Hi,

I hope you'll pardon me for putting my reply to your post as of
6/8/2004 10:37 PM here, because my cable newsgroup connection is not
letting me send messages out, its going to look a little out of order.

Okay, then use the 1R5 pentagrid and be done with it. That
worked fine for Motorola and Hallicrafters in the old days.

That's a definite possibility. I won't mind using a pentagrid
converter if there is really nothing better for glass.

My question is simply to ask whether "21rst century"
topologies for silicon such as DBM, Gilbert cell, or commutating
mixer might help make hotter equipment than the original designers
of the tubes intended.

However, if all topologies including pentagrid basically deliver
the same performance, than you are right: I should stick with
simple and be done with it.

Lacking that humongous EMP simulator, I don't know how you
are going to check the EMP-withstanding qualities you want.

Let's assume that someone living in a city, suburb, or large town
is going to be quite dead if they live in the same range as something
that could kill a tube (unless of course it was a "coldbringer" EMP
warhead). Let's posit that vacuum tubes are still more surviveable
than semiconductors, all else being equal.

1. You've never outlined the necessity of the double-balance in a
mixer. The non-balanced type has worked fine in the original
WW2 "handie-talkie" and on into the BC-1000 VHF manpack
transceiver and lots of battery-operated consumer radios.
Unbalanced mixers were used in the Korean War era PRC-8
series using subminiature battery tubes. For both the Tx and
Rx sections. Also the PRC-6 handy-talky, also VHF.

2. A balanced mixer of any kind is not necessarily a relief from
spurious responses. The choice of frequencies to mix will do
that...for any mixer type. Note: The intermodulation products
are a different situation and depend on the characteristics of
the mixer.

okay...

4. Designing a circuit using battery powered, directly-heated
filaments as a differential pair is going to be difficult...unless you
have a separate "A" battery supply for that differential pair.
Since the cathodes ARE the filaments, not separate as in
indirectly-heated tubes, those cathode-filaments are going to
be elevated or, if run near common, will require a "B-" supply
for the long-tailed pair's large "cathode" resistor.

But a 1.5 volt "AA" alkaline battery is cheap enough if I need a
seperate filament.

5. Battery packs are almost in the unobtanium category except
for the single, lower voltage variety. You could use DC-DC
converters but those are now all solid-state and that doesn't
meet the "EMP requirement." Electro-mechanical vibrators
could generate the higher B+ (or B-) but those are terribly
inefficient, short-lived, and get bulky with transformers that
must be at low AC frequencies. Primary batteries such as
the carbon-zinc variety don't last long, maybe several years
if kept very cold to slow down the internal chemistry...all those
being made 30 to 40 years ago are now NG.

B+ will likely be 4-6 9V alkaline batteries in series... cheap in bulk
at Target.

6. You CAN use techniques for suppressing ESD (electrostatic
discharge) to protect from EMP effects, then go ahead and
work with solid-state devices with some assurance of
surviveability. But, you MUST know the EMP characteristics
and do a thorough design task analysis on every part. Anyone
using battery-filament tubes should do the same thing although
I haven't any idea if anyone has done that.

Anything to which I can apply common sense or overkill to? I can't
possibly
hope for this to be Cold War equipment, I'm only just looking for some
kind of edge.

The Eternal Squire

Avery Fineman wrote:

In article ,
(The Eternal Squire) writes:


-- snip --

4. Designing a circuit using battery powered, directly-heated
filaments as a differential pair is going to be difficult...unless you
have a separate "A" battery supply for that differential pair.
Since the cathodes ARE the filaments, not separate as in
indirectly-heated tubes, those cathode-filaments are going to
be elevated or, if run near common, will require a "B-" supply
for the long-tailed pair's large "cathode" resistor.

-- snip --


I agree with everything else, but at RF you can just make a
bifilar-wound filament choke -- you'll be at DC ground but you can
inject whatever signal you want. Since everything is so high impedance
and you want low power you can make it the final inductor in a matching
network, for that matter.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Avery Fineman wrote:

In article ,
(The Eternal Squire) writes:


-- snip --

4. Designing a circuit using battery powered, directly-heated
filaments as a differential pair is going to be difficult...unless you
have a separate "A" battery supply for that differential pair.
Since the cathodes ARE the filaments, not separate as in
indirectly-heated tubes, those cathode-filaments are going to
be elevated or, if run near common, will require a "B-" supply
for the long-tailed pair's large "cathode" resistor.

