I have some ferrite toroids that could be used to match the valve output impedance to the filter characteristic impedance.
On 12/06/2025 7:06 pm, Liz Tuddenham wrote:
<snip>
I have some ferrite toroids that could be used to match the valve output impedance to the filter characteristic impedance.
Do you know the nature of the ferrite in the toroids?
Manganese-zinc ferrites tend to be lossy at frequencies above a few
hundred kHz. Nickel-zinc ferrites have a higher resistance but get
lossy above a few MHz.
If there are specialised ferrites for the 150MHz range I've yet to hear
of them.
Bill Sloman <bill.sloman@ieee.org> wrote:
On 12/06/2025 7:06 pm, Liz Tuddenham wrote:
<snip>
I have some ferrite toroids that could be used to match the valve output >>> impedance to the filter characteristic impedance.
Do you know the nature of the ferrite in the toroids?
Manganese-zinc ferrites tend to be lossy at frequencies above a few
hundred kHz. Nickel-zinc ferrites have a higher resistance but get
lossy above a few MHz.
If there are specialised ferrites for the 150MHz range I've yet to hear
of them.
They are FT-37-43, which are claimed to be good from 25 to 300 Mc/s.
I am using a common-cathode double triode as a balanced mixer to
generate a frequency in the range 144 to 146 Mc/s fo a 2-metre
transmitter.
The inputs are a 150 Mc/s signal from a crystal oscillator and 6 to 4
Mc/s from a VFO. (The crystal oscillator is modulated with narrow-band
FM by injecting a 90-degrees phase-shifted current from a reactance
valve.)
Both inputs are applied to the two grids in push-pull with the anodes >connected in parallel. The150 Mc/s input can be accurately balanced so
that very little 150 Mc/s signal appears in the output. The VFO signal >frequency is so far removed from the output frequency that accurate
balancing isn't needed.
Coming out of the anodes we have:
144 to 146 Mc/s wanted signal
150 Mc/s unwanted but at a low level
156 to 154 Mc/s unwanted, at the same level as the wanted signal.
I need to select for the 144-146 signal and reduce the 156-154 signal by >about 60dB. Some of this selection will take place in subsequent tuned >stages but it really needs a filter to reduce the unwanted signals >sufficiently. Some reduction at 150 Mc/s would also be desirable.
There are four possibilities which I have considered so far:
1) Use a sharply-tuned circuit to select a single wanted frequency and >re-tune it every time the VFO is altered. This means an extra operating >burden unless the two controls can be ganged, which is going to be a lot
of trouble to get right.
2) Use a band-pass filter to select 144 - 146 Mc/s.
3) Use a band-stop filter to remove 156 - 154 Mc/s (with possibly a
sharp rejector circuit to attenuate the residual 150 Mc/s).
4) Use a low-pass filter, the 'skirts' of which may also reduce the >residual 150 Mc/s sufficiently .
The second question concerns the physical form of the filter. It could
be a ladder network of coils and trimming capacitors in a die-cast box
or it could be made up of resonant lines or lengths of co-ax. I don't
know of a resonant-line low-pass filter but someone might have come
across one. There might be room in the enclosure for loosely coiled-up >co-axial cable resonators but trough-lines might be a bit too long
unless they are heavily capacitively loaded.
I have some ferrite toroids that could be used to match the valve output >impedance to the filter characteristic impedance.
Does anyone with experience of filter design have any recommendtions
that don't involve custom-made components or semiconductors?
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
Bill Sloman <bill.sloman@ieee.org> wrote:
On 12/06/2025 7:06 pm, Liz Tuddenham wrote:
<snip>
I have some ferrite toroids that could be used to match the valve output >>> impedance to the filter characteristic impedance.
Do you know the nature of the ferrite in the toroids?
Manganese-zinc ferrites tend to be lossy at frequencies above a few
hundred kHz. Nickel-zinc ferrites have a higher resistance but get
lossy above a few MHz.
If there are specialised ferrites for the 150MHz range I've yet to hear
of them.
