WA3VJB and W3GMS recordings - 20 kHz bw

[WB4AIO]

Here's an mp3 of Paul, WA3VJB the other day on 7290 kHz as heard on my Racal RA6790/GM in its widest -- 20 kHz -- bandwidth.

Although my urban Charlottesville location adds some noise and my receive-only antenna is far from optimal, Paul's Collins 300G still impresses with its round, dense, satisfying sound. It's not often I get to use the 20 kHz filter. It's great to hear a transmitter that I worked on many years ago (when it emitted 1 MHz waves instead of 7 MHz ones) on the air again and sounding better than ever.

http://liberty.3950.net/WA3VJB%207290%2020k%20bw%2020110320%200317PM%20ET.mp3

And here's another recent 7290 recording -- this one of Joe, W3GMS. (Joe, you dropped the 'A' from your call -- why not drop the '3' too and take on the actual old 'Good Music Station' callsign from Washington radio history?)

Although a local plasma TV created some interference, the fantastic down-to-almost-DC frequency response of Joe's rig (that makes any speaker sound better than an original Advent) comes through great in the Racal's 20 kHz position.

http://liberty.3950.net/W3GMS%207290%2020kHz%20bw%2020110321.mp3

All the best,

Kevin, WB4AIO.

[WA3VJB]

WOw, Kevin, thank you!

One thing I notice on your Racal is the lack of audible effects from your AGC, which lets the dynamic range of the modulated signal stand on its own.  On the R390A, for example, when I use "Fast" AGC it adds a significant amount of compression to the signals I monitor, and usually it's not an improvement.

The audio processing on that QSO was the Pacific Recorders & Engineering pair, dating back to the early 1970s. The AM MultiMax and Multilimiter.  I can hear some blower whine in there, and I see it on the scope.  A couple of guys running the 300-G have actually turned off the squirrel cage blower since everything runs so nominal anyway.  The mic is a cardoid and the tail null is aimed at the transmitter so it attenuates it some.

Mic was the EV RE27 into the RCA Type 76 console into the PR&E, into the 300-G.

I think the only recording that comes close to yours has been a synchronous detected Flex 5000 recording I got in the mail a while ago.  Deals with that QSB nicely.

[WB4AIO]

WOw, Kevin, thank you!

One thing I notice on your Racal is the lack of audible effects from your AGC, which lets the dynamic range of the modulated signal stand on its own.  On the R390A, for example, when I use "Fast" AGC it adds a significant amount of compression to the signals I monitor, and usually it's not an improvement.

The audio processing on that QSO was the Pacific Recorders & Engineering pair, dating back to the early 1970s. The AM MultiMax and Multilimiter.  I can hear some blower whine in there, and I see it on the scope.  A couple of guys running the 300-G have actually turned off the squirrel cage blower since everything runs so nominal anyway.  The mic is a cardoid and the tail null is aimed at the transmitter so it attenuates it some.

Mic was the EV RE27 into the RCA Type 76 console into the PR&E, into the 300-G.

I think the only recording that comes close to yours has been a synchronous detected Flex 5000 recording I got in the mail a while ago.  Deals with that QSB nicely.

I've modified the audio stages in the Racal and they're good down to 30 Hz. To get better I'd have to go transformerless. The 600 ohm line feed goes straight into the sound card.

Thanks for the kudos on the AGC. I've modified that, too, but it's a work in progress. I've slowed it way down from Racal stock and made it so SSB AGC is peak-controlled (as always) whereas AM AGC is now average-controlled. But it still responds to ultra-low frequency peaks, like popping a microphone, so I am still working on it.

There is an AGC "hang" circuit that prevents any but glacially-slow recovery while a strong signal is present and up to a second after the signal drops out. That's why the transmitted audio isn't compressed very much. I like that feature.

The Racal’s synchrodyne AM detector is very interesting and reasonably high fidelity (as long as the AM station being received does not hit the 100% modulation baseline). When a station hits baseline it generates distortion like a diode detector does -- but with the additional flaw of the distortion bandwidth _not_ being limited by the IF filter. I need to make a better detector for it some day.

Your audio chain sounds great! I used to use a modified Multimax into an RCA BA-146 limiter.

73,

Kevin, WB4AIO.

