[SOC] 'Scope question

[Madison Jones]

Paul:

I am shocked that you are a member of SOC!  I would have expected, with =
your
talents, that you would be an FOC [or higher, if there is such a thing].

But I have a question for you:  I have an elderly Techtronix 'scope.  It =
has
been so long since I have used one [mebbe 50 years] that I don't know =
much
more than how to turn it on.  I do have the book, but it assumes that =
the
uses knows more than that about its operation.  Where can I find a =
tutorial
on its basic operation and an overview of what it can do for me?

Other than that, all is well.  Now that the contest season is here [and =
half
over already] I need to get my antennas in shape.  I put up the =
rudiments of
your 160 Agatti wire, up 40' or so and out 75' or so on both sides.  I =
have
resonance on the two elevated radials, but I found the T is only =
resonant at
2300 more or less, so I must be quite short.  What is a suggested length =
of
the legs off the vertical wire?  I am limited to 40' vertical.

Regards,

Madison W5MJ
SOC 626 [I think]

-----Original Message-----
From: soc-bounces at mailman.qth.net [mailto:soc-bounces at mailman.qth.net] =
On
Behalf Of Paul Playford
Sent: Monday, November 12, 2007 10:41 AM
To: Second Class Operators' Club
Subject: Re: [SOC] 'Scope question

Congratulations on your efforts with an oscilloscope Tom.  My scope is =
the=20
first thing I turn on when sitting down at my test bench.

It sounds like you are doing everything as good as you can with the=20
equipment you have.

The 20 MHz bandwidth means your observations of a sine wave (rf carrier) =
at=20
20 MHz will be down 3 dB from what they really are.  So if you observe 6 =
vpp

at 20 MHz your are actually looking at 8.5 vpp.

The observed frequency will be the same as the actual frequency, =
depending=20
on your scopes calibration.

Depending on your 'scope probe, it can get worse.  If you are using an=20
inexpensive probe (not Tektronix or H-P that is matched to your scope) =
that=20
is rated at 20 MHz, then you are actually looking at 12.0 vpp.

Which also means if you see 6 vpp at 10 MHz you are actually looking at =
a 9=20
vpp signal.

I own a Tektronix 465 and three Tektronix 7000 series oscilloscopes that =
are

all rated to 100 MHz and I use Tektronix probes with them and I feel =
very=20
comfortable making observations below 30 MHz.  But when I get above 50 =
MHz I

have to allow a little windage for the bandwidth.

Most of what I look at when using an oscilloscope is the shape and =
frequency

of the waveform.  If I want an accurate rf voltage measurement I will =
use an

rf probe and my Fluke digital multimeter.

de Paul, W8AEF

ZF2JL/ZF2TA  FO8DX/FO8PLA  8Q7AA  XZ0A  VU7RG
soon to be TX5C


----- Original Message -----=20
From: "Tom McCulloch" <thom2 at att.net>
To: <thom2 at att.net>
Cc: <soc at mailman.qth.net>
Sent: Sunday, November 11, 2007 6:48 PM
Subject: [-] [SOC] 'Scope question


> snip

>    OK, so I wasn't able to get good Voltage P-P readings on the scope =
for=20
> any of the bands I tried (80 through 10 meters) -- they all seemed too =

> low.

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