They are FT-37-43, which are claimed to be good from 25 to 300 Mc/s.
Type 43 is okay. Type 62 is better for chokes and baluns, where you don’t care about loss.
For a one-off, I’d get some 50-cm micro coax jumpers with U.FL connectors and make open-circuit shunt stubs. 154 MHz is just under 2 metres, so at a velocity factor of 0.67, a quarter wave is 32.4 cm.
You’ll need a bit of series resistance between each stub and the next, because otherwise you’ll get a parallel resonance between stubs of slightly different lengths.
It’ll add some loss, and may need a transformer on each end to keep the notches narrow enough. ( You might want to be hanging 50Ω stubs off a 5-Ω point, for instance.)
If you don’t mind using half-wave shorted stubs, you can tune them by sticking a sewing needle through the jacket into the center conductor,
which lets you adjust in both directions. I use thumbtacks in RG-58 like
that fairly often. Good Medicine.
On Thu, 12 Jun 2025 10:06:26 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
I am using a common-cathode double triode as a balanced mixer to
generate a frequency in the range 144 to 146 Mc/s fo a 2-metre
transmitter.
The inputs are a 150 Mc/s signal from a crystal oscillator and 6 to 4
Mc/s from a VFO. (The crystal oscillator is modulated with narrow-band
FM by injecting a 90-degrees phase-shifted current from a reactance
valve.)
Both inputs are applied to the two grids in push-pull with the anodes >connected in parallel. The150 Mc/s input can be accurately balanced so >that very little 150 Mc/s signal appears in the output. The VFO signal >frequency is so far removed from the output frequency that accurate >balancing isn't needed.
Coming out of the anodes we have:
144 to 146 Mc/s wanted signal
150 Mc/s unwanted but at a low level
156 to 154 Mc/s unwanted, at the same level as the wanted signal.
I need to select for the 144-146 signal and reduce the 156-154 signal by >about 60dB. Some of this selection will take place in subsequent tuned >stages but it really needs a filter to reduce the unwanted signals >sufficiently. Some reduction at 150 Mc/s would also be desirable.
There are four possibilities which I have considered so far:
1) Use a sharply-tuned circuit to select a single wanted frequency and >re-tune it every time the VFO is altered. This means an extra operating >burden unless the two controls can be ganged, which is going to be a lot
of trouble to get right.
2) Use a band-pass filter to select 144 - 146 Mc/s.
3) Use a band-stop filter to remove 156 - 154 Mc/s (with possibly a
sharp rejector circuit to attenuate the residual 150 Mc/s).
4) Use a low-pass filter, the 'skirts' of which may also reduce the >residual 150 Mc/s sufficiently .
The second question concerns the physical form of the filter. It could
be a ladder network of coils and trimming capacitors in a die-cast box
or it could be made up of resonant lines or lengths of co-ax. I don't
know of a resonant-line low-pass filter but someone might have come
across one. There might be room in the enclosure for loosely coiled-up >co-axial cable resonators but trough-lines might be a bit too long
unless they are heavily capacitively loaded.
I have some ferrite toroids that could be used to match the valve output >impedance to the filter characteristic impedance.
Does anyone with experience of filter design have any recommendtions
that don't involve custom-made components or semiconductors?
What's the power level?
You might make a bandpass filter out of commercial inductors and caps
and a few padders or trimmer caps. Build it on dremel'ed FR4 and bolt
it into the box for good grounding. One narrow deep movable notch
might help a lot.
https://www.dropbox.com/scl/fi/d7x21xc720gq0ztl8am5e/Z452.JPG?rlkey=v3lr01 34wjl5dliqdh2aowlpd&raw=1
Just scale that up 100,000:1
The arithmetic is tedious. My NORMA program might help.
If you are running low power, you could build a bp filter on one of
these:
https://www.dropbox.com/scl/fi/pym7yn95rqopxlkt7x6wk/Z368_BP_Filters.jpg?r lkey=vijxk9kcqw0ve5iplw7p9h390&raw=1
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
Bill Sloman <bill.sloman@ieee.org> wrote:
On 12/06/2025 7:06 pm, Liz Tuddenham wrote:
<snip>
I have some ferrite toroids that could be used to match the valve output >>>>> impedance to the filter characteristic impedance.
