Your most distant AM DX catches

[davideduardo]

We can add, no doubt, Cuba not having the "oomph" it used to when the Soviets were bankrolling them.

Now the Chinese are bankrolling Cuba's radio infrastructure. Almost all stations have been rebuilt, using a structure of regional transmitting centers where four or even 5 AM stations use a common antenna and share a building. All new solid state transmitters, replacing the Czech junk the Soviets put in.

 

[cyberdad]

Now the Chinese are bankrolling Cuba's radio infrastructure. Almost all stations have been rebuilt, using a structure of regional transmitting centers where four or even 5 AM stations use a common antenna and share a building. All new solid state transmitters, replacing the Czech junk the Soviets put in.

Definitely better equipment than the Czech stuff. And, in most cases, much better audio too. But with more crowded channels, I'd say it's a "wash" here in the Chicago area. Better Equipment versus more crowded channels IME means hearing Cuba is neither more or less challenging than "back in the day".

BUT....at the place where we spend part of our winters on the beach near Pensacola, there are now more Cuban signals audible than previously, especially at night.

 

[gr8oldies]

Definitely a better sound, but I didn't think they were running power levels like 150kW anymore.

Now the Chinese are bankrolling Cuba's radio infrastructure. Almost all stations have been rebuilt, using a structure of regional transmitting centers where four or even 5 AM stations use a common antenna and share a building. All new solid state transmitters, replacing the Czech junk the Soviets put in.

 

[davideduardo]

Definitely a better sound, but I didn't think they were running power levels like 150kW anymore.

There are a bunch of 100 kw transmitters, but the 135 kw Czech transmitters are gone.

There never were any 150 kw stations in Cuba. The ones reported at that level were all the Czech beasts, which could not hit 100% modulation due to design, and could not do positive peaks at any higher level, either. There was on transmitter, the one on 1160 and / or 1180, which was a pair of the Czech rigs combined at roughly 225 kw. Hyperbole in power was a hallmark of the Cuban stations, too.

The biggest issue with the high power Czech rigs was that they tended to go through expensive and crappy Svetlana tubes pretty fast.

I was pitched a "deal you can't refuse" for a number of those transmitters for my stations, and the signing bonus was a paid trip to Moscow and then a side trip to the factory with a guide who likely was assigned by the KGB. They offered incredible financing and pretty much would install the rigs for free... they wanted any excuse to get into the country. The fact that they made this offer to an American indicated, to me, that they were better at ideology than technology. I did not buy one.

 

[wildthangjim]

I started DXing again after a long absence when I moved to Perth Australia in 2012. From my experience there, the level of co-channel interference has the biggest impact on hearing distant signals. Being on the west coast of Australia, when I got up in the morning, all of the other population centers in Australia were in total daylight (depending on the season, the Chinese were too), leaving the dial fairly quiet. Using only a PR-D5 and a Terk loop, I could easily hear, for example, VOA 1530 Sao Tome (7,500mi away), various Middle Eastern powerhouses (~5,000 miles), and Vesti 1413 in Moldova (7,600 miles). Obviously, the 500kw+ power helped, but at other times when the seemingly thousands of Chinese stations and the Aussies were there, it was much more difficult. Despite attempts, I was never able to catch anything from North America - the best time would be around sunset and the dial is crowded then and everyone is running their TV's etc then. I did try when I was near the beach at sunset, but no dice.

Here in Houston where I live now, a bit of a letdown from Perth, with much noisier band conditions. I'm guessing maybe Bonaire 800, at 2100 miles, might be my most distant so far. When I was a teenage DXer in Tulsa in the early 1970's I remember hearing the UK 1215 and a few others during the Monday morning silent period.

 

[pianoplayer88key]

There are a bunch of 100 kw transmitters, but the 135 kw Czech transmitters are gone.

There never were any 150 kw stations in Cuba. The ones reported at that level were all the Czech beasts, which could not hit 100% modulation due to design, and could not do positive peaks at any higher level, either. There was on transmitter, the one on 1160 and / or 1180, which was a pair of the Czech rigs combined at roughly 225 kw.

Ahh, maybe that could at least partly explain why I've never heard the "500 kW" listed stations in Cuba (that is, listed as 500 kW or whatever in the FCC database) -- either they weren't at that power level, or they didn't exist at all. (Also in a few cases I might have local or nearby stations on the same frequency, but not all of them.)

Hyperbole in power was a hallmark of the Cuban stations, too.

Heh, this reminds me of power supplies in the desktop computer (PC) building industry. I'll be simplifying things quite a bit with the basic examples I'll give. (Also I don't fully understand nor could I explain all the minute details in the advanced engineering (which would be beyond the scope of my post anyway) but I do feel like I have enough of an understanding / grasp of more basic concepts to know how to not make a dumb buying decision.)

Anyway .... let's say you have two different PSUs (their abbreviation for Power Supply Unit), both boldly advertised at 600 watts.

PSU A is a cheap one, poorly designed. It can only ever "do" that 600 watts *ONCE* in its entire lifetime, for a split second, like a transient peak / spike on power ... AND, that 600 watts is the power draw from the wall, not the output. (Also that PSU might only have 65% or 70% efficiency.) It might only be able to put out like half that, or even less, continuously for a short time (maybe a year if 8 hours a day, 5 days a week operation), AND only be rated for 25°C, if it's even rated at all. Also, the maximum continuous capacity might be somewhat evenly distributed between 3.3V, 5V and 12V rails (what the internal components draw their power from). Then, when it dies (which might likely be an early death), it takes other PC parts with it.

