Author Topic: HF Car-A 6557/5550 status  (Read 7012 times)

Offline InterpreDemon

  • Hero Member
  • *****
  • Posts: 514
HF Car-A 6557/5550 status
« on: April 10, 2013, 12:31:54 AM »
For the SelCal police out there, I thank you for your interest in this new feed, thought I would bring you up to speed on issues and plans, and plead with you to address your concerns directly to me instead of Dave who, though extremely competent, handsome and physically adept does not have the ability to reach down from New Hampshire and tweak an R-390 tuning knob in Connecticut.

First, this equipment is approaching sixty years of age and though state of the art in its day and until surprisingly recently, it does not benefit from modern PLL stability. Thus even if I were to turn on the crystal and PTO ovens in the two receivers (which I will not do due to heat, reliability and safety issues) the CV-157 sideband converter they both feed lacks the thermal stability to maintain it's LO frequency within 20 Hz, thus temperature variations of -5 to +10 degrees in the shack will have their effect. I do endeavor to keep the three devices netted as best as possible, but if I leave for the day and things heat up... things will drift. Further at 5-10 mHz the Doppler shift alone can be +/- 5-10 Hz for the aircraft, so the only way to net is via my generator when no transmissions are present and most accurately by zero beat when a SelCal is transmitted. The 6577 receiver is never changed, however I do re-tune the 5550 receiver to 8846 during the day if I am around. So that's the story at present... I'll do the best I can.

However since I do get pretty good, reciprocal reception from this location that closely approximates that of the ARINC NY ground stations and the frequencies are active 24/7, I have decided that making this feed permanent is a worthwhile endeavor, so I am in the process of assembling four to five suitable, identical, inexpensive, sand-state, PLL controlled receivers that I have qualified and that I can modify to operate in at least double or triple diversity, the aim being to cover all the Car A frequencies used in my coverage area, 3455, 5550, 6577, 8846 and 11396 throughout the day incrementing three of the five radios on adjacent frequencies up and down on a schedule, from 3455/5550/6577 at 2AM, to 5550/6577/8846 at 8AM, to 6577/8846/11396 at 2PM, to 5550/6577/8846 at 8PM and then repeating. Hopefully they will work as well in diversity mode, which is key, and sound almost as good as the vintage equipment, but at least I will not have to nursemaid the tuning or kick on the A/C this summer. The biggest problem is that the front ends of these solid state receivers are about as selective as a pig's diet, so I will have to brew up some very tight filters for each receiver. In addition I have decided to rebuild the 60m dipole into a trap dipole sharply tuned for at least 5550, 6577, 8846 and possibly 11396, which should definitely improve the reception on the two upper frequencies during the day.

My apologies for the long winded, to some incomprehensible rambling, but that is the price you pay if you were so foolish as to read this far :-)

Feed Purveyor:
(KJFK) NY DEP Liberty East
HF CAR-A  3455/5550/6577/8846/11396
HF ARINC LDOC  6640/8933

Complaints should be addressed to: City Hall

Offline RonR

  • Moderator
  • Hero Member
  • *****
  • Posts: 917
Re: HF Car-A 6557/5550 status
« Reply #1 on: April 10, 2013, 11:37:31 AM »
Hey ID, I have to say I was "foolish" enough to read through the whole thing!  :-D  It was worth reading as you have a way with words...  "selective as a pig's diet"?  That one had me rolling!

But seriously, thanks for all the effort.  I hope you have more success with the reception of the higher freqs during the day like 8918, 8846, 11396, etc...I've never had too much luck with those freqs.  I would definitely be a listener!

Feed Provider:
NY App (Liberty/North)