Radio Communication Labs SAFE SPEAK HF3 User manual

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RADIO COMMUNICATION LABS
SAFE SPEAK HF3 Hands-Free Microphone
User’s Manual
Revised March 29th 2020
Firmware Revision 7
Radio Communication Labs
Trading as Ralph Parkhurst and Associates
ABN 31 841 821 803
Ringwood North, VIC 3134
AUSTRALIA
Telephone: [phone]
Email: [e-mail]
Web: www.radcomlabs.com
Copyright © 2020 by Radio Communication Laboratories
ALL RIGHTS RESERVED

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Warranty
If this product fails due to defects in materials or workmanship during the
period of one year from the date of purchase, Radio Communication Labs
will repair or replace the device, at our option. This warranty covers defects
in manufacturing discovered while using the product as recommended by
the manufacturer.
The warranty does not cover loss or theft, nor does coverage extend to
damage caused by misuse, abuse, unauthorized modification, improper
storage conditions, lightning, or natural disasters.
Should the product fail, your sole recourse shall be repair or replacement, as
described in the preceding paragraphs. We will not be held liable to you or
any other party for any damages that result from the failure of this product.
Damages excluded include, but are not limited to, the following: lost profits,
lost savings, lost data, damage to other equipment, and incidental or
consequential damages arising from the use, or inability to use this product.
In no event will Radio Communication Labs be liable for more than the
amount of your purchase price, not to exceed the current list price of the
product, and excluding tax, shipping and handling charges.
Radio Communication Labs disclaims any other warranties, expressed or
implied. By installing or using the product, the user accepts all terms
described herein.
To obtain service under this warranty, please email [e-mail]

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Introduction
Congratulations on purchasing a SAFE SPEAK HF3from Radcom Labs, the
third generation of our unique Hands-Free microphone system for two-way
communications. The HF3 can be used with almost any radio (mobile, base
station or handheld). It is ideal for either permanent installation in a vehicle
or temporary use for emergencies or special events.
A frightening reality is that holding a mobile two-way radio microphone in
front of you and steering a car one handed is downright dangerous. The HF3
aims to help make operating a two-way radio safer, by minimising the time
your hand is off the steering wheel. It also helps to overcome the issue of
microphone placement (and the inherent acoustic problems within a car) and
lets the radio easily switch from receive to transmit and back again.
Why Hands-Free?
Safety – keep hands on the steering wheel whilst using your radio
Improved TX audio – the electret microphone is at a constant
distance from the user’s mouth and tailored for optimum frequency
response within your vehicle
No more curly cords– a tiny (8mm x 15mm) microphone (supplied)
can be discreetly installed to provide a neat and tidy installation.
XYL approved!

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Features of the SAFE SPEAK HF3
-Pre-built hardware for plug-and-play operation
-Adjustable microphone gain control
-Adjustable bass and treble audio equalisation
-All adjustments are made using multi-turn trim pots for fine ‘tweaking’
-8 choices of timeout timer duration can be configured:
o30 seconds
o60 seconds
o2 minutes (factory default)
o2.5 minutes
o3 minutes
o4 minutes
o5 minutes
o10 minutes
-Momentary pushbutton TX switch
-LED provides “on-air” indication
-Visual LED and audible piezo indication to warn of impending timeout:
o10 seconds before timeout, and
o5 seconds before timeout, with a different sound and flash rate
-Electret microphone included
-Mounting bracket included
-No adjustments or modification required inside your radio
-Designed to work with just about every radio transceiver
-Works with radios that provide +5v, +8v or +9v DC via the mic pins, or
instead via a 12-volt DC input socket at the rear of the device.
Add-ons
The following add-on options can be purchased on the RadCom Labs
website:
•Y RJ45 connector – use the HF3 in parallel with an existing mic
•RJ45-RJ45 cable, available for popular Icom, Kenwood, Yaesu radios
•RJ45-bare wire, to make your own cable

