It looks pretty good............I should take a look at my Drake schematics.
I hope they aren't using those impossible to get chips, you know, the ones
that all of the radio manufacturers have bought up!
Anyway, I got the AD607 board layout completed, but it required four layers.
I am going to try to reduce it to two layers, at least for the 1st article,
so I can build it up this weekend. Too bad that Analog Devices doesn't
internally bias their chips, the way that Philips does. With the quagmire if
external biasing resistors, this chip reminds me more of something like the
OLD,OLD MC1496, which came out in the last century, not the modern day chip
that it is touted as being.
I do have the AD607 Eval Board, but that thing is harder to use than just
doing my own board layout. I can understand why the manufacturers of those
external sync boards charge so much money. Quite a bit of development time.
I am still shooting for the 100 to 125 dollar range for this board, if I can
get it into existance!

Pete

starman wrote in message
...
John Crabtree wrote:

"Pete KE9OA" on 12/30/03 wrote:

I am not sure how to do the selectable sideband function, but
I can figure it out, I will sure throw that function in. I just
ordered some samples of the high speed op-amp that is used
for squaring up the signal to the phase detector. They should
be in on Wednesday. I am doing two versions of the
detector...........one of
them will use an AD op-amp, while the
other will use a Burr-Brown device. This sync detector will have
two ceramic bandpass filters in the signal chain.........one of
them will be between the mixer output and the I.F. input, while
the other will be between the I.F. output and the demodulator
input. It shoud be a low-noise system. AD specifies this
configuration as having an MDS of -90dBm. I will be feeding in
a -20dBm signal, so the earlier stages of the receiver will have
more than enough takeover gain. If there is enough interest in
the circuit design, I will post the AD application note up on my
website.
Thanks for encouragement!

Pete

You have some options as to how to provide selectable sideband in the
synchronous detector:

1. You can do it with passband tuning and move the signal carrier to
the edge
of the IF filter passband. IIRC this is the way that you can select the
sideband in the AOR7030. I suspect that doing this will cause some
phase
distortion to the carrier if you place it on the edge of the passband.
To what
extent this matters I do not know.

2. Once you have the I and Q signals from a quadrature detector, you
can use
all-pass networks to phase the outputs and then add or subtract as
necessary.
Sony did this with the ICF-2010. Trevor Brook in his Electronics and
Wireless
World article did this as well.

One issue with this approach is that the level of opposite sideband
reduction
is dependent upon the quality and number of stages in the phasing
networks.
IIRC Sony only achieve ca. 25db of opposite sideband reduction. The
quality of
phasing networks has been discussed in the ham radio literature re. the
generation of SSB signals. It is possible to design simple networks
which are
'OK' over the range 300 to 3000Hz.

Once you have the Q output, it then should be very straightforward to
offfer
quadrature detection as well, where you null out the strongest station
on the
frequency to which the detector has locked.

Which ever way you might choose, there are inevitable compromises.
snipped

Pete,

I'm not sure if you mentioned it but I assume you're working with an
I.F. of 455-Khz? The Drake-SW8 and it's clone the Sat-800, implement the
sync' detector in the second I.F. at 455-Khz while the Drake-R8x does it
at 50-Khz. It's basically the same circuit in both receivers, just
operating at different I.F.'s.
FWIW- I vote for the I/Q method for selectable sideband sync' detection.
It seems like the elegant solution to me.


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