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Oscilloscope help part 2 ;-)

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JEAN-FRANCOIS MENARD-2

Oscilloscope help part 2 ;-)

Ok, first thanks for all people that post something about using a
scope. Now I am more familiar with my scope.

My second question is, like in the manual of the K2 on page 75
regarding 40 meter transmitter alignement, telling that we could use an
oscilloscope to adjust all band pass filter in the K2.

Ok, now I have one, but now where do I put my probe in the K2 and what
should I expect to see on the scope when the bandpass are correctly
adjust or disadjust ??? I should expect that I go the same way for all
bandpass filters ???

As a newbie I am, I must have a more detail routine to do some stuff
like this. But be sure this will help me !!! ;-)

Big thanks again to all of you.

P.S. My scope is a Velleman HPS40 with the 60 Mhz 1x / 10x probe.

73

===============================================
Jean-François Ménard / VA2VYZ
[hidden email]

Amateur Radio Club of Sherbrooke, Quebec, Canada

Web site: http://homepage.mac.com/jfmenard
===============================================
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Don Wilhelm-2

Re: Oscilloscope help part 2 ;-)

When adjusting the bandpass filters for transmit, I do use a 'scope.
The 'scope is doing nothing more that acting as a sensitive analog RF
voltmeter, so nothing complex is required on setting the 'scope time base.

Just connect the 'scope probe across the dummy load (I use a 10x probe),
press TUNE on the K2 and you should see an RF envelope display on the 'scope
face - if not adjust the vertical amp and the trigger level until something
is displayed - then set the time base so you are seeubg the CW envelope
rather than a few cycles of the RF.

As you adjust the bandpass filter, you should see the vertical deflection on
the 'scope face shrink and grow in response to the tuning - adjust for the
largest display height.

73,
Don W3FPR

Life is what happens when you are making other plans

----- Original Message -----

My second question is, like in the manual of the K2 on page 75
regarding 40 meter transmitter alignement, telling that we could use an
oscilloscope to adjust all band pass filter in the K2.

Ok, now I have one, but now where do I put my probe in the K2 and what
should I expect to see on the scope when the bandpass are correctly
adjust or disadjust ??? I should expect that I go the same way for all
bandpass filters ???

As a newbie I am, I must have a more detail routine to do some stuff
like this. But be sure this will help me !!! ;-)

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JEAN-FRANCOIS MENARD-2

Re: Oscilloscope help part 2 ;-)

In reply to this post by JEAN-FRANCOIS MENARD-2

No problemo Rich, sharing is the key for people sucess !!!

73

Le 04-06-20, à 18:17, Richard Lim a écrit :

> Jean-Francois, please forward the responses you receive to me too if
> you don't mind. I am also a newbie with my first scope and I'd like to
> learn to use it as well. Thanks.
>
> Rich
> ____________________________
> 72/73 DE KQ9L K1 #1669, K2 #3232
> KX1 #21, FIST 10193, FP 548,
> QRP ARCI 11129 ARS #1565
> QRP-L #2552
>
>
> On Jun 20, 2004, at 4:55 PM, JEAN-FRANCOIS MENARD wrote:
>
>> Ok, first thanks for all people that post something about using a
>> scope. Now I am more familiar with my scope.
>>
>> My second question is, like in the manual of the K2 on page 75
>> regarding 40 meter transmitter alignement, telling that we could use
>> an oscilloscope to adjust all band pass filter in the K2.
>>
>> Ok, now I have one, but now where do I put my probe in the K2 and
>> what should I expect to see on the scope when the bandpass are
>> correctly adjust or disadjust ??? I should expect that I go the same
>> way for all bandpass filters ???
>>
>> As a newbie I am, I must have a more detail routine to do some stuff
>> like this. But be sure this will help me !!! ;-)
>>
>> Big thanks again to all of you.
>>
>> P.S. My scope is a Velleman HPS40 with the 60 Mhz 1x / 10x probe.
>>
>> 73
>>
>> ===============================================
>> Jean-François Ménard / VA2VYZ
>> [hidden email]
>>
>> Amateur Radio Club of Sherbrooke, Quebec, Canada
>>
>> Web site: http://homepage.mac.com/jfmenard
>> ===============================================
>> _______________________________________________
>> Elecraft mailing list
>> Post to: [hidden email]
>> http://mailman.qth.net/mailman/listinfo/elecraft
>> You must subscribe to post.
>> Subscriber Info (Addr. Change, Unsub etc):
>> http://mailman.qth.net/subscribers.htm
>> Elecraft page: http://www.elecraft.com
>>
>>

===============================================
Jean-François Ménard / VA2VYZ
[hidden email]

Club d'Astronomie Amateur de Sherbrooke
Club Radio Amateur de l'Estrie

Mon site web personnel : http://homepage.mac.com/jfmenard
===============================================

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JEAN-FRANCOIS MENARD-2

Re: Oscilloscope help part 2 ;-)

In reply to this post by Don Wilhelm-2

My oscilloscope have only an input amplifier bandwidth of 14 Mhz
maximum... will it be enough to adjust all bandpass on all bands ???

