dem doggone bloggin’ blues …

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latency and the pursuit of levity …

Published at Flexradio.com

As I mentioned in another posting, I am not a contester. Indeed … I think contesting is of minimal value and perhaps the bane of amateur radio. However, as an open-minded and accepting ham I realize that others may have opposing sensibilities and also might not appreciate the beauty of AM as I have held onto since becoming a ham in 1964. Different strokes as they say.

The latency threads did hold my interest in the comical vein, and as an engineering mathematician, many nights I lay awake exploring ideas at the extrema. And so, I chuckled as I envisioned the likely scenario of two SDR radios with high DSP latencies working each other. With that thought in tow, I headed to my engineering lab to take some measurements.

To ease the burden of calculations, let’s assume the DX station has no latency or turnaround delays. As shown in this image, once the spoken word ‘over’ radiates to our receiving antenna there is 163ms delay before we actually hear the word ‘over’. We now must introduce the auditory processing time between hearing the word and formulating our response. We can assume it zero for now .. acknowledging that there is an additional delay factor. Ignoring switching delays and as I have stated earlier, there is a reciprocal ~150ms latency in the other direction. That is, we speak and it takes 150ms before our response arrives at the antenna. Approximately one-third second transpires before the receiving DX station hears the first of our reply after their initial call. At my age with my own personal latencies, methinks .5 second would not be an unreasonable delay.

Greater comedy unfurls when you consider that the DX station may be running a similar configuration with associated SDR latencies. An issue? Certainly not for me and non-contesters, but it does exemplify a potential contribution that may be of concern. That, or simply fodder for discussions over a glass or two of a fine red wine.

73’s

dan W7NGA
San Juan Island, Wa.

scope_0

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just Phuket …

vn

aw

Debbie and I are giving our Summer adventure together a twist and heading for Vietnam, Cambodia, Thailand, and Malaysia for seven weeks. Visiting Vietnam has been a dream of mine and it feels good to have finally booked tickets to Hanoi. We’ll visit Sa Pa in the mountains, the islands of Hai Phong, and coastal hop on the train to Saigon (Ho Chi Minh City). From there we’ll visit Angkor Wat on our travels through Cambodia, to Bangkok, down through Thailand, and decompress in Phuket. We’ll finish our journey through Malaysia to Singapore and fly home in style.

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ghosts from the attic …

flight

Be careful of what you look for when digging in the attic. I bought this plane to teach my son how to fly. He had Coast Guard pilot dreams .. and this Cherokee 235 was a real muscle plane with 235 horsepower and state-of-the-art electronic navigation and communications. Those of you that saw my sailboat and all the wonderful systems I installed .. well, you should have seen the plane!

Somewhere in our reality, the flying dreams faded and my son decided to be a drummer instead. I bought him a drum set and he now owns a recording studio in Brooklyn, New York. My daughter has given us the ultimate blessing of three grandsons, and Debbie and I are about to celebrate our 34th year of marriage.

So that’s what I looked like with hair and a 32″ Levi waist?

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first steps …

robolane

Debbie and I are teaching a grades 5,6,7 Robotics class and having a blast. I’ve got my two other helpers (grandsons) assisting me with radio design and stringing up antennas, and Lane is getting his first course in robots.

starting them early in engineering!

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new arrivals …

meandlane

Grandson #3

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Dreamlining to Japan …

dreamliner

on vacation to Japan via 787 Dreamliner

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farewell Jim …

Williams

Jim Williams

Any engineer that has done analog circuit design owes tribute to Jim Williams of Linear Technology Corporation. Engineer extraordinaire .. Jim loved his oscilloscopes as I do.

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