-- snip --


I agree with everything else, but at RF you can just make a
bifilar-wound filament choke -- you'll be at DC ground but you can
inject whatever signal you want. Since everything is so high impedance
and you want low power you can make it the final inductor in a matching
network, for that matter.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

In article ,
(The Eternal Squire) writes:

I hope you'll pardon me for putting my reply to your post as of
6/8/2004 10:37 PM here, because my cable newsgroup connection is not
letting me send messages out, its going to look a little out of order.

No problem here...

Okay, then use the 1R5 pentagrid and be done with it. That
worked fine for Motorola and Hallicrafters in the old days.

That's a definite possibility. I won't mind using a pentagrid
converter if there is really nothing better for glass.

Those and pentodes (such as 1T4) work fine as mixers on
up to 10m in consumer radio receivers such as the Zenith
Transoceanic series...but they are starting to get rare, as
are 7-pin miniature tube sockets using ceramic or mica-
filled plastic dielectric!

My question is simply to ask whether "21rst century"
topologies for silicon such as DBM, Gilbert cell, or commutating
mixer might help make hotter equipment than the original designers
of the tubes intended.

One has to consider the type of active device as to configurations.
A "Gilbert cell" or double-balanced mixer-multiplier arrangement
is only practical in a single-chip semiconductor package. One
can also make a good operational amplifier out of two dual triodes
as George A. Philbrick Inc. once did under the "GAP-R" model
series. [Bob Pease likes to mention those in Electronic Design
since he once worked there] The sizes of the two, even if the GAP-R
was efficiently packaged, just doesn't compare to a typical 741 op-
amp can.

As to "hotter," let's put it this way: ANY radio can be made with
enough amplification to have the front-end noise come roaring
out the speaker like Yosemite Falls at the collecting basin. The
type of device or the device configuration doesn't matter...but the
bandwidth and the first device's inherent noise generation does
matter. There is some information on indirectly-heated tubes'
inherent noise generation in some older textbooks but I didn't
look at a sampling to see if directly-heated filament types are
included.

I once had a nice Hallicrafters "all-band" receiver using battery
tubes, bought in a PX about early 1955. After military days that
became a trial device for modifications and other ideas. With
some changes in the Ls and Cs in the front end, it could do a
2 uV sensitivity at 6 KHz BW with a 10 db Sig:Sig+Noise ratio.
Not terrific, of course, compared to modern solid-state receivers,
but adequate for SWL with its built-in telescoping whip antenna.
1T4 RF amp, 1R5 mixer, single conversion originally.

However, if all topologies including pentagrid basically deliver
the same performance, than you are right: I should stick with
simple and be done with it.

Actually, the Dan Tayloe design for a DC receiver front-end has
got to be the simplest. It can handle keyed CW and SSB right
off and the CMOS switch used as the "mixer" should be able to
handle large overloads of RF or broadband pulses, etc. What
you now have to contend with is low-noise audio amplification
following the mixer and (if used) the polyphase filter in between.

Lacking that humongous EMP simulator, I don't know how you
are going to check the EMP-withstanding qualities you want.

Let's assume that someone living in a city, suburb, or large town
is going to be quite dead if they live in the same range as something
that could kill a tube (unless of course it was a "coldbringer" EMP
warhead). Let's posit that vacuum tubes are still more surviveable
than semiconductors, all else being equal.

Posit what you will. If the community is killed off, there won't be
anyone to operate anything that survives the initial blast. Moot.

1. You've never outlined the necessity of the double-balance in a
mixer. The non-balanced type has worked fine in the original
WW2 "handie-talkie" and on into the BC-1000 VHF manpack
transceiver and lots of battery-operated consumer radios.
Unbalanced mixers were used in the Korean War era PRC-8
series using subminiature battery tubes. For both the Tx and
Rx sections. Also the PRC-6 handy-talky, also VHF.

2. A balanced mixer of any kind is not necessarily a relief from
spurious responses. The choice of frequencies to mix will do
that...for any mixer type. Note: The intermodulation products
are a different situation and depend on the characteristics of
the mixer.

okay...

