Ron, the "antenna" on a handheld is not the antenna, it is only
/half/ of the antenna. In a Marconi system reliance is placed on
"ground", of whatever character, to be the other half of the antenna.
Exactly as much energy flows into and is radiated by "ground" as flows
into and is radiated by the, in this case, rubber duck type of antenna.
It is the flux of electric and magnetic fields established between the
two that constitute the radiated (and received) signal. The
transceiver's chassis and the hand holding it are half of the antenna
system. The sole merit of flexible antennas on handhelds is convenience.
In the set up described, the "ground" was mostly the braid of the
coaxial cable.
There is much to be said on the topic.
If a fellow is bound and determined to have a resonant rubber
antenna, then a connector to take that antenna must be mounded in the
middle of a conductive, flat surface the minimum dimension of which is a
quarter wavelength in all directions from the connector plus 5% or more.
With that set up, Ron, antennas can be compared with each other to the
standards applicable here.
As others have noted, we are very much dealing with radar
wavelengths. Nearby objects, metal or meat, will establish standing
waves which will upset the purity of your test results.
If you care to experiment when in the field, connect, at the ground
of the antenna connector, a run of light braid cut for a quarter
wavelength at the frequency of interest and simply let it dangle
downwards over your hand. That is your counterpoise and that explicit
counterpoise will do you far more good out there in the real world than
trying to resonate a rubber antenna!
You may contact me off list if would like to pursue the topic.
John
at radio station VE7AOV
+++++
On 2019-09-11 1:36 p.m., Ron Webb wrote:
Just for additional information, I was doing the testing in a large conference room with very little in the room other than a table with chairs and a video projector pointing at a whiteboard. It isn't quite as acurate as a laboratory that tries to eliminate all RF radiation. On one end of the table was my laptop (nearest the door). I then placed the NanoVNA the distance of the USB cable that came with it away from the laptop. The little SMA cable is only about 6-8 inches long but I took a paper cup and made a small hole, just big enough for the SMA connector to pass through. I connected one connector to S11 and the other to the antenna. By setting the cup lid down, it made the antenna stay vertical with no real ground plane, as on a handheld radio, there really isn't a ground plane. I'm not really looking for absolute perfection, but at least something where I can compare one antenna to another.
On Wed, Sep 11, 2019 at 01:04 PM, Rune Broberg wrote:
Hi Ron,
interesting data, and an interesting use case! My limited experience with
antennas for handheld radios indicate, that they do change their impedance
based on whether a person is holding the radio itself, and thus providing a
sort of counterpoise to the antenna. I don't know entirely how much, nor
how to simulate it reliably for measurements, but I look forward to
learning about it :-)
--
Rune / 5Q5R
On Wed, 11 Sep 2019 at 21:55, Ron Webb <bigron@...> wrote:
I'm still new to posting here, so forgive the double graphics and title of
SWR/RL graphs not being seen. ;)
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