[Milsurplus] Strong Stomach Needed.

Thu Jul 16 20:02:44 EDT 2009

Right on brother.   I completely agree with your 
philosophy.  Pristine original is great -if- you can do it without 
bankrupting yourself.  Modifications needed to actually use the gear 
keep a fine old rig on the air where it belongs are too.  There's a 
difference between butchering a piece of gear for no good reason and 
doing what is necessary to get it running with hopefully reversible 
mod's -if- possible .   If a piece of gear isn't so rare then I like 
to do improvements too.  I DON'T mean solid stating the whole thing 
or converting AM rigs to SSB with major mods but using better 
resistors and capacitors and solid state plug ins for the rectifier 
tubes, things that actually make it work better and last 
longer.  I've even been known to add a biscuit fan when needed if 
there's room.
Keep what's good and fix what's bad.
73  Gary N9ZSV

At 05:13 PM 7/15/2009, Bruce Lane wrote:
>Good day,
>
>*********** REPLY SEPARATOR  ***********
>
>On 15-Jul-09 at 11:25 Michael Tauson wrote:
>
>         (snippage)
>
>I love the purists.  I really do.  Pretty
> >much like I love a rabid pit
>bull.  If it isn't NOS, NIB or an
> >exceptionally close approximation,
>it's just not worth having - or so they
> >say.
>
>         (more snippage)
>
>At the same time, I do what I can to preserve what I can
> >but in fully
>functional form.  That sometimes means going in and *gasp*
> >actually
>having to do soldering et al.  Real work kind of stuff.
>
>         (final bit of snippage)
>
>         I have to agree, up to a point. There's absolutely nothing 
> wrong with wanting to put together an original-condition radio 
> setup from, say, the 50's or 60's. Many have already done it, and I 
> suspect many others will do it.
>
>         HOWEVER - When the desire to do so reaches a point of 
> bashing anyone who makes mods to a radio to make it useful for 
> their application, you're venturing into the territory of trying to 
> force your beliefs on others, and that's not a Good Thing.
>
>         Permit me to cite an example. I have, sitting in my garage, 
> a gorgeous Harris HF kilowatt linear amp (the RF-110A, to be 
> exact). I want to use it, but finding a means to generate the 
> necessary final plate voltage (2250VDC at an amp) has been 
> challenging. Yes, it came with a power supply, but the thing 
> requires three-phase utility input (unavailable in my area). Also, 
> the amp itself requires 100mW of drive, unmodified, which is 
> incompatible with my radios (100 watts output is typical).
>
>         If I were to go the "purist" route, I would probably have 
> to take out a second mortgage for Puget Sound Energy to run in a 
> polyphase feed, or get hold of a single-to-polyphase rotary 
> converter. Either way, the cost would range into the mid-to-high 
> four-figure arena, and I simply don't have the room for one of 
> those rotary monstrosities.
>
>         I've tried to locate the single-phase supply for this amp 
> (they're exceedingly rare), but every one I've seen went for over 
> $300 WITHOUT shipping, and they're heavy enough I'd have to shell 
> out for truck freight costs. That's over twice what I paid for the amp itself.
>
>         Even if I did go that route, I'd be surprised if I got 
> better than, say, 40% efficiency out of it. Face it, it's a 
> transformer-based design done in the late 60's/early 70's. 
> Technology has improved a bit since then. ;-)
>
>         The solution I found is twofold: First, for the plate 
> voltage, scrap the three-phase supply completely, and replace it 
> with a high-efficiency SMPS design I found in some back issues of 
> QEX. The entire HV plate supply will then easily run from a 240V 
> single-phase input, drawing less than 12 amps, and tip the scales 
> at around eight pounds. The remainder of the specialized supply 
> circuits in the existing power supply, such as the 400Hz source, 
> will run perfectly well off single-phase 120VAC.
>
>         And, getting rid of that horrendously heavy three-phase 
> potted transformer will make the power supply chassis at least 80 
> pounds lighter.
>
>         Second: Modify the amp itself by bypassing the driver 
> stage, and feeding the final tube directly. I've already got the 
> details on doing so tucked away on my hard drive somewhere. That 
> also eliminates at least two other voltages I'd normally have to supply.
>
>         In essence: What I'm doing is making good use of older 
> technology, which might otherwise have been scrapped and melted 
> down, but taking advantage of newer technology to do it. How is 
> that harmful to anything or anyone? Does the fact I can't afford to 
> use it in original/unmodified condition make me a "bad person?"
>
>         Looking at the bigger picture: How much power would I be 
> wasting if I tried to use it unmodified? How much extra pollution 
> might that generate from the power plant(s) supplying my part of 
> the grid? Does it not make sense to be as efficient as possible, 
> even when using older stuff? How is seeking a balance between old 
> and new wrong?
>
>         I'm sure there will be purists Out There who will cringe at 
> the thought of any mod to equipment like this. If so, well... I'm 
> sorry you feel that way, but at least I'm trying to put a 
> well-built piece of gear to use, in as much original shape as 
> possible, rather than stripping it down to a bare chassis and 
> building my own design into it.
>
>         Happy tweaking.
>
>
>-=-=-=-=-=-=-=-=-=-=-=-
>Bruce Lane, Owner & Head Hardware Heavy,
>Blue Feather Technologies -- http://www.bluefeathertech.com
>kyrrin (at) bluefeathertech do/t c=o=m
>"Quid Malmborg in Plano..."
>
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Gary Pewitt  N9ZSV   garypewitt at centurytel.net  479 675 4376
1500 French Prairie Rd. Booneville, Arkansas  72927
Sturgeon's Law "Ninety percent of everything is crap."
Pewitt's Law: But it's that other 10% that makes life worth living."