The other day I send message to this net that included:
"In order to get a good effiency on 28 MHz why not lower the anode impedance
by inserting an inductance beetween the anode and filter? I see an example
in my 1991 ARRL HANDBOOK an example:
A tube with 3500 ohms anode impedance and 10 pF output capacitance is
transformed into 1481 ohms and 16 pF by inserting a 1 uH inductance beetween
anode and output filter. Will this inductance act as a parasite choke as
well?"
I did not get any answer on my very last question from you pi/piL
specialists. Is this not a better method to get rid of parasitics and at the
same time get higher output on 10 meters with tubes like the 813 that has a
high output capacitance??
Anybody?
de Hans SM5KI
----------
>FrÂn: measures <measures@vcnet.com>
>Till: "cd" <bearl@ozemail.com.au>, "AMPS" <amps@contesting.com>
>?mne: Re: [AMPS] Nichrome/Parasitics/ARRL Handbook 2000
>Datum: mÂn 7 feb 2000 18.58
>
>
>>Those of you that have not picked up, or had a look at the new ARRL
>>Handbook 2000, there is some mention now of Nichrome Parasitic
>>suppressors. It reads as follows in chapter 13.26.
>>
>>"Some designers use nichrome or other resistance wire for L2, but there is
>>no credible evidence of any fundamental difference in importance as a
>>result." It goes on to say that W4ETO, amplifier manufacturer has never
>>seen an HF amplifier using modern tubes that could not be made completely
>>free of VHF parasitics by using one of the simple parasitic suppressor
>>contruction described above" It does not mention what "advanced"
>>techniques should be used!
>>
>>Anyway for those curious have a read.
>>
>Craig -- This was written by Dick Erhorn / W4ETO for the 1995 Handbook,
>several years before N7WS/Wes' measurements of copper-wire vs
>resistance-wire suppressors. . My guess is that Dick never read G. W.
>Fyler's article on parasitic oscillation in the Institute of Radio
>Engineers' Journal. // Sure, the decrease in VHF Q is only about 41%
>with resistance-wire VHF parasitic suppressors, however, this might be
>enough to make a difference.
>
>cheers
>
>
>
>
>
>
>
>w4ETO
>
>>VK3HE
>>
>
>
>- Rich..., 805.386.3734, www.vcnet.com/measures.
>
>
>--
>FAQ on WWW: http://www.contesting.com/ampsfaq.html
>Submissions: amps@contesting.com
>Administrative requests: amps-REQUEST@contesting.com
>Problems: owner-amps@contesting.com
>Search: http://www.contesting.com/km9p/search.htm
>
>
----------
>Från: measures <measures@vcnet.com>
>Till: "cd" <bearl@ozemail.com.au>, "AMPS" <amps@contesting.com>
>Ämne: Re: [AMPS] Nichrome/Parasitics/ARRL Handbook 2000
>Datum: mån 7 feb 2000 18.58
>
>
>>Those of you that have not picked up, or had a look at the new ARRL
>>Handbook 2000, there is some mention now of Nichrome Parasitic
>>suppressors. It reads as follows in chapter 13.26.
>>
>>"Some designers use nichrome or other resistance wire for L2, but there is
>>no credible evidence of any fundamental difference in importance as a
>>result." It goes on to say that W4ETO, amplifier manufacturer has never
>>seen an HF amplifier using modern tubes that could not be made completely
>>free of VHF parasitics by using one of the simple parasitic suppressor
>>contruction described above" It does not mention what "advanced"
>>techniques should be used!
>>
>>Anyway for those curious have a read.
>>
>Craig -- This was written by Dick Erhorn / W4ETO for the 1995 Handbook,
>several years before N7WS/Wes' measurements of copper-wire vs
>resistance-wire suppressors. . My guess is that Dick never read G. W.
>Fyler's article on parasitic oscillation in the Institute of Radio
>Engineers' Journal. // Sure, the decrease in VHF Q is only about 41%
>with resistance-wire VHF parasitic suppressors, however, this might be
>enough to make a difference.
>
>cheers
>
>
>
>
>
>
>
>w4ETO
>
>>VK3HE
>>
>
>
>- Rich..., 805.386.3734, www.vcnet.com/measures.
>
>
>--
>FAQ on WWW: http://www.contesting.com/ampsfaq.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/ampsfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|