Re: [IRCA] TWO DX-ERS AND THE ECLIPSE

[Volodya S <canswl@xxxxxxxxx>]

Surely this is a joke.  it's not even April.  A 2k km CAT 5 line between
your SDRs, and it's a mighty large Terabyte storage you have!   ;-)   Walt

On Sat, Jul 15, 2017 at 12:02 PM, Mark Mobile <Mark4@xxxxxxxxxxxxxxx> wrote:

> There's been a lot of chatter in the Ham newsletters and the scientific
> community about RF-signal measurements during the August 21st eclipse.  But
> not much has appeared in the âDXâ newsletters.  In the hope of stimulating
> an exchange about proposed listening methodologies, we want to share the
> eclipse-monitoring plan of two DX-ers...Nick Hall-Patch and myself.
>
> We plan to take advantage of a technology that wasn't available during the
> last major eclipse: the Software-Defined Radio (SDR).  To give all signals
> an equal chance, the Medium-Wave antennas used will be high-gain
> omni-directional.  The SDR listening posts at Nick's Victoria British
> Columbia home and my cabin in North-Central Minnesota will be connected by
> a balanced wire-pair, with the separated antennas forming a
> Very-Long-Baseline Eclipse-Catcher Array ("VLBECA").  RF measurements will
> be taken from 9.01 kHz through 66.666 MHz in 1.1-Hz increments.
>
> For connectivity between us to form the VLBECA, we will use pair 3
> (green/white) of special Cat-5 cable with pink jacketing.  (From our recent
> desert DXPedition we found the pink outer jacket to be the best color for
> optimal velocity factor in the Cat-5, and we were already aware that an
> odd-numbered pair would maintain better polarity.)
>
> The exact distance between our two locations is 1,359.37 miles (or
> 2187.69395328 kilometers if you're Canadian).  Since there are a lot less
> miles than kilometers along the VLBECA, we chose to save money by buying
> the connecting cable by the mile rather than the kilometer, and that meant
> purchasing our Cat-5 in the United States.
>
> Further input on velocity factor from the National Bureau of Standards
> (NBS) led us to choose stranded rather than solid wire for the Cat-5.  This
> created some contention between Nick and myself, since stranded copper is
> more expensive.  However, when we realized the Cat-5 route took us through
> the Bakken Oil Fields of North Dakota, we knew the superior mechanical
> performance of stranded wire would provide additional integrity against
> rough handling.
>
> For Cat-5 pair 3 termination consistency on the two ends, we asked for
> bids for a pair of 2.2:1 matching transformers that would match the Cat-5âs
> native 110-ohm impedance to the 50-ohm input of the 273 dB-gain RF
> amplifier.  However no one could meet our specifications.  So we ended up
> using the Western Electric 111C ârepeat coilâ since this device is known to
> significantly reduce Group Delay https://www.jmu.edu/wmra-eng/
> archive/repeatcoil.pdf
>
> To guard against inaccuracies in the eclipse schedule, we agreed to begin
> recording at both monitoring stations at 0301 UTC July 27th, and to
> conclude at 1921 UTC, September 31st.  For the SDRs, 5600 Terabyte storage
> devices were acquired from Best Buy.
>
> Since we will be measuring signals expected to be at the very limits of
> receiver noise performance, we spent a good deal of time thinking about
> continuous battery power since, because of possible eclipse-schedule
> inaccuracies, we donât want to stop the recordings during the above period,
> lest we miss something.  Fortunately we were able to negotiate access to
> the battery rooms of the phone companies at our respective locations.  For
> Nick, thatâs BC Telus (formerly BC Tel; formerly the Victoria & Esquimalt
> Telephone Company and the New Westminster & Burrard Inlet Telephone
> Company) and, for me, the Upsala MN Telephone Company (formerly the Upsala
> MN Telephone Company).  Connectivity to these battery rooms will use
> fabric-covered lamp cord acquired from Mark Connelly.  We believe the color
> of the lamp cord fabric will not impact the Group Delay.
>
> Once the recordings have been made (assuming there really IS an eclipse)
> Nick and I will meet in Salt Lake City Saturday October 7th late afteroon
> to review all the recordings, and we plan to publish our results here and
> in QEX on Sunday October 8th.
>
> Please let us know if you think weâve missed anything in our planning.
> Nick and I are both âelderlyâ and we want to get this eclipse right so we
> donât have to wait for the next one.
>
>
> Cheers!
>
> Mark Durenberger, mobile
>
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