Download Speed/telephone wiring

Hope I'm posting to correct forum.........Helping a friend in trying to establish reason for rediuced (loss of) broadband speed

BT main telephone line, entering via garage terminates in the master bedroom (yes that's correct) in NTE5 box. The main phone is plugged in here. Satellite phones are used throughout the house. A secondary box is located downstairs in his office. These were the only sockets provided when the house was buillt and the routing of the cables is unknown but presumed to be within wall cavities and/or under the floor.

Testing this configuration using a BT Home Hub 3 router from his office, indicates he is achieving around 4,5 mbps download

Now, and additional secondary, dual socket, box has been fitted in the garage directly connected to the customer side of the NTE5 box by approx 3 metre cable (bedroom adjoins the attached garage) . Plugged into this box is an external bell. Again with this in circuit a download speed of 4.5Mbps is achieved. Phones and external bell ring.

Now the rub.....An approx 30 metre cable runs from secondary box in the garage, round the house and into the lounge terminating in another secondary, dual socket box. With this in circuit the download speed drops to approx 2.5mbps.

Remove termination in lounge, still 2.5 Mbps.
Remove termination in garage secondary box, speed back to 4.5 Mbps
Reterminate garage end, drops to 2,5 Mbps
Remove termination in garage secondary box, speed back to 4.5 Mbps and so on

So this 30 metre extinsion cable, terminated or unterminated at lounge end when terminated in the garage, drops the speed by 2 Mbps.

The cable has been renewed. Same issue. All sockets connections has been checked for correct pin usage and wire colour code assigment. No issues there.

Appreciate an explanation on the above scenario, possible causes and what to try next.

Is all cable CW1308 compliant? Does this extension run externally and if so, how long has it been out in the fresh air?

Is the master NTE5 fitted with a filtered faceplate? And if so, are all connections taken from the filtered side?

Deadbeat,

Yes, Genuine CW1308 telephone cable staraight off a new reel

The master NTE5 has unfiltered faceplate. All; customer side connections are terminated on this facepakte. Filtering is on BT network side

Forgot to add that cable newly installled so only hours old as external connection. Gives same results as original cablencessth 38.2

The filtering cannot be on the BT network side. The Master is the demarcation point and filtering must be after that.

What filters do you actually have and where are they in the circuit?

There must be confusion in usage of terminology. Perhaps I was being too simplistic in my response.

With regard to the NTE-5 Line box. the removable lower half face plate contains no componets (capacitors or resisters). This face plate is where all customers intermal wiring is taken from. Thus I said the face plate is unfiltered.

The fixed upper half of the NTE-5 line box belongs to the service provider and contains surge protection, ring capacitor and out of service resister. Thus I said filtering was on BT side.

The router, internal phone and external bell are all connected into the customer sockets (master or secondary) via approved filter units

Does the faceplate have 1 socket or 2?

NTE master line box has only one socket.

Secondary in office has one socket

Secondary in garage has two sockets

Secondary in lounge has two sockets