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Author Topic: Caribbean HF 6577 feed  (Read 7776 times)
Rob K
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« on: December 31, 2009, 03:35:24 PM »

Hi,

I usually spend quite a bit of time listening to 6577 via the tuneable radios on another popular site, so it was real nice to see this one added here!

I don't know how to get in contact with the person who runs it, but I'm just wondering why the NYC transmissions seem to fluctuate in terms of loudness?  The flights are VERY loud in all cases but over this past hour or so NYC has gone from being virtually inaudible to speaker-destroying loudness and now back to being virtually inaudible again.

I am well aware of HF propagation conditions and am very familiar with how they can go from one extreme to the other fairly quickly, but the difference was more akin to what you'd hear when switching from, say, an indoor antenna to an outdoor loop/long wire, for example.

I know the blurb says it switches freq every hour (I actually don't think it does on this one), but on all transmissions the flights have mentioned 6577 in the initial call so the 'speaker-destroying' loudness I mentioned was not from a difference frequency.   Not complaining - far from it - just looking for an explanation from the operator on why the huge differences?  I did compare the signal with another online radio and there was no difference in signal from NYC there.

Thanks. Smiley
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dave
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« Reply #1 on: December 31, 2009, 10:41:40 PM »

I run all the Atlantic HF feeds at the moment and they are all fed from the same active antenna.  I expect it was short-term propagation changes, but it sounds kind of odd.  Will take a listen tomorrow.
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Rob K
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« Reply #2 on: December 31, 2009, 11:31:57 PM »

I run all the Atlantic HF feeds at the moment and they are all fed from the same active antenna.  I expect it was short-term propagation changes, but it sounds kind of odd.  Will take a listen tomorrow.

Hi Dave, happy new year to you!

I didn't know you ran the HF feeds actually - thanks for putting them up for us HF nuts!  I've just done some more listening and witnessed the strange behaviour again - if you go to 1630z feed for 31 Dec it starts off with NYC virtually inaudible but ffwd 4 mins to 1634z and 45 seconds and NYC is now banging the needle off the scale  shocked and has me quickly reaching for the vol dial  grin

Just out of interest, what is an 'active' antenna?  Is that another name for a long wire/dipole/inverted-V or something completely different?  Also, do you have ATT or AGC set on?  The sudden difference in signal strength has the sort of feel of the ATT being switched on and off.

How well do you receive NYC on 8918 and 11330?  I think your location up there in NH could be a bit too far north to receive them as those freqs are for the southern half of the WATRS area but it doesn't always follow.

 smiley
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dave
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« Reply #3 on: January 01, 2010, 09:04:31 AM »

Happy New Year as well.  I reviewed the audio and it was definitely a propagation shift.

With current HF conditions New York is only loud here at certain times of the day.  Being in New Hampshire I am frequently inside their skip zone.  While they are not loud, they are almost always audible.  I am not certain, since I only have an old equipment list, but they could also have a directional antenna aimed south/southeast from their Long Island location, but not sure about that - if true, that could put even less energy up this way.  As you know, HF propagation can be crazy and you have to have good ears.  It is not like VHF-AM or VHF-FM communications - but in my opinion far more exotic and fun to listen to, in a different way.

A much better location for this particular feed would be further south, even as far south as South Carolina.  Even Ohio could be better.  Aircraft, on the other hand, are almost always loud.

I verified there is nothing wrong at all with the antenna, so I ruled that out.

AGC is definitely on and set to auto.  But I will double-check that - sounds find on the recording.

An active antenna typically consist of a short vertical whips (~275cm long) connected to a broadband matching circuit and broadband preamplifier.  This type of antenna presents a constant impedance to the receiver across a broad range of frequencies, so it is ideal for listening.  It is not suitable for transmitting since it is not designed for that application anyway.

New York does come in on 11.330 and I am figuring out whether I want to switch between 6.577 and 11.330 or add another spare receiver in on a separate feed or combine the audio - not sure how much collision there would be but I know at times both are active, though not nearly as active as the NAT sectors.

Hope this helps.

-Dave



I run all the Atlantic HF feeds at the moment and they are all fed from the same active antenna.  I expect it was short-term propagation changes, but it sounds kind of odd.  Will take a listen tomorrow.

Hi Dave, happy new year to you!