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Installation
Power Connection:Many modern radios provide +5v or +8v or +9v at the
microphone connector – this will power the HF3 directly from the mic socket
with a single cable to suit your radio (e.g. RJ45 to RJ45).
Radios that do not provide +DC power at the mic socket can still be used -
in these cases 12 volts can be applied separately to the HF3’s “12V DC”
external power connector (note that 12v DC power filtering and suitable
fusing is recommended). Note that the 12V DC connector is NOT protected
against reverse polarity.
IMPORTANT: The external 12V DC connector is only for radios that DO
NOT provide DC power via the microphone. If you use this external power
connector, then you must not apply power via the microphone cable as well.
How It Works
The HF3 incorporates the following circuit building-blocks:
Voltage regulator: The electronics inside the HF3 runs at 3.3 volts and a
LP2950 low-dropout regulator provides 3.3v internally and accommodates a
wide input supply-voltage range of up to 30 Volts DC. Normally, the
microphone socket on most radios will provide from 5 to 10 volts.
Mic preamp and audio equalisation: An MCP602 dual low-noise
Operational Amplifier provides an audio mic gain adjustment, a low-
frequency boost/cut and high-frequency boost/cut using a Baxandall bass
and treble tone control circuit.
Microcontroller: The low-power microcontroller provides all the timing and
switching functions associated with:
•Detecting a momentary push on the TX switch to start transmission
•Illumination of the LED indicator
•Activation of the radio’s transmit line (PTT)
•Operation of the built-in piezo buzzer to warn impending timeout

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The PTT transmit line to the radio is an “open collector” output that is driven
logic low (i.e. to ground) during transmit, as required by most transceivers.
In the rare instance you need to invert the sense of this PTT line, you can
solder a jumper on the PCB at position “A” (between IC2 and Q1) which will
invert the logic of the PTT line to the radio.
Rear Interface Connectors
NAME
PURPOSE
CONNECTOR
NOTES
12V DC
External DC power.
Only used when no DC
power is available from the
Mic connector
DC Power Connector Voltage range from 5v to 30v DC.
Centre pin is positive. In vehicles, fusing
and additional DC filtering is required.
RADIO
Provides interface between
the HF3 and the radio
transceiver
RJ45, 8P8C modular
socket
1 – DC Power, 5v to 10v typically
2 – Not used
3 – Not used
4 – PTT (Transmit)
5 – Ground
6 – Mic Audio
7 – Ground
8 – Not used
PTT
Input socket allows an
external PTT momentary
switch to be utilised
2.5mm mono
tip/sleeve socket
Tip – Connect to Ground to transmit
Sleeve – Ground
Use a normally open momentary
contact pushbutton switch
MIC
Input socket for the electret
microphone (supplied)
3.5mm stereo
tip/ring/sleeve socket
Tip – Audio
Ring – 3.3v DC to supply power to an
electret mic element via 2K2 resistor
Sleeve – Ground
Microphone Placement
Position and install the microphone as close as possible. The car’s “A Pillar” is
an ideal location. Connect the 3.5mm plug to the MIC socket on the HF3.

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RADIO socket (viewed from in front of the HF3’s RADIO connector)
Alignment of Mic Gain
Your HF3 is supplied with pre-set gain, bass and treble to suit most vehicle
situations. However, some adjustment of the MIC GAIN control is commonly
required and don’t be surprised if it takes you several attempts to get it just
right.
There is a fine line between effective microphone placement, trim-pot
setting, and background road noise transmitted. You need to find the best
balance between all three and what works for you.
With care, you should be able to achieve great results with only a minimal
increase in road noise – please note that depending on how far your
microphone is placed from your mouth and how “loud” your vehicle is, some
increased degree of background road noise is inevitable – the trick is to
make these adjustments carefully to prevent background road noise from
becoming objectionable. Adjust the gain control carefully – even half a turn
can make a lot of difference!
1 – DC Power from radio (5-10 volts DC)
2 – Not used
3 – Not used
4 – PTT Transmit (this pin is switched to ground when transmitting
5 – Ground
6 – Mic Audio
7 – Ground
8 – Not used

