Signal generator question

[Jean-François Ménard-5]

Hi,

I would like to learn and explore more «signal tracing» procedure and
technique. I actually have a Fluke 196C. But I don't have a signal
generator.

A friend of mine have his signal generator for sale. The model is an
Instek GFG-8216A. I would like to know if the device will be good for
signal tracing or the specification of this device is not enough for
this purpose??? I know that I could build the one in the K2 building
manual or at least use the technique «Cheap'n Dirty» from N0SS... but
that's not my point.... ;-)

The specification can be viewed at
http://www.instek.com/pdf/Generator/GFG-8216A8215A.pdf

Thanks for all your advice.

Best 73

J-F VA2VYZ

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[Jean-François Ménard-5]

OK, it seems that this model will not be suitable...... I will go now at
a more «basic» alternative..... as long as I learn something, this is
the most important part... :-)

I will build the «signal generator» in the K2 building manual. But I
would like to know something.... there is output level to adjust, I
guess that will depend on voltage using to run the device.

At wich level should it be set ??? I don't want to blow of damage
something while learning !!! :-))



Jean-François Ménard a écrit :

> Hi,
>
> I would like to learn and explore more «signal tracing» procedure and
> technique. I actually have a Fluke 196C. But I don't have a signal
> generator.
>
> A friend of mine have his signal generator for sale. The model is an
> Instek GFG-8216A. I would like to know if the device will be good for
> signal tracing or the specification of this device is not enough for
> this purpose??? I know that I could build the one in the K2 building
> manual or at least use the technique «Cheap'n Dirty» from N0SS... but
> that's not my point.... ;-)
>
> The specification can be viewed at
> http://www.instek.com/pdf/Generator/GFG-8216A8215A.pdf
>
> Thanks for all your advice.
>
> Best 73
>
> J-F VA2VYZ
>
> __________________________________________________
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[n6wg]

Hello J-F
I would not recommend this generator, as it
really isn't intended for your expected use.

It is a function generator, meaning it produces
sine waves, square waves, triangular waves,
and so on, but it only goes up to 3 MHz.

You want a regular rf signal generator, which
will usually produce a signal from below the
AM broadcast band to over 30 MHz.  Some will
even go up into VHF frequencies.

Good luck in your search for a generator.
73, Bob N6WG

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of Jean-François
Ménard
Sent: Thursday, October 26, 2006 6:32 PM
To: Elecraft Mailing List
Subject: [Elecraft] Signal generator question


Hi,

I would like to learn and explore more «signal tracing» procedure and
technique. I actually have a Fluke 196C. But I don't have a signal
generator.

A friend of mine have his signal generator for sale. The model is an
Instek GFG-8216A. I would like to know if the device will be good for
signal tracing or the specification of this device is not enough for
this purpose??? I know that I could build the one in the K2 building
manual or at least use the technique «Cheap'n Dirty» from N0SS... but
that's not my point.... ;-)

The specification can be viewed at
http://www.instek.com/pdf/Generator/GFG-8216A8215A.pdf

Thanks for all your advice.

Best 73

J-F VA2VYZ

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[Don Wilhelm-3]

Jean-Francois,

Signal tracing can be quite effective - I applaud your goals.

Signal tracing of a transmitter path can usually be done with only an RF
probe since the signal levels are usually large enough to measure easily,
although a 'scope is more informative because you can see the relative
frequencies involved.  For the K2, just follow the steps detailed in the
Transmit Signal Tracing section of Appendix E in the manual.

Receive Signal Tracing is a bit more 'iffy' - although the method in
Appendix E of the K2 manual works well, one must use a relatively strong
signal source (such as the oscillator shown in the manual) to have a large
enough signal in the receiver to measure (very small readings are likely
just noise picked up by the probe).  One must remember that in the RF and IF
stages, a signal that can be observed on a 'scope or RF probe is much
greater than the normal signal levels handled by the receiver -
none-the-less, the procedure can be informative in identifying a failing
stage, but it cannot be used to evaluate distortion levels since the stages
are being overdriven by the generator with this elementary test.  If one
uses a normal receiver input level signal, there are devices to effectively
measure those small signal levels (Spectrum Analyzer for instance), but the
signal path must usually be broken and the signal level transformed to 50
ohms to do proper measurements.

A more effective method of troubleshooting a receiver is to use a signal
generator to do 'signal injection' at each stage of the receiver - for the
sudio stages, that requires a generator that will produce audio frequencies,
and for the IF stages it requires a signal generator that can produce a
frequency equal to the IF frequency.  The RF stages require a signal
generator at the receiver tuning frequency.  This generator should have a
controllable output level so the levels can also be evaluated.  Normally one
would start at the audio stages and move toward the antenna one stage at a
time, injecting the level and frequency that each stage should respond to.
Using that procedure, it is sufficient to measure the ouput of the receiver
either with an AC Voltmeter or just the ears listening to the speaker.
There ued to be 'signal injectors' available that produced an audio square
waveform that was very rich in harmonics that could be used as a relative
indicator of functioning receiver stages - if you can hear a good response
when moving from the audio stages toward the antenna, it can quickly
identify a failing stage.

Bottom line - receiver signal tracing begins at the antenna and works toward
the receiver audio stages, signal injection works the other way around.
Both methods verify the operation of each stage in turn until the failure
point is found.

The generator that you referred to is a Function Generator which is great
for evaluating audio and low frequency IF stages, but if you are using a K2
for this 'education', the IF is at 4915 KHz and that generator will not go
above 3000 kHz.

As I indicated, if you are just trying to isolate a failing stage, the large
signal injected at the antenna (tune the receiver to the signal generator
frequency) will usually suffice, but if the problem is more subtle than just
a failing stage (distortion for example), the controlled level signal
injection at each stage is required - along with a good knowledge of 'what
is normal'.

73,
Don W3FPR

> -----Original Message-----
>
> I would like to learn and explore more «signal tracing» procedure and
> technique. I actually have a Fluke 196C. But I don't have a signal
> generator.
>
> A friend of mine have his signal generator for sale. The model is an
> Instek GFG-8216A. I would like to know if the device will be good for
> signal tracing or the specification of this device is not enough for
> this purpose??? I know that I could build the one in the K2 building
> manual or at least use the technique «Cheap'n Dirty» from N0SS... but
> that's not my point.... ;-)
>
> The specification can be viewed at
> http://www.instek.com/pdf/Generator/GFG-8216A8215A.pdf
>
> Thanks for all your advice.
>
> Best 73
>
> J-F VA2VYZ
>

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