There does exist information, rather detailed TMs on that old stuff,
from rare sites like August Johnson's fine collection of PDFs of
boat anchors (free download and he says he will come out with
CDs to order - small charge - for surface mail later). For slightly
newer stuff, like the PRC-25 and -77 VHF portable transceivers
and the current HF transceiver, PRC-104, the www.logsa.mil site
has some for distribution (a devil of a time trying to find their CD
listings but some files are downloadable by anyone). Those newer
radios are solid-state in the receiver front-ends.

4. Designing a circuit using battery powered, directly-heated
filaments as a differential pair is going to be difficult...unless
you
have a separate "A" battery supply for that differential pair.
Since the cathodes ARE the filaments, not separate as in
indirectly-heated tubes, those cathode-filaments are going to
be elevated or, if run near common, will require a "B-" supply
for the long-tailed pair's large "cathode" resistor.

But a 1.5 volt "AA" alkaline battery is cheap enough if I need a
seperate filament.

That brings up DC power control. Two many different batteries means
multi-pole power switches plus adequate bypassing of elevated A+
supply lines.

5. Battery packs are almost in the unobtanium category except
for the single, lower voltage variety. You could use DC-DC
converters but those are now all solid-state and that doesn't
meet the "EMP requirement." Electro-mechanical vibrators
could generate the higher B+ (or B-) but those are terribly
inefficient, short-lived, and get bulky with transformers that
must be at low AC frequencies. Primary batteries such as
the carbon-zinc variety don't last long, maybe several years
if kept very cold to slow down the internal chemistry...all those
being made 30 to 40 years ago are now NG.

B+ will likely be 4-6 9V alkaline batteries in series... cheap in bulk
at Target.

Okay, but add up the prices on those 9 Volters...allowing for the
income adjustment and COLA for monies, that sort of series
arrangement is today roughly twice the cost of the (adjusted) price
back in 1960. Primary batteries have taken a large price raising
(because they can) since portable consumer devices began
appearing three decades ago.

6. You CAN use techniques for suppressing ESD (electrostatic
discharge) to protect from EMP effects, then go ahead and
work with solid-state devices with some assurance of
surviveability. But, you MUST know the EMP characteristics
and do a thorough design task analysis on every part. Anyone
using battery-filament tubes should do the same thing although
I haven't any idea if anyone has done that.

Anything to which I can apply common sense or overkill to? I can't
possibly hope for this to be Cold War equipment, I'm only just looking for
some
kind of edge.

Okay, then drop the "EMP withstanding" personal specification.
Common sense says: Individual stage shielding and bypassing
anything that isn't an RF/AC signal; have the power switch also
short the antenna input; put in back-to-back switching diodes on all
RF/AC stage-stage lines that aren't handling more than a 0.5 volt if
you must have some kind of EMP withstanding capability.

"EMP" is ElectroMagnetic and is a very broadband impulse. It isn't
juju or magic, just very high level Ultra Wideband stuff. It doesn't
reach in to find out if a circuit has tubes or transistors, selectively
blowing out only the solid-state things. Approach the total design
with this super UWB environment, looking at EVERYTHING that
might pick up the super UWB of an EMP. If you want real
survivability, then get a sturdy metal box with an excellent
conductive seal all around and store the radio in there. Add a sign
telling others what is there since local humans can be fried by an
EMP through their own internal wiring.

Or, just have fun making whatever you want to make, hoping the
powers-in-charge never decide to use an EMP beastie.

In article ,
(The Eternal Squire) writes:

I hope you'll pardon me for putting my reply to your post as of
6/8/2004 10:37 PM here, because my cable newsgroup connection is not
letting me send messages out, its going to look a little out of order.

No problem here...

Okay, then use the 1R5 pentagrid and be done with it. That
worked fine for Motorola and Hallicrafters in the old days.

That's a definite possibility. I won't mind using a pentagrid
converter if there is really nothing better for glass.

Those and pentodes (such as 1T4) work fine as mixers on
up to 10m in consumer radio receivers such as the Zenith
Transoceanic series...but they are starting to get rare, as
are 7-pin miniature tube sockets using ceramic or mica-
filled plastic dielectric!

My question is simply to ask whether "21rst century"
topologies for silicon such as DBM, Gilbert cell, or commutating
mixer might help make hotter equipment than the original designers
of the tubes intended.

