(Note: I'm not a owner of a NRD-301A. Was able to use a sample for a test peroid.)
Discontinued Receiver (no
longer sold new)
Being a previous owner of a JRC-NRD-93, you will see references
to this model in the text below.
The first item that hit me be about his JRC receiver of the 90’s
when I discovered that it existed was the fact that it does not
include a keyboard for entry of frequencies. In my view it does
not make the set any more difficult to use, after all it is
marketed for the maritime/commerical market. The encoder that is
used for the Mhz/Memory Channel on this NRD-301A worked to my
liking and has a good feel to it, however once in a awhile it
will skip a beat if you turn it slow, that is it will take 2
clicks for a 1 MHz advance. Or it will go backwards, one click up,
it goes one MHz down. Appears not to be a optical encoder being
used here ?
Cabinet construction is almost a dead ringer to the NRD-93 (optional
cabinet included). Pretty much all aluminum, with the outer Green
optional cabinet being a die-cast alloy (perhaps aluminium as
well) of some kind.
A note
about the antenna connections on many JRC receivers. The female (Japan
mfg ITK) SO-239 connector found on the NRD-301A and the NRD-93
are of a strange metric thread. Many (if not most) USA style male
PL259 connectors/adapters will not fit correctly. You might get
it started but never tightened. And you risk cross threading it
if you force it. So the best idea, is to use the male PL-259 that
JRC supplies with these radios (marked as M-P-5), Antenna
Connector...you may say with the accessories... well that’s
so common..so why did they include this....ah.not as common as
you might think ?? Save it ,praise it, and put it to use as you
may not come across another one.
JRC continued to use the weird (Japan mfg "HRS")
AC”power plug/socket for interfacing the AC current to this
set (see picture) . This has not changed from the NRD-93 which
uses this very same arrangement. This is a good durable system
with that locking ring, but finding a replacement plug from a
more local source other than from a JRC dealer is going to be
almost impossible. I would have like to seen a standard
“Computer” style power socket here, as found on
JRC’s consumer sets. But maybe that’s too far away from
the commercial side ?? But a 3 wire power cord/plug is actually
needed (see below).
Ground it right / Noisy Internal Power Transformer that Also Runs Hot
You
need to really ground this receiver. Most of the time you think
of grounding as it might help to enhance the antenna system, but
in the case if the NRD-301A it’s for safety concerns. You
are dealing with a somewhat Hot chassis when powering with AC
current. The NRD-93 also has this same little buzz feeling to the
cabinet that can knock you off your feet if you are touching
something else grounded.
It is caused by 2 disc ceramic capacitors connected across the
rear of the AC input socket inside the set and then connected to
ground on the case of the set (marked as C1/C2 on the Chassis
Schematic). Solutions: The easiest cure is just to ground the set
correctly or second: removal of these 2 capacitors. These are not
required for correct operation of the set. They are used for RF
bypass when the set is being used with a transmitter. As most
Short Wave Listeners are not going to use a transmitter with this
receiver in its life time, just removing these will do no harm.
But grounding the set correctly will completely clear up this
stray AC current from the chassis.
The selection of the correct AC Input voltage is very much
improved. You just have a rotating disc on the rear panel that
selects the proper voltage for your country (with the set off of
course). This may not sound like a big deal....but on the NRD-93
it was a hard wired affair. That is you needed a soldering iron
and about a half an hour to make the change.
Operation of this set is very much on the HOT side. This is due
to the consumer quality power transformer used in the set (see
picture). It has no shielding, make a fairly noisy buzzing sound
when loaded down (probably due to the lack of proper coating of
the windings ??), and after say an hour..this transformer reaches
a temperature that you simply do not want to place even a finger
on it, it gets that hot. This is a part of the set that I was not
happy about at all !! The power transformer that was found in the
NRD-93 was of very high quality, shielded, made no noise, and
only got mildly warm. The voltage regulation circuits in the NRD-93
were the heat maker in that set, the total opposite in the 301A.
Both
of these sets use switching power supplies, however I do not hear
these bothering the receiver, at least of any concern, unless
what I have in the next paragraph might be involved??
Strange Noise ? / Fantasic Layout and LED Display
However there is another noise that exists , and is not
a new one for JRC. The NRD-93 has a sound that I have never heard
emitting from a radio. It’s a very high pitched whine. It
will get louder as you turn up the LED display brightness control.
This sound seems to be coming from the power supply part of the
set. This also is where part of the circuit is for the LED
brightness control is as well. JRC has continued to use a similar
circuit in the NRD-301A. It too whines the same way, and
increases in pitch and volume as you push the Dim button to
brighter display. This seems to bother some people but not others,
depending how good your hearing is. It drove me up the wall, and
was one of the main reasons why I did not keep my NRD-93.
This whine never enters into the receiver or audio chain of the
radio, but it sure does fill the room up with this sound of those
who can detect it..
The general layout of the 301A was very pleasing to me. Nice BIG
LED digits for frequency and channel display, with 4 step dimmer.
The continuos dimmer knob on the NRD-93 is more preferred, but
the step button gets the job done. I prefer LED’s, because
of long life and easy on the eyes. The lack of a light on the S-meter
is a disappointment, be this rules out having to change the lamp
down the road after it burns out (as just about all panel lamps
need to be changed sooner or later).
I do miss the green LED "PBS" display that the NRD-93
has. I gives you a reference of where you have the control set
excactly, and can return to the same spot again.
