Mike Maghakian wrote:

all these issues are covered by easy fixes, if you don't want to do them
, then the DX-394 is NOT the radio for you. My 394 is selective (mod),
quiet (inherently), has no pops(mod) and is a very nice radio.

I would pay a lot lot more than $50 for one and buy a dozen at a time if
I could.

What are the main weak points of the DX-394 that need to be addressed to
make it a decent receiver?


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starman wrote:
Mike Maghakian wrote:

all these issues are covered by easy fixes, if you don't
want to do them , then the DX-394 is NOT the radio for
you. My 394 is selective (mod), quiet (inherently), has
no pops(mod) and is a very nice radio.

I would pay a lot lot more than $50 for one and buy a
dozen at a time if I could.

What are the main weak points of the DX-394 that need to
be addressed to make it a decent receiver?

By joining the RADIOSHACKDX394 SIG at
http://groups.yahoo.com/group/RADIOSHACKDX394/, you will automatically
receive the DX-394 FAQ and an index to over 50 mods. From the FAQ:

Best Mods
Much depends on your listening objectives and the radio frequency
environment in your area. The DX-394 is certainly deficient in the areas of
selectivity, overload and shielding so these are areas of improvement that
are probably of common interest and benefit. Other modifications may be of
more special interest. Here are the key mods and tips:
1. Frank Cathell's Crosstalk mods are a must to correct a design deficiency
in all models that results in strong stations 15-40 kHz away from the
desired frequency being detected as though they were on frequency.
2. One of the IF filter mods is also highly advisable - Frank's "Poor Man's
Kiwa" that changes the logic to force the narrower filter in all modes is
the easiest.
3. The DX-394 is susceptible to overload from strong signals and internally
generates multiple appearances of them. Countermeasures depend on the
desired frequency band and the frequencies of the offending signals:
a) For SW listening bothered by LW/MW overload, a 1.8 MHz outboard high pass
filter is a great start.
b) For SW listening suffering from SW overload, a passive pre-selector
(tuned or fixed bandpass) or a high quality active pre-selector may help on
SW bands removed from the interfering frequencies.
c) For LW and MW listening, it may be necessary to shield or disable the
built-in antenna and use a tuned loop external antenna for added selectivity
and directionality to discriminate against the strong signals.
d) An outboard attenuator may also be necessary in difficult conditions in
any of these cases.
Fortunately, apart from shielding or disabling the ferrite antenna, all of
these are tips, not modifications of the DX-394, but are covered under Mods
because overload is such a common problem.
4. Shielding is also essential for the suppression of interference picked up
from computers and CRT's operating in close proximity to the DX-394. Its
plastic case is useless in this respect - SW signals can be picked up even
with the whip antenna removed. Tom Holden's "Ultimate Shields" mod is among
the most effective for both RF and magnetic screening

Tom

MY opinion is the following:


1) replace one or both of the IF filters, if both are done, a variable cap
must be added across X2 and a switch must be added to go between the
filters.
2) remove the purple wire and stop the tuning pops
3) add two caps for the Xtalk fix
4) add a cap to increase bass response
5) add a cap to further reduce AC hum

I would not do the hiss mod and I would either replace the speaker or use a
nice external one.

a lot of the other mods are a waste of time. I won't mention which they are
but I have tried most of them.

I think I recently made the worlds best DX-394 by doing all of these mods. I
used a Hi-Fi filter in the wide position, spec is 8/12. and a DX filter in
the narrow position, spec is 5/7. I can handle anything now

Mike


"starman" wrote in message
...
Mike Maghakian wrote:

all these issues are covered by easy fixes, if you don't want to do them
, then the DX-394 is NOT the radio for you. My 394 is selective (mod),
quiet (inherently), has no pops(mod) and is a very nice radio.

I would pay a lot lot more than $50 for one and buy a dozen at a time if
I could.

What are the main weak points of the DX-394 that need to be addressed to
make it a decent receiver?


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mike maghakian wrote:

MY opinion is the following:

1) replace one or both of the IF filters, if both are done, a variable cap
must be added across X2 and a switch must be added to go between the
filters.
2) remove the purple wire and stop the tuning pops
3) add two caps for the Xtalk fix
4) add a cap to increase bass response
5) add a cap to further reduce AC hum

I would not do the hiss mod and I would either replace the speaker or use a
nice external one.

a lot of the other mods are a waste of time. I won't mention which they are
but I have tried most of them.

I think I recently made the worlds best DX-394 by doing all of these mods. I
used a Hi-Fi filter in the wide position, spec is 8/12. and a DX filter in
the narrow position, spec is 5/7. I can handle anything now

Mike

What about the strong signal overloading (intermod's) that others have
mentioned?


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starman wrote:
mike maghakian wrote:

MY opinion is the following:

1) replace one or both of the IF filters, if both are
done, a variable cap must be added across X2 and a
switch must be added to go between the filters.
2) remove the purple wire and stop the tuning pops
3) add two caps for the Xtalk fix
4) add a cap to increase bass response
5) add a cap to further reduce AC hum

I would not do the hiss mod and I would either replace
the speaker or use a nice external one.

a lot of the other mods are a waste of time. I won't
mention which they are but I have tried most of them.

I think I recently made the worlds best DX-394 by doing
all of these mods. I used a Hi-Fi filter in the wide
position, spec is 8/12. and a DX filter in the narrow
position, spec is 5/7. I can handle anything now

Mike

What about the strong signal overloading (intermod's)
that others have mentioned?

That's a problem with every radio at some level, moreso with very sensitive
ones with wide tuning ranges and lower cost - that description fits the
DX-394. To the best of my knowledge, nobody has succeeded in making a marked
improvement to overload with internal mods. I experimented with increased
bias on the internal RF preselector switching diodes and obtained subtle
improvement. I have been wanting to replace them with PIN diodes but have
yet to source some suitable surface mount devices. However, I suspect the
main intermod generator is the RF amplifier or the 1st mixer.

Fortunately, huge improvement can be made by external pre-filtering; and
this is true for any receiver with an antenna input jack that suffers from
overload.

Mike, you are rightfully proud of your modified DX-394's but to assert it's
the "world's best DX-394" is an exaggeration. There are others who have
installed superior filters (narrower Collins mechanical, e.g. 2.3/4 to use
your notation) and have made the necessary changes so that the upper and
lower BFO frequencies and filter are properly aligned for true single
sideband, not the compromise you have made by placing the BFO in the middle
of the passband. That makes their modified DX-394 better than yours for
SSB/CW reception. And if that sharper filter is switchable for AM mode (a
trivial mod compared to replacing the filter), then it's better than yours
for picking out one sideband or the other in a crowded SWBC band where the
channel spacing is 5kHz.

To disparage other mods as a 'waste of time' is provocative. That reflects,
in part, your interests and values and perhaps your marketing objectives.
Elsewhere you have stated that you are not interested in SSB/CW and digital
modes - some of the other mods are of primary benefit to these modes. And to
make the claim of a "hi-fi" filter (the stock AM filter that is widely
denigrated for being too wide could be so described, too) and place so much
emphasis on audio improvements (bass and hum) without also recognising the
benefits to the quality of amplitude modulation reception of certain AGC
mods and the ANL Defeat mod seems to be inconsistent with achieving the
"best", even for AM.

"Best" for one person is not necessarily "best" for another. Cost ($ and
effort), location relative to powerful transmitters, bands/modes of
interest, etc. will all factor into each person's evaluation of a receiver
and the possible improvements that can be made.

Regards,
Tom