On Wed, 10 Sep 1997 01:01:54 +0000 w8jitom@postoffice.worldnet.att.net
writes:
>Wes was measuring two components in parallel. Look at the impedance
>of the nichrome by itself (8333 ohms) at 200 MHz, and the tinned
>copper wire by itself (43478 ohms). When that impedance is placed in
>PARALLEL with the fixed resistors (both approximately 100 ohms), the
>result is the terminal to terminal impedance of the suppressor as
>viewed from the outside world. It is THAT impedance that is
>considered to be in series with the anode system.
Something does not quite look right in those measurements. Are they
correct in stating that a pure copper wire has more impedence (
calculated) than a lossy length of resistance wire? Could there be an
error here?
>
>The higher the value of that resistance (since it is in SERIES with
>the anode impedance), the LOWER the system Q.
>
>In both cases, it is VERY close to the same result. The suppressors
>are essentially the same at VHF, but the nichrome has much lower Q at
>HF.
>
>By the way Carl, you may not be familiar with network analyzers.
>Components don't get "hot" and change value on a network analyzer.
>The 109 ohms was the value of the resistor that happened to be used,
>because of resistance tolerances in the components. What Wes was
>saying was the actual value was 109 ohms, normal tolerance for a +
>- 10% 100 ohm part.
Is that another one of your poorly disguised attacks Tom. In fact I am
quite familiar with Network Analyzers, having spent many years in the RF
Lab at Wang Labs with a HP-8505A. Here now I have to make do with the
older 8410B system since the newer ones are out of my price range.
I wonder if you even have a clue what you are talking about. First of all
Wes was not using a Network Analyzer. The ONLY item mentioned in his
report is the HP-4191A RF Impedence Analyzer. I will be glad to send
you the HP specs so you may understand the difference between the two.
I was also under the mistaken impression that the suppressors were run
hot in an amp and then evaluated on the 4191A. IMO a cold test of an
unused suppressor is only the first step in the evaluation process. I and
others would like to know what happens inside our amps over time.
>Peter, you are correct about using a "different suppressor for
>different applications or tubes". Tubes like the 572B and 811A
>require larger suppressor inductance and higher resistance values
>than other transmitting tubes because the tube's internal leads are
>so long.
I believe it was I who made that "correct" observation.
73....Carl KM1H
>73, Tom W8JI
>
>--
>FAQ on WWW: http://www.contesting.com/ampfaq.html
>Submissions: amps@contesting.com
>Administrative requests: amps-REQUEST@contesting.com
>Problems: owner-amps@contesting.com
>Search: http://www.contesting.com/km9p/search.htm
>
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|