>> >You claim lower Rp means less VHF gain. Lower Rp (plate load resistance)
>> >does NOT mean less VHF gain, because of shunting reactances.
>> >
>> ** what shunting reactances? How can reactance effect R ?
>
>Anyone who has tuned a tuning control on a transmitter understands reactance
>can affect gain.
>
** ? Say what ?
>>
>> The brass strip is in parallel with the anode?
>
>We took everything to a parallel mode, which is the parallel equivalent
>impedance of a two-terminal device.
** The brass strip is in series with the anode and the Tune C. The low
(series) Z of the brass strip transforms into a high Rp.
A low series R has a high parallel R equivalent. A high series R has a
low parallel R equivalent. [see Figure 18 on my Web site]
>Any system like this can be expressed in a series-equivalent impedance or a
>parallel-equvalent impedance.
** Not a "system", each specific Z has an equivalent Y. (see March,
1989 QST, page 7, 'Finding Impedance by Solving for Admittance')
>
>When we comnpare two systems, we must look at them the same way and use the
>same terms to avoid confusion.
>
** in order to begin to understand how an amplifier works, one must
understand its parts.
>> ** Wes' table shows that the W8JI suppressor had c. 60% more Rp than the
>> other guy's suppressor.
>
>That's great news, because when the higher resistance suppressor is placed
>in series with the anode lead it has more de-Qing effect.
** quite rightly, but the more R a VHF suppressor has, the hotter it
gets at 29mHz. Thus a parasitic suppressor is a tradeoff.
>
>The lowest Rp suppressor would be a dead short,
** The opposite is true.
>and the Measures nichrome
>suppressor is closest to a dead short.
>
** only if Ni-Cr alloy is a VHF superconductor at room temperature.
>The irony of this is the nichrome suppressor Wes tested actually would have
>MORE Rp than the stock suppressors you sell!
** Wes built the Ni-Cr suppressor from materials I sent him, so I don't
know much about it. If someone on AMPS has access to an
impedance/admittance-analyzer that will go to 100MHz, and has the time to
do the measurements, I will build a 3-500Z suppressor according to our
instructions and submit it for testing.
>
>> >The lowest Rp suppressor would be a dead short, or no
>> >suppressor at all.
>>
>> ** Downtown Backwardsville. A virtual dead short in series with the
>> anode would have a high parallel-equivalent resistance. A high series R
>> means a low parallel-equivalent resistance, or Rp. This subject is
>> covered in AC circuit analysis.
>
>You are mixing the models.
>
** clueless
>The two-terminal device consisting of a resistor and inductor by itself had
>a low Rp. We are NOT placing the low Rp of the suppressor directly from the
>anode to ground, it is in SERIES with the long anode lead! It is the long
>anode lead impedance it must modify.
>
>> >
>> ** so what caused the gold to evaporate off of the 8877 grid in Fig. 24
>> on my Web site ? Can you name another 8877 HF amp designer who does not
>> use a vhf parasitic suppressor?
>
>Gold migration is a common problem. It is explained on my web page in the
>vacuum tube failures section.
** gold boils off at 2966?C/5370?F. An 8877's grid weighs c. 50g. What
is the temperature of the Sun's surface?
>
>It does NOT prove an oscillation. It is actually caused either by excessive
>grid current or by manufacturing defects in the tube.
>
** NIH syndrome,
>> ** I do not recommend putting low-Q suppressors in series with the
>> tank-L.
>
>Your suppressors, like most suppressors, are in series between the tube
>capacitance and tank input. Like it or not, that places them in series with
>the tank and de-Q's the system.
** ________
>This is especially noticable on 15 and ten
>meters, when the anode capacitance is a large portion of tank input
>capacitance.
>
>73 Tom
>
>
- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
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