[Drake] Drake 4-line alignment procedure

Garey Barrell k4oah at mindspring.com
Wed Feb 23 12:07:51 EST 2005


Dave -

This is typical of the Drake separates.

The INJ cable capacity is part of the problem, along with the CAR OSC 
cable in the C Line.  The cable that was originally supplied with the B 
Line was a low capacitance microphone cable that looked almost exactly 
like the rest of the cables.  It had a small tag wrapped around one end 
to identify it.

All cables were 38" long tip-to-tip.

The INJ cable used a foam inner dielectric and phono connectors with a 
white insulation.  This cable measures 60 pF total capacity.

All other cables used the standard for the day clear polyethelene inner 
dielectric and phenolic (brown) insulated phono connectors and measures 
~100 pF.

Original Drake INJ Cable = 19 pF/ft = .160" o.d. (foam poly)

RG-62 = 93R = 13.5 pF/ft = 0.240" o.d.
RG-59 = 75R = 14.8 pF/ft = 0.242" o.d.
RG-6 = 75R = 16.2 pF/ft = 0.270" o.d.
RG-174= 50R = 30.8 pF/ft = 0.110" o.d.
Mic Cable (Belden 8410) = Hi-Z = 33 pf/ft = 0.160" o.d. (foam poly)
Mic Cable (Belden 8421) = Hi-Z = 16 pf/ft = 0.180" o.d. (foam poly)
R/S Audio Patch Cable = 28 pF/ft = 0.165" o.d. (poly)

The best choice is the Belden 8421 Audio cable from their "Brilliance" 
line.  It looks just like the other cables, and is very flexible.  The 
RG-62 is OK, but it is 50% larger and far less flexible.  RG-62 is also 
prone to shorting if bent over too small a radius or if gotten a little 
too hot in assembling the connectors.  The only pertinent factor is the 
total capacity, impedance and "loss" are not important.

The alignment procedure assumes a 60 pF cable is going to be used for 
the INJ spot.  This was the only way to align them originally since the 
receiver and transmitter were sold separately.  A cable that is higher 
or lower in capacitance is going to result in misalignment and loss of 
signal when controlling transceive with the "other" PTO.

The answer is, in fact, to touch up the INJ trimmers on both units with 
the pair cabled together.  Even at this it probably won't be "perfect", 
since there is also "some" loss between units, but it will be close enough.

Just in case this isn't enough for you to worry about regarding 
transceive with the B Line, you might take a look at my article at

<http://www89405.temp.w1.com/DrakeArticles/CrystalCodes.htm>

regarding the color coded crystals in the late A and all B Line units.  :-)

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual
<http://hr99.home.mindspring.com/R-4C_Servicez/>



Dave Maples wrote:

>All: I have been through the T-4X / R-4B alignment procedure per the Drake
>manuals a couple of times with my 4-line.  Regardless, they aren't "quite
>right".  I get a significant amount of TX drive difference with the RX VFO
>vs. the TX VFO, and the opposite for RX sensitivity.  Best results are when
>the VFOs are set to SEPARATE.
>
>I'm using 93-ohm coax between the two injection ports.
>
>Somewhere I read that the load resistor approach to tuneup was really a
>mistake, but I'm very interested in how else I should approach this.  Leave
>the two units connected together during alignment???  Some other approach?
>
>Thanks--this is always a great source for help on the Drakes...
>
>Dave WB4FUR
>
>
>
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