PSU B is a high quality, well-designed unit. It can do that 600 watts OUTPUT, with like 88-92% efficiency or thereabouts, ALL of it on the 12-volt rail (most modern PCs in the last few years primarily use this for most of their major parts), CONTINUOUSLY, 24/7 for the entire length of the warranty (I've heard of 12-year warranties on a couple models and 10-year on quite a few others), in an environment with an ambient temperature of 50°C. When the unit eventually dies, it dies a relatively peaceful death, and doesn't take other parts with it.

PSU B might be several times more expensive than PSU A, but to me it would be worth it, would pay for itself in lasting a lot longer, and not taking out other components when it croaks. Also most people I know in the enthusiast PC community (or even not necessarily enthusiast level but at least somewhat knowledgeable, beyond the level of "just buy a pre-made Dell or HP or whatever and they'll support me, hold my hand through things") would only call PSU B a 600-watt power supply. I even know of some who look at just the 12-volt rail and quote that as the useful power output. There are some in-between-quality units that while they run almost as well as a hypothetical PSU B (and not have the reliability / safety issues of a PSU A), while it might have 600 watts total output, might have like 540 watts on 12V, so they'd call it a 540-watt power supply. On the other hand, the enthusiasts like to call power supplies like "A" things like "fire starters", "bombs", etc.

 

[channel99]

...........................................

Anyway .... let's say you have two different PSUs (their abbreviation for Power Supply Unit), both boldly advertised at 600 watts.

PSU A is a cheap one, poorly designed. It can only ever "do" that 600 watts *ONCE* in its entire lifetime, for a split second, like a transient peak / spike on power ... AND, that 600 watts is the power draw from the wall, not the output. (Also that PSU might only have 65% or 70% efficiency.) It might only be able to put out like half that, or even less, continuously for a short time (maybe a year if 8 hours a day, 5 days a week operation), AND only be rated for 25°C, if it's even rated at all. Also, the maximum continuous capacity might be somewhat evenly distributed between 3.3V, 5V and 12V rails (what the internal components draw their power from). Then, when it dies (which might likely be an early death), it takes other PC parts with it.

PSU B is a high quality, well-designed unit. It can do that 600 watts OUTPUT, with like 88-92% efficiency or thereabouts, ALL of it on the 12-volt rail (most modern PCs in the last few years primarily use this for most of their major parts), CONTINUOUSLY, 24/7 for the entire length of the warranty (I've heard of 12-year warranties on a couple models and 10-year on quite a few others), in an environment with an ambient temperature of 50°C. When the unit eventually dies, it dies a relatively peaceful death, and doesn't take other parts with it.

PSU B might be several times more expensive than PSU A, but to me it would be worth it, would pay for itself in lasting a lot longer, and not taking out other components when it croaks. Also most people I know in the enthusiast PC community (or even not necessarily enthusiast level but at least somewhat knowledgeable, beyond the level of "just buy a pre-made Dell or HP or whatever and they'll support me, hold my hand through things") would only call PSU B a 600-watt power supply. I even know of some who look at just the 12-volt rail and quote that as the useful power output. There are some in-between-quality units that while they run almost as well as a hypothetical PSU B (and not have the reliability / safety issues of a PSU A), while it might have 600 watts total output, might have like 540 watts on 12V, so they'd call it a 540-watt power supply. On the other hand, the enthusiasts like to call power supplies like "A" things like "fire starters", "bombs", etc.

PSU A probably also puts out a strong signal across the AM band at 100 feet....

 

[pianoplayer88key]

PSU A probably also puts out a strong signal across the AM band at 100 feet....

Yeah, that too. I remember like 20 - 25 or so years ago, we had a PC at my parents house that, when you switched on the PC's power, even before an image was visible on the monitor, there was this nasty squeal across the AM band that was clearly audible even on most local stations way at the other end of the 2100 sq ft house. I don't even think a local 50kW station that was 6 miles away at the time, with something like 300 kW directed at us and audible on speakers that weren't connected to a radio, was immune!

I switched on my desktop PC just now (it was off) and dug out my Eton Traveler III.

A few feet from the front of the case, I can make out traces of what I presume is KSTP on 1500, from just east of San Diego. Of course move closer and it wipes it out.

KNX got buried as I had the radio near the side of the case, but was pretty good at the spot where KSTP was weak. KNX is about the same strength here day and night, with fading being a factor at night.

Putting the radio inside the case does wipe almost everything out, although KFMB (about 8 miles northwest) is still totally copyable through the noise with the radio in direct physical contact with the PSU.

The PSU here is a Corsair AX760, 80 Plus Platinum certified, and with an excellent reputation (but not quite top of the line in its power class), powering an ASRock Z97 Extreme6 motherboard, to which is attached an i7-4790K CPU, GTX 1060 (3GB) graphics card (connected to a 24" Dell U2414H monitor), 32GB DDR3 RAM, an SSD, about 10 or 12 or so hard drives (2 are PATA with a controller plugged into a PCIe slot), etc, housed in a Fractal Design Define R5 case with the side panels off.

I'd say the more modern system is a good improvement in not radiating RFI, although I'd still like to see some further improvement (for example being in direct contact with the device with the cover off, without picking up any interference).