I didn't know you ran the HF feeds actually - thanks for putting them up for us HF nuts!  I've just done some more listening and witnessed the strange behaviour again - if you go to 1630z feed for 31 Dec it starts off with NYC virtually inaudible but ffwd 4 mins to 1634z and 45 seconds and NYC is now banging the needle off the scale  shocked and has me quickly reaching for the vol dial  grin

Just out of interest, what is an 'active' antenna?  Is that another name for a long wire/dipole/inverted-V or something completely different?  Also, do you have ATT or AGC set on?  The sudden difference in signal strength has the sort of feel of the ATT being switched on and off.

How well do you receive NYC on 8918 and 11330?  I think your location up there in NH could be a bit too far north to receive them as those freqs are for the southern half of the WATRS area but it doesn't always follow.

 smiley
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Rob K
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« Reply #4 on: January 01, 2010, 05:13:23 PM »

Hi Dave,

Yes I concur it must indeed be the propagation but I've never heard it quite as extreme as that before.  I used to get something similar when I had my own HF set-up some decades ago, although not as extreme.  I actually found your post in the 'set-ups' forum showing your equipment and antenna and I originally started out with a similar whip antenna myself.  I am in the UK and had no problem picking up Shanwick and Stockholm (also Berne radio and Portishead radio then too) but Gander, NYC and Maria would all be hard work unless at night time.  This was with a Sony ICF2001D too, which was quite well known for its good filters over other cheaper sets.

I did some experimenting and bought one of those long wire antenna kits and basically bolted it to my upstairs window frame, extended it across my 25ft garden and bolted it to the shed at the other end.  The difference was phenomenal and I had no problems picking up 11300, 5658, 8942 (Singapore) and the Caribbean (8846) on an evening, which are all some distance from the UK.  The only problem was that it picked up a lot more noise as well but the signals were strong enough for it not to be too much of a concern.  Some time later, upon the advice of an HF 'expert', I changed to a horizontol wire loop and that cut out quite a chunk of the noise and I continued with that set-up til I had to move and no longer had the space for it.

I mention all this because as a fellow HF fan yourself (of 30yrs!) you might be interested in ways to improve your 'reach', and as you seemingly have a lot of (low noise) space to play with there in your wooded area, it may be something to look into perhaps.  You would be amazed at the difference a loop - or even normal long wire - would make.  The HF freqs certainly prefer these kind of set-ups over discones and whips.

As far as adding/changing the freqs on the feed goes, I would ask that it remains as is please.  11330 has all the same traffic as 6577 so you wouldn't actually be achieving anything.  Assuming normal daytime hours, flights from say NYC down to the Caribbean islands always start on 6577 until roughly Bermuda latitude, and then they are changed over to 11330 for the remainder of the flight, and vice-versa when they are coming north.  6577 has more traffic overall as that has the flights to and from Bermuda which generally come from the north/east direction and not up from the islands.  8918 is the other 'main' frequency in use through the day and that covers the traffic on the L451 and L452 routes that run SE/NW in the bottom left corner of the WATRS oceanic area.  L451 is JAINS > LETON and L452 is OXANA > GALVN > LNHOM.

The transmitter for the top half of the oceanic area faces SE from Long Island and covers 3455 5550 6577 and 8846.  The transmitter for the bottom half faces SSE and covers 2887 5520 6586 8918 11330 13297.  There is a 17 and 21 meg freq as well, but I've never known conditions to be that bad where they are used.

In terms of frequency usage, from my regular listening to that area you won't go far wrong with these :

2887 - very very rarely heard
3455 - 2100/2200z-0900/1000z
5520 - not used much but only during hours of darkness
5550 - 0900/1000z-1200/1300z and sometimes for a short period in the evenings before 3455 becomes primary
6577 - 1200/1300z-2000z/2100z every day
6586 - 2000/2100z-1200z virtually every night but 5520 sometimes used instead
8846 - only used if there's too much traffic for 6577 to handle.  Sat/Sun afternoons is usually the only time it is used
8918 - 1200-2100z daytime primary for all traffic on the L451/2 routes
11330 - 1200-2000z daytime primary for the southern half of the WATRS oceanic area
13297 - rarely used but sometimes used as an overspill for 11330 on Sat/Suns

6577 is certainly by far the 'best' frequency of the bunch!  grin

Hope you find some bits useful and thanks for providing the 24hr feed!

PS. I have PM'd you on a separate issue.
« Last Edit: January 01, 2010, 05:19:37 PM by Rob K » Logged
dave
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« Reply #5 on: January 01, 2010, 08:47:17 PM »

Excellent into which I didn't have...thanks!
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