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19.8 KHz as Received in Allen Park, MI on Z1501D Active Antenna

Ron, K8AQC, is a beta tester of my Clifton Laboratory products. In addition to knowing Ron for 40 years, he lives in a challenging location in suburban Detroit with respect to AM broadcast signal levels and locally generated noise.

The table extract below, from http://zipsignal.v-soft.com/, shows the magnitude of the AM signal strength challenge at Ron's QTH. The strongest station, WLQV, has a field strength of nearly 800 mV/m. With a Z1501D active antenna, this corresponds to approximately +5 dBm into a 50 ohm receiver. Ron regularly measures +3.0 dBm for WLQV, representing reasonable agreement with my computed estimate. (The 48101 zip code is large enough so that WLQV's signal is not constant through the area.)

I am familiar with WLQV; I spent two years there as a transmitter engineer, working my way through law school in the early 1970's.

 

AM Stations Covering Zip Code 48101:

Field (mV/m) Call Sign Principal City State Frequency (kHz) CDBS Facility ID
791.51 WLQV DETROIT MI 1500 42081
280.51 WLQV-N DETROIT MI 1500 42081
240.87 WJR-N DETROIT MI 760 8626
240.87 WJR DETROIT MI 760 8626
125.96 WCHB TAYLOR MI 1200 4598
122.97 WWJ-N DETROIT MI 950 9621
104.96 WDFN DETROIT MI 1130 59969
104.25 WWJ DETROIT MI 950 9621
 
The second challenging aspect of Ron's location is the general noise level. It's a typical close space suburban location, with high noise from power lines and neighboring computers and switching power supplies.
 
As an example of what is possible with the Z1501D even in a challenging location, Ron has been observing the 19.8 KHz VLF signal from NWC, Exmouth, Western Australia. NWC is part of the US Navy's VLF network and is difficult to observe in the eastern US.

The figure below shows spectrum analyzer plots centered on 19.8 KHz. Each plot is the average of multiple individual sweeps, using software Ron developed to control an HP3585A spectrum analyzer over the HPIB interface.

I've taken a series of plots Ron provided and made them into an animated GIF file. The images start at around 5 AM local (eastern time) and end at 10 AM local. There are 9 images in the animation. Each image is an average of 100 sweeps.

The best signal shows almost 15 dB S/N ratio. Note the 60 Hz power line spikes and the general noise level change somewhat during the observation period, but the signal makes a much sharper change, ranging between almost undetectable and clearly visible.