Richard

#87782

I have a 475 scope, but pretty much a beginner in its use.  I want to measure RF frequencies in a ham tranceiver that could be as high as 800 VDC, and up to 30 Mhz.  My question has to do with the proper type of probe.  Is anything special needed to measure RF frequencies that could be generating significant power other than a common probe?  Does the scope need protection from high power RF?  I want to at least see what is going into the grids of the final amplifier tubes.

#87783

Richard,

? Suggest you review a couple of web articles before digging into the rig with scope.? Typically if your trying to observe RF at the plate tank, there should be a RF sampler which brings the level down to scope range.

?

? Here are a couple of sites I found using a? search engine looking for "scope fundamentals" and "probe basics"

?

? Recommend that you research available probes and see what their specification limits are?before using one to probe a tank circuit.? And, I would strongly recommend staying on the cold side ((non HV) of the tank network.? Or, if needed, build a X10?attenuator into the rig to bring the levels down to managable voltages.

?Denis

?

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From: Richard
To: TekScopes@...
Sent: Sunday, February 17, 2013 8:53 PM
Subject: [TekScopes] Basic Probe Question

I have a 475 scope, but pretty much a beginner in its use. I want to measure RF frequencies in a ham tranceiver that could be as high as 800 VDC, and up to 30 Mhz. My question has to do with the proper type of probe. Is anything special needed to measure RF frequencies that could be generating significant power other than a common probe? Does the scope need protection from high power RF? I want to at least see what is going into the grids of the final amplifier tubes.

#87784

开云体育

Whatever probe you are using, you need to get the manual for it.?

?

The voltage limit decreases with frequency. Usually pretty quickly. For example, at DC your probe might be rated for 500 volts. At 30 MHz, it will drop down to perhaps 50 volts peak.

?

Regards,

Tom

?

Show quoted text

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

From: Richard

To: TekScopes@...

Sent: Sunday, February 17, 2013 11:53 PM

Subject: [TekScopes] Basic Probe Question

?

I have a 475 scope, but pretty much a beginner in its use. I want to measure RF frequencies in a ham tranceiver that could be as high as 800 VDC, and up to 30 Mhz. My question has to do with the proper type of probe. Is anything special needed to measure RF frequencies that could be generating significant power other than a common probe? Does the scope need protection from high power RF? I want to at least see what is going into the grids of the final amplifier tubes.

#87785

Richard,

     The Tektronix P6009 probe is rated up to 2.1kV peak (1.5kV rms, 4.2kV p-p), but not at full frequency.  It is derated to 1000V peak in the 3MHz to 6MHz range, and 200V peak at 30MHz.

     These ratings are from the Tek website.  The case of DC plus superimposed AC is not covered explicitly.

     There have recently been a number of imported high voltage, high frequency probes on eBay, one I saw was rated 4kV (DC+peak AC) and 100MHz bandwidth ($49.99), but I assume it cannot handle that high an AC voltage at the full 100MHz.

--John Gord

Show quoted text

--- In TekScopes@..., "Richard" <w6ccd@...> wrote:

I have a 475 scope, but pretty much a beginner in its use.  I want to measure RF frequencies in a ham tranceiver that could be as high as 800 VDC, and up to 30 Mhz.  My question has to do with the proper type of probe.  Is anything special needed to measure RF frequencies that could be generating significant power other than a common probe?  Does the scope need protection from high power RF?  I want to at least see what is going into the grids of the final amplifier tubes.

W6CCD

#87794

I have three probes that came with the 475.  The first one is a Tektronix
with what appears to be a 013-071 screw-on tip.  The ring of the probe
handle shows 10003A, 600V Max, Atten 10X, 10 Megohm, 10 PF.

The second one has a number P6053B and a little push-button near the word
"Ident."  The scope end has a little box on the BNC connector with 10Meg,
12.5pF, 6ft.  Also Tektronix.

The third one shows Hitachi Denshi Ltd.  AT-10AK.  There is a trimmer
capacitor accessible through a little hole in the connector body.  There is
also a slide switch on the probe body for X1 and X10.

I also have a direct probe that is just a coax with a BNC on one end, and
two, clip-on leads on the other end. 

Do I need anything else for general testing, calibration and
trouble-shooting of tube-type amateur radio transceivers?  I will stay away
from the 800 VDC in the tank circuit.  The highest voltage I would see then
would be <300 VDC.

Richard (Dick) W6CCD


--- In TekScopes@..., "Richard" <w6ccd@...> wrote:

I have a 475 scope, but pretty much a beginner in its use.  I want tomeasure RF frequencies in a ham transceiver that could be as high as 800
VDC, and up to 30 Mhz.  My question has to do with the proper type of probe.
Is anything special needed to measure RF frequencies that could be
generating significant power other than a common probe?  Does the scope need
protection from high power RF?  I want to at least see what is going into
the grids of the final amplifier tubes.

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf
Of johncharlesgord
Sent: Monday, February 18, 2013 12:42 AM
To: TekScopes@...
Subject: [TekScopes] Re: Basic Probe Question

Richard,

     The Tektronix P6009 probe is rated up to 2.1kV peak (1.5kV rms, 4.2kV
p-p), but not at full frequency.  It is derated to 1000V peak in the 3MHz to
6MHz range, and 200V peak at 30MHz.

     These ratings are from the Tek website.  The case of DC plus
superimposed AC is not covered explicitly.

     There have recently been a number of imported high voltage, high
frequency probes on eBay, one I saw was rated 4kV (DC+peak AC) and 100MHz
bandwidth ($49.99), but I assume it cannot handle that high an AC voltage at
the full 100MHz.

--John Gord