[Hallicrafters] AC/DC Set Alignment Questions

[Richard Knoppow]

----- Original Message ----- 
From: "Kenneth Goodwin" <krgoodwin at comcast.net>
To: <hallicrafters at mailman.qth.net>
Sent: Wednesday, July 20, 2011 8:07 AM
Subject: [Hallicrafters] AC/DC Set Alignment Questions


> For an alignment of an ac/dc set like the S-38D, I know 
> enough to have the
> receiver on an isolation transformer.  However,
>
> 1.        Would you put all of the test instruments (VTVM, 
> Signal Generator)
> on the same isolation circuit transformer.  All of the 
> test instruments have
> a 3-prong AC plug.  It has been my practice to put those 
> on a two prong
> interface device (whatever those plugs are called).
>
> 2.       I would presume that for the alignment of the 
> I.F. having nothing
> connected to the antenna connection is standard.
>
> 3.       I have a Hickok 6000A tube tester.  All the tubes 
> normally have a
> Shunt setting for testing as shown in the test data 
> manuals and/or the tube
> tester's scroll.  The Hickok manual says the meter is only 
> reading true
> micromhos when set to one of the three calibration marks 
> on the Shunt dial.
> Each of these three marks is associated with each of the 
> three scales on the
> tube tester meter.  The tube data tables show a 'passing' 
> Mutual Conductance
> parameter.  Is that the reading when the Shunt is set to 
> the tube table
> shunt value which is different than the meter calibration 
> setting?  If so,
> what scale of the three meter scales do you read?  The 
> scale closest to the
> mutual conductance number given in the tube test data?  Or 
> is the mutual
> conductance parameter in the tube tables only valid when 
> the shunt is set to
> one of the three calibration marks on the shunt dial?
>
> 4.       Isn't a simple capacitor across the antenna 
> connections good enough
> for a dummy load?  The RTMA model shown in the 
> Halllicrafters manual is made
> up of no less than four  R/L/C devices.
>
>
>
> Ken K5RG (krgoodwin at comcast.net)

    Can't help with the tube tester.
    The sets are easy to align. You could put the 
instruments on the isolation transformer so that you don't 
get any accidental shorts.
    You can feed the IF frequency directly into the antenna 
connection, there is plenty of feed through. For the RF 
alignment I would just couple the generator through a 
resistor of a couple of hundred ohms. The RETMA standard 
dummy antenna is useful for making sensitivity measurements 
but is not necessary for a general alignment.
    You will find that on the highest band at least that 
adjusting the RF trimmers tends to pull the oscillator so 
rocking the tuning control a bit while adjusting for maximum 
is helpful. Use the _minimum_ signal strength you can to 
adjust; the AVC changes the tuning slightly and you want it 
peaked for the weakest signals.
    Beware that there is almost no image rejection on the 
high band so be careful that you peak the desired signal and 
not the image.
    These are surprizingly good receivers considering they 
are just a gussied up AA-5


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com