Prodrone antenna user guide

Prodrone antenna user guide

1. What the antenna does

The antenna converts the signal from your transmitter into a radio wave, and back again at the receiving end. Its parameters determine range, video quality and link stability. An antenna that is correctly specified and correctly mounted will work for years. One that is poorly matched or badly mounted can cut your range several times over, and in the worst case damage your transmitter.

2. Types of antenna

Linear polarization — simple designs such as dipoles and J-poles. Transmitting and receiving antennas need to be aligned in the same orientation.

Circular polarization — crosshair, MiCross, cloverleaf and helical antennas. Better at handling reflections off the ground and surrounding structures. They come in two senses: LHCP (left-hand) and RHCP (right-hand).

Omnidirectional — radiate evenly all around, normally used on the aircraft.

Directional — concentrate energy in one direction, trading beamwidth for gain. Normally used on the ground station.

3. Compatibility — check before first use

Band. The antenna works in the range it was tuned to, stated on the label supplied with every unit. Using it outside that range means heavy losses and unnecessary load on the transmitter.

Polarization. LHCP and RHCP must match at both ends of the link. Pairing a left-hand antenna with a right-hand one costs roughly 20–30 dB — in practice, no usable range. If you are not sure what is fitted at the other end, check its description or ask the manufacturer.

Connector. SMA and RP-SMA look almost identical but have inverted centre contacts. Fitting the wrong type gives no electrical connection, and forcing it damages both the connector and the socket.

4. Safe use

Never power up a transmitter without an antenna connected. All the power reflects back into the output stage, and many transmitters are permanently damaged within seconds. The same applies to a transmitter running with a damaged antenna, a broken one, or one connected through a loose connector.

Check the antenna before every flight. A cracked housing, a deformed radiator, a cable pulling away at the connector, or signs of moisture inside all change the antenna's parameters and load the transmitter.

Inspect after every impact or crash. Internal damage is not always visible from outside, but a fracture at the connector or a broken ground gives exactly the same symptoms as no antenna at all.

5. Fitting

Turn the connector nut only, never the antenna body. Rotating the body twists the cable inside and after a few times breaks the inner conductor. This is the single most common failure we see returned.

Do not overtighten. SMA connectors go on finger-tight, with at most a light nip with a spanner. Excessive force strips the thread and deforms the contact.

Avoid adapters and extensions. Every extra joint degrades the match and adds loss. The antenna was tuned with its own connector fitted — an adapter changes the conditions it was measured in.

Respect the minimum bend radius. Coaxial cable has a minimum radius below which it stops behaving as specified. Bending tighter deforms the dielectric and shifts the centre conductor relative to the shield, which changes impedance locally and raises VSWR — the antenna then measures worse even though nothing is wrong with the antenna itself. As a working rule, keep the bend radius at least ten times the cable diameter, and where a permanent bend is needed, form it once, gently, and fix it in place.

Do not flex the cable repeatedly in the same spot. Folding the antenna for transport, bending it against the frame, routing it across a part that moves — each cycle fatigues the braid and the centre conductor. The result is an intermittent fault: the cable looks fine, and the link only fails in flight or in one particular position. That is harder to diagnose than a clean break and more often ends in a lost aircraft.

The tell-tale sign is performance that changes when you move the cable. An antenna behaving that way should be replaced.

If the antenna has to flex in use, plan that bend well away from the connector, over as long a radius as possible, and support the cable so the movement is spread along a length rather than concentrated at one point.

Secure the cable against vibration. A loose cable works itself back and forth in flight and fails where it leaves the connector. Fasten it to the airframe, leaving enough slack for movement.

Keep the antenna clear of conductive parts. Carbon frames, battery packs, ESCs and power wiring all shift the match when close by. The more free space around the radiator, the closer the antenna will perform to the figures on its label.

Do not paint the antenna or wrap it in metallic tape. Metallic pigments and conductive tapes change its characteristics.

6. Care and storage

Cleaning. Remove dust and mud with a damp cloth. Do not use solvents — they attack plastic housings. Do not pressure-wash antennas.

Moisture. If water gets inside an antenna, its parameters shift and usually do not recover once it dries. Have a suspect unit measured, or replace it.

Connector. Keep the contact clean and dry. A dirty or oxidised contact is pure added loss.

Storage. Never hang an antenna by its cable, and do not coil the cable tightly. Store it dry, with nothing pressing on the radiator.

7. The measurement label

Every Prodrone antenna ships with a label stating the frequency it was tuned to. On 5.8 GHz antennas the label also gives the measured span and the VSWR ceiling inside it.

Keep the label. When you order another antenna for the same set, those figures let us tune the new unit to match the one you already have.

8. Common mistakes

• Powering a transmitter with no antenna, or with the antenna not properly tightened.
• Mixing up LHCP and RHCP.
• Mixing up SMA and RP-SMA and forcing the connection.
• Tightening the antenna by its body instead of the nut.
• Mounting the antenna hard against a carbon frame or battery pack.
• Using adapters and extensions "just for now".
• Leaving the cable loose and unsupported against vibration.
• Carrying on flying after a heavy impact without inspecting the antenna.

9. When to replace or send it in

• Visible cracking of the housing or deformation of the radiator.
• Cable damage, particularly where it leaves the connector.
• Play in the connector, or a centre contact that is loose or rotates.
• A sudden loss of range with nothing else in the system changed.
• Signs of moisture inside the antenna.

If you are not sure, we can measure the antenna here. Contact us before sending anything: bartek@prodrone.pl, +48 725 908 725 (also WhatsApp).