[Yaesu] Radio Shack simplex repeater on FT90

[Pres Waterman]

Step-by-step modification instructions for the Radio Shack 19-345 simplex
repeater
for use with the FT-100/FT-90 which have discrete ( and multiplexed ) PTT
lines

UNHAPPY DEVELOPMENT: The FT-100 does not work well, I think in "beta 3" I
will try an optoisolator for PTT

BUT the FT90 works well and I am going skiing with it tomorrow!

Caution: this project involves Surface Mount Devices, and soldering tiny
wires directly to them at the point where they meet the PCB. Please do not
contact me for advice beyond what is given here. These steps worked for me.
There are NO schematics and no pictures of my project available. Just use
these steps and make it up as you go along! I did...

Intro: The Radio Shack simplex repeater, currently closeout/blow-out priced
at USD$4.97, is a dandy deal. It is used to hook up to an HT whose mic input
also causes PTT ( transmit ). Why would you want one, you say? Well, besides
boosting range between handhelds without using a "real" repeater there's
propagation/antenna testing, audio checks, and in general goofing around.
But it would be nice to use it with a higher power mobile such as the FT-90
or FT-100, or a base rig. But, alas, the mobiles and bases typically use a
contact closure to ground separately from the mic line. Here's where the mod
comes in. Try to score several of these little dandies to screw up your
first one and have 2 spares!

( receive signal valid is internal VOX in the repeater so it's quite simple
to use )

Items needed:
19-345 repeater ( Did I mention it's only FIVE BUCKS? )
6-pin modular RJ-12 plug with all 6 wires present and a cable
a single wire with mini-phone 1/8" or 3.5mm mono plug ( must be skinny
enough to fit into the speaker socket on the FT-90 which is recessed )
a nice option: two color, 3 lead red/green lead with common ANODE and a
470ohm resistor
100kohm resistor for PTT pull-up
1kohm trimpot for audio control to radio

1) remove the repeater from the case- there is a hidden screw under the
sticker on top! Also one attaching the PCB.

2) remove the battery contacts after noting +/- on the PCB with a permanent
marker- discard them

3) BONUS STEP: remove the green LED which only indicates receive signal
present. Replace it with a 3-LEAD 2-color LED, with green hooked up as
before. I used Radio Shack 276-207 Bi-Color LED which is kick-butt bright
and big. When you have put in the new LED you will have an unconnected wire
for the red element. Hook that through a 470ohm resistor via a flexible wire
( like ribbon cable stuff ) to the middle contact of the tiny three-lead SMT
transistor marked 433 which is by the stereo mini socket. That is, by the
way, the PTT output and we will be hooking to it later. The LED will be left
on the unpopulated side of the board. Or you may want to flip it. The "red"
lead connects via a 470ohm which runs across the board, through the hole
between the 2 jacks, and over to the SMT transistor, so a spaghetti tube is
called for. Also, insulate the connection between the "red" lead and the
resistor, because if that point shorts to ground you will bypass a current
limiting resistor and harm ( at least ) the LED.

4) Get a 6 conductor cable with RJ-12 ( NOT RJ-11 ) fully populated modular
plug. Looks exactly like a phone cord, but 6 pins, not 4. Get to know the
colors. Looking into the body of the plug, as if you were about to plug it
into the jack, left to right with the latch down:

pin 6: PTT ( and ACC and UP and DOWN )
pin 5: Mic audio in
pin 4: Ground
pin 3: +9v
pin 2: ignore ( packet audio out on the FT-90 ) ( shame it's not squelched-
would eliminate the speaker lead )
pin 1: other switches we don't need, ignore

So, we are interested in four of these, plus a connection to the speaker
socket. Remember the colors for each.

IF you decide to hack up the very long mic extension cable for the FT-100
separation kit, and you feel you CAN reattach a new RJ-12 plug to the cable,
the colors are: shield=ground; black <yup!>=+9v; yellow=PTT; white=mic to
radio

To tell the truth, I found the wire inside that cable to be between
difficult to impossible to solder, I would try other stuff. My prototype
used CAT5 network cable but it's rather stiff.

5) Run the 2 cables ( mic and a single wire for speaker ) through a PCB hole
and secure them, using plastic wire wraps or whatever else method makes
sense to you

6) connect the speaker lead by tack-soldering to the stereo submini socket
on the PCB at the outermost contact not counting the ground connection. Beep
it out with the original cable if not sure.

7) connect +9v and the ground braid to the areas where the battery contacts
were. At this point, plug it in and check for a flash of green when plugged,
and that opening the squelch triggers the green LED.

8) Connect the mic lead to ( watch carefully the description ) the tiny SMT
resistor by the stereo socket, that has continuity to the original "Y"
cable's submini 2.5mm or 3/32" tip when the "Y" cable is plugged in. Oh
Jeez, read that twice. You are trying to connect to the same place the "Y"
cable was connected to, except on the board.

8A) Unlike FT100, FT90 users have no mic gain menu. The output of this
simplex repeater is HOT even when the input is set right. There's a lot of
hiss due to excessive mic sensitivity also. So I also tack soldered a 1k-ohm
trimpot glued to the PCB. One leg to ground, the opposite lead TO the radio,
the middle to the simplex repeater output as mentioned in 8)

9) PTT goes to the point mentioned in "bonus' step 3. ALSO a 100k-ohm pull
up resistor MUST go to +5v. I got it from the center anode lead of the LED.

Adjustment steps:

A) After plugging in the speaker, plug in the cord to the radio. Observe the
green light flash and the red light glow. For some reason, the red LED glows
medium strength in standby, plus green in RX, and bright red in TX. I don't
know why, but I like it!

B) volume down, carrier mode, squelch open, advance the volume just until
the green receive light glows, then close the squelch.

C) Speak and hear yourself repeated, low and hissy. Advance the volume until
you are robust, or until no further volume increase is noted, and then back
off.

D) open the squelch and record up to 30 seconds of white noise. Bring down
the mic gain in FT-100 menu or the 1k-ohm pot on the FT90 until it begins to
"back off". At this point you should sound full but not overdriven, without
hiss in the background. I actually have it sounding pretty darn good.

E) play with various volume and mic gain scenarios.

FT90 bug: since the PTT is multiplexed with the "ACC" and UP and DN buttons,
sometimes, despite the pull-up resistor, the radio switches between the 2
"home" channels as you are plugging it in. I suggest you use the UHF or VHF
"home" channel and if it toggles them keep plugging it in until it settles
on the intended band. Sorry, this is beta testing and I haven't knocked
this. The 100k SHOULD have solved it by holding the PTT line at 5v until PTT
is called for.

Simplex repeater characteristic: it is rated to notice signal within 2
seconds. Typically it is faster. IF you have the volume just high enough it
will probably open right away. But you and your users might have to
"Aaaaaaah" before talking, or wait, and you will quickly get used to what is
necessary, especially since you have instant feedback!

You do not need coordination for this operation. Just be sensible. Don't set
up on a high hill in carrier on the national calling frequency. BTW: I
highly recommend you use tone squelch or even DCS... and you CAN use a
"repeater pair" on the simplex repeater radio... that way users don't hear
each other as they speak before they are repeated. Only themselves repeated.
With a cool little beep when they are done! ( 30 seconds capacity BTW ).
Identify the repeater as it is a separate transmitter ( like "This is W2PW
on W2PW repeater"... and only one of you have to do it. Maintain control:
local, wireline, 222+MHz link, you know the drill.

Pres Waterman, W2PW
c/o Patchogue 112 Ford//Kia 112
Long Island Ford and Kia Dealer

Currently 2 NEW 2002 T-Birds in stock, $50k ea.