john wrote in message
news:0pWMb.44127$5V2.62848@attbi_s53...
Hi guys and gals. Pretty new to shortwave and I know its late to be asking
but how many of you use a DX-394 communications receiver and what do you
think about it?
I paid $250 for mine on ebay (prolly too much) with a lot of mods done to
it
and got the super Zepp shortwave antwnna. Here are the mods!
1) SWITCHABLE I.F. FILTERS-A switch has been installed to the front panel,
using the Noise blanker switch of the radio that allows listeners to
choose
between Wide or Narrow Bandwidths! The two I.F. Filters have been set up
on
a switch so that you can listen to the wide AM filter for casual, easy
listening or flip over to a narrow bandwidth for Dxing or for listening to
weak signals on a crowded band! The Bandwidth of the narrow, outboard
filter
installed is a tight 3.5-4 KHZ, which is great for SSB and crowded SW band
conditions.

2) The "Chuff Chuff" noise when fine tuning was stopped with a simple mod.

Good mod.

3) Keyboard Beeps mod was done to stop the annoying Beeping.

4) Crosstalk Mod was done by adding components in the ceramic filter
circuit. This greatly reduces the problems from strong adjacent channel
interference or bleed thru from the filters. This narrows the bandwidth by
adding more capacitors to the circuit around Q13 is the second part of
this
mod.

The bandwidth is defined by the filter itself.................you can't
narrow the bandwidth. You can only eliminate the feedaround problem.

5) Weight added to Main tuning dial makes the radio feel like a "Real
Radio"
with a heavy flywheel dial. Approximately 4 oz. of lead was added to the
dial and helps the "Feel " of the dial.

6) RF Gain control mod provides better linearity when adjust gain of
radio.
This makes it much more flexible when tuning and listening to loud or
strong
SW signals. This mod had a big effect on the radio as well!

RF gain isn't that necessary a control, unless you are disabling the AGC. It
might be ok, if you want to eliminate the background noise, but then you
lose AGC control. We are dealing with a closed loop system here.

7) AGC mod done for a slower speed. This makes it easier to listen to on
AM
or Sideband. The original manufacturer had a very fast attack AGC speed.
Up
and down signals will not pump the audio sound unnatural now. In ham
lingo,
the AGC has been modified to compensate for fast QSB.

Good mod, if it is switchable.

8) Audio hiss removed from audio circuit by adding more capacitors to
filter
out some of the higher audio frequencies. Thus, this gives the audio more
punch and makes it easier to listen to. It also helps make up for the
cheap
built in speaker. An external, Good quality speaker is also recommended!

Once again, good mod, if it is switchable; otherwise, you lose high
frequency response. I never noticed a problem with any of my units.

9)Using the frequency counter in my $3000 transceiver the USB and LSB
readouts have been adjusted on the DX-394 to show correct readout with an
internal trimmer capacitor. Typically the frequency readout of the DX-394
shows the center frequency rather than the actual frequency of the SSB
signal.


10)Audio Quality-Additional capacitors have been added to the audio
circuit
which give the radio real bass punch and make it sound like a real
communications receiver!

Why would they add additional capacitors............you only need to
INCREASE the size of the coupling capacitors in order to lower the corner
frequency. (1/2PI RC).

11)Hum Reduction-A 2200 uF capacitor is added to the power supply to
reduce
the hum heard with low audio gain commonly used with headphones. With this
mod the hum disappears! Additional voltage regulation has been added to
the
power supply circuit to make the entire system more stable!

This receiver never had any stability problems. If you really did want to
improve the stability, replace the trimmer capacitors with Voltronics
multi-turn piston capacitors.

12) The top and bottom cases of the radio cabinet have been covered on the
inside with conductive, aluminum tape that will reduce interference. RFI
produced from nearby broadcast stations, computers, TV's and computer
monitors is greatly reduced with this new mod. Birdies, spurious signals
and
heterodynes caused by these and other electronic devices is shielded out
by
this new aluminum tape's shielding.

This was ok from a shielding standpoint, but now the internal loopstick has
been rendered useless. It is now enclosed in a shield!

Please let me know what you THINK!


Not a bad deal for 150 dollars..................you overpaid, but still it
isn't too bad of a radio. Probably, one of the biggest flaws of the design
are the front end filters. Instead of using even a 3 branch type of filter,
the designer decided to use a simple tunable LC filter. This would be ok in
a 50 dollar portable, but is not the way to go in a receiver that originally
was attempted to sell for 400 dollars. The glass epoxy boards are a good
idea. In the Chicago area hamfests, this receiver typically goes for 100 to
150 dollars.

Pete