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W1PJE USA flag USA

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Ham Member Lookups: 250

 

Professional:

I am an assistant director and head of the Atmospheric and Geospace Sciences group at Haystack Observatory, operated by Massachusetts Institute of Technology (MIT).  Haystack is located approximately 42 km as the crow flies from the main MIT campus on a 1300 acre parcel overlapping the towns of Westford, Groton, and Tyngsboro, MA (grid FN42go).  Since the late 1950s, Haystack has conducted frontier research into the properties of the near-Earth space environment, including the ionosphere, neutral atmosphere, overlying plasmasphere, and the magnetosphere that surrounds our planet.

I am a member of Nashoba Valley Amateur Radio Club (NVARC), a physical as well as spectral neighbor of Haystack.  Outreach programs and activities are being designed between Haystack and NVARC; stay tuned for more information.

I am also a member of the HamSCI citizen science initiative.

I'd like to credit Skip Youngberg K1NKR for the initial contact that is leading to significant Haystack-NVARC collaborations.

My professional page is here:  

http://www.haystack.mit.edu/~pje

 

Radio outside of work:

Vintage Department:

Here's my first SW receiver (valve based as the British would say).  It's a National NC-125 early to mid 1950s vintage general coverage unit (with octal plug in back for an outboard narrowband FM receiver!).  I learned quickly not to get a bad shock from the uninsulated jumper wire across the octal plug.  Our family acquired it in the mid 1970s.  The "Select-O-Jet" adjustable audio notch/boost filter didn't really work nearly as well as a dedicated IF selectivity crystal based filter, but it was OK and made interesting howling noises with the wrong settings.  Not quite pristine condition either as the AF switch on the volume knob left the planet years ago and was replaced by a red toggle switch.  This radio still works and has a nice sound.

National NC-125 front panel

For entertainment, working out the receiver specs shows that it's perhaps not the best receiver on the planet nowadays, and shows how far we've come.  This December 1952 QST ad ("What a Dial! What a Receiver! What a Value!") quotes 3 microvolt sensitivity for a 10 dB SNR, which works out to 1.3 uV at SNR = 3 dB assuming 500 Hz bandwidth (i.e. MDS=-99 dB).  A minimum figure to ensure we are not internal noise limited is 0.5 uV.  In fact, today's best receivers with preamp engaged are at 0.1 uV for SNR = 3 dB (-124 dB) at 500 Hz bandwidth, which beats that by 24+ dB or over 4 S-units.  

Another way to put it: this receiver is internal noise limited rather than sky noise limited on SSB for all bands > 80 meters.

Cost = $149.50 in 1952 (equivalent to $1,375 in 2017!).

Lifting the cover reveals lots of familiar items to older ops - 5Y3GT rectifier, 6SG7 amplifiers (one RF, two IF), 6H6 dual diode detector, the usual IF cans.  National thoughtfully labeled all the sockets.  Sorry about the dust.  

I'm also partial to the valve based Hallicrafters SX-110 receiver that I used at a family member's place, but no photos of that one yet (which again still works).

Update June 2017:  

My local club (NVARC) had a nice Field Day in Heald Orchard, Pepperell, MA.  I'm shown here with Skip K1NKR using my "I'm concentrating" face working an Icom IC-746 on a very active 6 meter band, and learning how to do this contesting thing.

Update August 2017:

I assembled a narrow ~500 Hz audio CW passive filter - only Ls, Cs, and transformers - with Ed Wetherhold W3NQN's help, from Jim Tonne W4ENE's design.  eHam review here: http://www.eham.net/reviews/detail/58 .  This is truly a spectacular audio filter; highly recommended.  Here's the plot of the frequency response:

 

8274072 Last modified: 2017-08-15 13:01:01, 4955 bytes

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