DRAKE DA7543 Installatiehandleiding - Pagina 5

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DRAKE MODELS DA100032, DA100042, DA7533, DA7543,

DA8632, and DA8642

These amplifiers are very versatile in regard to reverse (return)

path options.

If no return path is desired, remove jumpers J1, J2, and J3. These

may be stored inside the amplifier by plugging them into just a

single pin of the headers so that the one pin holds the jumper

mechanically but no electrical connection is made to other pins.

If a passive return path is required with or without attenuation, set

jumpers J1 and J3 to the passive return path settings. Leave

jumper J2 disconnected. The REVERSE PATH GAIN adjustable

attenuator may be used to set up to approximately 12 dB of

attenuation in this path, if needed. At maximum gain setting, the

insertion loss of the passive return will be nominally 1 dB. The

programmable reverse attenuator jumpers have no effect when

using the passive return path.

When gain must be added to the reverse path, set jumpers J1, J2,

and J3 to the active return path settings. This revision of the Drake

DA series of distribution amplifiers now provides a programmable

reverse step attenuator that is programmable in steps of 2 dB

between 2 dB and 30 dB. This attenuator is located electrically

after the first stage of gain in the active reverse path amplifier. This

allows a low noise figure and excellent carrier to noise ratio to be

maintained even at low reverse gain settings. The use of this

attenuator will be equivalent to using fixed output attenuators in

other commonly used amplifiers. Fine adjustment of the reverse

path gain can be accomplished using the variable REVERSE

PATH GAIN adjustment.

Set the gain using a combination of the programmable reverse

path step attenuator and the variable reverse path gain input

attenuator. Maximum reverse path gain is nominally 22 dB.

For reverse input signal levels around 15 dBmV or below, program

most of the needed attenuation using the programmable 2 dB step

attenuator and then fine tune the final dB or two using the variable

reverse path gain adjustment. If input levels are above 20 dBmV, it

is desirable to obtain as much of the needed attenuation as

possible, up to 10 dB, with the variable attenuator and then use the

step attenuator to obtain the rest.

PROGRAMMABLE REVERSE STEP ATTENUATOR SETTINGS

There are four internal jumpers used to set the programmable

reverse attenuation. Each jumper controls an attenuator. The four

attenuator values are 2 dB, 4 dB, 8 dB, and 16 dB. The total

attenuation is the sum of any attenuators that have jumpers set to

the 'IN' setting. When a jumper is set to the 'OUT' setting, that

attenuator is out of the circuit and is effectively set to 0 dB. With all

four programmable attenuators OUT and the REVERSE PATH

GAIN, variable input attenuator set to maximum gain, the active

reverse path gain is nominally 22 dB.

® is a registered trademark of R.L. Drake LLC

Programmable Reverse Path Step Attenuator

EXAMPLES

EXAMPLE 1

Assume that a particular installation requires a reverse path gain of

5 dB. Subtracting 5 from the nominal gain of 22 dB gives a result of

17 dB attenuation required to reduce the reverse path gain to 5 dB.

To reduce the reverse path gain by 17 dB, move the 16 dB

programmable attenuator jumper to the IN position. Then adjust the

REVERSE PATH GAIN adjustment counterclockwise to obtain the

additional 1 dB of attenuation.

(Jumper at the "16 dB" "IN" position)

EXAMPLE 2

Assume that an installation requires 15 dB of gain reduction in the

reverse path amplifier to achieve a gain of 7 dB. The step attenua-

tor can be programmed for 12 dB (setting the 8 dB and 4 dB

jumpers both to 'IN') or to 14 dB (setting the 8 dB, 4 dB, and 2 dB

jumpers all to 'IN') and then adjusting the variable REVERSE

PATH GAIN control to reduce the gain the additional 1 or 3 dB. The

idea here is that one should set the step attenuator slightly less

than the attenuation needed so that there can always be some fine

adjustment of the variable gain control.

(Jumpers at the

"4 db" and "8 dB" "IN" positions)

SUMMARY

If reverse input levels are low, in the 0 dBmV area, use as little

attenuation at the reverse path gain input attenuator as possible.

This will maintain the best possible C/N ratio by keeping the

reverse path amplifier noise figure low. Obtain most gain reduction

of the reverse path amp by using the step attenuator. On the other

hand, if reverse input levels are high, say around 20 dBmV, you

can safely dial in 10 dB to 12 dB of attenuation with the input gain

adjustment without degrading the C/N. This will keep distortion

products low. Obtain the rest of the attenuation with the step

attenuator.

R.L. DRAKE LLC

FRANKLIN, OHIO 45005 U.S.A

(Jumpers at the

"2 dB", "4 dB",

and "8 dB" "IN" positions)

P/N: 3852703 rev L-10-09