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OPLINK 430Mhz antenna tests
« on: January 27, 2021, 11:45:30 pm »
After having found what appeared to be temperature issues with some of the OPLINK air rcvr modules, I ordered several types of antennas and tested them - in this case on the base station module (on the theory that they are both the same xmtr/rcvr modules). The rcvr antenna is oriented at 90 degrees to the xmtr - this is normally the highest signal strength for a dipole like antenna. Antenna parallel to the ground. All tests with 10' spacing rcvr to base station.
The antennas tested are from left to right:
1) Antenna that came with OPLINK - when antenna parallel to rcvr antenna -40db on OPLINK sig strength

2) Version to try to match 1) above ordered on ebay link below - identical results to 1)
https://www.ebay.com/itm/Folding-433MHz-1-4-Wave-Antenna-2-dBi-SMA-Connector-105-mm/184610598934

3) Longer antenna on ebay - this seemed to be directional - when parallel, about -40db, but when end was pointed at rcvr, -32db - significant improvement
https://www.ebay.com/itm/433MHz-Rubber-Antenna-19cm-SMA-Connector/382614690368

4) Longest version - this too was directional as 3), but not as high gain - -36db
https://www.ebay.com/itm/SMA-M-VHF-UHF-Antenna-for-Baofeng-UV3R-Retevis-RT3S-YAESU-VX-3R-Two-Way-Radio-X2/362947038362
This antenna also seemed to shift around - sometimes signal strength would drop very low --60db or lower. All the others stayed pretty consistent in the -40db range or above.

Re: OPLINK 430Mhz antenna tests
« Reply #1 on: Today at 06:56:05 am »
The rcvr antenna is oriented at 90 degrees to the xmtr
For linear antennas outside of near field effects (us at say 10 meters or more and away from clutter, normal flying) they should be oriented to be parallel for best reception.  :)

Antenna that came with OPLINK
In the beginning, OpLinks and Revos came with a T wire dipole.  They now come with "Small, cheap wire coil style" which is what I think these are.

Your medium length antenna might be a loaded antenna instead of the standard cheap simple coil antenna, but every 433 that looked like that that I have cut open (only 2) has been a coil antenna in the bottom of the bottom and the rest of the antenna empty.  :(  The many different coil antenna case styles I have tried have varied from really bad to usable for local flying.  All my quads use the cheap coil type antenna for telemetry, but they aren't long range aircraft.  My fixed wing all use Retevis' whether they need it or not.  ;)

For a test that is perhaps more like a range test set both ground and air to lowest power.  Try to find a place in the house for the air where it does not connect.  You may have to go outside.  Find a max range place for that set of antennas.  Now change either antenna and try again.  I bet your best range is with 2 Retevis', by far.  8)  By my recollection I got 200+ meters outside at 1.6mW through trees and houses with a pair of Retevis' vertical / parallel at 1m (base) and 2m (hand carried airplane) off the ground.
« Last Edit: Today at 07:26:25 am by TheOtherCliff »