(This
light review is from 1998 and has been edited from that version)
Solid Construction / 5 Volt Switching Power Supply / Pass
Band Shift / Sensitivity Very Good
The JRC NRD-93 has not been sold new since 1995. Audio
quality is MUCH improved over "any" other JRC receiver
that I have owned before (except for the NRD-545).
The sound is sharper, clearer and the AGC works good (in fast
only, see text below). No "woolly" sounds, or hiss
coming out of this set. Construction innards are similar to the
NRD-525 , except there are no surface mount parts that I could
see ? Unlike the model that followed (the NRD-240) the 93 does
indeed have Pass Band Tuning.
Unit runs pretty cool, a bit more heat comes from it's 5v
switching power supply (did I say switching supply..yes I sure
did), but is more on the warm side than hot. The "Dimmer"
is a control and not a bloody 2 or 3 step button, a big plus. The
LED's are much easier on the ole' eye balls. All the controls
have a excellent feel, no wobbly knobs. All pot's are above
average (sealed) quality...not the usual consumer grade. Even the
metal plate that contains the serial number is impressive.
Speaker arrangement is a bit different from what we "consumer's"
are used to. The speaker audio output is at 600 ohms (1 Watt).
Jack is in the front for the included externa; speaker, 600 ohm
output. This speaker is a 8 ohm, but with a 600 to 8 ohm
transformer inside. There is actually a 4 ohm output on the rear
connector, but still uses a internal audio transformer. Even the
audio "Line" output is isolated with a 600-600 ohm
transformer.
"PBS" (Pass Band Shift) works great. Overall
sensitivity while very good is no barn burner. Most more modern
JRC sets (say the NRD-545) will give for better performance in
the deep down "in the mud signal" capture. Stable as a
rock. When you get the receiver and the optional NDH-93 memory
unit all placed in the cabinets the weight gets very close to 45
lbs....huffda.
LED Display Noise
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. 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 continued to use a similar circuit in the
NRD-301A as it too whines the same way, and increases in pitch
and volume as you push the Dim "button". This appears 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.
Limited Voice Bandwidths / Non JRC Filters A Pain To Make Work
IF bandwidth filter arrangement for voice modes is not
perfect for broadcast voice use. You have either a 3 or 6 khz as
it came new. As usual for me the 6 kHz was a bit too narrow for
my tastes. Thank goodness I still had around a 8 kHz filter that
I had pulled from my old "early version" NRD-535 that
fit the bill real well. From information that I received via Rob
Sherwood (Sherwood Engineering), you have to be careful
installing filters in a JRC receiver. JRC filters use a 600 ohm impedance (termination). Most other filters including the ones
that he sells are around 2000 ohms. No cigar if this is not met.
You can modify most JRC radio's to work with other voice
bandwidth filters from other sources. JRC never offered any
optional voice filters. I was not up to sending if off to have
any mods done and the 8 khz (perhaps closer to 10 ??) filter
worked good for me. I cannot help it, I like the wider filters. I
used manual ECSS with the 3 KHz filter for the trouble spots on
the dial.
To the left of the main display (green) indicates in Khz the
BFO/Clarfier
adjustment made, to the left indicates the PBS (Pass Band Shift)
adjustment in Khz. Each of the NDH-93 Memory unit channels store
the Frequency, Mode and the Bandwidth. Not bad as the older NDH-515
(memory unit for NRD-515) only stored frequency.
Nice S-Meter, But Not Lit / Sherwood SE-3 a No Go
Unlike the NRD-525-535 and even with JRC's NRD-545, the
93 has a good old standard S-Meter. I have yet to see it pin, and
is very useful. However , it lacks proper markings, also it takes
a pretty strong signal to make it start to read . It also doubles
as a "line level" audio indicator as well, but I found it to
read WAY low.
Rear panel has BNC jacks for a external 10 MHz reference, and a
455 kHz IF output. The Sherwood SE-3 "Sync" detector
will work right out of the box with this set (using the IF Output)
??
