Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: Valve frequency multipliers
Date: Sun, 2 Feb 2025 17:49:51 -0000 (UTC)
Organization: A noiseless patient Spider
Lines: 83
Message-ID: <vnob7v$q01n$1@dont-email.me>
References: <aapqpjppf0elhu02dp7274ltu2ra77tp1b@4ax.com>
 <1r72oaf.16af5itkanhnmN%liz@poppyrecords.invalid.invalid>
 <60fspj57qs7710nfhsqi0dqu37jk8jg51g@4ax.com>
 <1r7323m.mt72i81j97b36N%liz@poppyrecords.invalid.invalid>
 <vnlkei$6ktg$1@dont-email.me>
 <nsospj14ja03usjo4h7u3ipfd8m220619p@4ax.com>
 <1r73j2d.1uyhefbjyfnm6N%liz@poppyrecords.invalid.invalid>
 <c7ctpj11vupel88jeki7ps70rcufbitis9@4ax.com>
 <1r74b9w.o8sax655mkjkN%liz@poppyrecords.invalid.invalid>
 <5mbvpjtccb26pbpgtagee0vug20gpn6qho@4ax.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Injection-Date: Sun, 02 Feb 2025 18:49:55 +0100 (CET)
Injection-Info: dont-email.me; posting-host="0c87d26ce146c3951338bc6a5f46f922";
	logging-data="852023"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX18gxGr3g2+aYccdy2Ratll9"
User-Agent: NewsTap/5.5 (iPhone/iPod Touch)
Cancel-Lock: sha1:oJRuf8RHBensAUO3S7eJ2L6R+zA=
	sha1:+o1WbEU4EDogGQLRnPuqpcvVEkE=
Bytes: 4941

Cursitor Doom <cd@notformail.com> wrote:
> On Sun, 2 Feb 2025 08:00:09 +0000, liz@poppyrecords.invalid.invalid
> (Liz Tuddenham) wrote:
> 
>> john larkin <JL@gct.com> wrote:
>> 
>>> On Sat, 1 Feb 2025 21:53:43 +0000, liz@poppyrecords.invalid.invalid
>>> (Liz Tuddenham) wrote:
>>> 
>>>> john larkin <JL@gct.com> wrote:
>>>> 
>>>>> On Sat, 1 Feb 2025 17:08:20 +0000, Martin Brown
>>>>> <'''newspam'''@nonad.co.uk> wrote:
>>>>> 
>>>>>> On 01/02/2025 15:40, Liz Tuddenham wrote:
>>>>>>> john larkin <JL@gct.com> wrote:
>>>>>>> 
>>>>>>>> On Sat, 1 Feb 2025 10:50:22 +0000, liz@poppyrecords.invalid.invalid
>>>>>>>> (Liz Tuddenham) wrote:
>>>>>>>> 
>>>>>>>>> john larkin <jl@glen--canyon.com> wrote:
>>>>>>>>> 
>>>>>>>>>> On Fri, 31 Jan 2025 23:50:56 +0000, Cursitor Doom <cd@notformail.com>
>>>>>>>>>> wrote:
>>>>>>>>> [...]
>>>>>>>>> 
>>>>>>>>>>> Operating Point: Grid Voltage: Adjusting the grid voltage to
>>>>>>>>>>> operate closer to cutoff can increase harmonic distortion since
>>>>>>>>>>> the tube's response becomes more non-linear near cutoff.
>>>>>>>>>> 
>>>>>>>>>> Operate it deep in cutoff, off most of the time. A high amplitude
>>>>>>>>>> drive and grid-leak bias would be good.
>>>>>>>>> 
>>>>>>>>> That is exactly what I am doing and it doesn't appear to be
>>>>>>>>> working. With 100v on the anode,  15 Mc/s at 25v pk/pk on the grid
>>>>>>>>> and a 22k grid leak, the peak current for one triode of an ECC91
>>>>>>>>> is around 20 - 30 mA at the positive peak of the grid swing.  The
>>>>>>>>> average anode current is around 2.5 mA, so the conduction period
>>>>>>>>> is about 10%.
>>>>>>>>> 
>>>>>>>>> A 75 Mc/s parallel-tuned circuit in the anode circuit is giving so
>>>>>>>>> little drive to the following stage that I can't see any change in
>>>>>>>>> the average grid voltage of that stage caused by the drive.
>>>>>>>> 
>>>>>>>> Spice it!
>>>>>>>> 
>>>>>>>> LT Spice has tube models.
>>>>>>> 
>>>>>>> ...but I haven't got Spice.
>>>>>> 
>>>>>> LT Spice is free and works very well indeed. And you can't beat the
>>>>>> price. No idea how good it's valve models are but I bet they do exist.
>>>>> 
>>>>> It has a triode, a tetrode, and a pentode. I haven't tried them, but
>>>>> there are a zillion YouTube videos about LT Spice.
>>>> 
>>>> I'm afraid that doesn't sound very promising.  A triode could be
>>>> anything from a water-cooled UHF transmitting valve to a PX4 to a
>>>> 1.5-volt battery-powered miniature audio type.  At VHF all sorts of
>>>> things come into play, including the material of the valveholder.
>>> 
>>> Tubes have model files, and you can adjust various parameters.
>> 
>> I don't know the parameters that I need for this job, the valve manuals
>> only publish static figures and some basic curves.  Finding out things
>> like the gm of an EF91 when the signal is applied to G2 or G3 is almost
>> impossible as an academic exercise, it is quicker to solder up a test
>> rig and get the answer by experiment.
> 
> Then create your own Spice model from it. That's what the late great
> Jim Thompson used to do very frequently. He was our go-to guy here for
> anything to do with constructing models. Sadly missed <sigh...>
> 

Last February would have been his 21st birthday.

Cheers 

Phil Hobbs 

-- 
Dr Philip C D Hobbs  Principal Consultant  ElectroOptical Innovations LLC /
Hobbs ElectroOptics  Optics, Electro-optics, Photonics, Analog Electronics