hi folks,
i am not sure if this is already discussed before. I had a site where there were 5 users connected. The AP is TPLINK 501G with 15 dbi Omni Antenna. The clients r TPLINK 501G as well. Recently the clients started asking for 1-2 mbps speeds so I thought we should upgrade the AP. I got a 751U-2hnd configured as AP. Connected the MMCX connector to the 15 dbi Omni.
But now I see issues:
The nearest client earlier showed a signal of 72 db now the signal drops to 40 db. some clients go missing.

Can someone tell me what could be the cause?
1. Antenna is same.
2. Pigtail is same.
3. Site pole/mast is same

4. TPLINK 501G AP is 65mW replaced with Mikrotik 751u-2HnD 1000 mW

Please help resolve.

Welcome to the team of RB751 owners - It's not my first MikroTik device, but the only which I can't deal with.

Here are few links for you:
Boosting RB751U-2HnD Antennas! http://forum.mikrotik.com/viewtopic.php ... ilit=rb751
RB751U-2HnD - poor wireless performance & problems http://forum.mikrotik.com/viewtopic.php ... ilit=rb751
RB751 CPU usage get too high http://forum.mikrotik.com/viewtopic.php ... ilit=rb751
RB751u-2HnD wireless connection issues with Apple Macbook http://forum.mikrotik.com/viewtopic.php ... ilit=rb751

There are many more. You can search for them.
Please post output of command: /interface wireless export compact

The nearest client earlier showed a signal of 72 db now the signal drops to 40 db. some clients go missing.

-40dB is very good signal
-70dB is much worse

It looks like your signal actually improved.

The nearest client earlier showed a signal of 72 db now the signal drops to 40 db. some clients go missing.

-40dB is very good signal
-70dB is much worse

It looks like your signal actually improved.

nah normis. the client is a tplink CPE 501G the higher it is the better it goes at far distances it shows signal
as -5 db. i agree with mikrotik/ubnt clients the lesser the better. It shows something like:
Wireless
Operating Mode: Client
Signal: 71 dB
SSID: xyz
Channel: 6
Mode: 11Mbps (802.11b)
IP Address: 192.168.17.4