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Alignment of Bass and Treble equalisation
The Bass and Treble are pre-adjusted when the unit undergoes testing
before it leaves the factory. If you want to make changes, proceed as follows:
1. Start by rotating the Bass and Treble trim pots anticlockwise for at least
20 turns - this will ensure that they are all at their minimum value to
begin with.
2. Wind the BASS trim pot clockwise by 10 turns – this is halfway or
‘centre’ for the 20-turn trim pot.
3. Wind the TREBLE trim pot clockwise by 10 turns – this is halfway or
‘centre’ for the 20-turn trim pot.
4. The BASS and TREBLE trim pots are just like the Bass and Treble
controls on a HiFi amplifier, that is clockwise rotation from centre will
BOOST the Highs or the Lows, whilst anticlockwise rotation from the
centre will CUT the Highs and Lows.
5. Adjusting the BASS and TREBLE equalisation trim pots will affect the
overall gain, so you will find a degree of interaction is needed with the
MIC GAIN trim pot to compensate. Up to 12dB BOOST and CUT is
provided by the two equalisation trim pots.
Jumpers
Three solder jumpers are available on the PCB to provide additional
functions if needed:
Option A: When this jumper is soldered, PTT logic to the radio is inverted.
Option B: When this jumper is soldered, the timeout function is disabled.
Option C: Not currently utilised.
Powering on the HF3
Each time the HF3 powers on, the LED will flash and the piezo beeps three
times to provide confidence that hands-free mode is operating correctly.

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Operating the HF3
To transmit using the HF3, just briefly press the TX button. The LED will light
to indicate you are “ON THE AIR” and your radio will now be transmitting.
Initially your HF3 will have a timeout period set for 2 minutes – this means
that after 2 minutes of continuous transmission, the PTT line to the radio
transceiver will switch back to receive. Ten seconds before this timeout is
invoked, the LED will begin to flash fast giving a visual cue that timeout is
imminent. At the same time, a piezo buzzer warns you that only 10 seconds
remain before transmission stops. When only 5 seconds remain, the LED will
flash even faster and the piezo makes a different sound.
If you want to change the timeout from the default 2-minute period, please
proceed as follows:
a) Turn your radio off (which also turns the HF3 off when powered via the
Mic cable).
b) Whilst pressing and holding down the TX button on the HF3, power on
the radio. This will power up the HF3 and invoke the “configuration”
mode where you can adjust the timeout value. You can now release
the TX button.
c) Each time you briefly press the TX button again, the LED will flash
several times to indicate the new timeout setting:
•1 flash = 30 second timeout period is set
•2 flashes = 60 seconds
•3 flashes = 2 minutes (factory default)
•4 flashes = 2.5 minutes
•5 flashes = 3 minutes
•6 flashes = 4 minutes
•7 flashes = 5 minutes
•8 flashes = 10 minutes
After this, the configuration cycle rolls over, starting from 1 flash again.

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d) After you count the number of flashes appropriate to the timeout
period you desire, turn off the radio (and the HF3), pause for a
moment, then turn it back on again. The new timeout value is now
stored permanently.
e) If for some reason you don’t wish to use the timeout at all, it can be
disabled by soldering a jumper on the PCB in position B, but only do
this if you have a valid reason for doing so!
Specifications
DC Power 5 to 30 Volts DC, less than 9mA total maximum current
Controls Mic Gain, Bass (+/- 12dB), Treble (+/- 12dB)
Timeout 30 seconds to 10 minutes, user adjustable
LED indicator Yes, green front panel LED
Audible warning Yes, piezo warning buzzer when approaching timeout
Dimensions 90mm x 66mm x 30mm (overall)
Weight 200 grams, incl mounting bracket
Temperature 0° to 55°C operating
Included Mounting bracket, electret microphone, screwdriver,
user manual
FAQ
Q. Are there circumstances when the HF3 should not be used?
A. In our opinion yes, there are two; if you have a very noisy vehicle (truck
etc.) or you like to drive with the window down, you are probably better
to use the regular microphone rather than hands free - unless you can
position the microphone reasonably close to your mouth.
Q. Can the HF3 be used on HF/SSB?
A. Yes, it has been used with radios like the IC7000 (at 100 watts) and it
works exceptionally well. You are recommended not to use high levels of
audio compression when driving hands free - at high roads speeds,
excessive road noise can lead to a loss of intelligibility at the receiving end