. 2. The use of the Regeneration Control is learned through experience. It controls the sensitivity of the receiver and distinguishes between AM br

23、oadcasts and CW-SSB. 3. The tuning ranges are set up so that you can expect to find something interesting at any time of day or night. Bands A and B are most active in the evenings. Band C has something happening all the time. Bands D and E assure a variety of daytime reception but also can be busy

24、at night. 4. The audio circuit is designed for one or two pairs of Walkman stereo headphones or mini speakers. Other speaker options are mentioned in Section XX. IMPORTANT: The internal 9 volt battery will provide many hours of satisfying listening provided that you turn the receiver OFF when not in

25、 use! This advice may seem ridiculously obvious, but remember that battery replacement requires removing and replacing the 8 cabinet screws and that leaving the receiver on overnight will indeed run down the battery. If you wish, the battery snap wires can be re- routed to the battery clamp mounted

26、outside on the rear panel. Or, the receiver may be powered by larger external batteries in the 6 to 12 volt range. 4 to 8 D cells in plastic battery holders available from Radio Shack will provide months of service. NOTE: If a DC voltage other than 9 volts is used, readjustment of trimmer C5 will be

27、 required for correct frequency indications. MFJ-8100 World Band Receiver 14 SETTING UP A USEFUL SHORTWAVE ANTENNA The reason why we provided a universal binding post antenna connector (plus separate ground connector) is to make it as easy and economical for you as possible to try out different ante

28、nna setups. By universal, we mean that you can insert a banana-style plug OR make various styles of connection with a simple bare wire. Your receiver is so sensitive that even a few feet of wire strung indoors will provide reception of stronger signals, particularly at night. 20 to 30 feet of wire i

29、s much better. Therefore, you can count on good reception even if you are limited to keeping the antenna indoors as might be required in apartment complexes, condos, etc. Stringing all or part of your antenna outdoors is always better. An ideal antenna for this receiver would consist of 25 to 100 fe

30、et of wire outdoors, as high as is safely possible. Such antennas are called random long wires and also work fine in most attics. (Foil-backed insulation or metal roofing will reduce the usefulness of an attic as antenna space.) Your antenna can be horizontal, vertical or a combination of both. It c

31、an be tubing or pipe as well as wire. The wire can be bare or insulated. It could be something not intended to be an antenna such as a gutter, fence, flagpole or metal roof. In fact, radio hams and serious SWLs have experimented with thousands of imaginative antenna ideas. VERY IMPORTANT: Use care a

32、nd common sense when putting up outdoor antennas. Be certain that your wires or your ladder cannot come into contact with electrical power lines. You can be KILLED by accidental contact with power lines. YOUR RECEIVERS AUDIO CIRCUIT: MANY WAYS TO LISTEN IN! The LM386 audio amplifier IC circuit is de

33、signed to provide ample volume to not one but TWO headphone jacks. We used stereo jacks because todays economical personal music headphones are as inexpensive as were the bulky basic headphones of yesteryear. Your receiver provides two headphone jacks to make it very easy for two people to listen to

34、gether. MFJ-8100 World Band Receiver 15 The amplifier circuit provides sufficient output for moderate speaker volume. Miniature speaker systems designed for Walkman and similar personal stereo devices will plug right into J2 or J3 and work very well. However, please remember that the amplifier is sp

35、ecifically designed for headphone operation. If you prefer room-level speaker volume for long listening sessions, we recommend an external amplifier as discussed below. If you use personal FM, cassette or CD players, you probably also know all about those compact amplified speakers designed specific

36、ally to plug into the stereo jack of compact personal stereos. These speaker setups have a built-in amplifier circuit and their own separate batteries. Any of these devices should work well with your receiver. Radio Shack carries a variety of amplified speaker pairs as well as several monaural utili

37、ty amplifiers. Even though stereo jacks are used, remember that the receiver audio output is monaural. An external amplifier can also be a rewarding do-it-yourself construction project. One-half to 2 watts will provide generous and ample speaker volume. In fact, if building this receiver has kindled

38、 your interest in building something on your own, you could get started by duplicating the same LM386 audio circuit used in this receiver. Use the same parts values and physical positioning as we did. The volume control may be omitted, since you already can control the receivers volume. The amplifie

39、r will operate on 6 to 15 volts DC. All needed parts are available at Radio Shack stores. Youll get plenty of volume for any size of utility or communications speaker. (AUTHORS NOTE: I have fully tested this use of a second identical LM386 IC circuit with speaker and can recommend it highly to all w

40、ho cant confine all this listening excitement to one or two headsets!) VERY IMPORTANT: A monaural 1/8 plug will fit the receivers stereo jacks. HOWEVER, the plug must NOT be pushed all the way into the jack, because it will short out the audio output. If you have reason to use a mono plug, insert it

41、 just far enough for the tip to make firm contact with the first section inside the jack. ABOUT THE 5 TUNING RANGES OF YOUR RECEIVER MFJ-8100 World Band Receiver 16 The purpose of the following information is to give newcomers a general idea of what to expect to hear in each of the 5 frequency range

42、s tuned by your receiver. First, please understand that the frequency markings on the tuning dial can be only approximate. They indicate the general neighborhood of major frequency bands and have an accuracy only within a few hundred KHz. (If you are wondering what it would take to make the dial per

43、fectly accurate, imagine an adjustable trimmer capacitor AND an adjustable coil for EACH band! The process of making these many adjustments is called alignment and also requires the use of frequency measuring equipment far more costly than the receiver.) Whenever you hear a broadcast of special inte

44、rest to you which you would like to be able to find again, make a note of the time, frequency band, and approximate dial position. In fact, such notes are called a Shortwave Listening Log. A sample log page is printed in this book which you may copy to make your own logbook. Or, use your computer to

45、 design the style of logging pages best for you. Range A: 3.5 to 4.3 MHz. The primary purpose of this tuning range is to make it very easy for you to listen to ham radio stations at night on what is known as the 80/75 Meter band. From 3.5 to 3.8 MHz, youll hear mostly Morse Code signals. From 3.8 to

46、 4.0 MHz, you will hear SSB voice conversations from all around the nation. Youll hear both sides of most conversations. You may hear occasional shortwave broadcasts mixed in among the hams in the 3.9 to 4.0 MHz region and possibly in the 90 Meter band, 3.2 to 3.4 MHz. Range B: 5.85 to 7.40 MHz. The

47、 main purpose of this tuning range is to give you lots of strong shortwave broadcasts in late afternoon and throughout the night on the 49 meter band, 5.95 to 6.2 MHz. The 40 meter ham radio band is 7.0 to 7.3 MHz, and you will also hear foreign broadcasts among the ham CW and SSB signals. Range C:

48、9.5 to 12.00 MHz. This band lets you tune all of the popular 31 meter broadcast band, 9.5 to 9.9 MHz. You can also find the WWV time standard signal at 10.0 MHz (or on Band D at 15.0 MHz.) The MFJ-8100 World Band Receiver 17 30 meter ham band (CW and RTTY only in the USA) is at 10.1 to 10.15 MHz. This tuning range is generally busy 24 hours a day. Range D: 13.2 to 16.4 MHz. On the 20 Meter ham band (14.0 to 14.35 MHz), you can hear strong CW and SSB voice signals from around the world thr