One has to consider the type of active device as to configurations.
A "Gilbert cell" or double-balanced mixer-multiplier arrangement
is only practical in a single-chip semiconductor package. One
can also make a good operational amplifier out of two dual triodes
as George A. Philbrick Inc. once did under the "GAP-R" model
series. [Bob Pease likes to mention those in Electronic Design
since he once worked there] The sizes of the two, even if the GAP-R
was efficiently packaged, just doesn't compare to a typical 741 op-
amp can.

As to "hotter," let's put it this way: ANY radio can be made with
enough amplification to have the front-end noise come roaring
out the speaker like Yosemite Falls at the collecting basin. The
type of device or the device configuration doesn't matter...but the
bandwidth and the first device's inherent noise generation does
matter. There is some information on indirectly-heated tubes'
inherent noise generation in some older textbooks but I didn't
look at a sampling to see if directly-heated filament types are
included.

I once had a nice Hallicrafters "all-band" receiver using battery
tubes, bought in a PX about early 1955. After military days that
became a trial device for modifications and other ideas. With
some changes in the Ls and Cs in the front end, it could do a
2 uV sensitivity at 6 KHz BW with a 10 db Sig:Sig+Noise ratio.
Not terrific, of course, compared to modern solid-state receivers,
but adequate for SWL with its built-in telescoping whip antenna.
1T4 RF amp, 1R5 mixer, single conversion originally.

However, if all topologies including pentagrid basically deliver
the same performance, than you are right: I should stick with
simple and be done with it.

Actually, the Dan Tayloe design for a DC receiver front-end has
got to be the simplest. It can handle keyed CW and SSB right
off and the CMOS switch used as the "mixer" should be able to
handle large overloads of RF or broadband pulses, etc. What
you now have to contend with is low-noise audio amplification
following the mixer and (if used) the polyphase filter in between.

Lacking that humongous EMP simulator, I don't know how you
are going to check the EMP-withstanding qualities you want.

Let's assume that someone living in a city, suburb, or large town
is going to be quite dead if they live in the same range as something
that could kill a tube (unless of course it was a "coldbringer" EMP
warhead). Let's posit that vacuum tubes are still more surviveable
than semiconductors, all else being equal.

Posit what you will. If the community is killed off, there won't be
anyone to operate anything that survives the initial blast. Moot.

1. You've never outlined the necessity of the double-balance in a
mixer. The non-balanced type has worked fine in the original
WW2 "handie-talkie" and on into the BC-1000 VHF manpack
transceiver and lots of battery-operated consumer radios.
Unbalanced mixers were used in the Korean War era PRC-8
series using subminiature battery tubes. For both the Tx and
Rx sections. Also the PRC-6 handy-talky, also VHF.

2. A balanced mixer of any kind is not necessarily a relief from
spurious responses. The choice of frequencies to mix will do
that...for any mixer type. Note: The intermodulation products
are a different situation and depend on the characteristics of
the mixer.

okay...

There does exist information, rather detailed TMs on that old stuff,
from rare sites like August Johnson's fine collection of PDFs of
boat anchors (free download and he says he will come out with
CDs to order - small charge - for surface mail later). For slightly
newer stuff, like the PRC-25 and -77 VHF portable transceivers
and the current HF transceiver, PRC-104, the www.logsa.mil site
has some for distribution (a devil of a time trying to find their CD
listings but some files are downloadable by anyone). Those newer
radios are solid-state in the receiver front-ends.

4. Designing a circuit using battery powered, directly-heated
filaments as a differential pair is going to be difficult...unless
you
have a separate "A" battery supply for that differential pair.
Since the cathodes ARE the filaments, not separate as in
indirectly-heated tubes, those cathode-filaments are going to
be elevated or, if run near common, will require a "B-" supply
for the long-tailed pair's large "cathode" resistor.

But a 1.5 volt "AA" alkaline battery is cheap enough if I need a
seperate filament.

That brings up DC power control. Two many different batteries means
multi-pole power switches plus adequate bypassing of elevated A+
supply lines.

5. Battery packs are almost in the unobtanium category except
for the single, lower voltage variety. You could use DC-DC
converters but those are now all solid-state and that doesn't
meet the "EMP requirement." Electro-mechanical vibrators
could generate the higher B+ (or B-) but those are terribly
inefficient, short-lived, and get bulky with transformers that
must be at low AC frequencies. Primary batteries such as
the carbon-zinc variety don't last long, maybe several years
if kept very cold to slow down the internal chemistry...all those
being made 30 to 40 years ago are now NG.