Do you know the nature of the ferrite in the toroids?
Manganese-zinc ferrites tend to be lossy at frequencies above a few
hundred kHz. Nickel-zinc ferrites have a higher resistance but get
lossy above a few MHz.
If there are specialised ferrites for the 150MHz range I've yet to hear >>>> of them.
They are FT-37-43, which are claimed to be good from 25 to 300 Mc/s.
Type 43 is okay. Type 62 is better for chokes and baluns, where you donât
care about loss.
For a one-off, Iâd get some 50-cm micro coax jumpers with U.FL connectors
and make open-circuit shunt stubs. 154 MHz is just under 2 metres, so at a >> velocity factor of 0.67, a quarter wave is 32.4 cm.
That was my estimate - it would fit in the overall housing (though not
in a die-cast box of the type I am using to make the modules). It might
even work if it were simply threaded into the loom with all the other
wires.
Youâll need a bit of series resistance between each stub and the next, >> because otherwise youâll get a parallel resonance between stubs of slightly
different lengths.
Would it be better to use inductive or capacitive coupling, to reduce
the losses?
Itâll add some loss, and may need a transformer on each end to keep the >> notches narrow enough. ( You might want to be hanging 50Ω stubs off a 5-Ω
point, for instance.)
The impedances are high because it is in the anode circuit of a valve.
I could use a tapped resonant circuit or a ferrite transformer to bring
down the impedance to 50-ohms, which would make it easy to test with a
VNA.
Perhaps a quarter-wave line could be used as part of the impedance transformation? Audio screened cable has a characteristic impedance of
about 120 ohms, so a termination of 50 ohms at the outpute end of a
quarter wavelength would appear as 288 ohms at the input end.
If you donât mind using half-wave shorted stubs, you can tune them by >> sticking a sewing needle through the jacket into the center conductor,
which lets you adjust in both directions. I use thumbtacks in RG-58 like
that fairly often. Good Medicine.
I wonder how tightly you could roll it up without destroying the effect?
Some of the circuits I have already built for this project are at: http://www.poppyrecords.co.uk/Radio/G8HEH/2metretransceiver.htm
john larkin <jl@glen--canyon.com> wrote:
On Thu, 12 Jun 2025 10:06:26 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
I am using a common-cathode double triode as a balanced mixer to
generate a frequency in the range 144 to 146 Mc/s fo a 2-metre
transmitter.
The inputs are a 150 Mc/s signal from a crystal oscillator and 6 to 4
Mc/s from a VFO. (The crystal oscillator is modulated with narrow-band
FM by injecting a 90-degrees phase-shifted current from a reactance
valve.)
Both inputs are applied to the two grids in push-pull with the anodes
connected in parallel. The150 Mc/s input can be accurately balanced so
that very little 150 Mc/s signal appears in the output. The VFO signal
frequency is so far removed from the output frequency that accurate
balancing isn't needed.
Coming out of the anodes we have:
144 to 146 Mc/s wanted signal
150 Mc/s unwanted but at a low level
156 to 154 Mc/s unwanted, at the same level as the wanted signal.
I need to select for the 144-146 signal and reduce the 156-154 signal by
about 60dB. Some of this selection will take place in subsequent tuned
stages but it really needs a filter to reduce the unwanted signals
sufficiently. Some reduction at 150 Mc/s would also be desirable.
There are four possibilities which I have considered so far:
1) Use a sharply-tuned circuit to select a single wanted frequency and
re-tune it every time the VFO is altered. This means an extra operating
burden unless the two controls can be ganged, which is going to be a lot
of trouble to get right.
2) Use a band-pass filter to select 144 - 146 Mc/s.
3) Use a band-stop filter to remove 156 - 154 Mc/s (with possibly a
sharp rejector circuit to attenuate the residual 150 Mc/s).
