Communication-concepts EB27A Engineering Bulletin Manual de usuario descargar pdf (Pagina 2)

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2 RF Application Reports

Transformer Construction

For continuous operation at full power CW, it is

recommended that heat sink compound, such as Dow

Corning #340, be applied between the board surface and

and R

, and if possible have air circulating over the top

of the circuit board as well.

The effective base-to-base impedance, increased by the

RC networks is about 5 ohms at midband. As a result of

this and the 9:1 impedance ratio in the input transformer T1,

the input VSWR is limited to 1.9:1 or less across the band.

Transformer T2, in addition to providing a source for the

feedback and carrying the dc collector current, acts as the

rf center tap of the output transformer. To construct T2, wind

5 turns of 2 twisted pairs of AWG No. 22 enameled wire on

a Stackpole 57-9322 toroid (Indiana General F627-8Q1).

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Figure 1. Collector Efficiency,

Power Gain and VSWR vs Frequencv

A Stackpole dual balun ferrite core 57-1845-24B is used

for T1. The secondary is made of 1/8″ copper braid, through

which three turns of the primary winding (No. 22 Teflon



insulated hook-up wire) are threaded. The construction of

T3 is similar to that of T1. It employs two Stackpole 57-3238*

ferrite sleeves which are cemented together for easier

construction. The primary is made of 1/4″ copper braid,

through which three turns of No. 16 Teflon



insulated wire

are threaded for the secondary .

A. B.

Optional

Input

Atten-

uator

R10

MC1723C

C11

C13C12

Q1 Q2

EEEE

C7C6

C15

C14

L1 L2

C16

R11

= Terminal Pins and

Feedthroughs

= Feedthrough

= Eyelets.

= Stand Off’s

1 2 3 4 5

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