I am new to playing with any type of antenna analyzer/vector network
analyzer device but decided to get started learning by purchasing the
NanoVNA, as it was relatively inexpensive. The display on the device was
extremely small and my eyes are getting old, so I first wanted to workout
software that allows me to just use my laptop. I started with NanoVNASharp
and then on to Rune¡¯s NanoVNA-Saver. I have been playing with it a while
and I think I¡¯m starting to get the hang of it. I¡¯ve set the sweep count to
100, which I believe gives higher quality readings than a single sweep. I
calibrated using the short SMA cable that came with the device, along with
the double-female connector to calibrate out the short coax. Now, I wanted
to evaluate the antennas that came stock on some of my portable antennas. I
have a Kenwood TK-2180 VHF LMR portable, which I use primarily for the
Placer County Sheriff¡¯s Search and Rescue. My other radio I bought because
it was cheap, a Baofeng UV-82C VHF/UHF dual-band portable.
For SAR, my primary use is on a repeater with an input frequency of 150.790
MHz and output of 155.160 MHz (the National Search and Rescue frequency). I
also work an event each summer doing armed security where we have an input
frequency of 159.885 MHz and output of 155.655 MHz. Basically, my needs
then are between 150-160 MHz. After calibrating my NanoVNA, I did my sweep
with the Kenwood antenna from 130-180 MHz. I exported the data as an S1P
file and then imported it into Zplot in Microsoft Excel. With this, I
created a graph showing SWR and Return Loss. To my understanding, the more
the return loss, the more resonant the antenna is to that frequency,
meaning that it is more efficient operating at that frequency, correct? I
also took notice of the Smith Chart. For the Kenwood antenna, it hits it¡¯s
best at 152.022 MHz with a return loss of -10.682 dB and SWR of 1.826.
[image: KenwoodTK-2180StockAntenna.jpg]
[image: KenwoodTK-2180-Smith.jpg]
or the Baofeng, it appears that the dip is much narrower but has a much
¡°deeper¡± return loss at 148.558 MHz with -23.885 dB and SWR of 1.137.
[image: Baofeng VHF Antenna.jpg]
[image: Baofeng VHF-Smith.jpg]
I am trying to compare these antennas as best I can. It appears as if at
around 148 MHz, the Baofeng antenna is significantly better than the
Kenwood but fairly lousy at the frequencies I really need it. The Kenwood
appears to be a little wider bandwidth but not near as much return loss and
higher SWR. First off, are these findings typical and what does it say
about the antennas that came with each radio?
Sorry if you are receiving this as an email and getting multiple copies...
I tried sending it once before and tried to edit it, because it didn't
format correctly and deleted itself when attempting to edit.
_____________________________________
Ron Webb