4) Use a low-pass filter, the 'skirts' of which may also reduce the
residual 150 Mc/s sufficiently .
The second question concerns the physical form of the filter. It could
be a ladder network of coils and trimming capacitors in a die-cast box
or it could be made up of resonant lines or lengths of co-ax. I don't
know of a resonant-line low-pass filter but someone might have come
across one. There might be room in the enclosure for loosely coiled-up
co-axial cable resonators but trough-lines might be a bit too long
unless they are heavily capacitively loaded.
I have some ferrite toroids that could be used to match the valve output
impedance to the filter characteristic impedance.
Does anyone with experience of filter design have any recommendtions
that don't involve custom-made components or semiconductors?
What's the power level?
Milliwatts at high impedance.
You might make a bandpass filter out of commercial inductors and caps
and a few padders or trimmer caps. Build it on dremel'ed FR4 and bolt
it into the box for good grounding. One narrow deep movable notch
might help a lot.
https://www.dropbox.com/scl/fi/d7x21xc720gq0ztl8am5e/Z452.JPG?rlkey=v3lr01 >> 34wjl5dliqdh2aowlpd&raw=1
Just scale that up 100,000:1
That's only one section, I am going to need a lot more than that because
the wanted and unwanted frequencies are only 5.3% apart.
The arithmetic is tedious. My NORMA program might help.
I have found some calculations in the RSGB Handbook but my big worry at
these frequencies is unwanted 'components' in the form of wires (or box >sides) with inductance and stray capacitance everywhere. If I make a
simple tuned circuit with an air-cored coil (or helix) across the width
fo a small die-cast box, the return currents from the grounding of the >capacitor at one end will flow back through the box wall to the
grounding point of the coil at the other end.. These currents will
spread out and may interact with a similar circuit layout at the other
end of the box to give unwanted coupling.
I had this happen many years ago with something that worked at 100 Kc/s,
so the problem could be much worse at 150 Mc/s. (It also caught out the >designers of the RA17, hence the hacksaw slot most of the way through
the chassis.)
If you are running low power, you could build a bp filter on one of
these:
https://www.dropbox.com/scl/fi/pym7yn95rqopxlkt7x6wk/Z368_BP_Filters.jpg?r >> lkey=vijxk9kcqw0ve5iplw7p9h390&raw=1
I am avoiding the use of printed circuits, it is all being built on
tagstrips and standoff pillars - and a lot of the circuit can be
supported off the valveholder tags (but not the filters).
On Thu, 12 Jun 2025 17:02:59 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
Heck, 150 MHz is almost DC.
I am avoiding the use of printed circuits, it is all being built on >tagstrips and standoff pillars - and a lot of the circuit can be
supported off the valveholder tags (but not the filters).
Retro look.
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
Perhaps a quarter-wave line could be used as part of the impedance transformation? Audio screened cable has a characteristic impedance of about 120 ohms, so a termination of 50 ohms at the outpute end of a
quarter wavelength would appear as 288 ohms at the input end.
You don’t want much conductance at the open end. Just the featureless cut end.
john larkin <jl@glen--canyon.com> wrote:
On Thu, 12 Jun 2025 17:02:59 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
[..]
Heck, 150 MHz is almost DC.
Not with valves, it isn't
I am avoiding the use of printed circuits, it is all being built on
tagstrips and standoff pillars - and a lot of the circuit can be
supported off the valveholder tags (but not the filters).
Retro look.
Not appearance but practicality. The plan is to avoid semiconductors >altogether; with valves it is much easier to make one-offs on tagstrips
and try out different components and layouts. At 150 Mc/s there are >unspecified hidden capacitances and inductances waiting to catch you
out. Some valves for those frequencies were designed with a specific
layout in mind ( ECC91, QQVO 2-6, QQVO 3-10, QQVO 3-20, QQVO 6-40).
I have known laminated printed circuit boards to track across between
the layers. With transistors this would hardly be noticed but with the >higher voltages and much higher impedances of valves, it can cause all
sorts of strange intermittent faults.
