Will wrote:
Maybe all this is meaningful only when referring to really high-end
receivers. All I know is that I sometimes hear annoying distortion
when listening to a reasonable-strength SWBC station, and hitting
the "Sync" button on the Grundig 800 or the Sony 2010 makes it
stop. That increases my listening enjoyment. What more can I ask of it?

Will


I own several receivers, R2000, R390, R392 and a DX398. I currently
have a AOR7030+. From some experiments last summer to the
present I found that the "standard", and all too common, diode
detector wasn't the best choice for detection. In my quest for a
better detector I found many non obvious "things" can mess up
intelligibility. I built a micro power transmitter, with a high quality
modulator, driven by a MP3 player that loops a random set of
words that can be easily confussed. Copy/Coffee etc.

By reducing the transmitter power level to the minimum level where
I could achive 80% intelligibility I was pleasantly shocked to find
that by using better detectors I could drop the power from the
transmitter by up to ~12dB. The major weakness was, while my
signal is far enough away to insure my dB readings are reasonably
accurate, I could only deal with QRM/QRN impossed on top of my
test signal, I couldn't duplicate or even simulate the deep fades
caused by multipath.

I went to considerable trouble to design, test and redesign an
outboard detector complete with better IF filters.

I was somewhat satisified with the results, but I had been lead to
believe that a synch detector was an almost magical device that
could eliminate or reduce the unintelligibility caused by bad selective

fading. DL's experiments and observations showed me that perhaps
I had mad false assumptions.

At the time when I started I had the AOR for a couple of weeks and did
not have time to completly evaluate the AMSD capacity to moderate
the effects of deep fades.

Since our friend had to ship her AOR back to England for repair, and
since she now is living in New Zealand, she had it shipped to me for
a "check out". I have had enough experience with my AMSD to be
able to appreciate the AOR a little better. While it is not perfect I
would gladly give my left nu, er left foot for one.

But an AMSD is not a cure all. The better filters, better audio etc
make the AOR a joy to use. The multi-level control scheme makes
it a royal PITA! But even the AOR showed clear benifit from DLs
ELPAF. For a more pedestrian receiver like the R2000, a better
detector, see my posts for links, with a better audio chain, better
IF filter and the DL ELPAF my R2000 can dig out 99% of what the
AOR receives. True the AOR 7030+ has a much better choice of
filters(drool drool), and the audio chain is quiter then anything I
have
been able to yet build, but for less then 50$, I am a good scrounger
and love to trade, I have improved my R2000 significantly.

And we use a DX398 for mini DXpeditions and with a tighter IF filter
and
an add on DL ELPAF the radio is many times better then a stock version.

I bought a used DX-398, some what scuffed but I paid $5 at a local
"Good
Will" thrift store, and plan on adding a simple "improved AM detector",
with
a better(tighter) IF filter and see if the work is worth the effort.

One thing to keep in mind is that Dallas Lankford is a serious MW DXer.

And on the MW band every station you tune in will have one or more weak

stations underneath as it were, and during a deep fade, the "weaker"
station might become strong enough to upset an AMSD more then most
of us will experience on "most" HF/SW signals.

I brought the orignal thread up because I found the ELPAF really made
some signals more intelligible and made others much more injoyble to
listen to.

If I knew a year ago what I now know I might not have gone to the
trouble
to build the outboard IF strip with AMSD etc. Then again I likely would

have gone ahead in my typical bull headed way.

The "funny" thing is I am more into utility listening, where there is
very
little AM to benifit from a AMSD. Of course the Synch detector chip,
Analog Devices AD607, is a very good SSB product detector.

Given the lack of posts and threads that have ANYTHING to do with
SW, or indeed radio at all, I felt a need to pass this information on
to those who might find it as usefull as I have.


Terry