[WA1GFZ]

Take a look at the K2CU detector.
Racal detector needs a carrier source. Without it the carrier signal out of the 1357 gets very dirty. So when you hit baseline the distortion source is the cruddy carrier and noise demodulated in the 1496. I've considered a VCXO at 455 KHz locked with an XOR gate out of the 1357 output. This way when you lose carrier the XOR goes to 50% duty cycle and carrier continues.
I also like the long AGC setting for Hi Fi out of my RA6830 but fast helps a lot when there is static.
The Racal 16 KHz if filter is pretty nice if you can locate one. It is an LC filter not crystal. They show up on epay once in a while. This will reduce the noise in the radio.

[W3GMS]

Kevin,

Many thanks for the good sounding playback of GMS Radio!  Yes, about 10 years ago I dropped the "A".  Your right, if I could drop the "3" and get WGMS that would be a real blast.  During my working days at Unisys, I would often stream WGMS when it had its classical format. 

I think I will leave the audio chain alone based on your playback

Regards,
Joe, W3GMS 

[k4kyv]

Grrrrr! Them goddam AMers are 20 kc's wide!!!!   


 

[flintstone mop]

Only when band conditions warrant, I'll go to a wider BW. The sample from Paul wudda been 6kc and I would have opened it a little more for Joe. The distant SW B'cast and the adjacent stations would have stopped me at 6kc.
It makes me think that I was not tuned on center. Some folks tune off center to get more sibilance. Might be receiver BW or hearing loss.
Too much loud distorted music in those early years for some. Broke off too many hairs in the canals. I'm still good to 13kcs.
Fred

[WB4AIO]

Take a look at the K2CU detector.
Racal detector needs a carrier source. Without it the carrier signal out of the 1357 gets very dirty. So when you hit baseline the distortion source is the cruddy carrier and noise demodulated in the 1496. I've considered a VCXO at 455 KHz locked with an XOR gate out of the 1357 output. This way when you lose carrier the XOR goes to 50% duty cycle and carrier continues.
I also like the long AGC setting for Hi Fi out of my RA6830 but fast helps a lot when there is static.
The Racal 16 KHz if filter is pretty nice if you can locate one. It is an LC filter not crystal. They show up on epay once in a while. This will reduce the noise in the radio.

Thank you, Frank, for the informed suggestions. I don't know when I'll get around to working on the Racal some more, but I have saved your messages in the mods file on my hard drive.

I am actually using the nominal 16 kHz filter. But its rolloff is so gradual, at least at first, that the receiver's internal tests (and my own tests) classify it at 20 kHz.

Thanks,

Kevin, WB4AIO.

[WB4AIO]

Kevin,

Many thanks for the good sounding playback of GMS Radio!  Yes, about 10 years ago I dropped the "A".  Your right, if I could drop the "3" and get WGMS that would be a real blast.  During my working days at Unisys, I would often stream WGMS when it had its classical format. 

I think I will leave the audio chain alone based on your playback

Regards,
Joe, W3GMS 

Yes, your audio is very good-sounding on every listening setup I use, from a Sennheiser headset (best), to a little FM table radio that I use in another room fed by a mini transmitter in my main office.

I was only half kidding about the Advents. You have a low end that sounds generous on a good 3" speaker but even better -- but not boomy -- on a hi-fi system. What's your audio chain? Is it the same chain on all your transmitters?

All the best,

Kevin, WB4AIO.

[W3GMS]

   
Kevin,

Yes, I have a common audio chain.  Here is the sequence from Mic through to the transmitter: 

RE-27

Symetrix 528E where I only use the gain riding AGC feature.  Between 3 and 6db of compression.

ART 2/3 octave EQ  250 Hz -12 db down, 4 KHz + 5db boost, everything else flat.

Audio Arts Wheatstone R-17 Board

ATI 16 channel D.A.

Inovoics 222 negative peak limiter

The settings have remained the same for many years!  I tried to get the parametric EQ in the 528E to sound exactly like the ART Graphic EQ.  I managed to get it close but not exact, so in the end, I stuck with the Graphic EQ. 

Thanks very much for the compliments on the signal.  I remember your AM sound from years ago, and it was some of the best sounding audio on the band. So a compliment from you means a lot. 

Regards,
Joe, W3GMS