However we tried a Sherwood SE-3 external Sync with the NRD-93....and
FORGET IT ! It did not interface well. Audio distortion at ANY IF
level adjustment. I got much better just audio using manual ECSS
tuning with the wide filter..MUCH better in fact. So forget the
SE-3 with the NRD-93 ! To be fair, let me say that it did help
with the fading distortion very much. However the overall audio
quality that was being heard from the speaker and even more so
from the "Record Output" of the SE-3, was distorted and
buzzy, it did not sound overdriven either. The overall audio
comming from the NRD-93 without the SE-3 actually sounds better.
"MAYBE" some tinkering with the IF level inside the 93
would have helped, or maybe another buffering stage {maybe not
??}???, but I'm not about to play with the innards..no way !! So
was better without it.
Strange AC Power Input Plug / Grounding The Set is a Must
/ Changing AC Input Voltage is Hard Wired
AC power input is strange. They are using a oversize 2-pin
Microphone connector. Take a standard "Foster Type" 4-Pin CB microphone
connector..make it 2 pins centered in the middle, and a bit
larger and that is about it. From what I have been able to find
out from others, JRC used this as it was a standard on some other
marine radar system(s) ?? You have to make sure that the set is
well grounded, as the case carries at bit of a potential (can
give you a nasty buzz on your skin). I just used a 3 wire power
plug/cord and this problem goes away 100%. I have talked to
others who have owned NRD-92's and 93's and all have experienced
this same little gremlin. So if you ever get hold of one of
these..Ground
the case it BEFORE you plug it in !!
This is caused by 2 disc ceramic capacitors connected across the
rear of the AC input socket inside the set and those are
connected to ground (case) of the set.
If you need to change the AC (mains) input voltage , this is done
with hard wiring and not a switch. One will need a soldering iron
to get the job done. The manual covers this information well.
Is It Perfect ?? / Audio Quality / Slooooooow AGC
At this point you are saying....for a professional
receiver, it should be perfect ?? Well that would be nice..however
there is no such a receiver on this planet that is and the 93 has
it's share of bug-a-boo's. Remember that the 93 was on the
drawing board in very early 80's.
It's synthesizer is relatively noisy. If you pull the antenna off
and tune around the band, in certain areas (the 11 Mhz area is
full of them) they show up. However this is not as bad as it
seems. Just the noise in the band covers up most of these birdies.
The NRD-535 has a much worse problem as far as noise goes.
Now you might be wondering..."does the NRD-93 audio
sound as good as the AOR AR-7030" ?? Well that ones
easy....NO WAY !! For AM mode broadcast stations, the
audio is one of the best in a JRC product that I have ever used (up
to the NRD-545 which was the best JRC receiver in my view for audio).
SSB signals
actually sound better on the NRD-93 vs the AR-7030. Cleaner, and
less clipping distortion. If I used manual ECSS with the NRD-93 (which
by the way works very good) the audio distortion is almost nil.
AGC "Slow" decay rate is "way" too SLOOOooow.
Matter of fact the slowest I have ever used with the exception
of
the EARLY Kenwood R-1000's , which is the all time slowest for me.
If all signals are about the same strength, (let's say you are
tuning in a number of Hams on one frequency), it's useable. But
if you have one strong signal with a bunch of weak ones, you
better switch it to fast or you will not hear any of the weak
signals at all. Good news here is that the fast works well even
on SSB signals. No excessive distortion. On certain broadcast
signals the "Slow" setting can actually help iron out
really deep fading distortion (but not always). It's not a major
drawback.
Good or Bad ??
The NRD-93 is a fantastic piece of equipment. Built like a tank,
ease of operation and performance is excellent. However these are
"really" getting more rare and old on the used market,
and those who have one usually hang on to them until they are
cold in the ground. But once in great awhile one does surface.
Used prices seem to be hitting the sky as well (no where but
"up"). Also finding a sample that has not been aboard a
boat or ship is a important point to consider.
Something else to
keep in
mind. As is the case with ALL JRC receivers now, the NRD-93 is full of
mechanical relays and ever aging electrolytic capacitors and will require attention sooner than later.
