[Elecraft] ADT-200A Fully DSP transceiver

[Paul Christensen]

> There are many aspects of the ADT-200A that fall short of the K3 (only 
> 50W, some
> software upgrades
> being charged for, lack of front panel controls, non standard control 
> protocol, etc).
> It's an interesting development though, see: 
> http://www.adat.ch/index_e.html

>From the ADAT website:

"In the future, ADAT will publish a document with the control codes so that 
other programs may be updated to operate the ADT-200A...Software updates 
with new functions will be free and can be downloaded via website. Software 
options (see above) will be with costs."

I recently purchased an ADAT ADT-200A and have been using it along side the 
K3 for the past three weeks.  The ADAT unit's construction quality is 
superb.  Fit and finish are equal in quality to high-end test equipment from 
Agilent and R&S.

Presently, features like PA adaptive pre-distortion and the external 10 MHz 
time-base are active.  The CW envelope is generated by the Blackman-Harris 
window function and generates even less occupied spectrum bandwidth than a 
raised-cosine Gaussian function.  The rise/fall time of the envelope is 
determined by the CW speed.  It's interesting to watch the ramp time change 
as the WPM setting of the keyer changes.  The envelope is perfectly 
symmetrical and exhibits no ALC overshoot.  QSK is not implemented at this 
time but is scheduled for the next major firmware release -- as are many 
other features.

Obviously, with so few controls on the front panel, the ADT-200A will not 
appeal to everyone, especially contesters.  Features like "dual-watch" 
already exist, but engaging the function and complex splits requires going 
through 1-2 layers within the menu.  An experienced operator can manipulate 
this quite quickly.  It was an impediment at first, but I can engage the 
transceiver in split nearly as quickly as I can with the K3.  If a 
third-party control program (e.g., HRD, N4PY  etc.) was to support the 
ADT-200A in the future, there's no reason why manipulating the transceiver 
cannot be just as easy as it is for any other transceiver.

I have to stand by ADAT's decision to limit output power to 50W.  Since the 
majority of commercially-manufactured amateur amplifiers can be driven to 
full power with 50W or less, anything more than 50W, is "dumb" power until 
you get well beyond 100W (IMHO, at least the 750W level).  With internal PS 
and PA, the unit is smaller in size than the K3.  No built-in ATU is offered 
at this time.  Modules for 2m-70cm will be offered later.

The ADT-200A is the coolest running transceiver I've ever used.  Although it 
has a tiny convection fan, the unit stays cold (not just cool) to the touch, 
even after a 30-minute CW QSO.  PA and PS efficiency is excellent.

Rx audio is outstanding and it's the most "analog" sounding digital receiver 
I've heard.  By that I mean AGC, electrical interference "ticks" all behave 
as if its a traditional analog receiver.  The 'S' meter is precisely 
calibrated in both dBm and dBuV scales.  It's interesting to watch the 
digital "S" meter scale drop down to -142 dBm when the pre-amp is engaged 
and the antenna is disconnected.  The rig is plenty sensitive with dynamic 
range on par with other directly-sampled RF receivers like the Perseus and 
QS1R.  A 14-bit ADC is used but because dynamic range is a function of 
process gain (composed of sample rate and bandwidth with a 10log, rather 
than a 20log constant), going from 14-bits to 16-bits does not significantly 
add to dynamic range.

Like the K3, it's exciting to be a part of ADAT's long-term product 
development.  Being one of the first NA ops to use the ADT-200A will likely 
generate a lot of follow-up questions to this post that I'm not prepared to 
answer at this time.  In the future, I plan on publishing a report when time 
permits.

Paul, W9AC