[time-nuts] A Highly-Accurate and Stable SDR-IQ Using GPS-DO and DFS

J. Forster jfor at quik.com
Sat Jul 24 13:01:24 EDT 2010


Oops. Yes, typo. Sorry.

I don't know about the A version but the  and C are essentially identical
except the B used wierd Telco connectors. An new adapter might cost as
much as you'd pay for the receiver.

Their shortfall is the demodulation options are limited, but they do a
wonderful job of measuring carrier frequency.

Best,

-John

===========


> Indeed the do. I believe its actually a HP3586b a selective level
> voltmeter.
> One heck of a reciever measures signals to 100th of a db. As a heads up
> they
> have a very good xtal oven in them. I have 5 of these units. Just can not
> resist them.
> Often you find these quite cheap. Last one was $20 because it did not
> work.
> Well the oven had been taken. Ext ref did just fine. Mine are locked to a
> Rb
> standard.
> Another big caution these have a nicad in them with a resistor for
> charging.
> They leak.
> You need to pull the board and look at it and remove it before powering
> up.
> If the leakage has hit the traces, normal. It will raise holy heck and
> damage the regulators.
> Clean all the gook and repair any traces and you should be fine.
>
> On Fri, Jul 23, 2010 at 11:05 PM, J. Forster <jfor at quik.com> wrote:
>
>> If you want an HF radio that reads to a Hz, ready made, get a used HP
>> (Agilent) 3486 Selective Level Meter. It covers essentially DC to either
>> 20 or 30 MHz. It has a good internal ovenized oscillator, and can be
>> locked to an external standard.
>>
>> A virtually unique feature is that it will lock onto a carrier and read
>> that carrier frequency to a Hz or better.
>>
>> They are often abailable for a few hundred. The 3486A & B are similar.
>>
>> FWIW,
>>
>> -John
>>
>> =====================
>>
>>
>>
>>
>>
>> > I have been involved with many kinds of radio receivers for over fifty
>> > years -- amateur, military, and commercial. This modified SDR-IQ is a
>> > dream come true. When I was a young ham, I dreamed of the day when I
>> might
>> > have a receiver that would read out to one kilocycle (before we used
>> the
>> > term Hertz). Now I have assembled one that reads out to one Hertz and
>> is
>> > accurate to a few millihertz -- and thanks to GPS -- it will maintain
>> this
>> > accuracy as long as the GPS satellites keep working.
>> >
>> > I well remember the early radios that I used. I had to be very careful
>> to
>> > not bump the table where the radio was or it would jump completely off
>> > frequency. Whatever frequency it indicated was only approximate. It
>> made
>> > me nervous to operate near a band edge.
>> >
>> > Dave Powis, G4HUP designed and built a 66.66666 MHz DFS for me. I
>> really
>> > appreciate his help on this project, especially since several hams
>> told
>> me
>> > it couldn't or shouldn't be done. Some said that the frequency
>> read-out
>> on
>> > the SDR-IQ would not be accurate because the time-base in the
>> computer's
>> > sound card would be a variable factor, but this is not true. The
>> frequency
>> > accuracy and stability of this radio ONLY depends on the 10 MHz
>> oscillator
>> > in the Trimble Thunderbolt and that oscillator is locked to the GPS
>> > constellation.
>> >
>> > Dave and I worked together on this project for about one year. The DFS
>> box
>> > travelled across the Atlantic Ocean five times before we finished.
>> >
>> > Dave has written an article "Precise Frequency Locking for the RFSpace
>> SDR
>> > radios" and I have a web page showing how I connected all of this
>> > equipment together. Here are the links:
>> >
>> > http://www.braddye.com/g4hup_dfs.html
>> > http://www.braddye.com/gps_do.html
>> >
>> > 73s
>> >
>> > Brad Dye, K9IQY
>> > ex KN9IQY, KN4BK, KM5NK, WB4JCF, ZP5TQ, WA4VXU, WA9RVL, HH2FJ /TI2,
>> /9Y4,
>> > /6Y5, /KP4
>> > 53 years as a FCC licensed amateur radio operator
>> > 37 years as a FCC licensed first class commercial radio operator
>> >
>> >
>> > _______________________________________________
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>> >
>> >
>>
>>
>>
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