Thanks, Matt. I will definitely be going with a
synthesizer....................system noise floor will be down around -138
to
-142dBm. I worked in the Synthesizer Group at Rockwell-Collins for awhile,
so I learned all of the things that my mother was afraid to tell me about
synthesizer. Those Rockwell-Collins folks were great!
It probably will be DC powered, using a low noise power supply of my own
design.
Matt wrote in message
...


I think the idea of a high performance MW radio is a great idea!
There is definately a good market for it. The main competitor I would
imagine would be the CC Radio, so your end price would have to be
comparative to that. I am a MW DXer, so I hope I can give you some
helpful advice and encouragement. No matter how the radio takes
shape, it probably goes without saying that it should be able to be
powered by both AC and DC. If you can only pick one, go with DC.

First, I offer three suggestions if you must keep it cheap.

1. Analog tuning. However please keep the dial accurate and as even
and as spread as possible, with a marking for each kHz. This will
enable the listener to know if he is tuned to 832 kHz or 837 kHz for
example. The needle which shows the listener where he is tuned should
be narrow yet brightly colored. Many current radios suffer from
squashing the high end frequencies together... this should be avoided.
In fact, I'm sure many MW DXers would agree with me that although they
might prefer digital tuning, if you could produce a radio with a very
accurate and evenly spread analog dial, they would gladly accept the
trade-off. No matter what you do, please keep the noise floor as low
as humanly possible in this radio (another reason to go analog).

2. Make sure the radio's own antenna can swivel independently from
the radio itself. Some old radios have this helpful feature. It
allows you to keep the radio pointed right at you so you can read the
dial, and just swivel the antenna. Make the antenna as big and as
sensitive as possible, whether it be a loop or a stick.

I think that we will go this route, with the antenna. I've got several
pounds of Litz wire, to prototyping isn't a problem. I still need to get
ahold of some Type 61 ferrite rod stock for the antennas.

Also, please
allow for the ability to switch off this antenna so that an external
antenna could be added by the listener. Would it be possible to
incorporate some sort of phasing relationship between the external
antenna and the radio's antenna without adding much cost? If so, that
could be a third switch position on the radio's antenna controls.

That is out of my realm of knowledge, although it it a great idea.

3. Use high quality filters with 3 different positions... wide,
narrow, and super narrow. If only two are feasible, I would strongly
recommend narrow and super narrow.... not many listen to music for
enjoyment on MW radio these days, and since this radio is designed
mainly for distance listening I'm sure a wide position wouldn't be
missed.

I think that we will go with two. Even with the 6kHz bandwidth, though, the
skirt selectivity is sharp enough to separate the sideband component from
the carrier of an AM signal.


If you can add a few more expensive features, I'll rank them in
importance.

1. Sync detector. The sync detector on my Sony 2010 really helps me
dig out stations that my other non-sync radios cannot. How much per
unit would a sync detector cost?

This is a good feature, but so far, I haven't been able to locate a good
source of these chips

2. If this radio does take a digital form, a dozen presets would be
nice. If at all possible, it would be great to have a memory scan
feature where these 12 stations could be scanned repeatedly, with the
radio pausing 10 seconds on each frequency before moving on to the
next. The listener could program in 12 MW stations they use as
benchmarks for DX conditions, and then let the radio scan through them
automatically.

This is a good idea; we were also thinking of incorperating this feature
into some sort of Spectrum Scope function. Still up in the air on this one.


That's it for me... I really think this is a great project and wish
you all the luck in the world. I would be glad to publiicize too on
the various MW groups and lists on the net as well once it is
produced.

Thanks for your input, Matt! You've got some good ideas. I appreciate your
offer on the MW group thing!

Pete