Re: oscilloscope

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Craig,

At 09:56 PM 4/20/2002 -0500, you wrote:
>Hi,
>
>I got an HP 175a Oscilloscope at a hamfest, but it doesn't have the leads.
>It has BNC connectors.  Does it matter what kind of wire or connector I use
>to attach to the input?  

Almost all scopes have BNC connectors.  Virtually any common scope probe
can be hooked to it.  The "next" ham fest will have them to ;-))  "Scope
probes" are used to measure very high frequency signals, say above 1MHz.
"Plain ol' wire" will not work well at RF frequencies so they make these
fancy probes that give good readings up to 100, 200 ... MHz.  However, for
less than 1MHz signals. you can just use wire leads.

Here is a pic of the qvar experiment where long (50 feet) BNC cables go to
the test site:

http://hot-streamer-dot-com/temp/P4200028a.jpg

Here is a picture of where I use a BNC plug with clips on it to hook up to
a temperature probe voltage:

http://hot-streamer-dot-com/temp/P4200028a.jpg

Radio Shack, catalog, or on-line electronic places have all kinds of nice
BNC adaptors but a ham fest will be cheaper:

http://hot-streamer-dot-com/temp/P4200032a.jpg

If you like 5 way binding posts, Radio shack has a nice one bringing two
posts to a BNC adapter in the catalog (mail order 910-4804 for $6) that I
like a lot.  Don't hesitate just to go over to Radio Shack and browse their
BNC stuff.  Don't be afraid to cut cables and put alligator clips on the
ends ;-)

When you really get 'up there', look at real probes:

http://hot-streamer-dot-com/temp/P4200033a.jpg

The simple 1:1 or 1:10 100MHz (switchable) run about $70 from Tek and $35
from everyone else (lower right).  The mighty Tek 5100 (upper right) is
probably one of the best probes ever made at 250MHz, 2500V, 3pF loading
(that really IS true on this one) and carries a $250 price tag.  You
probably won't find these at ham fests...  If you like high voltage, look
for the big high voltage Tek probes like in the upper left.  The older
freon filled ones are very common at fests for great prices.

Don't be afraid of "BNC" stuff.  It is just a real nice way to hook things
up on test equipment.  It allows from DC up to like 500MHz signals to be
transferred with twist on ease.  For low frequency stuff under 1MHz, just
get a BNC cable and cut it in half and put on alligator clips.  Next ham
fest, look for the very common 10:1 scope probes.  They go to higher
frequencies but really are very easy to connect to things too.

Hopefully, you will not go to the insane lengths I have in "collecting"
things to hook to scope inputs :o))))

Cheers,

	Terry


>I want to use the scope along with a Heathkit LG-1
>Laboratory RF generator (also from hamfest) to characterize a secondary
>coil. I'm planning to eventually build a VTTC using 3 - 811a's.
>
>Another question:  The Heathkit RF generator has an RF output cable that
>terminates in 2 posts.  Do I connect to both posts with the 1K ohm resistor?
>I'm using a secondary characterization method detailed in the "Tesla Coil
>Instrumentation" video from TCBOR.
>
>I'm not familiar with either of these kinds of instruments, but they both
>appear to be working and I'm pretty sure I'll be able to use them if I can
>get the connectors figured out.
>
>
>Thanks for any help,
>
>
>Craig Shields
>