Evaluation of log periodic, 0.8-2.7 GHz
Created: Mar. 2023
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This log periodic aerial is advertised for cellular reception in the 0.8-0.96 GHz and 1.7-2.7 GHz bands but I saw no reason why the log periodic would not have continuous reception over 0.8-2.7 GHz. I desired a continuous coverage because my intended use is locating RF interference and measuring shielding effective. Incidentally, it also covers the ham bands 1296 MHz (23 cm) & 2420 MHz (13 cm).
Unlike most log periodic sold online, this one is NOT a PCB, but a conventional metal (steel?) construction. It is enclosed by a radome made of ABS plastic (fig. 1). Connection is made thru a 20 cm long pigtail with an N female. Peeking inside the radome reveals an 8 element aerial.
Fig. 1: Dimensions (cm) of the log periodic antenna. At the bottom is the mounting bracket and U-bolt for attaching to a mast.
Fig. 2: Sticker showing model "HGANT-0809/1727-2-1-10" and specifications
The advertised performances are:
800-960 MHz / 1710-2700 MHz
Gain: 9dBi/13dBi
Pmax = 50W
The aerial can be attached to a pole / mast via a mounting bracket with a U-bolt. The The U-bolt's position can be adjusted for down-tilting the aerial. Unfortunately, using the supplied bracket, only vertical polarization is possible.
I measured the return loss on a nanoVna v2. The minimum freq does go a little lower than advertised; i.e. the return loss is still acceptable at ~660 MHz (fig. 2). The max. freq is as advertised; i.e. 2.7 GHz. There are two unexpected mismatches at 2.0 GHz and 2.25 GHz.
Fig. 3: Plotting the return loss (RL) over 500~3000 MHz shows two mismatches at 2.0 GHz and 2.25 GHz. The lower frequency limit extends down to 660 MHz versus the advertised 800 MHz
Fig. 4. The RL plotted over a narrower range, with the blue areas denoting the advertised ranges
This post's most glaring shortcoming is that it lacks gain measurement and radiation pattern plot. I plan to measure these in the future, but I need to set up a measurement range first!