50 (FET) Field Effect Transistor Projects - Battery Portable

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Thus, over this range, a change of 0.8v in gate voltage hascaused a change of 3.4mA in drain current.Exact results will depend on the individual transistor and othercircumstances, but the control of drain current by the gate voltagein this way will be absent with a faulty <strong>FET</strong>.
RF AMPLIFIERS AND CONVERTERS144MHz PreamplifierThis preamplifier can be used with existing 2 metre equipment,or ahead of the 144MHz converter described later. TR1 is the40602 or 40673.Aerial input is to a tapping on L1, and will generally be byco-axial feeder. In some circumstances a short vertical aerial orwhip may be used and may provide sufficient signal strength. Ahigh aerial will naturally increase range and many different typesof aerial for 2m reception can be obtained. Alternatively, if a startis being made on this band, a simple dipole may be constructed.This can be self supporting, or of stout wire, and can be about38½in in length overall, with the feeder descending from the centre.Such an aerial will have little directivlty so need not be rotated,and can be raised on a light pole or mast.For 144-146MHz reception, L1 is permanently tuned to about145MHz by T1. Input is to gate 1, from a second tapping, and R3with the by-pass capacitor C2 provide source bias. Gate 2 is operatedat a fixed potential derived from the divider R1/R2. Outputfrom TR1 drain is to the tapping on L2, which is tuned by T2. Fora narrow range of frequencies such as the 2m Amateur band,variable tuning is not justified, especially as L1 and L2 do nottune sharply L3 couples to the existing 2m equipment - generallya converter working into a lower frequency receiver.L1 is wound with 18swg or similar stout wire, enamelled ortinned copper. It has five turns and is tapped at one turn from theupper end in Figure 4 for G1, and two turns from the groundedend for the aerial. The winding is 5/16th in in diameter and turnsare spaced so that the coil is ½in long. L2 is wound in the sameway with five turns, but is ¾in long and has a centre tap for thedrain. L3 consists of a single turn of insulated wire, wound overthe lower end of L2.
Page 3 and 4: INTRODUCTIONField effect transistor
Page 5: type of FET is thus very useful whe
Page 8 and 9: Type No.BaseMaximumRatingsOther Inf
Page 12 and 13: When building VHF units of this and
Page 14 and 15: FM BoosterFor long distance recepti
Page 16 and 17: y tapping the drain down L3. The su
Page 18 and 19: Range 3, 1.67-5.3MHz, or 580 to 194
Page 20 and 21: A metal cabinet about 6 x 4 x 4 in
Page 22 and 23: It the receiver has a signal streng
Page 24 and 25: Ham Band PreselectorAn amplifier or
Page 26: In view of the number of turns requ
Page 30 and 31: Layout should allow very short conn
Page 33 and 34: eak through. More care in finding a
Page 35: for each range is as shown below, w
Page 39 and 40: Any audio or general purpose FET ca
Page 41 and 42: Calibration of its scale can be by
Page 43 and 44: tion, VC1 tunes the inductor to res
Page 45 and 46: Should the field strength meter be
Page 47 and 48: here. The upper frequency limit at
Page 49 and 50: Coupling from the marker to the rec
Page 51 and 52: Coupling to the receiver can be by
Page 53 and 54: For the lower frequency range, C1 i
Page 55 and 56: A control knob is necessary on VC1,
Page 57 and 58: Two inputs are required to the FET.
Page 60:
much higher level, than that from a
Page 63 and 64:
nals, the box or case must be of pl
Page 66 and 67:
Values for Figure 33R1 1k C1 22uF 1
Page 68 and 69:
Preamplifier for PhonesFigure 35 is
Page 70 and 71:
The input socket, connected to C1,
Page 72 and 73:
The “Radio” socket is suitable
Page 75:
Audio power from the drain develops
Page 78 and 79:
Yet another top cut control is show
Page 80 and 81:
MISCELLANEOUS CIRCUITSThe miscellan
Page 82:
0.001 = 8000, so R1 is 8k. (Note th
Page 85:
type intended for this purpose, and
Page 89 and 90:
of the circuit, and 2nd, 4th, 6th
Page 92 and 93:
Components for Figure 47C1 4.7nF si
Page 94 and 95:
so that it can be swept about near
Page 96 and 97:
The following will prove of aid to
Page 98 and 99:
given, a deflection of somewhat ove
Page 100:
BABANI PRESS BP 3950 (FET) Field Ef
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50 (FET) Field Effect Transistor Projects - Battery Portable

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