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 Previous: The K7VVV Solar Update |  Next: Astronaut Greets his Children from Space via Ham Radio |
By Murray Green, K3BEQ
March 22, 2002
An unidentified transmission blocked the Maryland repeater. An out-of-town truck parked in a residential area gave up its secret when local hams arrived on the scene.
It never ceases to amaze me how rapidly members--and certain non-members--of the Green Mountain Repeater Association (Maryland) respond to problems affecting their repeaters. Over the past few years we have had our share of interference caused by faulty pager systems and other commercial transmitters. These were quickly isolated and corrected through a coordinated effort among amateurs and the commercial sector. On November 25, 2001, we added another success story to the GMRA record book.
Sometime between 1 and 4 PM a continuous signal timed out the 146.880 MHz repeater. The signal contained no audio although a tapping noise could be heard in the background--definitely an open microphone. At first, the tapping sounded like someone typing on a computer keyboard. We assumed the open-mike transmitter was in someone's radio shack. However, I received a call from George Stephens, W3GRS, who resides in Silver Spring, Maryland, saying that he could hear the input signal full-quieting on his H-T. He noted that it was raining heavily at his residence and the rain coincided with the tapping noise heard through the open mike. The microphone therefore was suspected to be in a parked vehicle in close proximity to his location. A reasonable deduction eh, Watson?
 GMRA President Paul Freirich, W3HFA, displays the Yagi he used to track down the troublesome transmitter. [Photos by the author] |
We sent e-mails to the membership and made several announcements on the association's sister repeater (146.610 MHz) and on simplex--146.880 MHz. GMRA President Paul Freirich, W3HFA, took the initiative, jumped into his car--despite the inclement weather--and took off toward the general area of the interference. Scott Stimpfle, KB3GJW, and Ron Montgomery, KC4QCE, quickly followed.
Using H-Ts, mobile units and an attenuator, they were also able to detect strong signals in the Aspen Hill, Maryland area, near Silver Spring. Despite driving up and down streets they could not isolate the transmitter, but they were close. The search continued. Paul drove back to his home to retrieve a small direction finding VHF beam. Shortly thereafter, Scott, KB3GJW, came across a parked truck near Bluehill Street and Janet Road in the Aspen Hill area. The truck had out-of-state Amateur Radio call sign plates. Fortunately, it was parked in front of a residence. Although Scott didn't realize it, he had hit pay dirt.
Walking up to the residence, he met the truck's owner who was visiting for the holidays. Accompanying Scott to the vehicle, the owner found the mobile unit on and the microphone jammed between the seats with the push-to-talk button pressed to the ON position. Listening to the input signal I could actually hear them opening the truck doors and talking as they turned off the transmitter. The input signal disappeared and the repeater returned back to service. It was 9:45 PM.
 The guilty culprit. Open mikes can be a problem to repeaters and may overheat the errant transmitter. |
The unidentified transmission was not intentional but it did cause a repeater to be shut down for many hours--an inherent flaw in amateur repeater systems, in my opinion. It inconvenienced half a dozen other hams who took it upon themselves to find the transmitter. A special acknowledgement to Scott, KB3GJW, who found the vehicle, and a big thanks to all for that extra special effort that is indicative of the professionalism and determination of GMRA members and the Amateur Radio Service. Also assisting in the effort from their homes were Hernan Hidalgo, N3OKP; Joe Nunemaker, KD3VR; John Creel, WB3GXW; Carey T. David, K3GXF and the author.
On the evening of November 26 the out-of-state ham came on the 146.880 MHz repeater to apologize for the open microphone. It takes a big man to admit his mistake. In retrospect, we all learned something from the experience.
Murray Green, K3BEQ, recently celebrated 50 years as a ham. He has
written several columns and feature articles for QST. Murray is one of five founders of The
Green Mountain Repeater Association that maintains and operates the 146.610 MHz
and 146.880 MHz repeaters serving the Washington, DC metropolitan area. He
resides in Cheverly, Maryland and can be contacted at k3beq@arrl.net.
| Previous: The K7VVV Solar Update | Next: Astronaut Greets his Children from Space via Ham Radio |
