To: <amps@contesting.com>
>>> Date: Fri, 15 May 1998 19:10:08 -0500
>>
>>> I think that's pretty cool! It shows that Rich's supressor idea *DOES*
>>> indeed work. In a sense you are getting extra resistance out of the
>>> inductor. And that extra gives you a lower Rp which means lower VHF gain!
>>
>>Hi Jon,
>>
>>Can you explain how lower Rp in the suppressor produces less VHF
>>gain?
>>
>>If lower Rp means LESS gain, why use a suppressor Jon? What is the Rp
>>of a dead short?
>
The answer is 0-ohms. . However, if the VHF suppressor R (Rs) is a dead
short, then the suppressor inductor (Ls) is shorted out and there is no
suppressive effect because there is no longer a semi-equal division of
VHF current in the Ls/Rs suppressor.
>Arrgh! I thought we worked through all that math! Gain is directly
>proportional to Rp. Rp is different from the R of the supressor
>resistor. Did you not just read Ian's notes? Anyhow, if gain is
>proportional to Rp doesn't it makes sense you want to lower it?
>
>So that's why......
However, like Murphy said, things are usually more complicated than they
look.
>>
>>It isn't the nichrome suppressor won't work, it's just that:
>>........
>>2.) Lower Rp is not always a good idea.
>
Good point, Mr. Rauch. One suppressor design consideration is fairly
equal distribution of current through Rs and Ls at the anode-resonance
frequency. Another consideration is to reduce Rp in order to reduce VHF
amplification -- but without destroying Rs at 28mHz.
>You cricizie the "hairpins." What difference does it make what kind of
>inductor one uses? It still has inductance?
90nH is 90nH whether it's a one turn coil, a ten turn coil, or c. 5.5"
of straight wire. A U/hairpin/one-turn-inductor parasitic suppressor
works ok on single tube amplifiers, however, on multi-tube amplifiers,
compact coil-inductor suppressors are easier to decouple from each other.
.
>
>Please explain why lower Rp is not always good.
>
see above
>..........
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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