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DX-390 (ATS-818) Enhancements

jruschme

Newbie
Joined
Mar 9, 2019
Messages
2
Location
Brick, NJ
I recently picked up an old Realistic DX-390 receiver which appears to be working pretty well, especially after doing the beep and mute mods. In reading about this radio, I noticed mentions of Kiwa Electronics selling an audio and, possibly, an RF filter enhancement kit for this radio. I assume, however, that they no longer sell this mod as it is not listed on their website. (They have not responded to an email which I sent to them on this issue.)

I'm assuming that the audio kit consisted mostly of higher quality capacitors and, possibly, a replacement speaker. If so, do any of you have a list of what capacitors were replaced and, if possible, the specs for the replacements?

Thanks...
JR
 

Boombox

Member
Joined
Sep 2, 2012
Messages
832
I don't know about any of that. The 390 stock has good filtering for SSB, I do know that much. I always use headphones with mine.

While modding your 390, you might want to add back to back diodes between the antenna post and the battery ground. Two diodes, back to back (reverse from each other, in parallel), connected between the negative battery post and the antenna terminal solder pad via hookup wire, the exposed wire portions well wrapped in shipping tape or electrical tape.

The 390 does not have internal diode protection and the RF transistor can get zapped via static electricity easier than many other radios.
 

jruschme

Newbie
Joined
Mar 9, 2019
Messages
2
Location
Brick, NJ
I was wrong about the filtering upgrade, apparently Kiwa only offered an audio upgrade. According to an archived copy of the web page:

Sangean ATS818-ATS818CS/RS DX390-DX392 Upgrade


Audio Upgrade
The Audio Upgrade kit replaces key components in the audio signal path. The end result is that the audio has better definition and clarity for improved intelligibility. The improved audio definition reduces listening fatigue. Full instructions are included.
Please Note: This upgrade is not difficult to install, however this should not be the first time using a soldering iron. If you feel uncomfortable about the installation, or cannot find a qualified technician to install the upgrade, then we suggest you send the receiver to Kiwa for installation.
ATS818-ATS818CS / DX 390-DX392 Audio Upgrade $15.00
Shipping and Handling within North America $2.00.
Shipping and Handling outside North America will depend on location. Please contact Kiwa for details.
Kiwa audio upgrade installation (includes components) $35.00.
Return shipping via UPS ground within the continental US is $12.00
For more information regarding Kiwa Audio Upgrades - please see Kiwa Audio Upgrades - A Brief History


Based on the text of the history page, I would assume that the upgrade consisted of replacing several capacitors in the audio circuit with higher quality Panasonic ones.
 

majoco

Member
Joined
Dec 25, 2008
Messages
3,252
Location
New Zealand
I carried out a similar Kiwa "audio improvement" mod to my JRC NRD-515 and it did remove the "muddiness" that several other users complained about - but if they were using the JRC accessory speaker perhaps that's where the "muddiness" was coming from! A metal cabinet undamped with a small speaker in it is not going to sound good! I put vehicle damping pads on all the metal surfaces inside and then filled it with BAF wadding and it's heaps better. Now I feed all my audios through a mixer and small amplifier to good speakers.
 

Boombox

Member
Joined
Sep 2, 2012
Messages
832
Audio upgrades to the 390 might have been appealing to a lot of guys, as the 390 has 'communications receiver' like sound on AM and SSB, a bit midrangey -- the whole "voice centered" thing. It never really bothered me that much, as I used my 390 mostly for SW and SSB. I still do, from time to time, although conditions have been so fair to middling at best I use my G2 and leave it at that until I get my 100 foot antenna back up (rains has kept me from rehabilitating it and remounting it lately).
 

Boombox

Member
Joined
Sep 2, 2012
Messages
832
I carried out a similar Kiwa "audio improvement" mod to my JRC NRD-515 and it did remove the "muddiness" that several other users complained about - but if they were using the JRC accessory speaker perhaps that's where the "muddiness" was coming from! A metal cabinet undamped with a small speaker in it is not going to sound good! I put vehicle damping pads on all the metal surfaces inside and then filled it with BAF wadding and it's heaps better. Now I feed all my audios through a mixer and small amplifier to good speakers.
I generally use headphones when DXing / SWLing, period. It seems to bring out the best sound from any of my radios. The only radios I have that have pleasing sound, using speakers, on the AM band or SW band are the FRG-7 and GE Superadio. A couple boomboxes are OK on those bands as well. Overall, in my experience speakers are mainly for convenience, i.e., when I don't feel like putting on a pair of headphones....
 

Boombox

Member
Joined
Sep 2, 2012
Messages
832
I have this same radio and really only use it for SSB dont waste your money and time,just get you a good pair of head phones......
Exactly. I only use speakers anymore if I'm listening to AM or FM and doing something else in the room or outside. DXing, I always use headphones. Every single radio I've got sounds better through headphones. And some radios have a better sound through different headphones.
 
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