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 Post subject: Mods & Tune Ups For the dx-160
PostPosted: Apr Sun 18, 2010 12:10 am 
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Joined: Oct Thu 01, 2009 7:10 pm
Posts: 25
I recently received the classic DX-160 realistic radio.

It works okay'

Wonder if anyone has current links for mods for this model?
I found many links but all are dead

:?


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PostPosted: Apr Sun 18, 2010 12:34 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 16063
Location: Utica, NY 13502 (USA)
What kind of mods do you want to do? I found that mine works just fine after proper restoration and alignment. I read somewhere that many of these left the factory with poor alignment which is why many people came up with "mods".

Dave


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PostPosted: Apr Sun 18, 2010 5:30 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: USA
Here's some DX-160 stuff I copied off the 'net. May as well be archived here on ARF instead of just languishing on my hard drive!

-Ed
-=-=-=-=

DX-160 receive help, noise and local broadcasters

There are some situations where a dial-type tuning radio comes in handy. For beginner and budget SWL's, price verses performance, a used DX-160 is a good deal. Unless you happen to live in a major city, or the DX-160 sits in a room full of fluorescent lights.

If you have one of these older but still usable communications receivers, and are plagued with local AM broadcast power-house transmitters over-loading the front end at seemingly all frequencies, or you bought a pre-selector and it still does not filter out the local stations, this modification will certainly help. Have you just installed fluorescent lights and their buzz in the audio is making you deaf? Even with a coaxial cable antenna feed? Does your DX-160 IF oscillator interfere with another electronic device nearby?

The problem with the DX-160, is that for those people that have no inclination to use an external antenna, this radio was made with the Band 'B' ferrite bar antenna mounted close to the open rear of the radio. This allows the radio to pick up AM broadcasts (540-1600Khz)without an external antenna. However it also allows strong 540-1600Khz signals and their harmonics, a way to get into the radio when not wanted. Fluorescent lights, light dimmers, brush type motors, also produce a lot of noise in this frequency range. The opening also allows R.F. from the radio's internal oscillator a way to exit, turning the DX-160 into a miniature low power transmitter.

The solution: Shield the radio circuitry, so the only signal path is through the external antenna terminals exclusively. This is what any quality "Communications Receiver" does.

Before you do anything, download, and print the manual for this radio available here on www.mods.dk.

1. Remove the rear fiberboard cover, the main top cover, and the bottom cover from the radio. Keep the radio on it's side or bottom so the AM rod antenna does not get damaged.

2. Use the fiberboard cover off of the rear of radio, as a pattern to fabricate a new cover from sheet metal. I used a sheet of plated steel from the bottom of a discarded video tape player. It had a few nice narrow vent slots punched in it, which I used. Use any sheet steel, copper, brass (roof flashing is great), or aluminum. Choose a thickness from .020 in. (0,5mm), to .040 in. (1,0mm). Venting is nice, but not really needed, as this radio does not produce much heat. Remove any paint from the inside of your metal cover, where the screw holes are. Grounding is the key to effectivness.

3. The new metal back cover will drop the sensitivity of the radio 2-4 'S' units unless the rod antenna bar is moved away from your new cover. Remove the 4 screws that hold the AM rod antenna to the metal chassis. Move the antenna about 1 inch (25mm) towards the radio front, and another 1/2 inch (13mm) to the closest side (left side viewed from back). Use a pencil, and use the screwholes in the plastic stands to mark the chassis. On mine, 2 holes went where the near-middle ridge in the chassis is. Look underneath, and be sure nothing is in the way. Drill new holes (3/32inch or 0,9mm dia.)DON'T GO THROUGH TOO FAR. Re-install the rod antenna in the new place. If you don't want to drill holes, rough up the metal chassis with sandpaper, and use a couple of dabs of a good industrial Epoxy adhesive. Once the rod antenna is secured, replace the top cover and install your new metal rear cover.

