[ARC5] Oh Say Can you say...

[Michael Hanz]

Just to underline AB5S' excellent points, there _were_ a very few hams 
modifying these sets who did the job for good engineering reasons, but 
they were few and far between.  They made the mods because they wanted 
to drive the little sets to a far higher power output than they were 
ever envisioned to go by the ARC engineers.  I have a couple of examples 
out in the storage area that were beautifully crafted by a career RF 
engineer with the Naval Research Laboratory, and had a long list of 
awards, accomplishments, and credentials to prove he knew what he was 
doing.  He was deliberately trying to produce a transmitter that would 
put out power in the region of 75 watts or more, using significantly 
higher PA voltages and currents than 550 VDC, and he correctly 
anticipated that the goal would produce TVI levels unlike the original 
design operated within its design envelope.  He used copper screen over 
every opening, and bonded it properly to the outer covers, with bypasses 
on all outgoing lines.  It's certainly not a goal I would entertain 
personally, but he wanted to explore the limits of the design and had 
the instrument resources of NRL and knowledge to do it properly.  I lost 
track of him years ago - he was retired when I made a presentation to 
the NRL ham club back in the 1990s, and may be a SK by now.  I'll try to 
take some photos of them in the near future if there is any interest.

73,
Mike  KC4TOS

On 6/13/2017 2:55 PM, Peter Gottlieb wrote:
> With freedom comes responsibility.
>
> Peter
>
> On Jun 13, 2017, at 2:49 PM, David Stinson <arc5 at ix.netcom.com> wrote:
>
>>> ... You have to read the book on modifying Command Sets to understand the reasons for modifying them. AND THEY WERE GREAT TVI GENERATORS! Bob Macklin
>> Respectfully:
>> Those ideas were/are repeated endlessly, friend to friend and magazine to magazine.
>> And they are myths.  Myths.
>> Examples of exactly what I've been saying.
>>
>> The only "understandings" in the Surplus
>> Conversion Manuls were mis-understandings.
>> They addressed "problems" that were of their
>> own making and created "solutions" that produced
>> even more problems. The "copper shielding for TVI"
>> is one such thing.  Utterly needless destruction and
>> trouble for something cured by a single capacitor
>> and few moment's reflection.  But "common knowledge"
>> becomes "fact" and then it's almost immovable.
>>
>> For instance:  The only reason TVI was a problem
>> with Command Set transmitters is because they were loaded and fed improperly to common "ham" antennas- which defeated their excellent harmonic isolation.   I'm not just talking through my hat; I put
>> them on modern spectrum display equipment years ago
>> and investigated several feeding options, including the
>> typical ham "just stick the coax/twinlead on it and go."
>>
>> When properly matched to a 50 Ohm coaxial line
>> and a 50-Ohm load through a simple series capacitor,
>> the rigs were as clean as any modern transceiver.  There were NO spurious products anywhere near VHF.
>> The equipment I used had a noise floor of, IIRC, better than -95 dBm and with the rig fed directly to its internal dummy load, nothing in  the TV ranges.  Zip. And the 2nd, 3rd and 5th harmonics were well within legal limits.   When fed the "ham way" of the 50s and 60s, all that "nice" was gone and there was plenty of ugliness.  Thus the rep for TVI and pink tickets which became
>> "beer talk" at ham club meeting, then fodder for magazine articles, then became legend and finally
>> matters of  near-religious dogma; unshakeable.
>>
>> If one abuses technology, bad things result.
>> It isn't the fault of the technology; the problem
>> is the lack of understanding and plain, old stubborn
>> "Joe and Jim said it's this way so by God it's this way."
>>
>> There was/is nothing wrong with the design.
>> There was/is plenty wrong with the lack of
>> understanding and of effort to understand
>> the transmitters before operatiing them.
>>
>> As far as doing what one wants with one's own
>> property:  I can't argue that it's legal to do so,
>> but why would one want to "do what one wants"
>> in a way that not only results in a poor outcome,
>> but causes needless destruction to one's property?  I mean, you can sledge-hammer your new Chevy
>> if you want; it's "yours."  But don't then complain
>> because you can't rid to the ham club meeting in it.
>>
>> 73 Dave S.

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