by way of The Whiting Household <firstname.lastname@example.org>
Tue, 09 Nov 1999 17:52:28 -0600
To: Rick.Whiting@airtouch.com (Rick Whiting)
cc: (bcc: Rick Whiting/Western/AirTouch)
Subject: Re: Cubic Receiver
Hi Rick - I looked at the very loose specifications for the Cubic receiver.
The poor NF is probably due to, either the so-called synthesizer "low phase
noise" (so low that it is not specified ?) being pretty high, or to bringing
the IP up to +30 without keeping the bottom DR end low enough. I am saying
the +30 is a trick to disguise the sensitivity. I can move my IP way up if I
insert an attenuator in front. However, my MDS comes up also. It is another
story to have an MDS of -147 and an IP of +50, hi!
So, if someone puts a low noise preamp in front of it (like someone
suggested), unless the system's SFDR is maintained, it will gain at the
bottom (provided the synthesizer is OK), but the +30 will come down also to
probably 0 or worse. In SFDR, It is not as simple as just adding an LNA, hi
like many hams believe! The result may be a NF of 5 dB with an IP3 of 0 dBm
Anyway, it looks like this is an answer to Collins' spook card radio
offering. It would be interesting to see what kind of automatic front end
filtering system is offered (if any?) from 0 to 3 GHz with these Cubic card
radios? You know, the auto switched half octave front end can be gobbles of
times more complicated than the receiver itself.
By the way, the Electrocom Division of Raytheon in cooperation with DARPA
makes a state-of-the-art card radio with DSP. I don't exactly remember the
SFDR, but it is higher than 90 dB.
The thing about the Raytheon card receiver is that it uses MEMS (miniature
electrostatic micro switches) to do the complex front end half octave filter
switching (the biggest part of the radio's job). The accent is on MEMS which
are a newly introduced switching technology which keeps these front end
filters embedded in the surface of the boards. MEMS are good over diodes
because they don't introduce any IMD since they are electrostatically
This receiver covers from 0 to a few GHz, I believe. I was supposed to talk
with these guys at the Raytheon RF Conference last week in LA, but my trip
was canceled because of mother's situation. I had presentations on it
In any case, I don't think these products (Cubuc, Collins or Raytheon) are
cheap at all. Judging by the Collins card, they are probably around $5000+
before adding the fancy front ends. This is low cost if you compare them
with the old WJ black and silver boxes selling for hundred of thousands.
73, Cornell - KW7CD