# jan/02/1970 01:28:36 by RouterOS 5.6
# software id = BX7Q-QEQV
#
/interface wireless security-profiles
set default authentication-types="" eap-methods=passthrough group-ciphers="" group-key-update=5m interim-update=0s \
management-protection=disabled management-protection-key="" mode=none name=default radius-eap-accounting=no \
radius-mac-accounting=no radius-mac-authentication=no radius-mac-caching=disabled radius-mac-format=XX:XX:XX:XX:XX:XX \
radius-mac-mode=as-username static-algo-0=none static-algo-1=none static-algo-2=none static-algo-3=none static-key-0=\
"" static-key-1="" static-key-2="" static-key-3="" static-sta-private-algo=none static-sta-private-key="" \
static-transmit-key=key-0 supplicant-identity=MikroTik tls-certificate=none tls-mode=no-certificates unicast-ciphers=\
"" wpa-pre-shared-key="" wpa2-pre-shared-key=""
add authentication-types=wpa-psk,wpa2-psk group-ciphers=aes-ccm group-key-update=5m interim-update=0s \
management-protection=allowed management-protection-key="" mode=dynamic-keys name=profile1 radius-eap-accounting=no \
radius-mac-accounting=no radius-mac-authentication=no radius-mac-caching=disabled radius-mac-format=XX:XX:XX:XX:XX:XX \
radius-mac-mode=as-username static-algo-0=none static-algo-1=none static-algo-2=none static-algo-3=none static-key-0=\
"" static-key-1="" static-key-2="" static-key-3="" static-sta-private-algo=none static-sta-private-key="" \
static-transmit-key=key-0 supplicant-identity="" tls-certificate=none tls-mode=no-certificates unicast-ciphers=aes-ccm \
wpa-pre-shared-key=netlite123 wpa2-pre-shared-key=netlite123
/interface wireless
set 0 adaptive-noise-immunity=none allow-sharedkey=no antenna-gain=0 antenna-mode=ant-b area="" arp=enabled band=\
2ghz-b/g/n basic-rates-a/g=6Mbps basic-rates-b=1Mbps bridge-mode=enabled channel-width=20/40mhz-ht-above compression=\
no country=india default-ap-tx-limit=0 default-authentication=yes default-client-tx-limit=0 default-forwarding=no \
dfs-mode=none disable-running-check=no disabled=no disconnect-timeout=3s distance=dynamic frame-lifetime=0 frequency=\
2437 frequency-mode=manual-txpower frequency-offset=0 hide-ssid=no ht-ampdu-priorities=0 ht-amsdu-limit=8192 \
ht-amsdu-threshold=8192 ht-basic-mcs=mcs-0,mcs-1,mcs-2,mcs-3,mcs-4,mcs-5,mcs-6,mcs-7 ht-guard-interval=any \
ht-rxchains=0,1 ht-supported-mcs="mcs-0,mcs-1,mcs-2,mcs-3,mcs-4,mcs-5,mcs-6,mcs-7,mcs-8,mcs-9,mcs-10,mcs-11,mcs-12,mcs-\
13,mcs-14,mcs-15,mcs-16,mcs-17,mcs-18,mcs-19,mcs-20,mcs-21,mcs-22,mcs-23" ht-txchains=0,1 hw-fragmentation-threshold=\
disabled hw-protection-mode=none hw-protection-threshold=0 hw-retries=7 l2mtu=2290 mac-address=00:0C:42:F8:5D:2B \
max-station-count=2007 mode=ap-bridge mtu=1500 name=wlan1 noise-floor-threshold=default nv2-cell-radius=30 \
nv2-noise-floor-offset=default nv2-preshared-key="" nv2-qos=default nv2-queue-count=2 nv2-security=disabled \
on-fail-retry-time=100ms periodic-calibration=default periodic-calibration-interval=60 preamble-mode=both \
proprietary-extensions=post-2.9.25 radio-name=000C42F85D2B rate-selection=advanced rate-set=default scan-list=default \
security-profile=profile1 ssid=xyz station-bridge-clone-mac=00:00:00:00:00:00 supported-rates-a/g=\
6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps,48Mbps,54Mbps supported-rates-b=1Mbps,2Mbps,5.5Mbps,11Mbps tdma-period-size=2 \
tx-power-mode=default update-stats-interval=disabled wds-cost-range=50-150 wds-default-bridge=none wds-default-cost=\
100 wds-ignore-ssid=no wds-mode=disabled wireless-protocol=any wmm-support=disabled
/interface wireless manual-tx-power-table
set wlan1 manual-tx-powers="1Mbps:17,2Mbps:17,5.5Mbps:17,11Mbps:17,6Mbps:17,9Mbps:17,12Mbps:17,18Mbps:17,24Mbps:17,36Mbps:1\
7,48Mbps:17,54Mbps:17,HT20-0:17,HT20-1:17,HT20-2:17,HT20-3:17,HT20-4:17,HT20-5:17,HT20-6:17,HT20-7:17,HT40-0:17,HT40-1:\
17,HT40-2:17,HT40-3:17,HT40-4:17,HT40-5:17,HT40-6:17,HT40-7:17"
/interface wireless nstreme
set wlan1 disable-csma=no enable-nstreme=no enable-polling=yes framer-limit=3200 framer-policy=none
/interface wireless align
set active-mode=yes audio-max=-20 audio-min=-100 audio-monitor=00:00:00:00:00:00 filter-mac=00:00:00:00:00:00 frame-size=\
300 frames-per-second=25 receive-all=no ssid-all=no
/interface wireless sniffer
set channel-time=200ms file-limit=10 file-name="" memory-limit=10 multiple-channels=no only-headers=no receive-errors=no \
streaming-enabled=no streaming-max-rate=0 streaming-server=0.0.0.0
/interface wireless snooper
set channel-time=200ms multiple-channels=yes receive-errors=no