B+ will likely be 4-6 9V alkaline batteries in series... cheap in bulk
at Target.

Okay, but add up the prices on those 9 Volters...allowing for the
income adjustment and COLA for monies, that sort of series
arrangement is today roughly twice the cost of the (adjusted) price
back in 1960. Primary batteries have taken a large price raising
(because they can) since portable consumer devices began
appearing three decades ago.

6. You CAN use techniques for suppressing ESD (electrostatic
discharge) to protect from EMP effects, then go ahead and
work with solid-state devices with some assurance of
surviveability. But, you MUST know the EMP characteristics
and do a thorough design task analysis on every part. Anyone
using battery-filament tubes should do the same thing although
I haven't any idea if anyone has done that.

Anything to which I can apply common sense or overkill to? I can't
possibly hope for this to be Cold War equipment, I'm only just looking for
some
kind of edge.

Okay, then drop the "EMP withstanding" personal specification.
Common sense says: Individual stage shielding and bypassing
anything that isn't an RF/AC signal; have the power switch also
short the antenna input; put in back-to-back switching diodes on all
RF/AC stage-stage lines that aren't handling more than a 0.5 volt if
you must have some kind of EMP withstanding capability.

"EMP" is ElectroMagnetic and is a very broadband impulse. It isn't
juju or magic, just very high level Ultra Wideband stuff. It doesn't
reach in to find out if a circuit has tubes or transistors, selectively
blowing out only the solid-state things. Approach the total design
with this super UWB environment, looking at EVERYTHING that
might pick up the super UWB of an EMP. If you want real
survivability, then get a sturdy metal box with an excellent
conductive seal all around and store the radio in there. Add a sign
telling others what is there since local humans can be fried by an
EMP through their own internal wiring.

Or, just have fun making whatever you want to make, hoping the
powers-in-charge never decide to use an EMP beastie.

in case of a nuke attack (far more likely than an EMP), the valves'
shell will shatter. you are better off storing your regular
transceiver inside a thick copper box with an 'rf tight' lid.

instead of EMP-proofing the transceiver from inside, EMP-proof it from
the outside.

your best bet would be to use a 7MHz CW transceiver with 5 watts
output. This will give you consistent communicability with reasonable
power to get through. More power will drain your battries (or your
legs, if u are pedalling a generator) faster. Avoid FETs and MOSFETs
in your design, stick to bipolars. also avoid ICs, use discrete
transistors, store a few spares in a bag inside the transceiver. have
soldering iron handy too, u might have to repair quite a few things.
you will also need an antenna tuner and a long wire.

this is a pretty grim discussion. in 1999, my country(india) and
pakistan were on the brink of war. my city was considered a high value
target. i have lived these thoughts far too close to comfort. there
are no nuclear shelters in india save a few for the president and the
prime minister etc. thinking back about those days, i find it ironic
that i thought that i would personally survive an nuclear attack and
have enough sense left to get on with establishing a wireless station.

- farhan

in case of a nuke attack (far more likely than an EMP), the valves'
shell will shatter. you are better off storing your regular
transceiver inside a thick copper box with an 'rf tight' lid.

instead of EMP-proofing the transceiver from inside, EMP-proof it from
the outside.

your best bet would be to use a 7MHz CW transceiver with 5 watts
output. This will give you consistent communicability with reasonable
power to get through. More power will drain your battries (or your
legs, if u are pedalling a generator) faster. Avoid FETs and MOSFETs
in your design, stick to bipolars. also avoid ICs, use discrete
transistors, store a few spares in a bag inside the transceiver. have
soldering iron handy too, u might have to repair quite a few things.
you will also need an antenna tuner and a long wire.

this is a pretty grim discussion. in 1999, my country(india) and
pakistan were on the brink of war. my city was considered a high value
target. i have lived these thoughts far too close to comfort. there
are no nuclear shelters in india save a few for the president and the
prime minister etc. thinking back about those days, i find it ironic
that i thought that i would personally survive an nuclear attack and
have enough sense left to get on with establishing a wireless station.

- farhan

Those and pentodes (such as 1T4) work fine as mixers on
up to 10m in consumer radio receivers such as the Zenith
Transoceanic series...but they are starting to get rare, as
are 7-pin miniature tube sockets using ceramic or mica-
filled plastic dielectric!

