How to Join Coaxial Cable: Methods, Loss and When Not To
Quick Answer: The reliable way to join two coaxial cables is a properly crimped F-type barrel connector on correctly prepared cable ends. Push-on couplers and twist splices work temporarily but add loss and reflection. For digital or satellite signals, replace the run rather than adding joints.
A joint in a coaxial cable is an impedance discontinuity, and every discontinuity reflects part of the signal. The question is not whether a joint costs performance but whether the system has margin to absorb it.
The Three Ways to Join Coax
Each method suits a different situation, and the difference in loss is measurable at high frequency.
F-type barrel connector
Two correctly prepared cable ends meet inside a female-to-female barrel. This is the standard field method for RG6 and RG59, and it preserves the shield if both connectors are crimped or compression-fitted properly.
Push-on coupler
A quick coupler slides over the prepared ends. It is convenient for testing and unreliable for permanent use, because the shield contact is not mechanically stable.
Twist or solder splice
Twisting the centre conductors and taping the shield destroys the geometry. It may pass a low-frequency signal and will fail at video or digital rates.
Preparing the Cable Ends
Most joint failures are preparation failures. The connector can only perform as well as the cut behind it.
Strip depth and dielectric
Use a stripping tool set for the cable type. The centre conductor must protrude enough to seat in the barrel without the dielectric entering the mating surface, and no braid strands may touch the centre conductor.
Shield contact
Folded braid or a compression sleeve must make solid contact with the connector body. A single stray strand bridging to the centre conductor produces a short that looks like a dead cable.
Loss at the Joint
Insertion loss for a good F-type joint is small but not zero, and it rises with frequency. The table gives typical planning values for a single joint.
| Method | Insertion loss | Return loss | Permanent |
|---|---|---|---|
| Compression F barrel | 0.1-0.2 dB | Good | Yes |
| Crimp F barrel | 0.2-0.3 dB | Good | Yes |
| Push-on coupler | 0.5 dB or more | Poor | No |
| Twist splice | 1 dB or more | Very poor | No |
| Wall plate with F connector | 0.2-0.5 dB | Fair | Yes |
When a Joint Is Acceptable
A joint is acceptable when the system has margin and the signal is not near the edge of its modulation scheme. Analogue television tolerates more than digital satellite, where a small reflection can push the receiver below its threshold.
Measure before and after
If a meter is available, compare signal level and bit error rate before and after the joint. A joint that costs 0.2 dB is fine; one that costs 3 dB indicates a preparation fault.
Count the joints
Two joints in a run are usually tolerable on a strong signal. Five joints, each with a coupler, add up to more loss than the amplifier can recover.
Better Than Joining
If the cable is short, replace it with a single length. If the run is fixed in a wall, install a wall plate with a proper F connector rather than pulling the cable through a hole and joining it behind the drywall. For satellite and digital audio, treat every added joint as a risk to be justified by access rather than convenience.
Two Joints That Had to Be Made
Sometimes the cable cannot be replaced, and the joint has to be good enough.
Extending a satellite drop to a moved television
A compression F barrel and two correctly prepared ends add about 0.2 dB. The receiver still has margin, so the joint is acceptable.
Relocating a CCTV camera by 3 m
The existing cable is short. A push-on coupler held for a week and then failed in damp conditions, which is why the permanent fix was a proper barrel inside a housing.
Frequently Asked Questions
Can you splice coaxial cable without a connector?
You can twist and tape the conductors, but the result has poor shielding and a large impedance mismatch. It is a temporary repair at best and will fail on digital signals.
What connector do I need to join two coax cables?
A female-to-female F-type barrel, plus an F-type connector on each cable end. The barrel and connectors must match the cable impedance and diameter.
Does joining coax reduce signal strength?
Yes. A good compression joint costs about 0.1 to 0.2 dB; a poor one costs far more and adds reflections that damage digital reception.
Can I join RG6 to RG59?
Mechanically yes, with F connectors sized for each cable and a barrel between them. Electrically it creates an impedance step, so keep the joint short and avoid it on critical runs.
How many joints can a coax run have?
There is no fixed number. Each joint adds loss and reflection, so count the total against the system margin; more than two or three is usually a sign the run should be replaced.
How this guide was built: Built from coaxial field-termination practice: strip geometry, shield bonding, joint insertion loss and reflection at impedance steps. Disclosure: No manufacturer names or prices are given. Loss values are planning figures; measure the installed link where signal margin is critical.