Speaking of "binaural" reception. In this sense it is using a setup that is able to put the lower sideband information in the left ear and upper sideband information in the right ear. As one tunes thru a signal (SSB, or AM or CW with a product detector) it will appear to come from one side , go thru your head and go out the other ear! Some very interesting effects occur in so doing. If you have say an AM signal and it is phase locked to zero beat (true exalted carrier reception), you can very easily hear the selective fading in each sideband independently! One also gets a "sense" about which way to tune to make the signal appear in the right place. It also allows you hear which side of "zero beat" the signal is on. All these effects could be heard using an old General Electric YRS-1 SSB adapter, which was modified to allow "ISB" reception with stereo headphones. ISB reception is REALLY interesting and weird, hearing two programs at once! I don't know if there is any ISB feeders for the SWBC stations anymore, but there used to be. This way one channel could relay two separate programs at once on a single RF channel. Probably redundant now as I'm sure whatever is relayed now is via satellite link! This is just a comment in case someone, somewhere wanted to experiment with "ISB" reception using an ancient GE YRS-1 unit.
73, Sandy W5TVW ----- Original Message ----- From: "Jerry Volpe" <[EMAIL PROTECTED]> To: <elecraft@mailman.qth.net> Sent: Thursday, May 25, 2006 1:35 PM Subject: [Elecraft] Re: Binaural CW Reception | I have done a couple of Binaural CW reception projects and found the | results very appealing. Let me begin by sharing a few thoughts: | | 1. With binaural reception you normally would NOT use tight CW | bandwidths as the object is to allow more audible information to | be processed by our brain. I think that you would want at least 600Hz or | greater. I typically use a 1000Hz type filter or wider but generally | nothing tighter. A stereo 'soundscape' is created within your head with | the primary signal (the one centered in the Binaural filter) appearing | in the center of your head, and the ones higher in pitch progressively | off to one side and the ones lower in pitch off to the other side. | 2. Due to the sound dividing by frequency you notice only the lower | frequency background 'noise' component in one ear and the higher | frequency component in the other. It is surprising how much LESS in | intensity the noise is overall than what it was with combined energy to | both ears. This alone is worth the price of admission. | 3. Many of today's CW operators have not trained themselves to use their | own brain as a CW filter and instead rely on very sharp band-pass | filters for single-signal reception. Binaural CW reception provides | multiple signals which many find too confusing. | 4. Binaural CW reception should be great for NET, roundtable, and even | contesting where you often need to hear many stations on slightly | different frequencies. | | My first project was a stand-alone Binaural CW filter using a pair of OP | Amp ICs. Basically, the audio input passed into both a low pass filter | and a high pass filter with the low and high frequency cutoffs at the | desired center frequency.... 700 Hz for example. The output of the each | filter was further amplified (as needed) and then applied to either | stereo speakers or to stereo headphones. | PRO: Small package. Simple approach. Low cost. Easy to build. Works well | enough for a single design cross-over frequency. | CON: I could have used better quality OP Amps for lower distortion. The | ones I got were from Radio Shack (sigh). Still not bad. Can't change | cross-over frequency. This is OK if your receiver has a fixed CW offset. | Myself, I like to change my offset to minimize long term listening | fatigue. But then again only a couple of my transceivers allow for | that.... most don't. Another CON was the fact that I had to build this | filter. It was amazing to me how many hams were interested in the | project (I posted the info on the Ten-Tec reflector last year) but were | unwilling or unable to assemble a project without a kit. | | I think it would be wise to use two pass-band filters rather than a | low-pass and a high-pass configuration. That way you can also take away | the unnecessary lows... say below 300 Hz and the unnecessary highs | perhaps over 1500 Hz. These filters should not have sharp slopes as that | will add ringing. | | My second project began with the following in mind: | 1. Using band-pass filters rather than low-pass and high-pass. | 2. Include the ability to move the combined filter cross-over for | different CW offsets. | 3. Get the lowest distortion possible in the filtering. | 4. Use something commercially available rather than 'build your own'. | | My first thought was to obtain two SCAF audio filters (highly | programmable as far as band-pass characteristics, no ringing, low | distortion). SCAF filters are not too expensive (you need two) when | found used. I have seen them sell for around $40 to $60 each. However, | before I found the two filters I decided t use another approach using a | 62-band, two channel, Pro Audio equalizer. The one I obtained (for $65 | used!!!) was a practically new Crate LS3-231. With this approach I can | move my cross-over frequency as desired and have good control of the | high and low frequency roll-offs. Distortion is negligible. I would not | recommend this approach with a typical home stereo equalizer as the | filter quality is not good..... the band separation is poor.... and you | don't typically have near enough bands (the Crate has 1/3 octave bands) | to allow selection of the appropriate cross-over frequency.... and I | doubt they hold up well in a high RF environment. Anyway, I am currently | using the Crate solution and it does a great job. Trouble is I want to | use this equalizer for other types of reception so I am continually | reprogramming it. For that reason, and for a bit better cross-over | programmability, I am still planning the simpler approach using two SCAF | filters (as soon as I find what I am looking for at a price I want to pay). | | About DSP filters in this application: | | I know of one commercial manufacture, TimeWave, that includes Binaural | CW reception in their high end DSP filter. I had my suspicions regarding | DSP signal path delays and QSK CW operations. I obtained a TimeWave | DSP599zx and found that the resultant binaural audio was very good but | that the delay was as bad as I had anticipated and unacceptable for QSK | over about 15 wpm. Your mileage may vary. :) Anyway, if you don't use | QSK or you are very casual at speed and you don't mind spending a | sizable sum for one of these filters go for it. Please note that the | actual firmware version in the DSP-599zx is important and that only the | most recent firmware's have the Binaural CW function (or so I was told). | | Lastly, I do know that there are at least one current amateur radio | transceiver with binaural CW reception built in.... perhaps more than | one. I am talking a fairly expensive transceiver (not named) so for me | it wasn't a reasonable path to just for this extra capability when I | would make or configure binaural reception for a lot, lot less. Try | before you buy! | | 73, | Jerry, KG6TT | Fairfield, CA | | _______________________________________________ | Elecraft mailing list | Post to: Elecraft@mailman.qth.net | You must be a subscriber to post to the list. | Subscriber Info (Addr. 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