On Fri, 13 Jun 2025 11:30:13 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
On Thu, 12 Jun 2025 17:02:59 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
[..]
Heck, 150 MHz is almost DC.
Not with valves, it isn't
We were discussing building a bandpass fiter. At low power, the parts
can be one per cent of a wavelength long.
And at low power, tubes should be small, so plate capacitance will be
small, and can be rolled into the first bp filter capacitance.
What's the plate capacitance of the tubes you plan to use?
Is your
output differential?
Come on, try it. It's 2025.
r qweqqaew;ewq john larkin <jl@glen--canyon.com> wrote:
I can go out and buy a ready-made transceiver but I want to make one
using valves. It's a hobby but I want to approach it in a professional manner.
r qweqqaew;ewq john larkin <jl@glen--canyon.com>
wrote:
On Fri, 13 Jun 2025 11:30:13 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
On Thu, 12 Jun 2025 17:02:59 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
[..]
Heck, 150 MHz is almost DC.
Not with valves, it isn't
We were discussing building a bandpass fiter. At low power, the parts
can be one per cent of a wavelength long.
And at low power, tubes should be small, so plate capacitance will be
small, and can be rolled into the first bp filter capacitance.
I was intending to make the characteristic impedance of the filter 50
ohms so I could set it up easily with a VNR.
What's the plate capacitance of the tubes you plan to use?
ECC91= 2.5pf max with anodes paralleled
EF91 = 2.1pf (3.1pf if shielded)
On Fri, 13 Jun 2025 16:46:18 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
r qweqqaew;ewq john larkin <jl@glen--canyon.com>
wrote:
On Fri, 13 Jun 2025 11:30:13 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
On Thu, 12 Jun 2025 17:02:59 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
[..]
Heck, 150 MHz is almost DC.
Not with valves, it isn't
We were discussing building a bandpass fiter. At low power, the parts
can be one per cent of a wavelength long.
And at low power, tubes should be small, so plate capacitance will be
small, and can be rolled into the first bp filter capacitance.
I was intending to make the characteristic impedance of the filter 50
ohms so I could set it up easily with a VNR.
What's the plate capacitance of the tubes you plan to use?
ECC91= 2.5pf max with anodes paralleled
EF91 = 2.1pf (3.1pf if shielded)
Xc is over 400 ohms. Basically a pure current source.
There are filter forms that are 50 ohms on one end and Hiz on the
other.
john larkin <jl@glen--canyon.com> wrote:
On Fri, 13 Jun 2025 16:46:18 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
r qweqqaew;ewq john larkin <jl@glen--canyon.com>
wrote:
On Fri, 13 Jun 2025 11:30:13 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
On Thu, 12 Jun 2025 17:02:59 +0100, liz@poppyrecords.invalid.invalid >> >> >> (Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
[..]
Heck, 150 MHz is almost DC.
Not with valves, it isn't
We were discussing building a bandpass fiter. At low power, the parts
can be one per cent of a wavelength long.
And at low power, tubes should be small, so plate capacitance will be
small, and can be rolled into the first bp filter capacitance.
I was intending to make the characteristic impedance of the filter 50
ohms so I could set it up easily with a VNR.
What's the plate capacitance of the tubes you plan to use?
ECC91= 2.5pf max with anodes paralleled
EF91 = 2.1pf (3.1pf if shielded)
Xc is over 400 ohms. Basically a pure current source.
There is an inductor in the anode circuit, which resonates with the
valve capacitance (and a trimmer) at the output frequency.
At lower frequencies, pentodes are generally considered to be current
sources and triodes are nearer to voltage sources. As they approach
their highest operating frequencies, electron transit time messes that
up. The triode is a mixer, so Miller capacitance doesn't apply because
the two input frequencies are not the same as the output frequency.
There are filter forms that are 50 ohms on one end and Hiz on the
other.
What form do they take? Are they band-pass, band-stop or low-pass?