4. Now, to improve reception, remove R-2 and replace it with a 5K ohm resistor and a salvaged neon light bulb in parallel. These lights were used in wall switches, nite-lites, toolbox electrical outlet test lights. The original 220 ohm resistor acts as an antenna signal direct shunt to ground to help the protection diodes with static electricity. The neon bulb will short away any static over 60 volts, and the 5K resistor will handle anything below the diode threshold. The 220 ohm resistor killed off about 3 'S' units of signal on ALL bands. I like all the gain I can possibly get.

5. If you listen to the lower frequencies, and find that the antenna tuning capacitor is lacking in capacitance, short out capacitor C77. This capacitor is wired in series with the tuning capacitor, it does nothing but limit the maximum tuning capacitance of the input circuit for the first stage R.F. amp F.E.T.. Shorted out, the tuning will be more efficient, especially on the 'A' band. Some antennas will not need the extra capacitance, so you may not see any change except for the knob changing position for the same tuning effect.

I use a 60 foot (19 meter) long wire antenna feeding into a 600 to 50 ohm bauln and 50 ohm coaxial feed line.

After these changes, my DX-160 does not pick up fluorescent light noise, dimmer noise, or tool noise, from 1 meter away. I now hear marine beacons on 'A' band, where there use to be nothing but broadcast noise from several 50 kilowatt stations in the Los Angeles area. I now hear 160 meter Hams where before I heard a harmonic from a 640Khz station. The addition of a pre-selector/pre-amplifier, works very well, as the DX-160 is now fairly well shielded.


-=-=-=-=-=


Howard provided some information on improving the audio response of the DX-160. Here are his recommendations:

* C54 - 22 mfd 50V (If any instability is observed such as excessive time before hearing any sound when powering up, change this capacitor to 10mfd 50V)
* C56 - 220mfd 16V
* C58 - 10 mfd 35V or greater
* C63 - 1000 mfd 16V or greater
* C64 - Remove this capacitor as this will limit top end response

Howard says that while he doesn't get the bass response he does from a DX-302, he was able to get rid of the nasal sound and adds a lot of punch that it didn't have before. Thanks Howard!

-=-=-=-=-=-=-=-=-=-=-=-=-=-=

If you ever plugged in a decent pair of headphones into a DX-160, and wondered where the deep tones of WWV, or your favorite AM station music are, well they never make it through the audio amp.
Here's how to make your DX sound decent. A better speaker will help, but only a little. The audio amplifier chip in this radio is intentionally restricted by it's external capacitors. The manufacturer did this for 2 reasons; 1. A "Communication Receiver" sound, and 2. No need for decent DC filtering of AC ripple hum.

The upc575c2 audio chip is a 2 watt audio amp, and found it's way into many small radios and stereos. To help the amp, we must change the DX capacitors to the chip manufacturer's values as follows;

1. replace C58 (.1 mfd.)with a 5 mfd. electrolytic (16v), +facing r55.

2. replace C62 (.001 mfd.) with a 100-120 pf disc.

3. replace C63 (100 mfd.) with a 470 mfd. electrolytic (16v)

4. replace C57 (3.3 mfd.) with the old pull from C63 (100 mfd.)

5. Add a additional filter capacitor (3,300mfd @16V) between ground and the switch side of the fuse. If you do not add this capacitor, the 2 times line frequency A-C ripple hum will now be quite noticeable from the new bass response.

6. If you want dead quiet dc, add a choke between the fuse output and the circuit board connection. I used an old 2 amp filament transformer that had a open high voltage winding. There is space on the chassis to add a choke.

With these changes, your bass will be much better down to 100 hertz, and the flat high end response will increase to over 8k. I find that these changes make the radio much more pleasurable.

Please note, the schematic is page 19 of the manual, available right here on mods.dk. The capacitor values that I suggest are right from the NEC datasheet for this integrated amplifier.

-=-=-=-=


Alignment of DX-160
Notes :
1. Use a signal generator or receive a station on a well-known frequency.

2. Position of the coils and trimmer capacitor for the tuner
There is a ferrite bar antenna coil on the rear side of the chassis.
There are 14 coils on the coil pack.
The 4 coils at the front side row are T3 , T4 and T5 from right to left.
T2 is a ferrite bar antenna and covers for band A and B. They are the antenna coils.
The second row is T6, T7, T8, T9 and T10. Those are the mixer coils.
The last line close to the rear chassis is T11, T12, T13, T14 and T15. Those are the local
oscillator coils.
There are trimmer capacitors next to T6 to T15. Those are CT1 to CT10.

