Jay in the Mojave wrote:
This circuit used the 47 light bulbs variable element resistance vs
variable current, as a sound cushion for SSB. Works prett good.

Jay, not sure what you mean by cushion... please explain.

www.telstar-electronics.com

Hello TE:

During the 70's when a lot more SSB activity was on the CB Band, like 16
LSB, (27.155 Mc) and the big rig guys could slide down to 27.150 or even
27.145 with there ham rigs, or modified cb radios. And a bunch of CB
Radio Clubs sprang up. It was great!.

The poor design of the CB radios had a problem when the Squelch was set
to remove the background noise, then a strong SSB station would come
blasting in actually hurt your ears, you couldn't hear the far away SSB
stations, as you needed to turn up the Volume to hear them, hoping a
near by strong SSB station didn't come in blasting you out of your
chair. The AGC in the receiver was at fault.

The Sonic Cushion would allow the far away stations, and not so loud
stations, and Loud Stations to have closer audio levels going to the
speaker. So that you are not constantly adjusting the Volume Control up
and down. It was a real problem.

There where trick audio buffer amplifiers out there and they worked quit
well. But you had to be with a group or the in crowd to have access to
one of these constant Volume Buffer Amplifiers.

So many of these Sonic Cushions where sold at CB Breaks, and even CB
Stores. It is pretty clever. It uses the variable resistance of a GE 47
light bulb element as the audio cushion.

The audio from the radio is feed across the end terminals a 25 ohm, 2 or
3 watt Pot. The ground and wiper is then feed to the GE 47 Light Bulb
and speaker. The GE 47 Light Bulb is in series with the speaker coil.

The Radio Volume is turned up to say half way or even more. The Sonic
Cushion is then adjusted to allow a nice comfortable listening level.
The light bulb lights to the radios audio output, and of course brighter
for loud SSB stations, which the light bulb has more resistance when
more current is flowing thru it, and less resistance when a lower
current is flowing thru it, then leveling the audio voltage feed to the
speaker.

I have a Heil DSP External Speaker, connected to a Icom Pro 746 Radio,
and it could use a slight degree of audio leveling, or cushioning. For
SSB and CW. Its a big help when the beam gets turned around and
different stations come crashing in.

Jay in the Mojave


Telstar Electronics wrote:
Jay in the Mojave wrote:

This circuit used the 47 light bulbs variable element resistance vs
variable current, as a sound cushion for SSB. Works prett good.


Jay, not sure what you mean by cushion... please explain.

www.telstar-electronics.com

Jay... good explanation. Do you feel the audio AGC in todays radio has
been improved to the point where you don't need such a device?

www.telstar-electronics.com

Hello TE:

Yep I sure do.

Not only do they need a good tracking AGC, but a variable audio level
control that would adjust the audio levels from all stations the same or
at least with in a few dB of each other. A Automatic Level Amplifier
can't be to hard to run down off the net.

The Sonic Cushion does a very good job with all this. Worth the parts
and time to experiment with. With the rigs DSP (Digital Signal
Processing) Noise Reduction, digital filters, attenuator, and nose
blanker, the addition of a sonic cushion will also help, I think.

By being able to rotate the beam away from atmospheric noise and
unwanted stations is also a big help. The use of the beams rejection and
rigs attenuator and filters, its amazing what unwanted stations signals
can be put in the noise. Even loud and strong local signals!

The Moonraker 4 has a 45 dB null 110 degree's off the front of the beam,
by turning the beam null to the unwanted signals direction will drop em
like fly's.

Jay in the Mojave


Telstar Electronics wrote:

Jay... good explanation. Do you feel the audio AGC in todays radio has
been improved to the point where you don't need such a device?

www.telstar-electronics.com