Yes indeed, the 1L5 and 1T5 are getting extremely costly.

I had been doing other surfing between our exchanges. I found a
duo-triode battery tube, one of those could make a long-tailed pair
mixer. I also found a duo-diode plus pentode, and a diode plus
pentode. Two of the former tubes could make a 4-diode mixer plus
signal/buffer amps on each side. Two of the latter tubes could make a
2-diode mixer pls plus signal/buffer amps on each side.



Okay, then drop the "EMP withstanding" personal specification.
Common sense says: Individual stage shielding and bypassing
anything that isn't an RF/AC signal; have the power switch also
short the antenna input; put in back-to-back switching diodes on all
RF/AC stage-stage lines that aren't handling more than a 0.5 volt if
you must have some kind of EMP withstanding capability.

"EMP" is ElectroMagnetic and is a very broadband impulse. It isn't
juju or magic, just very high level Ultra Wideband stuff. It doesn't
reach in to find out if a circuit has tubes or transistors, selectively
blowing out only the solid-state things. Approach the total design
with this super UWB environment, looking at EVERYTHING that
might pick up the super UWB of an EMP. If you want real
survivability, then get a sturdy metal box with an excellent
conductive seal all around and store the radio in there. Add a sign
telling others what is there since local humans can be fried by an
EMP through their own internal wiring.

All very good suggestions, thank you. So if EMP is simply a noise
spike from DC to daylight, is it that I should employ traps on all
input and output leads to shunt everything outside the band of
interest to ground? And the metal box makes sense.


Or, just have fun making whatever you want to make, hoping the
powers-in-charge never decide to use an EMP beastie.



Um yeah, like I said, this design is for my daughter and her cousins
for thier 10th-12th birthdays, with another for myself, so I have at
least 7 more years
to get this working.

So how's this for a possible lineup for the receiver?

Preselector: grounded grid amplifier with variable tanks on each
side.
VFO: triode oscillator with low voltage neon bulb as
regulator and
variable tank.
All three tanks use a single section each of a 3 section variable
capacitor.
Converter: duo-triode differential amplifier as mixer.
IF filter: Crystal lattice filter, 8 Mhz IF, 3-6 khz bandwidth
Detector: single-tube regenerative detector fixed to 8 Mhz with +-
6 Khz
tuning through a small variable capacitor added to the
capacitor
in the 8 Mhz fixed tank. Also has a manual regeneration
control.
Audio amp: standard OTL implemented with battery tubes.
Output to 1 Watt speaker.

In theory, the IF filter with the 3-6 Khz bandwidth provides me with a
window open either to SSB or CW. The fixed detector would allow me to
receive either SSB or CW depending on the setting of the regeneration
control. The detector would be 'tweakable' +- 6 Khz to provide some
degree of passband tuning against the IF window.

Now the transmitter:

I have a novel idea for the CW transmitter to reduce the size of the
final amplifier tube and the heat dissipation. Implement the final
as a high frequency pentode or beam tetrode wired in triode mode,
running as class E. I could possibly take that type of battery tube
meant for 200 mw IF amplification, and run it at 5 watts class E
without much great harm to the tube.

Anything I am missing with this lineup?

The Eternal Squire

Those and pentodes (such as 1T4) work fine as mixers on
up to 10m in consumer radio receivers such as the Zenith
Transoceanic series...but they are starting to get rare, as
are 7-pin miniature tube sockets using ceramic or mica-
filled plastic dielectric!

Yes indeed, the 1L5 and 1T5 are getting extremely costly.

I had been doing other surfing between our exchanges. I found a
duo-triode battery tube, one of those could make a long-tailed pair
mixer. I also found a duo-diode plus pentode, and a diode plus
pentode. Two of the former tubes could make a 4-diode mixer plus
signal/buffer amps on each side. Two of the latter tubes could make a
2-diode mixer pls plus signal/buffer amps on each side.



Okay, then drop the "EMP withstanding" personal specification.
Common sense says: Individual stage shielding and bypassing
anything that isn't an RF/AC signal; have the power switch also
short the antenna input; put in back-to-back switching diodes on all
RF/AC stage-stage lines that aren't handling more than a 0.5 volt if
you must have some kind of EMP withstanding capability.