BAND ANT MIXER LOCAL TRIMMER
A T2 T6 CT1 T11 CT6
B T2 T7 CT2 T12 CT7
C T3 T8 CT3 T13 CT8
D T4 T9 CT4 T14 CT9
E T5 T10 CT5 T15 CT10

3. Alignment:
Set the Bandspread fully to the high end of the dial (Fully clockwise).
Set ANT TRIM to about 1 clock position.
Set the dial to a frequency between 10 and 20 on the log
scale... the lower side frequency of the band.
Adjust LOCAL coil (T11 to T15) core to the frequency of the dial pointer position.

4. Adjust ANT and MIXER coils to the maximum sensitivity/reading on the S-meter.

5. Set the dial to a frequency between 80 and 90 on the log scale...the higher side frequency of the band.
Adjust ANT TRIMMER and CT (CT6 to CT10) to receive the signal at the correct dial location..

6. Adjust CT (CT1 to CT5) for the maximum sensitivity.

7. Do this for each band before going to the next. Repeat the
alignment of lower side and higher side frequency until the alignment
is correct. This will require several repetitions, even by a skilled
person.



Notes :
1. You must adjust the coils at the lower frequency of each
band. Do not adjust the trimmer capacitor at the lower frequency.

2. You must adjust trimmer capacitor at the higher
000200000C750000077F
frequency.

3. The higher frequencies in band E are extremely hard to align
to the dial.

Before you start the alignment you have to know about image
receiving.
For bands A to D the DX-160 local oscillator frequency is
designed 455 kHz above the receiving frequency. (IF amplifier
frequency is designed 455 kHz.)
For example at 10.000 MHz signal, the local oscillator
frequency is 10.455 MHz.
This applies for bands A to D.

Band E uses 455 kHz on the lower side of the receiving
frequency. It also receives the signal when the local oscillator
frequency plus receiving frequency equals IF 455 kHz. This is image
reception.

For example image frequency on Band D at 10 MHz is 10 + 2 X
0.455 = 10.910 MHz.
But for band E at 28 MHz, IF is 28- 2 X 0.455 = 27.090 MHz
This 27.090 MHz is close to the 28.000 MHz that we want to
receive.

The image ratio at 28 MHz is about 6 to 10 dB. It is about 25
dB or so at 14 MHz. So while you adjust CT10 it is very easy to
adjust it to the image frequency. This requires a skilled technique
to avoid. (Simply, set the SG to 28 Mhz and tune to the higher
frequency of the two signals.)

IF alignment
1. Receive suitable level of signal, or inject a signal at 455 kHz.
2. Adjust T16, T17 and T18 to maximum reading on the S-meter.
3. Adjust RF gain if the signal gets too strong while doing the IF alignment.

BFO alignment
1. Receive any station even the AM broadcast station.
2. Tune the station for the maximum reading on the S-meter.
3. Turn on the BFO.
4. Adjust the BFO PITCH to the 12 o lock position.
5. Listen the beat and adjust T3 to the beat.
6. T19 will be located just back of the spread dial and the front left corner of the board from
front side. You can find T19 if you follow the wiring of BFO PICH. It is in the largest can.


You can confirm image receiving by the following steps ;
1. Practice at band B. Receive signal at 1000 kHz using your signal generator.
2. Set the signal generator frequency to 1910 kHz.
3. Adjust the SG output about 40 to 60 dB so you can receive the 1910
kHz signal at 1000 kHz on the dial. The image frequency is 910 kHz
above the dial frequency on band A to D.
4. After you become familiar with image receiving, adjust the
receiving frequency for example to 20 MHz.
5. Get the signal from SG at 20 MHz on the SG dial.
6. Increase the SG output about 30 dB.
7. Adjust SG frequency to 19.090 MHz. You can also receive the
19.090 MHz signal at the 20 MHz dial setting. The image ratio at 20
MHz is about 15 dB. The image ratio at 28 MHz is only 6 dB or so.
8. If you misalign, you may receive the image frequency at the dial
frequency. On the lower side of E band it might be fairly easy, but
the high end can be extremely hard.
When you align band E, you have to confirm on each adjustment
that it is the correct frequency rather than the image frequency.
Please note when you adjust band E CUT (it is trimmer
capacitor for mixer coil) the local oscillator frequency is shifted.
So you need to track to tune the SG dial.
You need to dial SG frequency very slowly otherwise you miss
the signal from SG.

