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.