"Pete KE9OA" wrote:

Hi Eric,
It has come along pretty well. I just met with one of the
vendors yesterday, and it looks as if they will be able to wind the
loopstick antennas on 8 inch rod stock. We just have to work out the minimum
buy details.

Cool. Do you know how big your first run will be?

I tried several different I.F. transformers, to couple the mixer to the
ceramic filter, and was able to find a good source.
Toko looked promising at first..............I told them that we would only
be ordering 500 of the transformers to begin with, and they said that was
fine. After about 8 weeks, they sent me 20 samples. When I read the fine
print on the paperwork, they had submitted an annual usage of 100k. When I
explained to them once again that we would only be needing 500 pieces to
start with, they said "is that all? We can't give good pricing on small
quantities".
I then explained that Mouser has just what I need in stock, at one quarter
of the Digi-Key price. It looks like the Mouser unit is a winner. With this
transformer, overload doesn't occur until a 140mV level is present at the
antenna input.
I am not sure where Philips got that 500mV overload spec from, but I tried
several different transformers, with impedance ratios from 3 to 1, up to 60
to 1. The Philips folks couldn't explain how to achieve that figure either.
Later this week, I am going to string a 200 foot longwire, and do some field
testing. I am fairly optimistic that the receiver will handle those
conditions pretty well.
We've been working on a 3 million dollar project for the past few months, so
that put the radio on the back burner, as far as the software development
goes. Hopefully, in the next couple of months, things will take shape.
All of the RF design work is completed....................I think I will
have a switchable attenuator ahead of the front end for those super strong
signals.
Oh, one other thing about that overload point...............it only occurs
on signals in the I.F. passband. As soon as you tune off center frequency,
the strong signals are out of the picture. No desense problems.

That's good to know, although I'll bet I can find the 140mV signal
without problem.... :-)

The sync detector sounds so good that I don't know if the receiver even
needs an envelope detector.

I think it would be necessary for digging out the weakest of the weak.

Using the sync detector, 8 extra poles of
selectivity are cascaded at 455kHz, so the skirt selectivity is very good.
Still, I would like to come up with some sort of phasing scheme, so that the
receiver could have continously variable bandwidth, but I haven't figured
out how to do that yet.
I needed a way to test the receivers at our facility, and I didn't want to
bring any of my RF generators from home, so I designed an AD9851 based
signal generator. I will be building it up at work later
today..............I want to make some distortion measurements after I get
it completed. Wouldn't that be a cool product, if it could sell for under
200 dollars?
I still haven't convinced the boss about that one!

Do you have a release target date?

I recall some mention of LF/VLF capability -- is that still in the
design?

Eric


Pete


"Eric F. Richards" wrote in message
...
Hi, Pete,

Out here in the peanut gallery we want to know what's happening with
your new receiver and antenna -- how is it going?

Eric

--
Eric F. Richards

"The weird part is that I can feel productive even when I'm doomed."
- Dilbert


--
Eric F. Richards

"The weird part is that I can feel productive even when I'm doomed."
- Dilbert