No play in the tuning knob, either side to side or in and out...great
to see this. This tuning knob does have a way to adjust the
rotating torque. This is done by loosening the set screws on the
knob and sliding the knob closer or further on the encoder shaft.
The knob is pretty stiff as it comes stock.
Above average grade of sealed variable controls are being used,
as was on the NRD-93. I found the small knobs being used for
volume/RF Gain etc..were a bit small for my liking. The NRD-93
wins here. Spacing of the volume/rf gain/squelch/PBS knobs was
also a bit tight to me as compared to the 93 (with the bottom and
top rows being too close together).
I could not tell for sure what type of encoder was used for
tuning (knob). The schematic gave information that was incomplete.
It should be of a optical quality ? A peer inside at the encoder
itself still does not give enough information. Marked on the
encoder: Manual Encoder MKE-005-2 Nemicon Corp, Toyko , almost
makes you think that it NOT optical ? But it never skipped a beat,
so I'm guessing that it has to be optical ??
The tuning knob can be selected for different rates. The NRD-93
had only one fairly slow tuning knob rate, which I did not care
for. Band scanning with the tuning knob was very slow for me on
the 93, even with the slewing up-down buttons right next to it.
So the arrangement on the NRD-301A (as it is on the NRD-545),
where you may select many different rates of the main tuning knob
is a huge improvement for my tastes.
The RF Gain control takes a bit of getting used to. When adjusted
it has a step type sound. That is it adjusts in steps. A study of
the schematic indicates that the control is tied into the main
CPU for adjustment. First set for me to see a digital adjustment
for the RF Gain.
Better Speaker Connections over NRD-93 / AC Power Input
Still Weird
The speaker and line outputs always bothered me on the
NRD-93. The main speaker output was at 600 ohms, and used a
isolation transformer before it seen the output jack (however a 4
ohm was available at the rear), another small 600 to 8 ohm audio
transformer was installed inside the external speaker for
matching. This has been improved to a more traditional standard
in the 301A with all being at 8 ohms, and standard plug on the
rear panel and no isolation transformers. The 600 ohm balanced
line output continues to use a matching transformer.
However, other connections continue to be via the very strange so
called BK (Break) connector (see picture), that is Line Audio
output, other speaker connections and muting. As for the line
connections, for a correct connection, the 301A's output which is
at a Balanced 600 ohms..to properly match to consumer
equipment..an external matching transformer (forget the ones that
radioshack sells ...too small and light...been there done that)
should be used to approach the 30K~50K ohms unbalanced line
inputs that is used for most consumer tape equipment. Mind you it
will work the way it is...however the audio quality might suffer
a bit due to impedance mismatch. But the correct audio
transformer might cost around $ 100, for a Good broadcast quality
one. So give it a try without.
Tip: Using a standard shelided audio cable...Use one connection
of this 600 ohm "Line" for the center conductor of the
cable and shieled to the other. However try and use a jumper wire
to connect the "shieled" to chassis ground. This also
goes for the NRD-93 and the WJ HF-1000 / WJ-8711A along with
others that are using a balanced output.
The NRD-301A has a similar trait that I also noticed on the NRD-545.
On many AM (DSB) signals that have low modulation ..it sort of
runs out of volume control. That is I have to turn the volume
control up well past 12 o’clock to even start to hear the
signal. On any SSB or normal AM signal you never notice this.
Better Sensitivity Over NRD-93 / Limited Included
Bandwidths
Sensitivity is a definite improvement over the NRD-93. How much
..I cannot say, But I could tell only after 30 mins of operation
that this set is better. The NRD-93 was good, but not in the
Excellent/Superb category. Both of the sets are using a dual-conversion
scheme.
The audio quality of the NRD-301A : I will have to say that it is
average, that is not really that good or poor. More distortion
than I would like to see in a receiver , and comes no where close
to the AR7030 in the audio department..
You must watch the adjustment of the RF Gain control on this set.
The NRD-93 was also in this same situation. However , it is even
more important on the 301A.
On AM mode signals, I notice if you have the RF Gain up too far,
distortion sets in very quickly. Even ECSS mode operation suffers
if you run the Gain control wide open. The distortion level on
SSB signals with the AGC in the Slow position is nil, however in
“Fast”, distortion creeps in quickly and the RF Gain
control has little effect.
Operation of the NRD-93 with signals in the SSB mode and using
AGC Fast decay rate, sounded good with no distortion. But the
Slow rate was very SLOW (unusable matter of fact). So overall the
arrangement on the NRD-301A sounds better to me.
The two bandwidth filters that are installed in this set for
“broadcast" (manual ECSS or other) listening, are
adequate. Adding any additional Voice Bandwidth filters (say a
bit wider), is always a problem as JRC does not offer any, and
other people who do..most of the time the radio has to be
modified in order to use them. It’s not just a simple solder
in affair. I feel it does need another, bit wider voice bandwidth
filter (but that's me).
Better Receivers Around For Less Money
In conclusion, the NRD-301A is a set that keeps the tradition of
JRC alive in the High end commercial market, however for my needs
and likes it simply does not show enough features and quality (major
power transformer flaws to name one) plus its steep price tag to
make me run out a purchase one. In general it's internal board
construction and overall quality is no different then JRC's lower
cost receivers . The metal front panel and above quality rotary
controls are of a higher standing.
To us comsumer types this set is already "Long in the Tooth"
(old stuff) as compared to the newer DSP sets, even it's NRD-545
actually outperforms it (filter wise) at less than half the price
(at time of writing).
Dave N9EWO
© 2008 N9EWO
Discontinued receiver