"EMP" is ElectroMagnetic and is a very broadband impulse. It isn't
juju or magic, just very high level Ultra Wideband stuff. It doesn't
reach in to find out if a circuit has tubes or transistors, selectively
blowing out only the solid-state things. Approach the total design
with this super UWB environment, looking at EVERYTHING that
might pick up the super UWB of an EMP. If you want real
survivability, then get a sturdy metal box with an excellent
conductive seal all around and store the radio in there. Add a sign
telling others what is there since local humans can be fried by an
EMP through their own internal wiring.

All very good suggestions, thank you. So if EMP is simply a noise
spike from DC to daylight, is it that I should employ traps on all
input and output leads to shunt everything outside the band of
interest to ground? And the metal box makes sense.


Or, just have fun making whatever you want to make, hoping the
powers-in-charge never decide to use an EMP beastie.



Um yeah, like I said, this design is for my daughter and her cousins
for thier 10th-12th birthdays, with another for myself, so I have at
least 7 more years
to get this working.

So how's this for a possible lineup for the receiver?

Preselector: grounded grid amplifier with variable tanks on each
side.
VFO: triode oscillator with low voltage neon bulb as
regulator and
variable tank.
All three tanks use a single section each of a 3 section variable
capacitor.
Converter: duo-triode differential amplifier as mixer.
IF filter: Crystal lattice filter, 8 Mhz IF, 3-6 khz bandwidth
Detector: single-tube regenerative detector fixed to 8 Mhz with +-
6 Khz
tuning through a small variable capacitor added to the
capacitor
in the 8 Mhz fixed tank. Also has a manual regeneration
control.
Audio amp: standard OTL implemented with battery tubes.
Output to 1 Watt speaker.

In theory, the IF filter with the 3-6 Khz bandwidth provides me with a
window open either to SSB or CW. The fixed detector would allow me to
receive either SSB or CW depending on the setting of the regeneration
control. The detector would be 'tweakable' +- 6 Khz to provide some
degree of passband tuning against the IF window.

Now the transmitter:

I have a novel idea for the CW transmitter to reduce the size of the
final amplifier tube and the heat dissipation. Implement the final
as a high frequency pentode or beam tetrode wired in triode mode,
running as class E. I could possibly take that type of battery tube
meant for 200 mw IF amplification, and run it at 5 watts class E
without much great harm to the tube.

Anything I am missing with this lineup?

The Eternal Squire

Farhan,

I saw your post re nukes on my personal account new server but can't
post out, and I don't see your post on Google yet. I hope you don't
mind my answering your second message here.

I understand what you mean about the India/Pakistan conflict. I
really don't know what to say. Yes, it is a grim business. But I'm
thinking about the kind of world my daughter will inherit, and I want
her to be equipped for it.

I think that an attack meant to wipe out a country will simply not
happen, thank gawd, because the balance of terror still exists today
and that balance works just fine. Thats why India and Pakistan came
to thier senses, and that's why the US and USSR shadow-boxed each
other without doing anything serious.

The only likely scenarios I see are two-fold:

1) Terrorist sneaks in by motor boat or rogue sub to the seashore,
walks into a major city with a 50 kilotonne warhead in a backpack and
ignites it kamikaze style. The city is wiped, the suburbs are
fried, and the farm and ranch country gets hit with the EMP. It's the
people in the farm and ranch country that would be in the best shape
to use my design and coordinate with FEMA
about how to handle the survivors and the damage.

2) In response to our conventional defense of Taiwan when China
inevitably loses patience and invades, China fires a single large
coldbringer warhead in the ionosphere above the center of the
continental US. The purpose of a coldbringer is not to ruin a city,
although it still might very well do so. It is to generate a large
EMP across the country to ruin a country's ability to communicate or
compute, thereby ruining thier economy and ability to mobilize
anything larger than a single army or marine division for some period
of years.

It is most likely the unwritten policy within members of UN Security
Council that a massive retalitation will never be made in response to
the detonation of a single warhead. China would likely say: "oops,
so sorry, it was an accident, some general had an itchy trigger
finger. We'll execute him and make reparations.". Plausible
deniability. In the meantime, our country is powerless to defend
Taiwan because while our teeth might be there, our supply lines still
originate in the US. China then conquers Taiwan with ease.

In a scenario like this, the entire country will be physically
unharmed but will be in chaos, needing operators with equipment not
damaged by EMP. I'd like my daughter to be able to help out if she
can.

That's all I have to say for tonight.

The Eternal Squire