10112	2014-06-29 11:13:28	Chris Howard w0ep	free: noise blanker article delay device
Message	Date	From	Subject
http://home.earthlink.net/~christrask/Noise%20Blanker.pdf Referenced in the above URL is an article by Chris Trask containing a design for a noise blanker. At one time I was thinking of building this and I called suppliers to find the Delay Data Devices 1515-100A delay line specified. It seemed that the piece was no longer available but there was still a sample rolling around (or so I recall). And they sent it to me. But I have never built the thing and I'm starting to feel guilty that I have the last piece and am not using it. If anyone wants this thing in order to build the noise blanker, let me know and I will send it to you. (If it is not cost prohibitive to do so.) Chris Howard w0ep Columbus, MS
10113	2014-06-29 11:48:15	Chris Trask	Re: free: noise blanker article delay device
> >http://home.earthlink.net/~christrask/Noise%20Blanker.pdf > >Referenced in the above URL is an article by Chris Trask >containing a design for a noise blanker. > >At one time I was thinking of building this and I called >suppliers to find the Delay Data Devices 1515-100A >delay line specified. It seemed that the piece >was no longer available but there was still a sample >rolling around (or so I recall). And they sent it to me. > Lucky you, but a bummer for future builders. I was concerned at the time I designed that as I knew from past experiences that using any part that was from a sole supplier could potentially jeopardise the design if the supplier chose to discontinue the part. Most of my experience along that line came from using unique parts from Motorola, who was notorious for stopping production of all sorts of devices after lots of people had designed them into manufacturable products. Even now, as the highly regarded MPS6521 and MPS6523 devices were discontinue by ON Semiconductor (inherited from Motorola) with no replacement available. Fortunately, Central Semiconductor is now supplying the MPS6521, but the MPS6523 has yet to be made available. Those are my favourite devised for linear HF circuitry as they are basically the 2N2222 and 2N2907 with twice the current gain. It's odd that those devices were never available in SMT. That would have kept them alive. As for the demise of that 1515-100A from Delay Data Devices, a suitable length of low-loss coax can be substituted, though it will be a bit larger. Maybe more than just a bit. Chris Trask N7ZWY / WDX3HLB Senior Member IEEE http://www.home.earthlink.net/~christrask/
10115	2014-06-29 13:26:54	David	Re: free: noise blanker article delay device
I think some FM two-way radios used a similar circuit to remove the burst of noise from the loss of quieting after the transmitter shut off. An easier way however was for the transmitter to drop tone coded squelch before shutting off. CCD delay lines were used in the receiver for this but I always thought it would be trivial do duplicate that function in one package at audio frequencies with a microcontroller that includes enough RAM, ADC, and DAC. On Sun, 29 Jun 2014 13:13:25 -0500, you wrote: >http://home.earthlink.net/~christrask/Noise%20Blanker.pdf > >Referenced in the above URL is an article by Chris Trask >containing a design for a noise blanker. > >At one time I was thinking of building this and I called >suppliers to find the Delay Data Devices 1515-100A >delay line specified. It seemed that the piece >was no longer available but there was still a sample >rolling around (or so I recall). And they sent it to me. > >But I have never built the thing and I'm starting >to feel guilty that I have the last piece and am not >using it. > >If anyone wants this thing in order to build the >noise blanker, let me know and I will send it to you. >(If it is not cost prohibitive to do so.) > >Chris Howard >w0ep >Columbus, MS > >
10118	2014-06-29 14:40:10	dx11	Re: free: noise blanker article delay device
In every analog European color TV receiver of the PAL standard there is a delay line of 64 microseconds. This is the time it takes to write one image line on the screen in the PAL format (625 lines, 25 full frames per second). These work with the demodulated video signal that has a bandwidth of 5MHz. Whether they work beyond 5 MHz I don't know. After having seen an article on the use of one of these in a noise blanker about 30 years ago I have always kept one in my junk box for a rather vague plan for a project with it. An IF-strip below 5MHz with the delay line in it should be feasible. I suppose they must still be for sale as a spare part, but that may fade out rather soon I am afraid. Cor Beijersbergen PA4Q -----Original Message-----