April 2018 Club Meeting - Digital Mobile Radio

Friday, April 20, 2018

7:00pm MST

Ascension Lutheran Church 1220 West Magee Road, Tucson, AZ

 


 

Handyman Corner

By Tom, W8TK

 

Kit of the month: To be announced

Project: To be announced

 


 

DMR 101

Digital Mobile Radio

What you need to know

 

Presented by Bob Molczan, KA7VPR

Click here to download the presentation

 

Are you a New Ham with a Technician license just itching to QSO with others across the country or around the world? Are you a Ham with HF privileges that lives in an HOA with antenna restrictions? Are you turned on by the thought of being able to communicate worldwide with a 1 watt Handi-Talki while sitting in your favorite chair in your living room? If any of these situations sound like you then DMR is your savior!

Digital Mobile Radio has been around for years in the commercial radio industry, and has only become available to Amateurs over the last several. Radio equipment prices have come way down from the once only available commercial gear from companies like Motorola. Today’s Ham can jump on the fastest growing Digital Voice mode for slightly over $100. How exciting is that?

If you are now saying to yourself “I need to know more”, then my presentation at the April OVARC membership meeting is the place to be. I will fill you in on the history of DMR as well of the basics of how to get started, and where it will take you. If you love technology and are ready to try new things, make sure to join me.

 Click here to download the presentation

March 2018 Club Meeting - Noise Origins, Effects, and Mitigation Strategies

 

Friday, March 16, 2018

7:00pm MST

Ascension Lutheran Church 1220 West Magee Road, Tucson, AZ

 


 

Handyman Corner

By Tom, W8TK

Kit of the month: To be announced

Project: Cable Management

 


 

Click here to download the presentation in PDF format.

 

Noise

Origins, Effects, and Mitigation Strategies 

 

Presented by Jim Duffey KK6MC (Cedar Crest, NM)

 

Noise is the fundamental limitation for reception of signals. With the recent proliferation of wireless and RF based devices and switching mode power supplies/converters in modern electronic devices, the problem of noise to the radio amateur has increased over the past decades. I will discuss the origins of the noise we hear on the ham radio bands, the expected levels of noise as a function of frequency, time of year, and location. The noise we hear in our receivers has many origins; there is cosmic noise which is generated by galactic and intergalactic sources and has a well-defined noise power spectral density decreasing with frequency, there is man-made noise generated by a variety of appliances and transmission line sources, there is noise generated by atmospheric storms, noise generated by solar storms, and lastly, internal noise generated by our receiving devices themselves, which ultimately limit our receive capability. While industrial locations generally have the greatest noise, urban and suburban locations can have very high noise as well and sometimes the only low noise locations that can be found is in a very rural location, miles from civilization.

Strategies for mitigating noise at the receiving location will also be presented. These strategies involve using narrower bandwidth filters and modern digital modes that provide some immunity and robustness to noise, using the noise limiters and blankers built in to our rigs to reduce noise levels, elimination of common mode currents on antenna transmission lines, and substitution of linear power supplies (wall warts) for switching supplies.

Jim’s Background:

Jim was first licensed in 1965 as WN0MWN, upgrading a year later to WAØMWN. As a Novice he dabbled in VHF with a Heathkit Twoer and a three element beam from “Understanding Amateur Radio” whose feed system bore a striking resemblance to the present day WA5VJB easy Yagis. The Twoer, with that antenna, was capable of QSOs out to 60 miles! He held the call N7ATB in Utah and received the present KK6MC call in California. Jim’s primary amateur radio interests are VHF/UHF/microwave operating and experimenting, contesting, antennas, and QRP. He is an avid rover in both VHF/UHF contests and state QSO parties. He is one of the founders of the New Mexico VHF Society. He was honored with the 2015 W3IY Rover Recognition from the Mt. Airy VHF Radio Club and in 2007 he was elected to the QRP-ARCI Hall of Fame.

KK6MC holds a PhD in solid state physics from the University of Nebraska. He earlier received a Bachelor of Science degree in Engineering Physics from South Dakota State University. After a two year postdoctoral fellowship in the University of Utah Physics Department he went to work at the old Hughes Aircraft plant in Culver City, California, managing a thin film lab and working in the areas of infrared detectors, electro-optical systems, and radiation hardened electronics for space. In 1992 he moved to New Mexico working for Maxwell Laboratories, which was then acquired by SAIC which then split to form Leidos. While there, he continued his work on infrared components and radiation hardened electronics and worked on high power microwave systems and antenna design. Dr. Duffey lives in Cedar Crest NM.

Click here to download the presentation in PDF format.

January 2018 Club Meeting - Digital Voice Modes - the next step in repeater technology

Friday, January 19, 2018

7:00pm MST

Ascension Lutheran Church 1220 West Magee Road, Tucson, AZ

 

Handyman Corner

By Tom, W8TK

Kit of the month: Simple regenerative receiver

Project: Cable Management

 

Digital Voice Modes - The next step in repeater technology

Presented by Bob, AF9W

Digital Voice Modes

With the advent of digital voice in commecial radio it didn’t take long for those technologies to move into ham radio. With all the major Japanese and Chinese radio manufacturers selling digital voice products, this segment of ham radio is booming. Digital voice is easily transferred over the internet allowing even Technician licensees to have conversations with hams in other states and countries through their local repeater or hotspot. Software development around digital voice has lead to significant homebrewing to overcome some of the early limitations of digital voice. The presentation will discuss the growth of digital voice in ham radio, some history, the similarities and differences among the modes, and the current state of the art.

Bob, AF9W, has been licensed since 1979 and an OVARC member since April 2011. As a snowbird, he became interested in internet based digital voice as a means of keeping in touch with fellow hams as the sunspot cycle dipped into it a cyclical minimum. As a retired software engineer, he is also interested in ham radio software and mixing computers and radio.