new PA installed into home brew SSB transceiver

Talked to India, the Ukraine, Brazil, and others using the new PA. Will continue to test this week :)

adding a 70 watt PA to my homebrew SSB transceiver

I found a MaComm DU2880V transistor at a local hamfest for $10. I've decided to use that as the final output PA. This transistors is a dual mosfet, capable of providing 80 watts at 2-175 Mc. I've built up a pa from this by swamping the input gate impedance and using broad band transformers on the input/output. Getting about 70 watts out with 1 watt of drive.

In order to maintain a constant bias over the operating temperature i recently heated up the amplifier with a heat gun while monitoring its temperature, i then used two silicon diodes and a potentiometer to pull down the bias voltage as the transistor heats up. This is a method used to help compensate for increased bias voltage with temperature that RF mosfets typically experience (see 2010 ARRL handbook mostfet PA project).

Planning to incorporate this into my radio sometime next week, stay tuned for the results....

Slides Posted: An Ultrawideband (UWB) Switched-Antenna-Array Radar Imaging System

For those who are interested I've posted the slides from one of my papers presented at the 2010 IEEE Symposium on Phased Array Systems and Tech., 'An ultrawideband (UWB) switched-antenna-array radar imaging system.' For more info go to this project's website.

2011 MIT IAP course, build a synthetic aperture radar in 4 weeks

I might teach an Independent Activities Period (IAP) course at MIT this winter on how to build a synthetic aperture radar imaging system in 4 weeks. Stay tuned for more details as they evolve.

Here are the courses offered last winter of 2010.

DIY Phased Array Radar to be presented at the 2010 IEEE International Symposium on Phased Array Sys. & Tech.

I will be presenting this DIY phased array radar system this week at the 2010 IEEE International Symposium on Phased Array Systems and Technology, in Waltham MA.

This is a near-field phased array radar capable of forming images in near-real-time at the rate of 0.5 Hz. In general, this shows what one might be capable of when you have limited resources and some time to think about working the problem. It was built in my garage and basement laboratory while in grad school as part of my dissertation.

If you are interested in this topic it will be presented on Wednesday, see the technical program for further details. (You can register at the conference if you have not done so already.)

20M home-brew (DIY) SSB transceiver success!

This morning i worked Santa Barbara, Mexico City, on 20M with the
home-brew SSB transceiver transmitting about 20 watts into a half-
wave dipole.

The radio still needs a few additional things done to it including an
accurate TX power meter (to verify that i am transmitting :) and an
RX AF chain mute while transmitting.

Surprised at how easy it was to make this contact this morning. It
is very exciting to build something from scratch then get it on the
air with a successful contact!

Free student event: learn about phased array antennas and systems at the IEEE Symposium on Phased Array Sys. & Tech, sign up now!

Are you a student who is interested in learning about phased array systems, what they are, how they work?

Then be sure to sing up to the free 1-day student event at the 2010 IEEE Symposium on Phased Array Systems & Technology, October 12, 2010 in Waltham, MA.

The IEEE is trying to encourage young people to study engineering as a profession, as a result many of our interesting conferences like this one are offering 1-day student events free to anyone.

The event is free, it includes lunch and a lecture by Eli Brookner, who is well known in the field of phased array radar systems and a great speaker. After lunch the students will get to see the symposium welcome speech by Mark Russell, and keynote by Dennis Picard. Finally, students will get to meet with companies, talk to engineers in the field, and meet other students who are studying antenna arrays in grad school.

As you might guess, it's not easy getting attendance levels up for something as specific as phased array antennas, or even raising awareness of how much fun phased array engineering can be as a career path.

For more information please visit:

website:

http://www.array2010.org/student.htm

student event flyer:

http://www.array2010.org/pdfs/past2010_studentevent_flyer.pdf

student event schedule:

http://www.array2010.org/pdfs/past2010_studentevent_schedule.pdf

To register, go here:

https://mandalore.tchmachines.com/%7Eqtzycpf/forms/phased_array_stu/student_pa_regpay.php

Please encourage any students or student groups that you know to check out this unique and free event. Looking forward to seeing you at the Phased Array Symposium!

Greg

Chair AP-S Boston Chapter