[AMRadio] SP600 Question

Jim Wilhite w5jo at brightok.net
Mon Sep 14 12:41:27 EDT 2009

In line with your message, some time back  maybe a year or more, 
John/K5PRO found a DX 100 in stock state.  He began to read and look 
for modifications for the transmitter.  And as most of you know, 
there are many that have been published so he gathered them together 
and, one at a time, made those modifications.  They even included 
changing the modulation transformer and almost all were to increase 
the audio range and gain additional headroom.  The simple mod was to 
parallel the coupling caps in the audio section only.  I wish John 
would join this discussion to explain what all happened.

Some of them actually made the audio worse than the stock 
configuration in terms of distortion.  I am not sure where John left 
the DX 100 but from what I remember, the mods did not provide much, 
if any, gain.    So after all that you have a piece of equipment 
that is not like the manual.  And as most of us know, the paperwork 
done when mods are made is not kept and transferred with the radio. 
This leads to hours of tracing the circuit then deciding if we 
should  keep the mod in place.

This is amateur radio at its finest.  People actually working on 
something to improve it and we are one of the only groups that is 
allowed to make modifications and use the radio on the air. 
Everyone else must get approval from the FCC.  Where we go wrong is 
failure to properly access and prove our work.  Most of us rely on 
the ear of another ham or their S meter readings.  These two topics 
are for a long discussion at another time, but my message is think 
about what you are doing before taking the clippers to a radio.  You 
actually may be doing more harm than good and you will definitely 
reduce the value of the equipment if either of these two things are 
important.  To me, removing a unit of a radio that I will not use 
does not make sense.  However, that said, it is your radio to do as 
you wish and one thing we try to do as operators of AM equipment is 
preserve the equipment and mode.


----- Original Message ----- 

> Hi Don,
> How about those vintage Johnson Ranger & Viking transmitters with 
> all of the
> "classic" hi-fi audio mods done on them by the latest & greatest 
> AM
> ghuru(s)...?
> ...And I do NOT mean mods that might entail a simple increase in 
> capacitor
> value here, the removal of a bypass capacitor there, etc. etc.---I 
> mean the
> whole enchelada, where some current "expert" corrected the 
> "faults" of the
> original Johnson engineer by (literally) completely gutting & 
> re-building
> the entire audio section, from beginning to end...!
> ...And then they peddle these abominations as "classic" rigs...
> It's like dropping a Chevy V-8 into a '32 Ford, & selling it as a 
> "vintage /
> classic" car---hardly! And you are right-on: such butchery DOES 
> (IMHO,
> anyway) detract from any possible re-sale value of something that 
> has
> morphed into someone else's "ideal" personal creation...
> ~73~ Eddy VE3CUI - VE3xZ
> **************************************
> You know the mods I meanAU

>> >  I have started replacing caps in an SP-600 JX-17. I removed 
>> > the crystal
>> > unit and was wondering if there is a need for it other than 
>> > using
>> > crystals. In other words can I leave it out and if so what 
>> > connections
>> > need to be made to bypass it.
>> >

>> If you are not using the crystal unit, but it is not impairing 
>> the
> function
>> of the receiver, what is the point of removing it?  You might 
>> find it
> useful
>> sometime in the future, or if you eventually sell or swap the 
>> receiver, a
>> subsequent owner might want it in original condition.  Besides, 
>> you will
>> either have a useless function control on the front panel or some 
>> empty
>> holes.
>> IMO it decreases the value of a piece of equipment to butcher it 
>> with a
>> "modification" that serves no useful purpose.
>> That reminds me of AM transmitters that sometimes appear at 
>> hamfests that
>> have had all the components in the speech amp and  modulator 
>> removed to
> make
>> "CW transmitters" out of them after SSB came along.  Or a 
>> Hallicrafters
>> receiver I saw once in which a CB'er had removed all the coils 
>> except for
>> the band that had 11m.
>> Don k4kyv

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