-=-=-==-=-=

Adding digital display to DX-160
Contact author. Contact author Print Print this article. A new window is open.

This mod is fairly easy if you can solder, and is real neat to do. If done with the other mods listed here, you will have a neat little radio with features the newer digital portables don't have, for 1/3 the cost. Some would consider it a waste of time to digitize an analog radio, but this little receiver has a tuned front end, a real signal meter, and antenna tuning that the new little digitals don't have. And just try to replace a surface mount transistor in one without a microscope..

As with all the Mods and general projects, we hope you know how to solder small wires with a small 20 watt class iron using rosin solder.

This project works most of the time, the only issue is what you obtain for a counter. If the counter is sensitive enough, with a high enough input impedance, it will not affect the DX-160 operation. Most good lab type counters will work fine. Counters made for coax antenna transmission line use (like CB counters), will not. They will load the DX-160 to where it will not work. These are easily identified since they have Radio transceiver type PL-259 connector(s). Most lab counters have a BNC (push-n-twist) type connector. There are also specialty frequency counter modules made for this use, and are just as easy to install.

1. First, obtain a frequency counter, or a frequency counter module. I like the module you can get from www.aade.com, model DFD1S, because it displays the actual receive frequency. Otherwise, with standard lab type frequency counters, you will need a calculator handy to subtract 455Khz from the reading. Why? The radio signal the counter reads is actually the oscillator that sings along 0.455Mhz higher than the received signal. If you tune to hear the Time Standard at 10Mhz, the oscillator and counter will be at 10.455Mhz. If you want to tune LOWFERS on 180Khz, the lab counter will show 635Khz (455+180=635). Some counters come with the subtraction feature built in. Watch E-bay, lab type 5 and 6 digit frequency counters are bargains, and sell for 1/2 the cost of the custom module. I'm cheap, so I used an old heathkit 5 digit counter, $8 at a yard sale.

By knowing a station's frequency, you can dial up that frequency, before the station comes on the air. You can spin through a frequency range, hear a interesting signal, and get the frequency withut waiting for a identification call. Try that with a new digital radio. Sure the new receivers scan, but they lock on to any signal, dead carriers, digital, Navy buzz, television IF's, computer network leakage, any old junk signal. Some don't work at all with SSB signals. You brain discriminates by sound, the new radios just go by signal strength. You forever are pushing buttons to bypass the junk signals.
000200000E6900000B28
2. The secret of adding a counter to the DX-160, is knowing where to connect the frequency counter. Our target is resistor R12. You will need about 2 feet (0.6 meter) of RG-174 coax, a 68picofarad disc capacitor, and a connector that matches your counter.

If your lab counter has a BNC connector (push-and-twist), the small coax can be connected to a standard BNC connector, the coax center wire connects to the center pin, the shield connects to the connecter body or shell. If you are cheap and lazy like me, buy a Radio Shack #278-964 cable, cut it. Now you have 2 cables with BNC ends attached for $6. The cable is the stiffer RG/58, but will work.

Some other small coaxial cables will work, like thin video cable (some shields are aluminum, unsolderable and useless!!), and real thin magnetic cartridge phonograph shielded line (what's a phonograph?).

Now unplug the radio before you remove any covers!!

3. Either make a small hole in the radio's rear press board cover,(or metal sheet if you performed the #2 mod listed here on mods.dk) just slightly larger than the coax, or pass the coax through a vent slot.
If metal, add a small rubber grommet to stop insulation cuts.

4. Remove the radio's top and bottom covers. Looking at the top side of the circuit board, locate Q4, R12, and C12. On the bottom side there is a copper trace that connects all three of these components together. This common connection is the pickup point, and where the 68 picofarad capacitor lead connects to.

