TW1000/ rs446 review.

Thanks to Rob on the Euroscanner mailing list:
The receiever sensitivity on them is awesome when peaked up! way better than my T8E!

Mine are better than -129dBm for 12db SINAD - seriously ! I had to put an external attenuator on the sig genny to peak them! they are also probably one of the few sets that lend themselves to "modding" (not that anyone would do that of course!) but the effects are possibly irreversible mechanically - beware! ('Bigbloke' says : "I have measured it (TW1000) under lab conditions as being around -126 dBm for 12dB SINAD - gobsmackingly sensitive for a cheap and cheerfull radio!")

Squelch threshold was set way too hard as well - fortunately its a pot on the board!

Mic sensitivity is quite down - but that can be "upped" by a chap of your calibre "Sans doubte!" ;-)

The thing I find most annoying is the volume control and the "keyboard bleep" loudness.

The minimum volume is still quite loud and the irritating "BE-BE-BE-BEEP" when you are at a maximum of minimum on the volume control.The keyboard bleep can be turned off (Hurrah!) but the volume control ony has 4 steps :-(

External speaker mike attachment is via a 3.5mm stereo jack plug but it is wired "Bass ackwards" to the way you might expect (i.e. plug a standard one in & it goes onto constant TX). Switching arrangements are "A la icom" by switching a DC feed driving the electret.


Pressing the power button gives the annoyingly loud "doodle-it!" type noise but it soon passes - dont plug it into an active earpiece !

pressing & holding function key invokes keylock - repeat to unlock.

pressing CH/VOL buttons increments / decrements the volume.

"Dapping" (a quick press and release for those not familiar!) the function key causes the following with each successive press:
RF channel select 1-8 (press FUNCTION again after selecting chan for CTCSS)
CTCSS select 1-38
toggle roger bleep (same "diddle-it" type noise as power up)
toggle keyboard bleep
invoke channel scan (NB! no CTCSS in this mode - tone defaults to 00)
invoke fixed channel CTCSS tone scan A la T8E
back to RF channel select ....

Not shown to the side are the PTT and the lamp button. A Short "Dap" causes green LED lights to illuminate for 5 seconds. "Dap and hold" - illuminates & breaks squelch You use the CH/VOL keys to change each selection & clicking the PTT once makes the changes complete.

Power is via 4 * AAA - a compromise for size. Use NiMH as its quite current hungry! you might get decent days heavy use at a rally with good NiMHs Not with 500mAH nicads I assure you!.

Receiver has an economiser which is shown by the flashing of the "P SAVE" (under the channel) indicators. There is a battery life indicator to the left of this but its not too clever. Economiser is silent unlike a PF1 ;-)


You'll need to pull out the bottom battery clips with pliers and whack 'em with a centre punch or similar as by default the battery clips didn't quite reach nicads or nimh's.

On the rear of the case are two spring loaded "slot in charger" type fittings but I've never seen a slot in charger or pack for these (easy enough to make though).

The call function sends a "Robotic-Turkey in distress!" type noise over the channel for about 4 seconds and you cant curtail it or stop it via the ptt.

There is no S meter but the antenna on the "radio" icon lights up during RX & TX it also lights up when there is someone using the channel on a different CTCSS tone.

I've seen some intermittency with these devices caused mainly by the connection of the PCB to the antenna (this I believe to be the cause of the problem on RF mans page -see last paragraph of text description on site)

There is a screw beneath the antenna on the rear panel which screws into a pillar on the front of the case. around this pillar slips a chromed metal "loop" which is the base of the helical ( not very bendy BTW! after your T8 experiences be warned Clive! ;-)) and the "Daughter board" slips over that before the rear case is applied.

The "daughter board" has a copper "ring" on the PCB through which the pillar passes.

The screw is the only thing that connects the antenna to the daughter board and as such if it comes loose or the set gets bashed you can end up with a "capacitive connection" rather than a physical one.

30 seconds with a file & soldering iron effects a semi permanent repair (worked for me!)