AMT 5K....
schematic Included? Yes
Pre Order? He accepted a pre order from me
Cost? $229.95 Plus shipping for indoor unit
will be nice if the AMT5k ships in time for christmas will make a nice present to myself this year 🙂
It all sounds very exciting! A toast! Here's to the success of the new AMT 5000! (ding!)
As to the BE 10 C-QUAM exciter driving the AMT 5K, most professional C-QUAM exciters have two paths of output...the RF output which is the carrier plus the L-R info and 25hz pilot..the second is a standard balanced 600 ohm audio output with the L+R info.
Obviously the audio output of the BE 10 will be easy to interface. Goes into the audio-in on the AMT 5K.
But..what about the RF signal path? Is the AMT 5K going to have the capability to accept RF drive from an outside unit?
Will be interesting to see how it all works out! Let us know!!
RFB
All this talk about C-QUAM stereo has gotten me curious. I know what stereo sounds like, so that isn't what I'm curious about. What I wonder is.....
What are the comparisons with FM stereo as far as technical process is concerned... does it have a sub-carrier that takes up part of the carrier?
Does the signal go farther with the stereo turned off?
When listening in mono, I assume the L+R gets mixed, but is there any way for the mono listener to know a station is sending stereo?
What might be another good question to ask?
Well Carl, I can tell you about AM Stereo.
It does NOT affect Range.
It is compatible with Mono AM radios,
if the station did not tell you it was in stereo the mono AM listener would not be able to tell.
Information on how C-QUAM is used (taken straight of Wikipedia)
QUAM uses quadrature phase and amplitude modulation: the phase of the audio is rotated ahead or behind the carrier and the amplitude of each phase is also changed; thus giving 16 points for reference. The QUAM signal (L-R info) is then phase modulated on the transmitter (the QUAM exciter replaced the crystal in the AM transmitter) and the L+R still modulated the transmitter as it had in the past. C-QUAM is a modified QUAM and thus called Compatible (C- in C-QUAM).
"What are the comparisons with FM stereo as far as technical process is concerned... does it have a sub-carrier that takes up part of the carrier?"
No. AM C-QUAM does not use a sub carrier. AM C-QUAM works by taking the carrier frequency in the early stages within the exciter and produces a main phase carrier and then a second which is 90* of phase to the main. The 90* is then fed into a modulator circuit, which injects a 25 cycle tone and the L-R audio. The 25 cycle tone tells a C-QUAM receiver to activate the decoding, to properly place the L-R info which rides on the 90* shifted phase portion of the modulation envelope, back into proper phase in the receiver in relation to the main L+R phase.
Since the detectors in AM receivers works by decoding the "envelope" as a whole, the detector in a standard mono receiver will properly demodulate the mono L+R despite the 90* shifted phased L-R information. It does not care that the L-R info is 90* phase shifted. The audio still sounds normal because the receiver is looking at the envelope as a whole...not just one phase or one that is 90* shifted or other.
In a C-QUAM capable AM receiver, the L-R info comes in 90* out of phase from the L+R. The 25 cycle tone, picked up on the L-R path, turns on the C-QUAM decoding and locks its phase demodulators to the 25 cycle tone, making the chip see only the L-R information for that path. This chip then re-phases the L-R audio back into phase with the L+R audio path, mixes them together in the chip, and wala.....full stereo audio at the output then fed to amplifiers etc.
"Does the signal go farther with the stereo turned off?"
No. In FM, the pilot signal actually occupies and rides on a sub carrier, which requires borrowing some bandwidth and amplification ability in the amplifier chain from the main carrier. And that is to only turn on the FM stereo decoding circuits!! The actual L-R information, which rides on another sub carrier (38Khz), will rob more bandwidth and amplifier energy from the main carrier as well...thus is why in FM, if you turn off that pilot, you regain the bandwidth and amplifying energy back to the main carrier, and only the 19khz pilot part! To get the full benefit back of the bandwidth AND amplifier capability, you must also kill that 38Khz sub carrier, that is still present even though you shut off the pilot sub carrier!!!
In AM C-QUAM...there is no sub carrier. Thus the range is not affected with the stereo on, or off.
"When listening in mono, I assume the L+R gets mixed, but is there any way for the mono listener to know a station is sending stereo?"
The only way to know, other than calling and ask them or they advertise it, if a station is sending stereo on a standard mono receiver is to run the IF path into an analyzer and examine the 25 cycle tone. This method requires a brick wall filter in the IF circuitry to properly filter out the 25 cycle tone, which is what the C-QUAM decoding chips/circuits have so you dont hear this 25 cycle tone.
Or adapt your mono AM radio with a C-QUAM circuit, tie that into the tail end of the IF path (usually around the 455Khz IF crystal) and then feed the output of that C-QUAM circuit to the stereo audio paths in the amplifier/system.
