(Bunia3) wrote in
:



does anyone know of a way to increase sensitivity especially below 5
mhz on these radios..i notice sensitivity is low at 3 mhz but
improves, the higher one tunes..at 29 mhz it's actually pretty good.

i suspect some type of filtering was added to reduce overload on low
freqs???

suggestions r invited.

TX


What kind of antenna are you using? How long? Are you using a balun?

Bunia3 wrote:

does anyone know of a way to increase sensitivity especially below 5 mhz on
these radios..i notice sensitivity is low at 3 mhz but improves, the higher one
tunes..at 29 mhz it's actually pretty good.

i suspect some type of filtering was added to reduce overload on low freqs???

suggestions r invited.

TX

It may be more a matter of the whip sensitivity which is not very good
with these two models compared to some other portables. You can find a
lot of mod's for them on Yahoo and other sites. I did a whip mod' that
was particularly succesful. It involves adding an impedance matching
balun transformer between the whip and it's circuit input.

BURNIA3,
..
The RadioShack DX-398 (Sangean ATS-909) has both a
Whip Antenna and External Antenna Jack:
..
The RadioShack DX-398 / Sangean ATS-909 is noted for
being some what deaf off of it's built-in Whip Antenna.
..
Generally the RadioShack DX-398 has a reputation for being
better using an External Antenna connected via the 1/8" Jack
on the Side of the Radio. This is a Stereo Jack and you should
use a Stereo 1/8" Plug with the End-Tip connected to the External
Antenna Wire and the Rear-Barrel connected to the Ground Wire.
NOTE: The Center-Middle-Barrel of the 1/8" Stereo Plug is NOT Used.
..
READ - These Messages posted to the RadioShack DX-398
(Sangean ATS-909) eGroup on YAHOO !
..
* Antenna Connection for a RadioShack DX-398
http://groups.yahoo.com/group/DX398/message/5515
..
* Antenna Wiring - Help Needed Please for the RadioShack DX-398
http://groups.yahoo.com/group/DX398/message/4063
..
* Diagram of HOW TO WIRE the External Antenna Plug RadioShack DX-398.
http://groups.yahoo.com/group/DX398/...na/antenna.jpg
..
* External Antenna Troubles and the RadioShack DX-398
http://groups.yahoo.com/group/DX398/message/5939
..
* MW/LW Reception with External Antenna (Sangean ATS-909)
http://groups.yahoo.com/group/DX398/message/5375
..
* RadioShack DX-398 (Sangean ATS-909) External Antenna
http://groups.yahoo.com/group/DX398/message/4310
..
iane ~ RHF
..
All are WELCOME and "Invited to Join" the
RadioShack DX-398 / Sangean ATS-909 eGroup on YAHOO !
http://groups.yahoo.com/group/DX398/message/4310
Where the Topic is the RadioShack DX-398 / Sangean ATS-909
Radio-Receiver.

RHF wrote:
BURNIA3,
.
The RadioShack DX-398 (Sangean ATS-909) has both a
Whip Antenna and External Antenna Jack:
.
The RadioShack DX-398 / Sangean ATS-909 is noted for
being some what deaf off of it's built-in Whip Antenna.
.
Generally the RadioShack DX-398 has a reputation for being
better using an External Antenna connected via the 1/8" Jack
on the Side of the Radio. This is a Stereo Jack and you should
use a Stereo 1/8" Plug with the End-Tip connected to the External
Antenna Wire and the Rear-Barrel connected to the Ground Wire.
NOTE: The Center-Middle-Barrel of the 1/8" Stereo Plug is NOT Used.


These fine people disagree.

http://www.mods.dk/mod/radio_shack/dx-398antjack.gif



==================================================

The radio accepts a 1/8" stereo headphone jack for its external antenna.
It's wired a little differently than you think.

The tip goes to the antenna terminal and the sleeve goes to ground, just as
you would expect in this unbalanced antenna input. Shortwave signals are
routed from the external antenna jack when a connector is plugged in.

The ring--the terminal in the middle of the plug--has a special purpose.
When you ground it, medium wave signals are also routed from the external
jack instead of the radio's internal loopstick. This is why some people have
reported poor MW reception when they use regular 1/8" mono patch cables to
connect their antennas.

But for medium wave DXers, this is an opportunity to connect their favorite
antennas to the radio; the lack of a good MW antenna connection has made
some otherwise good radios less than desirable.

If you prefer to use the internal loopstick for MW, simply leave the ring of
the plug unconnected.

Ingo Truppel has another approach:

An important note to the MW/LW - external antenna. It is not useful to
connect the ring terminal of the antenna plug to ground. Instead of that it
should be connected also to the antenna terminal and parallel via a 1 kOhm
resistor or an inductance (some mH) to ground - that way you get more
sensitivity for MW/LW (look at the scheme for that). I use an self made
active antenna (150kHz-30MHz tuned) with an output transformer which grounds
the antenna for DC. So I only connect the ring of the antenna plug to the
antenna terminal.

[I haven't tried this. The antenna I use is also DC grounded, so Ingo's idea
should work for me...DM]
How do I disable the internal MW antenna?

Using a 1/8" stereo connector, ground the ring terminal to the sleeve. Or
else use a 1/8" mono connector. The FAQ author much prefers the former
method as this can be controlled by a SPST switch to disable and reenable
the internal antenna, thus saving the antenna jack inside the radio from wear.

http://www.mods.dk/view.php?ArticleId=2301


=================================================







mike

MII,
..
Click-On-the-Links.
..
Follow the Path of Knowledge.
..
And All Will Be Revealed.
..
Something To Think About !
..
for those who seek the truth ~ RHF

RHF wrote:

MII,
.
Click-On-the-Links.


My teachers all just shook their heads, muttering something about 'Missing
Link'. I can't possibly click on something that's missing...




mike