[R-390] Alignment

[Llgpt@aol.com]

In a message dated 4/1/02 8:40:34 PM, jetemp@insightbb.com writes:

<< My main concrern was how critical setting the -7 volts @150uV, IF Gain wa=
s

in completing the alignment.  >>

Read the following............


------------------------------------------------------------------------
Setting IF Gain for Optimum Performance
The most common single item responsible for holding an R390A back is not lac=
k=20
of sensitivity. Rather it is internally generated IF deck noise. In an=20
otherwise properly operating R390A, the cause of this excessive noise is IF=20
gain control being set to high. Even the mfg spec of setting the IF deck gai=
n=20
such that -7vdc at the diode load when fed by 150uv @455kc into J-513 is far=
=20
too hot.
Here is a recently refined procedure to set the IF deck gain control. Anyone=
=20
can perform the procedure whether they have access to a signal generator or=20
not:
Procedure to set R390A IF Gain:
Once the receiver has been fully mechanically and electrically aligned, the=20
final procedure to perform before "buttoning it up" is to set the IF gain=20
control. Many otherwise very sensitive R390A's are thought not to be due to=20
weak signals being covered by noise generated by excess IF deck gain.
=A0Allow the receiver to warm up for at least 1 hour then:
=A01- Terminate the antenna input
=A02- Set receiver for 15.2 mHz
=A03- Set the "FUNCTION" control to MGC
=A04- Select the 4kc filter with the "BANDWIDTH"
=A05- Set "RF GAIN" control to 10 or maximum
=A06- Peak the "ANTENNA TRIM" for maximum noise as indicated on the "LINE=20
LEVEL" meter
=A07- Set "Line Meter" switch to -10db scale
=A08- Set "Line Gain" control to full CW or "10."
=A09- Adjust IF gain control, R-519 to cause "Line Level" meter to indicate=20
between -4 to -7 VU.
10- Re-zero the carrier meter control, R-523
11- Set controls above for normal operation and reconnect antenna
Discussion:
This will yield the best compromise on all bands. I usually "poll" those=20
bands which I normally spec out. Then, using an HP signal generator set for=20
internal modulation of 800 hz @ 30%, "massage" the gain setting and even=20
specific signal path tube selections for the best overall performance.


This came from Chuck Rippels web site.......http://www.r390a.com/




Les Locklear
Gulfport, MS.

"A lot of good arguments are spoiled by some=20
fool who knows what he's talking about".=20