This is the classic reference:
https://www.amazon.com/s?i=garden&srs=12653393011&bbn=1063498&rh=n%3A10553 98%2Cn%3A284507
Is there any chance you can make enough room in your setup for
something of the following sort?
https://www.pa0nhc.nl/IMDfilter/EN/Notch/Single/HelicalNotchfilters2mEN.htm
john larkin <jl@glen--canyon.com> wrote:
[...]
This is the classic reference:
https://www.amazon.com/s?i=garden&srs=12653393011&bbn=1063498&rh=n%3A10553 98%2Cn%3A284507
Amazon won't let me see it because I am not in the USA. In any case,
won't buy anything from Amazon Do you have another reference to the
book (I presume it is a book)?
john larkin <jl@glen--canyon.com> wrote:
[...]
This is the classic reference:
https://www.amazon.com/s?i=garden&srs=12653393011&bbn=1063498&rh=n%3A10553 >> 98%2Cn%3A284507
Amazon won't let me see it because I am not in the USA. In any case,
won't buy anything from Amazon Do you have another reference to the
book (I presume it is a book)?
Dave Platt wrote:
Is there any chance you can make enough room in your setup for
something of the following sort?
https://www.pa0nhc.nl/IMDfilter/EN/Notch/Single/HelicalNotchfilters2mEN.htm
That's exactly the sort of thing I had in mind. The author's dimensions
of 4" diameter and 6" high might be a bit of a problem but I could try scaling it down and adding more turns to the helix. Perhaps a piece of
35mm copper pipe would make a good starting point.
A length of thinner pipe would be easier to accommodate, so perhaps I
could experiment with something intermediate between between a coaxial
stub and a helical resonator.
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
john larkin <jl@glen--canyon.com> wrote:
[...]
This is the classic reference:
https://www.amazon.com/s?i=garden&srs=12653393011&bbn=1063498&rh=n%3A10553 >>> 98%2Cn%3A284507
Amazon won't let me see it because I am not in the USA. In any case,
won't buy anything from Amazon Do you have another reference to the
book (I presume it is a book)?
From the description, I expect John means Williams & Taylor, ><https://archive.org/details/ElectronicFilterDesignHandbook4thEd/page/n2/mode/1up>
or Zverev ><https://www.amazon.com/Handbook-Filter-Synthesis-Anatol-Zverev/dp/0471749427>.
Zverev is my personal faveIve used it occasionally for over 40 years, but >thats probably a minority taste.
Cheers
Phil Hobbs
On Sat, 14 Jun 2025 12:52:49 -0000 (UTC), Phil Hobbs ><pcdhSpamMeSenseless@electrooptical.net> wrote:
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
john larkin <jl@glen--canyon.com> wrote:
[...]
This is the classic reference:
https://www.amazon.com/s?i=garden&srs=12653393011&bbn=1063498&rh=n%3A10553 >>>> 98%2Cn%3A284507
Amazon won't let me see it because I am not in the USA. In any case,
won't buy anything from Amazon Do you have another reference to the
book (I presume it is a book)?
From the description, I expect John means Williams & Taylor, >><https://archive.org/details/ElectronicFilterDesignHandbook4thEd/page/n2/mode/1up>
or Zverev >><https://www.amazon.com/Handbook-Filter-Synthesis-Anatol-Zverev/dp/0471749427>.
Zverev is my personal faveIve used it occasionally for over 40 years, but >>thats probably a minority taste.
Cheers
Phil Hobbs
Yes, Williams.
Does Zverev have tables of filter values? I generally nab a table from >Williams, denormalize and maybe transform it with my program, then
Spice it with part values that I can get, or preferably already have.
On Sat, 14 Jun 2025 12:52:49 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
john larkin <jl@glen--canyon.com> wrote:
[...]
This is the classic reference:
https://www.amazon.com/s?i=garden&srs=12653393011&bbn=1063498&rh=n%3A10553 >>>> 98%2Cn%3A284507
Amazon won't let me see it because I am not in the USA. In any case,
won't buy anything from Amazon Do you have another reference to the
book (I presume it is a book)?
