At 12:01 5/14/98 +0000, you wrote:
>A recent post implied, incorrectly, that measurements of a HF PA are
>difficult to make.
Your opinion. (Since you insist on doing this, Tom)
There is no basis for such claims.
Also your opinion.
These aren't
>GHz band measurements of complex systems.
Several people have managed to span two continents and many months debating
the characterization of a little coil and a resistor, sounds pretty complex
to me.
They don't require SMA
>connections. Even BNC's and SO-239's are perfectly;y acceptable
>through VHF.
Well we do agree here, the only gotcha is that my (employer's) network
analyzer's all come with APC-7's on the front panel. The cal kits I buy
have APC-7 to 3.5 MM adapters (That's a real expensive SMA) My copy of the
MA-COM/OMNI-Spectra catalog does not list a single APC-7 to SO-239/PL-259
adapter or even a SMA to SO-239/PL-259 adaptor.
>The general rule is a one degree long impedance bump can be tolerated
>with no ill effect on impedance measurements. That's over one foot
>on 160 meters, and 1/4 inch on two meters. It's pretty darned easy to
>use BNC's and homemade fixtures to get into the 500 MHz range with
>excellent accuracy. On 160 meters you could use a Radio Shack clip
>lead!
Now I understand! On my planet that rule is not currently enforced. I bet
that the Radio Shack franchise on your planet also stocks APC-7 to UHF
adapters.
>Even a slight error isn't a problem for generalized discussions, and
>a four degree guideline would apply.
Also makes it a lot easier to come up with a good story.
>
>I personally own an HP-4191A Impedance test set, as well as two
>network analyzers. I have multichannel RF vector voltmeters, as well
>as selective and sweep generators.
Now you got me jealous.
I'm sure others have nice equipment
>also.
On my planet, only guy I know with equipment like that at home drives a 35
year old car and has no life. Life seems to be a lot tougher over here.
>
>All I need to do is attach a calibrated test probe to the anode, and
>another to the point I want to measure. Pressing a few buttons and
>entering a few keystrokes provides many hundreds of data points over
>any frequency range between 100 kHz and 1 GHz that are sorted by the
>instrument according to what parameter I am interested in, and
>displayed as a list of measurement points or as a graph.
>
>With even modest equipment someone could make very accurate
>measurements at home. The big bucks of fancy equipment has only
>bought me time and traceable calibration that is accurate beyond
>anything necessary for this discussion.
>
Hmmmmm. Could I talk you into a favor? Get a 10 ohm 1/4 watt film resistor
and stick into that little fixture that interfaces your Impedance Test set
to devices like axial lead pin diodes( no doubt you have several of those
in your collection). Run off say 50 data points across the frequency range
of your instrument. Then do the same thing using using your radio shack
clip leads as the interface. Now if you would be so kind as to publish that
table of data on the list, the guys over here on my planet could use that
as a calibration factor and be able to do traceable impedance measurements
with their radio shack gear.
Hey, you guys on the second planet over: Can you take a break from
consuming world class beverages heated to the temperature of horse piss and
do a VHF characterization of a couple of two-port networks hooked up with
clip leads? I'd really be interested to see if this measurement technique
holds up across the big void.
>73, Tom W8JI
>w8ji.tom@MCIONE.com
To coin a phrase: Cheers.....
Larry - W7IUV
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