[Elecraft] Scope recommendations

Fri Aug 1 11:52:01 2003

Hi

I agree with most of this recommendation except I would stay away from =
the 7000 series. I was a field maintenance instructor for Tektronix for =
5 years and my specialty was the 7000 series among other things. The =
7000 series was a great scope in its day but it used more proprietary =
Ic's and other parts than any of the other scopes. Even if you can find =
someone to give you a warranty it will be very hard to keep one of these =
scopes running without a couple of spares to rob part out of. They are =
very complex and difficult to troubleshoot. Even the power supply is =
unconventional and a bear to troubleshoot for someone not familiar with =
it.=20

The major cost item in any scope is the CRT if you are looking to buy a =
used scope check the CRT to see that it is bright does not have any =
burned spots and does not double peak. Check for double peaking by =
slowly increasing the intensity from zero to full. The brightness should =
increase and eventually bloom out but should not go dimmer as the =
intensity increases. If the brightness first goes up then gets dimmer =
then the CRT is on its last leg. It may last a year or a few years but =
if you have a choice pick the one that has the best CRT. On most of =
these older scopes the CRTs are no longer available from Tektronix and =
even if they were would cost over $1000.

Check each attenuator step for intermittents and noise also check the =
AC-GND-DC switch and the time base switch on both time bases if it has =
more than one. The internal attenuator modules and cam switches are also =
getting hard to find so make sure they all work. Connect a probe to the =
calibrator and check the attenuator accuracy and the time base accuracy =
and make sure the trigger circuit works.

Get a good set of X10 probes with at least as high of bandwidth as the =
scope bandwidth

Remember a scope will be 3 db down at its rated bandwidth so they are =
not useful for making accurate measurements at close to the rated =
bandwidth. This is why you need a 100 MHz scope to make accurate =
measurements at 30-40 MHz

Don Brown
KD5NDB
  ----- Original Message -----=20
  From: Michael Melland, W9WIS=20
  To: Roy Vickers ; [email protected]=20
  Sent: Friday, August 01, 2003 9:34 AM
  Subject: Re: [Elecraft] Scope recommendations

  Tektronix is king.... like all older scopes parts may be an issue as =
they
  use typically proprietary IC's.  If you buy one on eBay buy from =
someone
  that gives an inspection period and/or warranty.  Lew Coppes (
  http://www.thetestequipmentstore.com )is a good dealer as is Tom =
Gootee (
  http://www.fullnet.com/u/tomg/tek.htm#1 ).... you'd pay a bit more =
perhaps
  then eBay but have a fully checked working scope with a warranty =
period.
  Tom has what I think would be a very nice Tek 465B for $279 listed on =
his
  page now...if he still has it.  The 465B is an EXCELLENT scope.

  Models 465B 100MHz, 475 200 MHz

  Models 2235 100 MHz, 2445 150 MHz

  Model 7603 100 MHz frame with 7B53A time base and 7A26 plugins.... if =
you
  have the room (they are big and heavy is nice)

  I have owned a 7603 and it was nice but simply too big for my shack.  =
Next
  had a 2235.... these start the more modern looking compact Tek scope
  types..... currently have a 2445 which is fantastic.  This scope also =
has
  readout and cursors for measuring voltages and frequency... expect =
these to
  cost about $400 +/- on eBay.  The 465B and 475 are a bit older but =
excellent
  scopes and value if you locate a good one.

  Remember bandwith of a scope for radio use is important.  Always buy =
as much
  bandwith as you can.... high bandwith =3D more $$$ but is well worth =
it.  The
  usual recommendation is to buy a bandwith of a minimum of 3 to 5 times =
the
  freq of the highest signal you may look at. For HF 100 MHz is the low =
end...

  73 de Mike, W9WIS

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