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Homemade Stuff old and new
Homemade Cross Band Repeater VHF UHF
First I like to say, YES many new DUAL band radio models allready got a local repeater mode / cross band function.
however they cost money, and are no fun at all to install, unpack box, power up, forget and use, where is the fun.
I wanted to make a NO MONEY remote or home located cross band repeater system to use with my friends,
so I started to ask arround for free stuff we all got to put into this system.
Thanks to all nice radio amateur friends who donated equipment and their time into this project.
I am happy to say I did manage to create a full remote station, no money was spend at all,
the system even ended up with internet access for remote on/off and audio listen via Teamview (free PC/android program)
simplified function block schematic.
Centre top: power distribution, with voltage and current measurement
Sensor used ACS755SCB-150 nice floating sensor handle hundre amperes
Top right: Procom duplexer filter, modified with N connector on antenna port.
An old Procom duplex filter, with this it is possible to connect TWO radios using two different bands
to ONE cable, the antenna is offcourse a two band model.
closeups of the power distribution and current sensor
system voltage is also measured in this point and feeds the controller box too
DEANS connectors are very cheap, easy to get, handle VERY hight currents.
Controll box LED readout
VHF squench, VHF TX, UHF squench, UHF TX, Alarm, Disable via PC, Enable, Power
The radios, Stornophone 5000 VHF 2meter band, 21Watt out
Philips FM1000 UHF 70cm band, 27Watt out
Inside the controller box, a standard IO-100 board is used (own design)
Top right, trimmers for modulation levels,
Bottom right, simulating Squelch open signals for software development with no radios connected.
The two gray wires are PTT out via open collector transistors.
After this picture was taken, temperature sensor wire added
Both radios was modified with DB9 MALE connector, 6-7-8-9 = Ground
5: + 12V out after power switch via diode
4: Squelch open signal, active hight
3: Line Audio out before squelch circuit
2: PTT Transmit signal, pull low for TX
1: Mic input (attenuated 5 times in the radio so higher voltage level is used in the cables)
After this picture was taken, temperature sensor LM60 on little PCB mounted on the UHF radio
I could also add a sensor on the VHF radio, but it just made most sense to mount ONE on the hottest radio
and use this temperature for alarm and shut down in case fan stops due to error.
I used two 24V fans, connected to 13V they run very nice and quiet, and still keep the radios cold enought
the idea with two fans is : if one brakes down the system can still work.
Audio out to PC from both radios with speaker out and transformators.
it is a normal solution to avoid ground loops and humm on audio lines, using transformators between radio and PC equipment.
The two secondary windings of each trafo are connected in series, this way the signals are added together
so both can be listened to via a remote internet link using various software types,
I use TeamView, so far it works good, however in the Android version for cellphones audio listen is NOT possible,
the PC version works good with audio listen.
some notebook PC's dont have a LINE input connector nor such mode using the mic input.
so I added a 10:1 signal attenuator and signal spiltter as close to the pc input as possible,
it always give better signal to noise ratio when you use higer signal levels in the cables.
so far the serial out/in is simply connected to a PC, using a terminal program to monitor and controll
the text scrols fast up, so simply read the last line is all I need to do.
the information read out from left:
Supply Voltage, Total Current, UHF radio temperature in celcius, Actual VHF TX time in sec, Actual UHF TX time
TIME OUTS is activated, total transmit time days hrs mins sec.
so far the remote commands are only TWO :
E or e for Enable
D or d for Disable
Since only I know how to remote access this computer with ID code and password,
there is no need to add any hard to handle or hard to remember command strings
it actually works from my phone too..
Here is how it repport if link is disabled
it is possible to enable and disable the system WHILE a QSO is going on
and see a LIVE change of the transmitter in use.
Here is all the parts on the table.
I think a nice case for all of it could be smart, maybe I fix it one day.
The most important item is.... a good antenna position.. I think this one looks ok.
The Antenna IS straight up, just fine ! it is the tower that is not straight, it is a special tower.
A little side note on cross band / private repeaters
we found it only makes sense for ONE person to use it at one time
the MAIN frequency can be used by many, they MUST offcourse as normal be able to reach each other.
the ONE persion who can not reach all others, can use his own cross band repeater.
For example a person is located in his own garden with a little handie on low power,
he is connected to his own home repeater wich is using a tower/roof antenna.
he now got now full range. Another user far away could actually use his repeater at the same time,
but he will not be able to hear the input signal on his little one band handie radio.
so doubling and trouble is very likely to happen, since the other user can maybe hear the little handie
if he got a DUAL band radio and can listen on the output too,
avoiding feed back if hard if you listen on both bands at the same time,
This is one of the most important disadvantage of a crossband repeater, more info here: