[Premium-Rx] JRC NRD-630 reviews

[Michael O'Beirne]

Good evening Group,

Harry's post this evening is spot on.  I too read the review in "Monitoring 
Monthly" on the new NRD-630 and was rather depressed by the end, 
particularly if I had paid the going UK price of £6,999 (not that I 
would!!).  It has IFs of 70.455 MHz, 455kHz and 17kHz where final 
selectivity is achieved in DSP.  Yet, bizarrely only 6 bandwidths are 
provided, by dedicated push buttons on the front panel, of 300, 500,  1000. 
2700, 3000 and 6000 Hz.

Even more interesting is the more technical review in the February 2008 
"RadCom" by Peter Hart, G3SJX.  If you are thinking of buying this radio, it 
is essential reading.  Sadly, you won't be impressed.  The effective USB 
selectivity curve bottoms out below -70dB due to LO phase noise.  It is no 
better than the old Racal RA1772 of 1974.  In fact in some regards, the 1772 
will still run rings round this receiver (and many others too for that 
matter!).

However, the review states that the killer is the AGC.  You need to read the 
fine detail, but suffice to say the AGC headroom is poor, only about 2dB, 
and that causes considerable overshoot and a long settling time of 10mS. 
The distortion may be due to IF amplifier overload or (more likely) A/D 
converter clipping.  In contrast, a check on the much cheaper Yaesu FT-950 
showed an overload headroom of 16dB and gives a far better AGC response. 
Peter suggests that "AGC clipping is really an area that needs to be 
resolved by JRC".

The dynamic range is good but not brilliant:  on 7MHz at a spacing of 50kHz 
and using the 2700Hz USB bandwidth, the dynamic range with preamp out is 
95dB and an IP3 of +16.5dBm.  With preamp in the dynamic range is 93dB with 
an IP3 of +5dBm.

Compare those figures with the specs for the RA3701 also using a 2700 Hz 
bandwidth but at a much closer signal spacing of 25kHz:  preamp out  IP3 
+32dBm and preamp in of +24dBm.  And no unpleasant AGC overloading.

One other problem:  The NRD-630 has a panel height of 150mm.  This is more 
than 3U but less than 4U, which means that if you stick it in a standard 
rack there will be a gap top and bottom.  This may not worry some members, 
but is not acceptable here.  I think other JRC receivers do this too, but 
why I have no idea unless it is to force you to buy their special cabinets.

Here are Peter's final words:
" Overall I was rather disappointed in the performance and the somewhat thin 
level of features that the radio provided."

I am sticking with my 1772 and 3701.
73s
Michael
G8MOB