I saw the long thread on Antenna Field Mapping, which lead me to suggest this idea has been bumping around in my mind for some time now; wanting to know what the real world radiation pattern of my HF antennas are.

Basically, take something like a TinySA or just a receiver (stripped down version, perhaps somewhat specialized to allow setting frequency & record signal strength?) up on a drone and fly it in some ever increasing circles & altitudes around the antenna, recording the signal strength & GPS coordinates, at the desired frequency.? You then plot the signal strength result on a google map using colors to indicate signal strength...

This should give you a fairly good depiction of your antenna radiation pattern.? Various flight patterns might even give you an idea of the NVIS radiation pattern of HF dipoles.

There are a fair number of drone control software programs that are available (i.e.: Litchi, esri, etc.) that can be programmed to fly specified routes, which would be centered around the test antenna.? It would of course require a drone that could carry the payload.

I have some experience with drones, antenna modeling & programming, but a project like this might take a bit more skills than I have.
?? ? Might be a good idea for a college project???
????????? Just a hopeful idea...
--
Mike, W0IH

Hi Mike,

I know George AA7JV (C6AGU) has flown a drone with small 160 meter transmitter (really just a small oscillator as I recall) around one of his island locations to check pattern on one of his 160 meter directional receive antennas.

Just FYI,
Don wd8dsb

Somehow the first part of my reply was cut off.? Here it is again:
The idea of putting the RF source on the drone seems to be a good one.? It simplifies the problem of recording the field strength remotely, allowing that to be done on the other side of the antenna, in the shack.
It should be relatively easy to construct small rf beacons for HF bands that could be deployed on small drones; just need a ultra-qrp signal with a known power.

开云体育

check the VE6WZ YT channel.? Steve published a recent video to use on 160.

73 charlie, k1xx

Sounds like there is a little bit of confusion here.?
?? My idea is to take a receiver (not a transmitter) up with the drone, record the signal strength & GPS using a watt or two from the antenna.

--
Mike, W0IH

Hi Mike,

No real confusion, simple oscillator acting as the transmitter on the drone is a much lighter payload and still allows you to plot the antenna pattern while having ?all the data recording equipment land based.

Just a possible alternative versus having the receiver on board the drone depending on your needs.

Don

On a similar theme, I have checked the radiated field strength from my 2m horizontal Yagi to compare calculated field strength against measured. I used a half wave dipole on a wooden broom shaft. The calculation from dBm to Volts/metre is done with a spreadsheet, a copy of which is in the files section.

A portable wideband HF active antenna could be calibrated to give the necessary antenna factor (needed to convert dBm to field strength). I haven’t got around to making/calibrating such an active antenna, but it’s not particularly difficult.

73 Dave

Consider that just as "educative" information. In Europe, antenna measurements with the help of drones are rather common since 7-8 years. Colibrex company in Germany is probably one of the most involved in this field. I have NO interest in this company, but when I worked as an engineer, whe have asked them to do radiation patterns measurements for us.

The target is clearly not ham radio (!), but this short video gives an idea of the concept :?

73 Jean-Roger / F6EGK

On Sun, Mar 24, 2024 at 07:25 AM, G4AON wrote:

A portable wideband HF active antenna could be calibrated to give the necessary antenna factor (needed to convert dBm to field strength). I haven’t got around to making/calibrating such an active antenna, but it’s not particularly difficult.

I have used a high impedance "E-Probe" type amplifier with a 1m long whip, fitted to a car roof with a magnetic mount. The intention at the time was to build a cheap drive around VDSL interference measurement system. But with fibre to the home now being rolled out, it doesn't seem to be such a big issue any more. However, EEV vehicle chargers may be the next problem.



I calibrated it using the Equivalent capacity substitution method.

You can either calculate or measure the whip capacitance.



And then use the Equivalent capacity substitution method to obtain the antenna factor.





Regards,

Martin

On Mon, Mar 25, 2024 at 01:22 PM, Martin wrote:

The intention at the time was to build a cheap drive around VDSL interference measurement system

With this in mind, it would be really useful if the TinySA app could take in real time GPS NMEA data, and create updated log files with time, date and position stamped signal level or plot file information.

Regards,

Martin

There are companies in the US who do this as a commercial venture.? They also have the wherewithal to perform the required near-field to far-field transformation of the data - without which renders meaningless numbers, even in pattern strength and directivity.

They have to pay for very expensive waivers and jump through hoops to allow for flight in non direct line of sight (LOS) situations.

You do know that it is illegal for a non part 107 sUAS pilot to fly in a non direct LOS manner, correct?? To be clear, we're not talking about radio LOS - If you can't see the sUAS with the unaided eye, you are in violation.? Only a part 107 pilot with a waiver can operate non-LOS.

The FAA actively monitors the interwebs for such violations, and actively pursues those who violate the laws pertaining to "drones" (sUAS) nowadays.? There's been too many stupid people operating the aircraft in stupid ways as of late - and they've ruined it for everyone who never did, including your basic RC airplane/helicopter enthusiasts.