DKARS Magazine 201507

UV5R, UV82, BFF8, F8HP, UVB5/6 series
Cross Band Mini-Repeater Project / Fox Hunt made Easy
This project demonstrates the capability of the radios as a one-way cross-band directional ham repeater. Proper licensing and identification
is required when using and testing in this configuration.
This project shows how to configure a pair of Baofeng/Pofung
radios as a:
- Remote Base
- Fox Hunt Transmitter
- Mobile Cross-Band One-Way Repeater
Requirements
The requirements are Simple. All that is necessary for the initial
construction is a pair of Baofeng/Pofung series transceivers and
a 2.5mm/3.5mm audio cable.
Connection
The 2.5mm end is plugged into the top jack on the side of the
transceiver as shown below. This unit will serve as the receiver.
The 3.5mm end is plugged into the lower jack of the transmitter
unit.
This applies to the antennas as well. The greater the separation
between antennas, the less interference between radios.
Duplexers (Two radios using a single antenna)
To operate cross band (VHF/UHF) using a single antenna, a small
dual band duplexer such as a Opek DU-500 or MFJ 916B would
be required. This allows both radios to use a common antenna
without the VHF TX/RX interfering with the UHF TX/RX. This
eliminates the separation requirements of two antennas. To
operate both radios on the same band, a single band duplexer
must be added. These are much more expense and may be way
too impractical for such a simple project. Most duplexers are
designed for indoor or mobile use. Outdoors, they should only
be used under good weather conditions avoiding use when
there is precipitation.
Side Notes:
- A ‘Kitchen Table’ test may show the radios appearing to work when both are
set in the same band, but in reality, the transmitter will saturate or overload the
receiver. This is where field testing comes into play;
- Another consideration is Power. Handheld radios have limited heat dissipation
and will tend to overheat if used for long continuous transmissions. For long
duration use, consider running low power and keep transmissions short to avoid
damage to the transmitter;
- To legally run as a free standing repeater, the addition of an identifier may be
required, depending on your countries regulations. Some countries only require
the control operator or licensed operators to properly identify.
Accessories
An accessory that you may want to consider for long duration
use is a 12VDC Battery Eliminator. This will power the radios
from either a power supply or battery source.
Configuration
The VOX on the TX unit needs to be turned ON.
With VOX Level set to 1, the TX will drop approximately 2 seconds
after the RX squelch closes. With VOX Level set to 10, the
TX will drop immediately upon RX squelch closing.
Adjust the volume from the RX radio to a comfortable level.
Added Considerations for Field Operation
To conserve power:
- turn OFF the ABR (display illumination)
- turn OFF the Roger Beep
- use good antennas, such as J-Poles
- put he RX antenna up about 15' above the TX
Separation / Isolation
As shown above, one radio must be set to a UHF frequency
while the other is VHF for these radios to function with minimal
interference The frequencies selected should be set as far apart
as possible.
2.5mm / 3.5mm audio cable
UV-82 12V Battery Eliminator
Audio Auxiliary Stereo Cable
Tip to Tip
Ring to Ring
Sleeve to Sleeve
UV-5R 12V Battery Eliminator
This is meant to be a fun table top and learning project with a
practical use and a minimal cost investment.
Auxiliary Station FAQ information can be found here.
Choose your frequencies carefully and avoid frequency multiples.
A signal on 151,0 will be heard loudly on its 3rd harmonic
of 453,0 MHz
Thanks to John LaMartina
Website: http://www.miklor.com/
DKARS Magazine, editie 13 -10- juli 2015