Very Simple Yet Effective Dipole Antenna for EVDO 800MHz

One of my mobile broadband Internet provider (EVDO Rev A) planned to close its service in a near future, due to Qualcomm has decided to stop EvDO evolution. The service has real unlimited budget-plan. Currently most of mo-bro providers (both CDMA and GSM) in here are moving to early stages of 4G LTE (either FDD or TDD).

So the impact is, many BTS (base transceiver station) nearby my house have been sold, signal was going worse. Several months ago my EvDO modem (without external antenna) could easily resonated at -70 dBm of HDR power. But since the collapse was announced, signal was suffering at only around -85 down to -90 dBm typically.
(with external antenna, signal can be received at -50 dBm, but I prefer the antenna for another HSPA+ service)

Fortunately I keep an old unused indoor TV antenna. Sure it's dedicated for lower frequency band for TV broadcast. While that my dying ISP works at higher 800MHz of carrier frequency.
Hoho... then I imagined to build a simple dipole antenna to recycle that my old antenna.


A simple formula is needed : lambda = c / frequency.
lambda = wavelength to be calculated.
c = speed of light = 299,792,458 metres per second.
frequency = 800 MHz.

We have pole length of,
1/4 lambda = 1/4 * 299,792,458 / 800,000,000 = 0.093685143125 m = 9.368 cm

Simply cut both poles to around 9.3 cm in order for the microwave to resonate at around 800MHz. Mounted on horizontal direction (omnidirectional in vertical plane due to polarity of the microwave).

Plug the cable to modem's antenna connector via a pigtail. (I'm too lazy to install a BNC connector =D)
Voila....

Signal has now HDR power of around -72 to -74 dBm (blue plot Rx). Quite significant improvement, not bad for upcoming several months of "emergency helper", until the ISP is going to finally be closed.
A no cost antenna! 




(In deep condolance for the missing AirAsia QZ8510's passengers and crews, their families and relatives)