QEX

Ticipants many people have inquired about filters that would ease the interference problem between 40-meter SSB and CW stations. Here is an actual design that is a starting point for others to improve on. I'll mention many of the cost-cutting compromises I made, as there is no sense making such a project more expensive than necessary. The usual technology of narrow HF filters is based on quartz crystals, which feature an exceptionally high Q. This means that the crystals have little loss...

Info

500 1000 Frequency Correction Rate (Hz s) 500 1000 Frequency Correction Rate (Hz s) 5 MHz VFO and 32 MHz crystal. VFO divided by 216 (16 divide - by-two stages), clock at 76 Hz giving step 11.9 Hz. Figure 4 Examples of performance predictions. Page 19, QEX, November 1998, published by The American Radio Relay League, Inc. an example. From the stability plot shown, one can deduce the drift that can be canceled over a range of correction rates (Hz s) together with the ripple that can be expected....

Paul Protas Antennas

Fig 7 Characteristic curve family for 2N5089 transistor (20 pA per step, vertical divisions are 2 mA, horizontal divisions are 2 V). VHF front ends, whereas the NE68133 finds similar usage in UHF and L-Band receivers. Both are very good low-noise transistors, but they require some degree of care in selecting their bias points. Surprisingly, the MPS2369, a plastic version of the 2N2369 switching transistor, shows good performance in both saturation and Kj, making this a suitable device for...

Qex Articles By Paul Protas

Fig 6 The Junk Box Special, a low-cost shortwave receiver. circuit's stability for CW and SSB reception. C7 is the throttle-capacitor REGEN ADJUST control. As C7's capacitance is increased, more RF energy is coupled from Q2's drain to ground (and therefore the ground end of L2) this eventually initiates an RF oscillation. RF choke L3 isolates Q2's RF feedback from the detected audio, allowingjust the audio signal to pass on to L4. L4 is the primary winding of a small 6.3 V filament transformer....

Features

3 ARRL Radio Designer and the Circles Utility, Part 2 Small-Signal Amplifier Design 1 7 The Fast Digital Oscillator Stabilizer 24 High Performance Regenerative Receiver Design 37 Nonlinear Distortion in Bipolar Transistors 43 A Space-Age Look at Polar Cap Absorption Events 46 Practical Hot-Guy-Wire Antennas for Ham Radio

Nonlinear Distortion in Bipolar Transistors

Everyone talks about IMD, but few of us do anything about it. Here's a chance to learn about the problem and its causes. A little knowledge gives you the power to fight back. Learn how to optimize bipolar circuits for minimum IMD. It has long been recognized that even with the wide range of inte grated circuits available, their performance with respect to dynamic range limits them to applications in the IF and AF stages of communication receivers. The use of ICs considerably reduces the time...

Practical Hot Guy Wire Antennas for Ham Radio

Do you use your tower as a vertical antenna for the low bands Would you like to Either way light up your towers metallic guys, too, for gain and directivity What is a hot-guy wire HGW antenna It is a vertical antenna designed to use tuned guy wires as parasitic elements to create a directional radiation pattern. That is, the guy wires increase the radiation from a tower in the desired direction when you transmit and reduce QRM and QRN from other directions when you receive. Tuning an existing...

End Data

MRF901 S MP RREF 50 MRF901 0.4GHZ 0 . 5GHZ 2 50.0 1 VCE 10V IC bMA 0.2GHZ 0.63 -69 9.69 13b 0.05 57 0.79 -25 O.bGHZ 0.53 J 35 b.hb 101 0.07 4 3 0.54 38 Q.5GHZ I.R0 0.6 3 7 O.'.i In DAT ., bleck, S rear a S-pa rameLe rs, MP means niacin I r ikio rind phase, RRFF leans reference Z0 for S-parameters. Fig 3 Amplifier circuit description. the ability to tune the input output matching networks. Tunability can be poor if adjusting one circuit causes the other to become detuned because of S12 feedback....

Old Regenerative

Transitor J310

This article will show that, if properly designed, a modern regen is quite capable of direct-conversion or superheterodyne-level performance, although it does require greater operator skill. Attention to a few simple details can provide an excellent receiver for ham or general-coverage shortwave use. For beginners and veterans alike, studying, building and using regenerative circuits can add new interest, excitement and fun to the radio hobby. The regenerative circuit was used in both...

Vfo

Figure 1 Block diagrams of the basic A and fast B stabilizers. Five - Stage Shift Register Integrator Input, Average Volts Figure 2 Mixer output variation with clock-frequency changes. 18 QEX the stabilizer. A theoretical analysis of the decoder workings is given in the Appendix. Effect of the Fast Stabilizer on VFO frequency The action of the stabilizer on the VFO frequency is shown in Figure 3A. From the graph we can tell that this particular VFO has a downward drift. The stabilizer is...

Add Some Stability to Your Life

Rock-solid frequency sources are common. The trouble is, the frequencies set by rocks crystals vary with temperature. Grab control of that rock's frequency with a home-brew thermal mass, oven and control circuitry A spectrally clean and stable oscillator is a key element in the design of transmitters and receivers used in today's communication systems. This article deals with a method of improving an oscillator's frequency stability by embedding its components in a controlled thermal...

Qex Bugcatcher Paul Protas

Issues 186 through 191 All dates are 1998 unless otherwise indicated. Central States VHF Society 1998 Sep, 49 Conference Proceedings Available Jan, 58 Southeastern VHF Society 1998 Sep, 49 Amateur Radio Development Smith Nov, 2 Antennas Severns May, 2 First Bimonthly Issue, The Severns Jan, 2 New Editor Doug Smith, KF6DX Smith Sep, 2 One Year Since QEX Restart Severns Jul, 2 QEX Editorial Approach Severns Mar, 2 A Solid-State R-390 Johnson Mar, 58 About Wave Interference and Impedance Matching...

High Performance Regenerative Receiver Design

There have been several popular Regen projects in recent QSTV and ARRL Handbook . Look at the design process and progress then build one or both oj the receivers described. Many hams have tried regenerative receivers with mixed results. Some people are quite attached to regens, while others consider them only suitable for beginner experimentation. I have spent several years researching this subject and have come away with a great respect for the technical knowledge possessed by the old-timers...

Superegen Recieve

Fig 8 Optional receiver accessories. control. For general-coverage receivers, use a large knob or a vernier dial on the main tuning capacitor for ham receivers, put the vernier on the FINE TUNING control for maximum bandspread on the amateur bands. Build the electronics on a small fiberglass board and then attach it to the wooden base. Many common items can be used for coil forms, including plastic film cans, pill bottles, PVC pipe etc. You can test the coil form by heating it along with a cup...

Rf

A Narrow-Bandwidth 40 Meter Band-pass Filter Forty meters is a tough band for receivers this part of the spectrum is popular with both amateurs and shortwave broadcasters. Funded by governments with a bit more resources than any amateur, some shortwave transmitters run tremendous amounts of power and huge antennas. Not surprisingly, inexpensive receivers crunch when subjected to such an onslaught of RF during hot band conditions. While increasing dynamic range of your receiver is a possible...