Racal 6217 calibration question
 

I just got a Racal 6217 but the frequency dial needs to be calibrated.
What is the procedure for doing this? What frequency should I place
the dial to do this?

Appreciate your help.

Reggie wrote:
I just got a Racal 6217 but the frequency dial needs to be calibrated.
What is the procedure for doing this? What frequency should I place
the dial to do this?

Appreciate your help.

Hi,

A full calibration of the KHz dial on a Racal 6217 is a difficult process,
but seldom needed.

What is the problem with yours? (note, spec is +/- 1KHz at 100KHz markers)

-Chuck

I'm a little confused. When I try to pick up WWV at 10 mhz I can't
find it...a hundred up...a hundred down. Picks up fine on SSB and AM
(International Shortwaves) but I don't really know where I'm at on the
band. The preselector seems to work ok on the selected MHz tick. What
do you think might be going on here?

Reggie wrote:
I'm a little confused. When I try to pick up WWV at 10 mhz I can't
find it...a hundred up...a hundred down. Picks up fine on SSB and AM
(International Shortwaves) but I don't really know where I'm at on the
band. The preselector seems to work ok on the selected MHz tick. What
do you think might be going on here?



Hi Reggie,

First, the preselector is very sharp, so it must be tuned carefully.
If you look on the preselector switch, you will see 2 positions marked
WB, which are intended for when you are tuning the VFO onto the desired
signal frequency Once you are receiving the signal, switch the preselector
selector to the frequency band desired, and carefully tune the center knob
of the preselector switch for a peak in signal strength.

Second, there is a calibrator that will give the usual 100KHz reference
signals for checking the KHz knob.

You might not be aware, but the 6217, uses a very strange setup for the
MHz selection knob. The knob actually turns a cap that tunes a VFO that
both down converts the RF to a 1st IF freq, and is mixed down so it can
also down convert the 1st IF to the 2nd IF frequency. This double mixing
cancels out any error in the MHz selection VFO's frequency setting.

Pretty cool!

This saved RACAL from needing the fist full of crystals, and switch contacts
that were used in the R390, yet still gives crystal stability in band
selection.

-Chuck

Chuck, come to find out that the frequency received is 17 khz down from
what the dial reads. Is this an alignment problem. If so do you know
where I can a copy of alignment procedures?

Reggie wrote:
Chuck, come to find out that the frequency received is 17 khz down from
what the dial reads. Is this an alignment problem. If so do you know
where I can a copy of alignment procedures?


Hi Reggie,

There is a knob on the front panel called "Calibrate/Fine Tune". It is
connected to a 25T pot. It allows you to shift the received frequency
relative to the displayed frequency by something more than 50KHz.

The correct proceedure is to set the KHz dial to zero, and turn the AGC
switch to "CAL", Detector mode to "0", and BFO tune to "0". Then you
adjust "Calibrate/Fine Tune" for a zero beat.

Doing an instrument calibration on a 6217 is a very daunting task. I have
done many, and once was quite good at it. It requires (and by that I really
mean requires): RF signal generator (HP606), AF signal generator (HP200AB),
VTVM (HP410C), frequency counter, noise generator (Marconi TF1106), wave
analyzer (HP302A), or better still a spectrum analyzer, Oscilloscope, DVM,
RF voltmeter (Boonton 91H), Sweep Generator (1-7MHz, with accurate markers),
Logrithmic amplifier (Jerrold 500, 1-7 MHz, or HP7562A).

And further, you need a host of adapter cables for the little microdot(IIRC)
connectors that are everywhere in the unit. Depending on the model you have,
the back panel will either have BNC (preferred), or SMC connectors all over
it.

To make matters worse, all of the tuning slugs have square holes, and they
are extremely fragile. If you don't use the correct tool, they fracture
and freeze inside the coil forms.

