clanon

1:1 50ohms to 50 ohms... The antenna is BALANCED ... (imho)

Length is any size ...more than 3/4 lambda...(more directivity more lenght)

Yurik says...: (about this LPDA) 1) isolation between ports. if, for example, the decoupling is zero, then VSWR = 1 for the measured port (all 100% of the energy has consistently crossed over to the second port). To achieve an isolation of at least 20 dB, extremely stringent requirements for line symmetry are required. One line (pair of plates) does not interfere with the second pair only in case of precision symmetry. Due to the installation of elements as a continuation of the plane of the plate from which the line is made, symmetry is impossible. For symmetry, the elements of the dipole must enter perpendicular to the plane of the collecting strip. 2) the design of the balun. LPDA, like most antennas, has a balanced (differential) output. A 1: 1 balun is required to match an unbalanced line (coaxial cable). Most often it is done by laying the cable inside a hollow line to the point of zero potential. in MIMO, the cable can no longer be laid like this (in laboratory antennas this is done using a hollow profile of a complex cross-section) from this video it is not clear how it is laid 3) The LPDA antenna must have a short-circuited line behind it (continuation) of a certain calculated length. in the video, this structural element was simply excluded by an effort of will 4) to create antennas with a direct output to 50 Ohm, collecting lines with a very low impedance have to be used. The distance between the stripes should be many times less than the width of the stripes. But for MIMO, a constructive restriction is imposed that the distance between the lines is greater than their width (at least by the value of the constructive gap). Two strips with a distance between them equal to their width have Zo = 160 Ohm, which does not allow designing an LPDA with an output of 75 or 50 Ohms.In addition, any LPDA has an unstable phase center (too mobile even for one single band, only within one 3G range, the difference between uplink and downlink reaches 2.5 centimeters

LPDA.pdf

What dielectric...? thickness , dielectric constant... (there's ALWAYS losses , you know)

Gain:2х 30 dBi... more like 2x13

Yes...need LOGPERIODIC and reflector data...

Here you go...: Enjoy! 14dbi.cst

Thank you! Swarg , (now i get it)

?

like this...?

Puting the modem RIGTH by the antenna (waterproof enclosure) , could be nice...(shortest possible cable RF)

Here is the POWER you have ...https://fccid.io/QISB525S-65A and other specs There's NO sensibility values for 3g...and wlan sensibility seems bad...i'll check the chip... huawei_b525s_65a_lte_modem_datasheet.pdf

well , ALL i can say is ; FR and any cheap dielectric (Non Microwave specific , expensive) in every antenna i've simulated ...takes the "juice" of small signals away...you lose in the best cases 5% 7% ...or even MORE...it may seem small...but when you have low sensibility , bad SNR ...and long cables...it all add up for worse...maybe you should try a feeder...ALL METAL...designed for your frecuencies... LOTs of FR here...https://www.wifi-antennas.com/topic/229-broadband-mimo-irradiator-kip9-17002700-dp-for-satellite-dish/ Good for Manufacture...bad for small signal

i think on 3/4...check the MATH... Diameter x Pi = length (perimeter)

https://www.youtube.com/watch?v=Az7Zda_pd-Y

it's a 1" OD (2,54mm exterior) conduit for electric cables...PVC...(Really THIN WALL) any PIPE would DO The LESS plastic the BETTER

GND would have continuity to any of those IC EMI SHIELDS (aluminum tin covering circuits) that's COAXIAL SHIELD (MESH) GND...just to be sure...

Yellow ring is SHIELD (GND) (careful with those hairs, make a ring with solder) RED line is inner WIRE...50ohms feed point https://www.wifi-antennas.com/uploads/monthly_2020_09/5f714c7f94137_frontdesoldered.jpg.c2757e4d0fc1d166241bf1cbe9d605d3.jpg.7e186604399d80e2a8f10e2d24415cec.jpg

Electromagnetic Fields at HIGH Frecuencies...behave like witchcraft ...(before simulations was hard to figure it out...and still is)

It's a PIFA antenna (low gain)...Check continuity ...but i think cable (50ohms shorter you can) goes like this Try with a DIPOLE