RFB
It sounded WONDERFUL on my
Sony SRF-A100. Aside from the
fact that is was stereo in the
first place, it had a very full Hi FI
sound. I don't know the specifics.
But I guess diode detection in a
"Regular AM Radio" kind of messes
up the fidelity somehow. But that
was not the case with 1980s AM
stereo. It detected the audio in
a different, better way. It sounded
like FM radio to me.
On another thread a couple of days
ago, we were talking about AM stereo.
I have a 1 kW daytimer on 1220 about
25 miles from here that is still using
C-QUAM. As of a year ago, I could
hear AM stereo from that station on
my Sony SRF-A100. The signal was weak,
but no doubt about it, the stereo was
obviously there. And the separation was
good.
RFB mentioned that some of the new "HD"
radios will receive the C-Quam transmissions
and decode the stereo.
My brother had given me a Radiosophy HD-100,
a small stereo table radio the gets IBOC on AM and FM.
(It is a fantastic FM DX receiver, by the way,
better than some of my good vintage analog tuners.)
I ran and got it a few days ago and with great anticipation,
tuned into the 1220 signal during the day. The HD-100
is on a list of HD radios that get the C-Quam signal.
Something must have happened at the 1220 station.
The signal is MUCH weaker than it was last year.
I could barely hear it at all, so I couldn't test the
HD-100 to see it get C-Quam.
I'll have to get the Sony SRF-A100 to check 1220.
The SRF-A100 works fine, but the front panel is
badly broken and I am trying to put a new front
on that at least will make it look like a radio again.
So the SRF-A100 is on the bench, not in the Dog
Radio Studio 2 shack.
There are lists on the net of stations that are still
transmitting C-Quam stereo, and perhaps some
of the other 1980s AM stereo formats. If anybody
out there has seen these lists, or knows any info
about what stations are still on the air transmitting
this great old mode, please let me know.
Bruce, Dog Radio Studio 2
build a magnetic loop tuned for midband. it should bring in the signal really good. you might have to add antenna terminals to the radio. most magnetic loops are 50 ohm unbalanced cable. regular am loops usually are 300 ohm balanced. the other method is one of those am boosters that were sold in edmund scientific catalog many years ago.
"But I guess diode detection in a
"Regular AM Radio" kind of messes
up the fidelity somehow. But that
was not the case with 1980s AM
stereo."
Actually the limiting factor with AM audio fidelity is the incredibly limited bandwidth in the IF circuits. Receiver manufacturers of standard mono AM radios do not go much beyond 6khz if even that.
Although most of the modern HD radios can decode the C-QUAM AM Stereo standard, there are a few of them that also limit the bandwidth to around 7 or 8Khz. The AM Stereo C-QUAM radios of yesteryear were built to take advantage of the full 10Khz bandwidth, and a few even went a tad beyond that...out to about 12Khz.
Most of the 80's Sony units did in fact hit the 10Khz bandwidth spread. Now compared to FM's cap at 15Khz, your only 5Khz off on the high end in AM C-QUAM with a receiver capable of "opening the bandwidth floodgates" in its IF circuits.
Some of those 80's receivers also included a "Narrow/Wide" function selection so you could choose between the standard narrow 5Khz bandwidth, or the 10Khz bandwidth.
What this all means? Well if you have an AM receiver capable of C-QUAM reception, you will hear something incredible from even a mono transmitting AM station! You will hear its full hi fidelity quality because the C-QUAM equipped receiver is either by default set to see the whole 10Khz bandwidth, or has the selection between Narrow and Wide bandwidth. Hearing a regular mono AM station in wide band mode will knock your socks off!!
RFB
"If anybody
out there has seen these lists, or knows any info
about what stations are still on the air transmitting
this great old mode, please let me know."
Take a look here:
http://users.hfx.eastlink.ca/~amstereo/amsstations.htm
About half way down the page are the US AM C-QUAM stations. Not sure if this is up to date as the site was last updated in April 2001!! :/
RFB
Wow! I had no idea that so many stations were
still using C-Quam back in 2001!
Well you and I and a bunch of other people
can celebrate the wonderful old AM stereo
and keep it alive as long as we tell other
people about it. And people can hear
recordings of it on YouTube.
In your case, you can transmit and receive it,
which is beyond cool.
And yup, I have listened to AM mono stations
playing music on my Sony SRF-A100. They sound
great!
The list gave me one more station to check, WICC,
600 kHz, 1 kW day/night, Bridgeport, CT. It has
a great signal up here in Hartford - it's 30 miles
away - but that low channel of 600 makes for
great groundwave. At night, it's covered up by
a big mess.
By the way, have you ever listened to one of the
jumbly sounding local channels at night on one
of your C-Quam stereo radios? Or maybe on your
SRF-1, which I believe gets some of the other old
stereo transmission formats, such as the Khan (sp?)
system? 1230, 1240, 1340, 1400, 1450, 1490 --
(I know you know what the frequencies are - I just like
listing them!)
