In his nice article Andreas uses a spectrum analyzer to measure LoRa performance of the boards. Finally we have some more hard data on what several people had already noticed: the sub-optimal LoRa performance of these boards. (Nice to see that this topic was used as a source for the article and is linked back to.)
I had a nice talk with Andreas during The Things Conference where we also talked about these boards. Andreas has not yet tested the TTGO V2, which I expect will have better LoRa results because it uses a standard LoRa module. Andreas was interested in also testing the TTGO V2 (but don’t expect any results soon because he has many other interesting projects waiting for him).
In response to the video:
It’s not clear to me whether the Heltec V1 or V2 was tested.
The part where the poor PCB antenna placement of the Heltec is discussed appears to be the Heltec V2 because it has the PCB antenna on the bottom (which is not connected).
The LoRa antenna’s included with all Heltec and TTGO boards are (helical) monopoles. For a monopole the ground plane acts as the dipole counterpoise element.
The size and location of the ground plane will have significant impact upon the antenna’s VSWR and gain.
For a more representative judgement of the included antennas, the ground plane aspects should have been included in the testing. While most users will probably use the antenna just ‘as is’ and not take care for any proper ground plane, proper judgement of the antenna’s performance can still only be done when using the antenna’s correctly (and monopoles require a good ground plane for proper functioning because the ground plane is the counterpoise, it’s the other half of the antenna).
A larger ground plane will lower the resonant frequency and widen the bandwidth.
Which is exactly what could be observed in the video when Andreas touched the antenna’s ground connection with his hand.
Typically antennas are designed on a counterpoise that is one wavelength in radius.
Significant performance reductions occur when the radius is a quarter-wave or less.
Source: Linx - Understanding Antenna Specifications and Operation
For better performance: the performance of true dipole antennas does not rely on the presence of a good ground plane because the counterpoise is already included in the antenna itself. Like this antenna which is a true dipole: 868Mhz 19.5cm SMA antenna
(Btw, his name is Andreas, not Andy.)