The MW receiver is progressing pretty well.................I have completed
the synthesizer, and am now doing the final pass on the receiver board
itself. MDS measures at .2uV right now, with strong signal handling up to
about 900mV.
Next week, I plan to design the sync detector, but there are a couple of
things to keep in mind. If there are two closely spaced signals, the
stronger signal will capture the system. For this reason, I may also include
the envelope detector function.
The initial results are very encouraging....................in the "RF
Alley" that I live in, with three 50kW MW broadcasters, no overload problems
were noted. I will keep all of you posted on the progress of the design.

Pete

"Pete KE9OA" wrote in message
...
The MW receiver is progressing pretty well.................I have
completed
the synthesizer, and am now doing the final pass on the receiver board
itself. MDS measures at .2uV right now, with strong signal handling up to
about 900mV.
Next week, I plan to design the sync detector, but there are a couple of
things to keep in mind. If there are two closely spaced signals, the
stronger signal will capture the system. For this reason, I may also
include
the envelope detector function.
The initial results are very encouraging....................in the "RF
Alley" that I live in, with three 50kW MW broadcasters, no overload
problems
were noted. I will keep all of you posted on the progress of the design.


Any ballpark idea of what this little jewel will end up costing??

Hi Brenda,
I am not sure yet..............it depends upon what features
folks are looking for. If we put in the spectrum analyzer type of display,
and the sync detector, it will probably be in the just under 300 dollar
range. For this price, the performance will be in the class of the
multi-thousand dollar offerings from Harris, Racal, Rockwell-Collins, etc.
The unit will have a tracking preselector for the active loopstick antenna,
which will tilt in both planes. I am not sure if I will go for multiple
bandwidths, or use a couple of narrow bandwidth filters, and use a phasing
technique to achieve continous bandwidth control.
Still a few more ideas to implement.

Pete

Brenda Ann wrote in message
...

"Pete KE9OA" wrote in message
...
The MW receiver is progressing pretty well.................I have
completed
the synthesizer, and am now doing the final pass on the receiver board
itself. MDS measures at .2uV right now, with strong signal handling up
to
about 900mV.
Next week, I plan to design the sync detector, but there are a couple of
things to keep in mind. If there are two closely spaced signals, the
stronger signal will capture the system. For this reason, I may also
include
the envelope detector function.
The initial results are very encouraging....................in the "RF
Alley" that I live in, with three 50kW MW broadcasters, no overload
problems
were noted. I will keep all of you posted on the progress of the
design.


Any ballpark idea of what this little jewel will end up costing??

Joseph Worcester, who developed and sold the SPACE MAGNET ferrite active
antenna, also built a high-performance MW receiver and got a patent on the
circuit which changed the bandwidth as the signal strength changed. I remember
reading the patent and thinking he'd invented AM stereo. Jis radio sold for
$700 in the 70s.
Matt

...got a patent on the circuit which changed the bandwidth as the signal
strength changed.

Automatic regeneration control? I guess that would be shortened to ARC.

On a HW-101 I once had, I added manual regeneration control. Actually, I
modified the stage that had the RF gain control by adding a tickler feedback,
to do just that. To pick out a weaker signal, I would increase the RF gain,
effectively increasing the regeneration which would decrease the band width in
the process.

Bill, K5BY

Thanks for keeping us in the loop on this, Pete, I'm *really* looking
forward to this one hitting the market.

Eric

--
Eric F. Richards,
"Nature abhors a vacuum tube." -- J. R. Pierce, Bell Labs, c. 1940

EFR, Ditto That !

Pete, nice to have your status report, and
to hear the progress that you are making.

kutgw ~ RHF
..
..
= = = Eric F. Richards
= = = wrote in message . ..
Thanks for keeping us in the loop on this, Pete, I'm *really* looking
forward to this one hitting the market.

Eric

Thanks, Eric, and all the other folks! I just got through building up the
2nd pass of the prototype, and it looks good. The MDS is less than .1uV, and
the system doesn't go into clipping until 50,000uV, so I would still like to
bump that up a bit. The sensitivity figure is with no RF amplification ahead
of the mixer. I am using a doubly-balanced diode ring mixer, followed by a
diplexer, crystal filter, and another matching network, followed by a
TDA1572. Audio distortion is .5%, with a 100uV signal.
I still would like to be able to implement the 1572's on-board oscillator,
but it just doesn't seem to work with a fundamental mode crystal. Using the
recommended values from Philips only yields an oscillator with the LC
network dominating the circuit.
Next week, I will start the Sync detector design. This weekend, I will be
winding some prototype loopsticks. I was able to purchase a few samples of
ferrite rod stock from Elna, but unfortunately, the minimum order from them
is 3,000 pieces @ $1.50 each. Sure beats Palomar's prices, at $15.00 each!
There are still a few other issues with the design................with a
1kHz tuning step size, the loop filter needs to have a natural frequency of
about 15Hz. This gives a settling time of around 100mSec, which is okay, as
long as you don't make large tuning changes (memories). There are some
solutions..........one of them is to use a DAC to pretune the VCO to the
desired frequency, and let the PLL take over afterwards. National
Semiconductor does have some chips in their LMX-XXXX series of synthesizer
chips, but unfortunately, the fractional N types with the speedup circuit
that I had in mind don't go low enough in frequency. Then, you have the
fractional N sidebands to contend with, unless you use a Modulated
Fractional N Divider (MFD). This technique used Sigma_Delta Modulation to
translate the noise sidebands far out from the carrier, so they are much
easier to filter. Hewlett-Packard used that design in their 8642 series of
signal generators, but in my web scouring, I did discover that Philips
supposedly had a Sigma-Delta type of synthesizer. Now, that sounds
interesting...............

Pete

Eric F. Richards wrote in message
...
Thanks for keeping us in the loop on this, Pete, I'm *really* looking
forward to this one hitting the market.

Eric

--
Eric F. Richards,
"Nature abhors a vacuum tube." -- J. R. Pierce, Bell Labs, c. 1940

Behold, Pete KE9OA signalled from keyed 4-1000A filament:

........in the "RF Alley" that I live in, with
three 50kW MW broadcasters, no overload problems were noted. I will
keep all of you posted on the progress of the design.

All thanks to that diode-ring mixer ;-)

Thanks for keeping us posted Pete!

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

Anytime, Gregg. I live very close to WBBM, 780kHz, and no IM products were
noted on 1560kHz. Things are moving ahead!

Pete

Gregg wrote in message
news:vrGzb.8122$d35.6541@edtnps84...
Behold, Pete KE9OA signalled from keyed 4-1000A filament:

........in the "RF Alley" that I live in, with
three 50kW MW broadcasters, no overload problems were noted. I will
keep all of you posted on the progress of the design.

All thanks to that diode-ring mixer ;-)

Thanks for keeping us posted Pete!

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca