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Messages - redhat

Pages: 1 [2] 3 4 5 6 7 8 9 10 ... 93
16
Equipment / Re: DRM pirates
« on: July 24, 2020, 2043 UTC »
Most professional DRM exciters, like AM stereo, produce a phase modulated carrier signal and a envelope signal to feed the transmitter.  To produce a compliant signal of sufficient quality to decode, a lot of alignment has to be done in the exciter to compensate for the response and group delay in the transmitter.  I did one trial about 8 years ago.  The signal output by dream can be either I/Q or just the composite waveform.  In my case, the IF input on my upconverter was used to modulate the DRM signal as double sideband.  By the time it fought its way through the amplifier chain I had about 50-75W of DRM power and it was heard by one guy.  It does work, I'm just not convinced of the utility of it with the power levels that most of us play with.

+-RH

17
Yup, you can hear it plainly on FM's too.  I described it as broadcasting from a broom closet, or talking through a paper towel tube.  Its one of the principle reasons I stopped listening to major market stations.  Often the streams are encoded as well.

+-RH

18
Huh? / Re: You Were In Radio, When!!!!!!!!
« on: July 14, 2020, 2339 UTC »
I walked into a small market station in 2000's and they were using alarm clocks to start Otari MX-5050B's to record satellite feeds.  By the time we rebuild their studios, they had a hard disk based logger to time shift things, and real automation.  They were nominated for a Marconi award the next year.

+-RH

19
...In addition, I wonder how they got the approval for less than 50kW. That is the minimum power for SW broadcasting in the US. I actually looked into starting a SW station once and was turned off by the high minimum power requirement.
CFR 47 part 73.751;
Quote
73.751 Operating power.

No international broadcast station shall be authorized to install, or be licensed for operation of, transmitter equipment with:

(a) A rated carrier power of less than 50 kilowatts (kW) if double-sideband (DSB) modulation is used,

(b) A peak envelope power of less than 50 kW if single-sideband (SSB) modulation is used, or

(c) A mean power of less than 10 kW if digital modulation is used.
[70 FR 46676, Aug. 10, 2005]

+-RH

20
I'd like to see a microwave shot across the Atlantic...  My guess is that the accrued latency in passing through the various networks is longer than a direct HF circuit.  If they were smart, they would just run their own fiber across the pond and be done with it.

To me its all a reminder that the game is rigged, and those with deep pockets will find ways to screw the little guy.

+-RH

21
Equipment / Re: The Best Active Loop Antenna 2019 = MLA-30?
« on: July 14, 2020, 2027 UTC »
Plug-in cards were usually used for serviceability, and the ability to add more functions in a limited space.  Look at any piece of professional broadcast gear, processors, routers, and the like all make use of plug in cards.  Most of the film audio equipment I've run across in the past was build this way as well.  Outside of WJ or Harris, this was an uncommon thing in the HF equipment world, as these were all commercial class receivers.  I imagine this was one of the design criteria for the NRD stuff, although I've never had the chance to see one in the wild.

Just a guess....

+-RH

22
Equipment / Re: The Best Active Loop Antenna 2019 = MLA-30?
« on: July 14, 2020, 1804 UTC »
Quote
I don't know about RTL dongles at all, as I have not used them :D, but if you think about NRD545 from this day, you cannot deny that it is a grossly over priced product. What it is - I have had a few NRD receivers myself in the past = the 515, 525 and some of the marine models). They were nothing special or different from other receivers such as Trio R600, R1000 or YAESU FRG7000 in reception ability and quality. And the construction of the NRD radios are externally they are excellent with heavy metal casings, but internally they are just made of plug in PC boards just like your personal desktop computers in the 1980s and 1990s.  Surely these PCBs have been manufactured by automated system in the factories, and all of them depreciated the price to tens and hundreds folds. The personal computers prices plummeted rock bottom from about 20 years ago due to this situation, but the radio prices which used exactly same infrastructure haven;t. They had been priced still premium, and even now they are going for high prices in the used market.  So, if you are aware of this situation, it is natural to feel that their prices sucks compared to other products which uses plug-in PCBoards.

I'm not sure where this axe-grinding has its roots, but it seems unfounded to me.  The 545 was a top of the line receiver in its day, and had a price tag to match.  Because they were relatively rare, they are still expensive.  Plug in cards were the professional way of doing things and keeping the footprint down.  Most everything else from that era was a one-board-wonder, like my R8B.

+-RH

23
I suspect it will be something that looks like DRM but isn't.  In that regard, any sort of COFDM modulation could be used, most likely with LDPC or similar error correction to keep the delays down.

+-RH

24
Equipment / Re: The Best Active Loop Antenna 2019 = MLA-30?
« on: July 11, 2020, 0625 UTC »
FWIW, too many people base 'best' on whatever fits their wallet.  Hams are real bad about that, as are CB'ers.  The other end of the spectrum holds true too.  Just because it costs 10x as much, don't expect 10x the performance.  A friend of mine used to complain of similar devices, "for that much money, it should have come in a gold box, or at least with a kiss."

FWIW #2, I have an MLA-30 and find it to be a fine performing loop for the money in an average high noise suburban environment.  Don't expect miracles, but it seems to work as well as my home-built remote tuned loop.  In a low noise environment, the story may be very different.

+-RH

25
We are in storm season.  Its possible someone took a hit to their array and something got goosed by that electrician in the sky.  I had a Gates 5 take a lightning hit which damaged the tank resonator, and consequently ran like that for a number of years before I found it and fixed it.  Meanwhile the meter readings were always off, and the PA's would blow about once a year.

+-RH

26
General Radio Discussion / Re: Russian Kerosene Powered Radio
« on: July 07, 2020, 2102 UTC »
It is a dream of mine to have a self contained reactor power my transmitter, kinda like Doc Brown's Mr. Fusion :)

+-RH

27
Software / Re: FM broadcast SCA audio from SDR software?
« on: June 29, 2020, 1846 UTC »
Primarily because receivers were not widely available and adding subcarriers does cause degradation to the host stations program audio, as well as loudness loss.  SCA injection needed to run around 20%, and this meant the host stations program audio would have to be reduced by that amount to keep the peaks under 100%.  The commission later added an exception stating that for every percent of subcarrier injection, the peak modulation could be increased by 0.5%.  This means if you are running 20% injection of SCA (or RDS interestingly) your new peak ceiling is 110%.

+-RH

28
Software / Re: FM broadcast SCA audio from SDR software?
« on: June 29, 2020, 0036 UTC »
...I'm wondering if any major FM stations from major metro areas are doing it anymore.

https://youtu.be/fdCkFrde4jQ

When I started in broadcast engineering, some of the local public stations did "books for the blind" using SCA equipment installed at the transmitter sites.

+-RH

29
I'm glad to hear there was a happy ending  ;D

+-RH

30
Shortwave Pirate / X-FM 6285 AM 0250 UTC 28 JUN 2020
« on: June 28, 2020, 0324 UTC »
We are on 6285 KHz tonight with some new music.  Come on in, the water is fine :)

+-RH

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