Experimental aircraft has VHF reception problem on ground and low altitude. Tower frequency only.

Attributes
ACN	198009
Time
Date	199112
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : dfw
State Reference	TX
Altitude	agl bound lower : 0 agl bound upper : 100
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : dfw
Operator	general aviation : personal
Make Model Name	Small Aircraft
Flight Phase	climbout : takeoff ground : holding ground other : taxi
Flight Plan	VFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 9300 flight time type : 30
ASRS Report	198009
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance other anomaly other
Independent Detector	other controllera other other : unspecified cockpit
Resolutory Action	aircraft : equipment problem dissipated
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

On 2 separate flts in an experimentally registered, fiberglass aircraft, communications with the tower at dfw were garbled, weak, or missed. Both occurred only when the aircraft was on the ground or very near to the ground, and only on tower frequency. Both occurred on the west side of dfw. During landing on 36L and takeoff on 18L, it was difficult to hear tower transmissions, and during landing, the tower reported that we missed 3 transmissions. It is important to note that all transmissions (with approach, tower, and departure) were fine once the aircraft was more than, say, 100 ft AGL. The radio is an xx model and using an xx manufacturer headset. It might be noteworthy that the communication antenna on the aircraft is mounted in belly (lower fuselage) skin. I speculate that this low antenna location, perhaps coupled with a tower transmitter signal anomaly which created a weak signal very close to the ground, could cause this problem.

Original NASA ASRS Text

Title: EXPERIMENTAL ACFT HAS VHF RECEPTION PROBLEM ON GND AND LOW ALT. TWR FREQ ONLY.

Narrative: ON 2 SEPARATE FLTS IN AN EXPERIMENTALLY REGISTERED, FIBERGLASS ACFT, COMS WITH THE TWR AT DFW WERE GARBLED, WEAK, OR MISSED. BOTH OCCURRED ONLY WHEN THE ACFT WAS ON THE GND OR VERY NEAR TO THE GND, AND ONLY ON TWR FREQ. BOTH OCCURRED ON THE W SIDE OF DFW. DURING LNDG ON 36L AND TKOF ON 18L, IT WAS DIFFICULT TO HEAR TWR TRANSMISSIONS, AND DURING LNDG, THE TWR RPTED THAT WE MISSED 3 TRANSMISSIONS. IT IS IMPORTANT TO NOTE THAT ALL TRANSMISSIONS (WITH APCH, TWR, AND DEP) WERE FINE ONCE THE ACFT WAS MORE THAN, SAY, 100 FT AGL. THE RADIO IS AN XX MODEL AND USING AN XX MANUFACTURER HEADSET. IT MIGHT BE NOTEWORTHY THAT THE COM ANTENNA ON THE ACFT IS MOUNTED IN BELLY (LOWER FUSELAGE) SKIN. I SPECULATE THAT THIS LOW ANTENNA LOCATION, PERHAPS COUPLED WITH A TWR TRANSMITTER SIGNAL ANOMALY WHICH CREATED A WEAK SIGNAL VERY CLOSE TO THE GND, COULD CAUSE THIS PROBLEM.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.