Le 04-06-20, à 18:29, Don Wilhelm a écrit :

> When adjusting the bandpass filters for transmit, I do use a 'scope.
> The 'scope is doing nothing more that acting as a sensitive analog RF
> voltmeter, so nothing complex is required on setting the 'scope time
> base.
>
> Just connect the 'scope probe across the dummy load (I use a 10x
> probe),
> press TUNE on the K2 and you should see an RF envelope display on the
> 'scope
> face - if not adjust the vertical amp and the trigger level until
> something
> is displayed - then set the time base so you are seeubg the CW envelope
> rather than a few cycles of the RF.
>
> As you adjust the bandpass filter, you should see the vertical
> deflection on
> the 'scope face shrink and grow in response to the tuning - adjust for
> the
> largest display height.
>
> 73,
> Don W3FPR
>
> Life is what happens when you are making other plans
>
> ----- Original Message -----
>
> My second question is, like in the manual of the K2 on page 75
> regarding 40 meter transmitter alignement, telling that we could use an
> oscilloscope to adjust all band pass filter in the K2.
>
> Ok, now I have one, but now where do I put my probe in the K2 and what
> should I expect to see on the scope when the bandpass are correctly
> adjust or disadjust ??? I should expect that I go the same way for all
> bandpass filters ???
>
> As a newbie I am, I must have a more detail routine to do some stuff
> like this. But be sure this will help me !!! ;-)
>
>
>

Vic K2VCO

Re: Oscilloscope help part 2 ;-)

JEAN-FRANCOIS MENARD wrote:

> My oscilloscope have only an input amplifier bandwidth of 14 Mhz
> maximum... will it be enough to adjust all bandpass on all bands ???

Yes, because all you care about is a relative voltage indication -- you
are not trying to view a waveshape accurately or measure the absolute
voltage.

--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco

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JEAN-FRANCOIS MENARD-2

Re: Oscilloscope help part 2 ;-)

Big thanks !!

Le 04-06-21, à 21:59, Vic Rosenthal a écrit :

> JEAN-FRANCOIS MENARD wrote:
>
>> My oscilloscope have only an input amplifier bandwidth of 14 Mhz
>> maximum... will it be enough to adjust all bandpass on all bands ???
>
> Yes, because all you care about is a relative voltage indication --
> you are not trying to view a waveshape accurately or measure the
> absolute voltage.
>
> --
> 73,
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco
>
>

Ron D'Eau Claire-2

RE: Oscilloscope help part 2 ;-)

In reply to this post by JEAN-FRANCOIS MENARD-2

Keep in mind, Jean-François, that if you use that 'scope to search for
distortion in a waveform, you probably shouldn't try to investigate
waveforms above 1 or 2 MHz with a "14 MHz" oscilloscope. It will work well
at 14 MHz and above for simply "peaking" a signal for maximum amplitude as
Don says, but not for looking for spikes, noise and other artifacts in a
waveform.

That's because noise, spikes, etc., appear at frequencies much higher than
the fundamental signal. For example, if you had access to a variable
frequency square wave generator and applied it to the scope input terminal,
you'd see nice square waves on the display until you raised the frequency
above 1 or 2 MHz. Then they'd start looking less square and more rounded. As
you continue to raise the frequency by the time you raised it to 14 MHz the
waveform on your scope would look more like a sine wave than a square wave.

That happens because the leading and trailing edges of a square wave are
really at a much higher frequency than the fundamental frequency of the
square wave. If you look at the plot of a square wave and carefully traced
over it a sine wave whose rise and fall matched that of the leading and
trailing edges of the square wave, you'd see that many cycles of sine wave
would fit in the space of one cycle of square wave. Unless your 'scope can
handle that higher frequency, it can't reproduce the steep shape of the
leading and trailing edges and they will look rounded.

So you might have a really distorted signal at 10 or 15 MHz showing noise or
parasitic oscillations, etc., but on your 14 MHz scope the signal might look
like a very clean sine wave.

In practice, the usual "rule of thumb" is that the vertical amplifier in a
oscilloscope should have about 10 times the bandwidth of the
highest-frequency signal that you want to view to see the "shape" of the
signal and to look for artifacts. That's why most 'scopes used for HF up to
30 MHz have vertical amplifier bandwidths of several hundred Megahertz.