From the description, I expect John means Williams & Taylor,
<https://archive.org/details/ElectronicFilterDesignHandbook4thEd/page/n2/mode/1up>
or Zverev
<https://www.amazon.com/Handbook-Filter-Synthesis-Anatol-Zverev/dp/0471749427>.
Zverev is my personal faveIve used it occasionally for over 40 years, but
thats probably a minority taste.
Cheers
Phil Hobbs
Yes, Williams.
Does Zverev have tables of filter values? I generally nab a table from Williams, denormalize and maybe transform it with my program, then
Spice it with part values that I can get, or preferably already have.
john larkin <jl@glen--canyon.com> wrote:
On Sat, 14 Jun 2025 12:52:49 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:
john larkin <jl@glen--canyon.com> wrote:
[...]
This is the classic reference:
https://www.amazon.com/s?i=garden&srs=12653393011&bbn=1063498&rh=n%3A10553
98%2Cn%3A284507
Amazon won't let me see it because I am not in the USA. In any case,
won't buy anything from Amazon Do you have another reference to the
book (I presume it is a book)?
From the description, I expect John means Williams & Taylor,
<https://archive.org/details/ElectronicFilterDesignHandbook4thEd/page/n2/mode/1up>
or Zverev
<https://www.amazon.com/Handbook-Filter-Synthesis-Anatol-Zverev/dp/0471749427>.
Zverev is my personal fave?I?ve used it occasionally for over 40 years, but >>> that?s probably a minority taste.
Cheers
Phil Hobbs
Yes, Williams.
Does Zverev have tables of filter values? I generally nab a table from
Williams, denormalize and maybe transform it with my program, then
Spice it with part values that I can get, or preferably already have.
Yes. Zverev was a pioneerthe tables were generated directly by a computer, >including the typesetting, which was pretty rad for 1968.
He also has really good plots, as well as a unique design, the equiripple >delay filter. That one maintains flat group delay well into the stopband, >unlike Bessels and suchlike.
Cheers
Phil Hobbs
That's exactly the sort of thing I had in mind. The author's dimensions
of 4" diameter and 6" high might be a bit of a problem but I could try >scaling it down and adding more turns to the helix. Perhaps a piece of
35mm copper pipe would make a good starting point.
There is an inductor in the anode circuit, which resonates with the
valve capacitance (and a trimmer) at the output frequency.
There's no Miller effect only if the grids are zero impedance to
ground at 150 MHz.
Am 13.06.25 um 22:54 schrieb john larkin:
There is an inductor in the anode circuit, which resonates with the
valve capacitance (and a trimmer) at the output frequency.
There's no Miller effect only if the grids are zero impedance to
ground at 150 MHz.
There is no Miller effect when there is no voltage gain between
grid and anode that could be fed back via Cga. A shorted grid
just shorts the feedback.
There is also no feedback when input
and output frequencies are really different
Am 13.06.25 um 22:54 schrieb john larkin:
There is an inductor in the anode circuit, which resonates with the
valve capacitance (and a trimmer) at the output frequency.
There's no Miller effect only if the grids are zero impedance to
ground at 150 MHz.
There is no Miller effect when there is no voltage gain between
grid and anode that could be fed back via Cga. A shorted grid
just shorts the feedback. There is also no feedback when input
and output frequencies are really different or if the voltage
gain of the input device is kapputted by a cascode stage.
Cheers, Gerhard
Gerhard Hoffmann <dk4xp@arcor.de> wrote:
Am 13.06.25 um 22:54 schrieb john larkin:
There is an inductor in the anode circuit, which resonates with the
valve capacitance (and a trimmer) at the output frequency.
There's no Miller effect only if the grids are zero impedance to
ground at 150 MHz.
There is no Miller effect when there is no voltage gain between
grid and anode that could be fed back via Cga. A shorted grid
just shorts the feedback. There is also no feedback when input
and output frequencies are really different or if the voltage
gain of the input device is kapputted by a cascode stage.
A unity gain common cathode stage has a Miller gain of 2, because it’s inverting.
Cheers Gerhard
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