[AMPS] Re: two questions

[km1h @ juno.com]

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
>
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