On Sun, 3 May 2020 15:40:55 +0100 (GMT+01:00), Jimk
wrote:

I bit the bullet & ran some network cables revently to get away
from using power line plugs.
I had some long patch cables in stock so threaded those through.

One through a gigabit switch, serves 2 raspberry pis running cctv .

When connected by dlink300av powerline adaptors the data
throughput seems higher than the new cable, with smoother
playback of recorded events & no lag.

Switch to the cable & it's very different & slower.... I was
hoping it would be at least as good if not quicker?

(The cable is in reality two CAT5 patch cables joined with a
straight through connector. Initially with a moderately priced
cat6 labelled connector it didn't work, with a cheapo but still
called cat6 connector it does, sort of, see above).

Next steps to resolve please?
TIA

In addition to the advice about checking whether operating speed is
10, 100 or 1000 Mbit/sec, you should also check the interface counters
to see if the error rate is significant.

If you're running Linux, then "ifconfig" should give you something
like this - see the "RX errors" and "TX errors" lines:

ens33: flags=4163UP,BROADCAST,RUNNING,MULTICAST mtu 1500
inet 192.168.159.138 netmask 255.255.255.0 broadcast
192.168.159.255
inet6 fe80::20c:29ff:fe3f:43fb prefixlen 64 scopeid
0x20link
ether 00:0c:29:3f:43:fb txqueuelen 1000 (Ethernet)
RX packets 4088 bytes 523484 (511.2 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 3597 bytes 406309 (396.7 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

Note that many (all?) modern linuxes has depreciated "ifconfig" for
the "ip" command. You can normally install the net-tools package to
obtain ifconfig.

"netstat -i" also shows the counters like this:

Kernel Interface table
Iface MTU RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP
TX-OVR Flg
ens33 1500 4145 0 0 0 3653 0 0 0
BMRU
lo 65536 8395 0 0 0 8395 0 0 0
LRU

For network equipment, you might be able to use SNMP to read the
counters.