5. There are 2 ways to connect the coax and capacitor, either topside, or on the bottom. Topside is easy access but small soldering, bottom side has easy soldering but will require an access hole to run the coax through. If you moved your antenna rod as outlined in Mod #2, use one of the old open screw holes to run the coax through. As long as the coax does not interfere with the tuning strings, run it through a opening in the front.

6. Strip a coax cable end about 1 inch (25mm). Unbraid the shield, gather it into a single line, and twist it into a wire. Take the 68 pico farad capacitor and trim the wires back to 1/4 inch long (6mm). Strip back some of the center wire insulation, and solder the 68 pico farad capacitor to the center lead. The outer coax shield braid will get soldered and connected to ground, so don't cut it away.

Our 68 picofarad feed capacitor connects to R12 on the end that goes to Q4 and C12. The coax braid connects to the grounded side of R12.

If you top side connect, polish the wires on R12 with a pencil eraser, soldering will be much easier. Having a stick type eraser around for this purpose is a electronics technician's secret. Typewriter erasers even have a brush!

7. If you have a module, follow it's instructions for connection, mounting, and power. The DX-160's power supply will easily power the module from www.aade.com, just remember the DX-160 runs on 14 volts, the module is less. You might have to cobble a power supply using a LM7805, or get lazy and buy a plug-in wall wart power supply. I used a old wall wart from a discarded portable telephone base. Another 50 cent garage sale item.

8. Put the covers back on, add your BNC connector to the coax, and fire it up! Connect the counter, set it for high impedance and 0-31Mhz operation, and you should see the frequency, always .455Mhz greater than where your ears are. If you have a 455Khz subtracting counter or module, then you see the received frequency.

Now you know what frequency you are listening to, and can look up the frequency of that funny sounding odd language station to see where it is.

Good DX to you!

-=-=-=-=


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 Post subject:
PostPosted: Apr Wed 21, 2010 12:56 pm 
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Joined: Oct Thu 01, 2009 7:10 pm
Posts: 25
so much good stuff!

thanks


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 Post subject:
PostPosted: Apr Thu 22, 2010 1:18 am 
Member

Joined: Oct Thu 01, 2009 7:10 pm
Posts: 25
Dave Doughty wrote:
What kind of mods do you want to do? I found that mine works just fine after proper restoration and alignment. I read somewhere that many of these left the factory with poor alignment which is why many people came up with "mods".

Dave


Well I found a good cheap tested signal generator.
Im hoping to try my first radio alignment soon.

But I need a dummy antenna. Im good at soldering but having trouble
understanding basic schematics.

I found this link:
http://www.freeinfostuff.com/DX160/DX-160_Alignment.htm

but not sure which parts I need,

hope you can help.

-wes :?


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 Post subject:
PostPosted: Apr Thu 22, 2010 2:18 am 
Moderator

Joined: Jan Thu 01, 1970 1:00 am
Posts: 16063
Location: Utica, NY 13502 (USA)
I don't think the dummy antenna is all that necessary. Just wrap the "hot" lead of your signal generator around your regular antenna lead-in wire. The main thing is to first get the IF's aligned properly.

Dave


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 Post subject:
PostPosted: Apr Thu 22, 2010 12:35 pm 
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Joined: Oct Thu 01, 2009 7:10 pm
Posts: 25
Dave Doughty wrote:
I don't think the dummy antenna is all that necessary. Just wrap the "hot" lead of your signal generator around your regular antenna lead-in wire. The main thing is to first get the IF's aligned properly.

Dave


Really? It seems that everyone including the manual is asking for one. But I'm happy with shortcuts as long as it is safe for my radio.

So do I only connect the hot/red wire to the antenna input (A1 on back panel), not the black lead?


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 Post subject:
PostPosted: Apr Thu 22, 2010 2:35 pm 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34328
Location: Sandpoint, IDAHO 83864
The dummy antenna can help when aligning the RF section of the set, but while you are concentrating on the IF section, it serves no useful purpose.
Curt

_________________
Curt, N7AH
(Connoisseur of the cold 807) CW forever!


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