New Radio Antenna Avoids Unwanted Signals

A new, simpler, cheaper and potentially more effective way to prevent radio antennas from picking up unwanted signals has been created by researchers at University of Texas, Austin, United States.

It is hoped with further development of the technique could also be used to help prevent thermophotovoltaic cells from re-emitting radiation they absorb.

The laws of electromagnetism work exactly the same way if you run time in the opposite direction. One logical consequence of the design is to broadcast at a certain radio frequency will also absorb radiation at that frequency.

This issue is problematic for broadcast radio antennas, which will absorb radiation that has bounced back from surrounding objects – something that can have a negative impact on operation.

The team at the University of Texas have based their design on a traditional leaky-wave antenna, in which electromagnetic waves of certain frequencies couple to the space around the antenna and "leak out" as they travel along it

Full story - http://physicsworld.com/cws/article/news/2016/mar/29/new-radio-antenna-avoids-unwanted-signals

Ramsey Kits Calls Time

Ramsey Hobby Kits, a purveyor of inexpensive electronics kits for hobbyists, enjoyed by the Amateur / Ham radio community, have ceased operation.

“We end our heritage with a smile, not a frown, and say thank you, to all our customers and fellow hobbyists,” Ramsey’s announcement said. 

The Victor, New York, company sold a wide array of hobby kits over the years, starting with its LED Blinky kit in the 1970s and eventually including simple ham radio transmitters and receivers, aircraft band receivers, and other devices. Ramsey kits were frequently available at hamfests.

The Ramsey RF Test Equipment Group is unaffected by this change.

ARRL story - http://www.arrl.org/news/ramsey-kits-calls-it-quits

Ramsey announcement - http://www.ramseyelectronics.com/ce.htm

Reflectorless Yagi Radio Antennas Designs

Chris Moulding, G4HYG has added a new webpage to the Cross Country Wireless website detailing some of the reflectorless yagi designs he has been experimenting with.

Included in the article are  designs for VHF antennas for portable operation and a home station HF version.

Chris’s designs are optimized using the freeware antenna modeling software 4NEC2, and were recently tested during a RSGB UKAC contest.

Antenna Article - http://www.crosscountrywireless.net/reflectorless_yagi_design.html

4NEC2 - http://www.qsl.net/4nec2/