XPost: rec.radio.shortwave   
   From: dpetermaus@att.net   
      
   On 11/27/11 10:45 , D. Peter Maus wrote:   
   > On 11/27/11 10:18 , NT wrote:   
   >> On Nov 27, 4:08 pm, NT wrote:   
   >>> On Nov 26, 5:54 am, rruss...@hotmail.com wrote:   
   >>>   
   >>>   
   >>>   
   >>>> On Nov 25, 6:44 pm, NT wrote:   
   >>>   
   >>>>> On Nov 11, 5:52 am, rruss...@hotmail.com wrote:   
   >>>   
   >>>>>> With the survivalist market as well as the DIYers who would   
   >>>>>> build a   
   >>>>>> kit I have given thought to the idea of building a new tube   
   >>>>>> shortwave   
   >>>>>> receiver as a usable, practical set.   
   >>>   
   >>>>>> That means no regens, no DC bullshit, and no plug in coils. It   
   >>>>>> must   
   >>>>>> have production grade RF and IF coils, a bandswitch, and require   
   >>>>>> alignment. If sold as a kit the builder will need a RF   
   >>>>>> generator and a   
   >>>>>> scope (or a spec an or CSM with a track gen).   
   >>>   
   >>>>>> It should use off the shelf parts even if those shelves are   
   >>>>>> bare, as   
   >>>>>> it is better to copy an existing item than design from scratch. I   
   >>>>>> would clone the Eddystone dial mechanism and the bandswitch   
   >>>>>> and coils   
   >>>>>> from some Hallicrafters or Hammarlund set, they could be sold as   
   >>>>>> desperately needed replacement spares for the old sets too. I   
   >>>>>> would   
   >>>>>> use a seeing eye tube mounted in a hole in the dial as opposed   
   >>>>>> to a   
   >>>>>> meter movement, again, getting a run of new tubes made is   
   >>>>>> possible if   
   >>>>>> you are buying several thousand. There are some surplus that   
   >>>>>> could be   
   >>>>>> used if really needed too.   
   >>>   
   >>>>>> I would use a separate power supply and speaker for several   
   >>>>>> reasons.   
   >>>   
   >>>>>> I would have the radio take in B+ and heater voltage and put   
   >>>>>> out 600   
   >>>>>> ohm +4 audio. A regular supply could be used at home or car   
   >>>>>> battery   
   >>>>>> and a switchmode brick for B+. A headphone jack would be   
   >>>>>> supplied off   
   >>>>>> this tube.   
   >>>   
   >>>>>> The set should cover 500 kHz to 30 MHz, AM, SSB and CW, with a   
   >>>>>> product detector of course. A 455 kHz IF is needed so as to   
   >>>>>> use common   
   >>>>>> mechanical or crystal filters, which are optional. There   
   >>>>>> should also   
   >>>>>> be a 455 kHz IF out for an external synchronous detector.   
   >>>   
   >>>>>> Any other comments?   
   >>>   
   >>>>> The need for testgear to align the IF will wipe out 99.9% of any   
   >>>>> potential market.   
   >>>   
   >>>>> As pointed out, its going to be far too expensive. If you took   
   >>>>> that to   
   >>>>> heart and tried to make something far cheaper, regeneration,   
   >>>>> although   
   >>>>> a definite compromise, is a dead sure way to cut costs a lot,   
   >>>>> and has   
   >>>>> angelic AGC performance. I recall a simple 3 valve 1930s regen set   
   >>>>> giving rock steady audio on a signal even an exceptionally complex   
   >>>>> modern dx set couldnt stabilise.   
   >>>   
   >>>>> NT   
   >>>   
   >>>> One of the very reasons I DON"T like regens and direct   
   >>>> conversions is   
   >>>> "No Alignment".   
   >>>   
   >>>> You need to have some kind of sig gen and preferably a scope.   
   >>>> That's   
   >>>> a feature, not a bug.   
   >>>   
   >>>> Any hamfest in the US will net a working scope for a twenty dollar   
   >>>> bill and probably a usable RF generator for a similar sum. The   
   >>>> guitar   
   >>>> amp twats will part them out for the tubes and throw them in the   
   >>>> dumpster often as not.   
   >>>   
   >>>> In a pinch a grid dipper and a solid state RF probe attached to   
   >>>> a DMM   
   >>>> will work.   
   >>>   
   >>> If I were designing such a product, I'd do everything in my power to   
   >>> avoid end user alignment with testgear, for one very simple   
   >>> reason: it   
   >>> wipes out 99.9% of your potential customers, its business suicide.   
   >>>   
   >>> Perhaps one could use resonators instead of LCs, if you dont like   
   >>> the   
   >>> interstation garbage of agced reaction.   
   >>>   
   >>> NT   
   >>   
   >> Of course a valve radio is business suicide to begin with,   
   >> performance   
   >> per dollar has come a long way since the valve era. Number of valve   
   >> radios currently on the market is zero, so no-one has managed to make   
   >> them compete with 30cent ICs and 2cent transistors.   
   >>   
   >>   
   >> NT   
   >   
   >   
   > Valves have a place in audio, for the truly faithful. But then,   
   > audio only requires a few valve types, frequencies are easily   
   > managed, and circuitry remains stable for much longer periods of   
   > use. Whereas radio applications require more sophisticated valve   
   > construction, and significantly different valve types for given   
   > applications, to accomodate frequencies that stretch from 10X to   
   > 100000X audio frequencies.   
   >   
   > What's comforting in radio with valve technology, is the general   
   > sense that the technology itself is accessible. And widely   
   > understood to be more forgiving. That valves may be removed, tested,   
   > and replaced by the techologically limited, and operated under   
   > conditions that would destroy solid state. Whereas, SS receivers,   
   > self service requires a much higher level of skill, with a much   
   > lower threshold of abuse. For those with limited technological   
   > experience, this can be daunting. Especially, as in the case of this   
   > receiver, during an emergency, where supply lines are uncertain, and   
   > technical support is nonexistent.   
   >   
   > I can see where the OP is coming from. Build an accessible receiver   
   > that's fairly forgiving to extremes in noise, signal levels,   
   > voltage, and hostile events, and you'd have a generally useful rig   
   > for the general population in an emergency. It's a nice thought.   
   >   
   > But as has been pointed out here multiple times, SS technology in a   
   > proper design has proven more resistant to EMP than generally   
   > believed, operating voltages are easier to generate, and manage,   
   > power requirements are lower, and performace of the technology is   
   > dramatically improved since the days of valve receivers. All at a   
   > fraction of the cost. And in an emergency, valve supplies will be   
   > just as short as SS components.   
   >   
   > All of which points to the fact that a well designed kit radio for   
   > use in emergencies would be more like the Ten-Tec 1254, than it   
   > would be like a Hallicrafters S-40. And the Ten-Tec 1254 is a kit,   
   > costs $200, and requires no user alignment, but offers significant   
   > performance across the spectrum from LF through HF.   
   >   
   > In a package that's available now.   
   >   
      
      From Ten-Tec:   
      
   "Model 1254 combines the satisfaction of the kit building experience   
   with the performance features expected in a modern HF receiver.   
   Building one’s own receiver from a kit has launched countless   
   thousands of people into communications careers or the hobbies of   
   amateur radio and shortwave listening (“SWLing”). You will build a   
   true dual-conversion superhet with a microprocessor-controlled   
      
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