Anyway, on those channels at night, the jumble sounds
really weird on my SRF-A100. I can't explain it, it
just is a really weird sound.
And, you probably know that Sony still markets
the SRF-A300 radio in Japan. If I was rich, I'd
have one.
Lastly, when I hear somebody mention Khan,
I still hear Captain Kirk screaming, "KHAN!!!!!"
in Star Trek 2.
But that's just me.
Bruce, Dog Radio Studio 2
Here is the fascinating rule for AM stereo, 73. 128...
http://www.hallikainen.com/FccRules/2011/73/128/
Is it easy to apply all this in Part 15?
"By the way, have you ever listened to one of the
jumbly sounding local channels at night on one
of your C-Quam stereo radios?"
Yep. I believe this is caused by all the night time "skip" from stations piled up on top of each other on those frequencies. Since some of them are "beating" with each other, the "jumbly" sound is two or more stations causing the C-QUAM decoder to literally go crazy, thus the jumbly warbble sound.
In mono receivers, usually what is heard is a sort of "scramble" mix of these mixed mashed signals fading in and out of each other. Sometimes when they fade away, there might be one signal that begins to come in clear, then the skip effect happens and its all a scramble again.
"when I hear somebody mention Khan,
I still hear Captain Kirk screaming, "KHAN!!!!!"
in Star Trek 2."
LOL!! Ya I remember that scene! The Khan-Hazeltine system was a rather weird approach. This one worked by having the lower side bands and upper side bands from center carrier be the L-R platform. This system would allow a listener to use either a single radio for regular mono reception, or two radios tuned slightly off center frequency to get the stereo effect, or a single radio equipped with the Kahn-Hazeltine decoding circuits.
Only problem was that the unwanted effects of whistling, rumbling and incorrect phase correction due to wave propagation would really mess with the audio. It would sound like your speakers were put into a bathtub and listening to sound through the water.."wah-wah" or similar to the very old early stereo audio approach of spinning loud speaker arrays at a certain RPM to get stereo effect..which worked well for a set of speakers, but on a carrier wave subject to skywave and co-channel clutter...it really was problematic.
Today, an off-shoot of that Kahn-Hazeltine system, called "Power Slide" for mono stations. This uses the same approach as the earlier stereo system did by taking advantage of the lower and upper side bands from carrier center. Basically borrowing from one side band to boost the other, thus resulting in increased modulation depth and clarity. This is not to be confused with the NRSC curve as the NRSC is simply applying a band pass filter in the audio chain and does nothing with either lower or upper side bands in a modulated AM signal.
"Sony still markets
the SRF-A300 radio in Japan."
Yep. A very nice and well designed unit. Does anyone know why Sony primarily sells this unit mostly in Japan??
It is not because of a lack of interest or lack of AM Stereo stations in the US or elsewhere. Japan has a very limited number of FM channels. As anyone knows, Japan is not exactly a gigantic land mass, but heavily populated. To make up for the lack of FM spectrum available, the majority of stations on the MW band transmit in C-QUAM stereo!
AM stereo certainly has it's history. A history that goes back to the pre WWII era. The earliest known and documented AM Stereo broadcast was in 1924, station WPAJ (now WDRC AM)by using two MW transmitters on two separate frequencies. And trust me...the stereo separation in that approach would seriously give even today's FM stereo a run for its money! And beat it hands down!!
RFB
"Is it easy to apply all this in Part 15?"
The specifications called for in the C-QUAM standard is applicable to Part 73 gear as well as Part 15. There are only two units that I know of that are fully C-QUAM standard and sold in the Part 15 market.
ASMAX-1/100 exciter/transmitter
Chris Cuff "Alfredo/Alfredo-Lite" exciter/transmitter
Both of these units meet every specification called for in 73.128, though neither of them fall under any certification. In the Part 73 world, your going to be required to use a Part 73 certified C-QUAM exciter just as you would be required to use a Part 73 standard mono exciter.
For Part 15, we refer back to the 3 famous words..."Good Engineering Practices". Naturally one would want their AM Stereo station to sound professional. Both the ASMAX and C-CUFF boards will not disappoint in their performance and specifications.
RFB
Do power lines running 60 hz have any negative affects on a carrier current AM running a c-quam exciter??
"Do power lines running 60 hz have any negative affects on a carrier current AM running a c-quam exciter?"
None that I have encountered. If the CC system is designed properly and installed correctly, the AC hum rejection should also be just as effective in AC hum rejection for a signal transmitting C-QUAM.
So if your CC system running a mono signal has excellent AC hum rejection through a proper coupler such as the LPB TCU-30 coupler or RS CP-15 coupler, that same rejection ratio (3000:1) will block out that annoying AC hum in a C-QUAM signal as well.
RFB