On the bright side, there are only a few failures that commonly happen to
6217's, and they don't require calibration. The first is the germanium transistors
in the front end are easy to blow, and impossible to find. NTE used to
have some NOS transistors that worked fairly well, and the second is a 1/4 watt
resistor that protects the VFO burns out when the capacitors get charged up
for the first time after a long period of disuse. The resistor is under one
of the little metal plates on the bottom of the receiver, near the VFO's. The
symptom is noise, but no tuning. And the third problem is the filter caps
in the powersupply. Like all 1960's caps, they are getting leaky by now.

-Chuck

In article . com,
Reggie wrote:
I'm a little confused. When I try to pick up WWV at 10 mhz I can't
find it...a hundred up...a hundred down. Picks up fine on SSB and AM
(International Shortwaves) but I don't really know where I'm at on the
band. The preselector seems to work ok on the selected MHz tick. What
do you think might be going on here?

Maybe a dead band? Try 5 and 15 MC.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:
In article . com,
Reggie wrote:

I'm a little confused. When I try to pick up WWV at 10 mhz I can't
find it...a hundred up...a hundred down. Picks up fine on SSB and AM
(International Shortwaves) but I don't really know where I'm at on the
band. The preselector seems to work ok on the selected MHz tick. What
do you think might be going on here?


Maybe a dead band? Try 5 and 15 MC.
--scott


The Racal is incapable of having a dead band. There are no bands!

Propagation might be bad at 10MHz, but surely it would be good at
some point.

-Chuck

Chuck, I followed you procedure and was able to pull it back to within
11 Khz, then the knob quit turning (was turning to the left). I had
the radio on 15,000 Khz. Turn the cal knob all the way to the left and
all the way to the right and was not able to hear the tone. Then I
turned the cal knob back to 14,089 and could hear it, but that's when
the knob quit turning. What does this mean?

Reggie wrote:
Chuck, I followed you procedure and was able to pull it back to within
11 Khz, then the knob quit turning (was turning to the left). I had
the radio on 15,000 Khz. Turn the cal knob all the way to the left and
all the way to the right and was not able to hear the tone. Then I
turned the cal knob back to 14,089 and could hear it, but that's when
the knob quit turning. What does this mean?

Hi Reggie,

There are a couple of possibilities, the voltage source for the varicap
that is adjusted by the calibrate knob could have drifted, or the shaft
coupling that goes between the tuning cap and the counter shaft could have
been set incorrectly. To check for proper fine tuning operation, it should
shift the receiver frequency a total of 8KHz when you turn it from one end
to the other.

It is easy to adjust the shaft coupling. It has two set screws, one goes into
a brass shaft, and the other presses on a phenolic sleeve that goes around
the capacitor shaft.

Here is the proceedu

1) measure the RF voltage out of the 2nd VFO output on rear panel, is should
be 250mv
2) connect a frequency counter to the 2nd VFO output on rear panel. Set the
KHz dial to 1000KHz (up at the high end) The counter should read 3.6MHz

3) set the 2nd VFO to 0000KHz, and the counter should read 4.6MHz+/- 500Hz.
If it doesn't, adjust trimmer C4 for correct frequency.
4) set the 2nd VFO to 1000KHz, and adjust the mechanical coupling for 3.6MHz.

5) repeat steps 2-4 until the ends match. When they do, check each 100KHz
point for correctness. If they are wrong, the tabs on the main tuning
cap will need tweaking (DON'T DO THIS UNLESS YOU ARE REALLY SERIOUS!!).

6) check that the VFO varies from 0 to 8KHz when you adjust the fine tuning
control.


OK, that is the official factory sanctioned alignment instruction for the
VFO. Before you do any of it, check with a freq. counter to see what the 2nd VFO
frequencies are at 1000KHz, and 0000KHz. If you are lucky, they will both be
off by the same amount in the the same direction. If this is true, you just
need to slip the capacitor's shaft coupling. Don't go nuts on tightening the
set screw, it only needs to be snug.

Just out of curiosity, have you tried the BFO check position to see if your
BFO tuning knob is really at zero when its pointer shows zero? The BFO can
tune +/-15KHz.

-Chuck