Audio Output Comparison: Analog vs. Digital vs. Analog-Digital Speakers

Ghot · Friday at 1:20 PM

bobkn said:
Nah.

Not even close.

Before GPS there was LORAN. (Long Range Aid to Navigation).
The military could buy whatever they wanted. They bought McIntosh 275's

Our signal had to be accurate to ten to the -15th seconds.
No other amp could handle that.

You got EXACTLY what you put in, for the output, except amplified. Zero distortion.

HeavyHemi · Friday at 3:18 PM

Ghot said:
Not even close.

Before GPS there was LORAN. (Long Range Aid to Navigation).
The military could buy whatever they wanted. They bought McIntosh 275's

Our signal had to be accurate to ten to the -15th seconds.
No other amp could handle that.

You got EXACTLY what you put in, for the output, except amplified. Zero distortion.

Ehhhh... the 275 from 1961 (quite some time after the introduction of LORAN) is an audio amp, not suitable for transmitting radio signals at 100Khz and higher. Even the earliest LORAN transmitters operated at thousands of watts.

Ghot · Friday at 4:45 PM

HeavyHemi said:
Ehhhh... the 275 from 1961 (quite some time after the introduction of LORAN) is an audio amp, not suitable for transmitting radio signals at 100Khz and higher. Even the earliest LORAN transmitters operated at thousands of watts.

We used them as pre-amps.
The LORAN A transmitters put out 160kw, and LORAN-C transmitters could do anything from 200kw to 2MW.

And I was almost out of the service before LORAN D came about.

bobkn · Friday at 5:00 PM

Ghot said:
Not even close.

Before GPS there was LORAN. (Long Range Aid to Navigation).
The military could buy whatever they wanted. They bought McIntosh 275's

Our signal had to be accurate to ten to the -15th seconds.
No other amp could handle that.

You got EXACTLY what you put in, for the output, except amplified. Zero distortion.

It was a joke. Futterman was crazy. (Vaccum tube amp with no output transformer.) I don't know anything about the distortion numbers of his hand-made amps.

I'm not knowledgeable about LORAN. But its accuracy didn't require femtosecond (1E-15 second) precision. The Wikipedia article mentioned 0.15 microseconds for an improved version. But what's 8 orders of magnitude among friends?

(Light travels about 0.3 micron in vacuum in a femtosecond, or about 1/2 wavelength of orange light.)

What utility did an audio amp have for an RF nav aid?

Ghot · Friday at 7:24 PM

bobkn said:
But its accuracy didn't require femtosecond (1E-15 second) precision

We used Cesium Oscillators to build the signal that we transmitted.
They had to be accurate to the femtosecond.

On the users end, we only had to be accurate to the millisecond.
There was a lot of attenuation due to atmospherics, so our signal had to leave our antennas with very high accuracy.
Which is why we built the signal with timing pulses with femtosecond accuracy.

If you want to read accurate information, try here...

https://navcen.uscg.gov/loran-c-specification

bobkn · Friday at 7:57 PM

Ghot said:
We used Cesium Oscillators to build the signal that we transmitted.
They had to be accurate to the femtosecond.

On the users end, we only had to be accurate to the millisecond.
There was a lot of attenuation due to atmospherics, so our signal had to leave our antennas with very high accuracy.
Which is why we built the signal with timing pulses with femtosecond accuracy.

If you want to read accurate information, try here...

https://navcen.uscg.gov/loran-c-specification

Looked at the first few links. All were 404. Was the coast guard DOGE-d?

Cesium oscillators were commonly called atomic clocks by us laymen, if memory serves.

The microwave frequency of the cesium clock seems to be about 9GHz. One cycle is roughly 100 picoseconds, or 1e5 femtoseconds. I have no idea whether NIST or others could divide one cycle that finely.

The transmitter had to be 12 orders of magnitude more precise than the receivers? In my ignorance, that makes no sense to me.

Ghot · Friday at 8:11 PM

bobkn said:
The transmitter had to be 12 orders of magnitude more precise than the receivers

No.
The transmitted signal had to be accurate to microseconds, so the received signal could be accurate to milliseconds.

There were no satellites involved. The transmitted signal bounced off the ionosphere.
As I mentioned, there was a ton of attenuation to the signal.

bobkn · Friday at 8:17 PM

Ghot said:
No.
The transmitted signal had to be accurate to microseconds, so the received signal could be accurate to milliseconds.

There were no satellites involved. The transmitted signal bounced off the ionosphere.
As I mentioned, there was a ton of attenuation to the signal.

So why did you mention femtoseconds?

You needn't answer. I'm out of this thread.

Ghot · Friday at 8:22 PM

bobkn said:
So why did you mention femtoseconds?

You needn't answer. I'm out of this thread.

Like I mentioned above... we "built" the signal we transmitted from scratch.
The timing pulse we used came from a Cesium Oscillator that was accurate to the femtosecond.

Here's a pic of the LORAN-C pulse that we transmitted...

And here's a pic of the Cesium Oscillators we used...

Audio Output Comparison: Analog vs. Digital vs. Analog-Digital Speakers

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