Let me reiterate, that is a concern only if you are looking at the shape of
the waveform. As long as you can see some vertical deflection, it is FB for
"peaking" a stage for maximum output.

Ron AC7AC

-----Original Message-----

My oscilloscope have only an input amplifier bandwidth of 14 Mhz
maximum... will it be enough to adjust all bandpass on all bands ???

Le 04-06-20, à 18:29, Don Wilhelm a écrit :

JEAN-FRANCOIS MENARD-2

RE : Oscilloscope help part 2 ;-)

Thanks Ron for your clear answer. I understand, I think this is will be fine
for me for now. You know higher they can take, higher will be the price
also. This scope is actually around 500$ CDN.... That the maximum I can
affort for a scope for now... But maybe in the futur, I could get a hand on
a better scope (maybe a used one) for a good price.

Anyway, for now, I think it will be very handy, at least for my
understanding of a scope and for basic readings I need.

Another good message I will keep in my files !!!

Thanks again.

-----Message d'origine-----
De : [hidden email]
[mailto:[hidden email]] De la part de Ron D'Eau Claire
Envoyé : 22 juin 2004 11:12
À : [hidden email]
Objet : RE: [Elecraft] Oscilloscope help part 2 ;-)

Keep in mind, Jean-François, that if you use that 'scope to search for
distortion in a waveform, you probably shouldn't try to investigate
waveforms above 1 or 2 MHz with a "14 MHz" oscilloscope. It will work well
at 14 MHz and above for simply "peaking" a signal for maximum amplitude as
Don says, but not for looking for spikes, noise and other artifacts in a
waveform.

That's because noise, spikes, etc., appear at frequencies much higher than
the fundamental signal. For example, if you had access to a variable
frequency square wave generator and applied it to the scope input terminal,
you'd see nice square waves on the display until you raised the frequency
above 1 or 2 MHz. Then they'd start looking less square and more rounded. As
you continue to raise the frequency by the time you raised it to 14 MHz the
waveform on your scope would look more like a sine wave than a square wave.

That happens because the leading and trailing edges of a square wave are
really at a much higher frequency than the fundamental frequency of the
square wave. If you look at the plot of a square wave and carefully traced
over it a sine wave whose rise and fall matched that of the leading and
trailing edges of the square wave, you'd see that many cycles of sine wave
would fit in the space of one cycle of square wave. Unless your 'scope can
handle that higher frequency, it can't reproduce the steep shape of the
leading and trailing edges and they will look rounded.

So you might have a really distorted signal at 10 or 15 MHz showing noise or
parasitic oscillations, etc., but on your 14 MHz scope the signal might look
like a very clean sine wave.

In practice, the usual "rule of thumb" is that the vertical amplifier in a
oscilloscope should have about 10 times the bandwidth of the
highest-frequency signal that you want to view to see the "shape" of the
signal and to look for artifacts. That's why most 'scopes used for HF up to
30 MHz have vertical amplifier bandwidths of several hundred Megahertz.

Let me reiterate, that is a concern only if you are looking at the shape of
the waveform. As long as you can see some vertical deflection, it is FB for
"peaking" a stage for maximum output.

Ron AC7AC

-----Original Message-----

My oscilloscope have only an input amplifier bandwidth of 14 Mhz
maximum... will it be enough to adjust all bandpass on all bands ???

Le 04-06-20, à 18:29, Don Wilhelm a écrit :

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Robert McGwier

RE: RE : Oscilloscope help part 2 ;-)

Jean Francois:

I recently purchased a 4 channel, auto scaling, 400 Mhz Tektronix
scope for under $500 US on Ebay and this included 3 probes, two
of them 400 Mhz, one 100 Mhz. This is much more capable
than what you are talking about. Have your looked there lately?

Bob
N4HY

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]]On Behalf Of Jean-François
Ménard
Sent: Tuesday, June 22, 2004 3:27 PM
To: [hidden email]
Subject: RE : [Elecraft] Oscilloscope help part 2 ;-)

Thanks Ron for your clear answer. I understand, I think this is will be fine
for me for now. You know higher they can take, higher will be the price
also. This scope is actually around 500$ CDN.... That the maximum I can
affort for a scope for now... But maybe in the futur, I could get a hand on
a better scope (maybe a used one) for a good price.

Anyway, for now, I think it will be very handy, at least for my
understanding of a scope and for basic readings I need.

Another good message I will keep in my files !!!

Thanks again.

_______________________________________________
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http://mailman.qth.net/mailman/listinfo/elecraft
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