I have a custom built radio
unit to run with comms that I acquired from a broadcast OB van. they have basically built a belt pack and a
uhf radio into one
unit inside a box, using the exisiting circuitry of both, if you talk on the radio it is broadcast to all comm stations and the radio can be set to transmitt what is said on the comms loop or switched off. it is very useful for some shows, i have also used it as a
venue supervisor to listen to comms during a client operated show.
If all goes to plan, what I will have is in each
beltpack, the guts of two
UHF radios, one continuously transmitting and the other receiving. I will make my own battery pack for each one so that I can have enough
power for continuous transmission, and to save space. I am assuming that if I remove the casing of the
UHF, the
speaker and the battery pack, the remaining components should be relatively compact. If so, I will make a case out of sheet-metal and mount allof the components inside.
For the
base station I will have one
UHF receiving from each
beltpack and another transmitting to all beltpacks for the listen
channel.
From what I have read, I will need a big
capacitor on the signal
line to remove the
call signal (possibly trying to use the
call signal to trigger a
call on the radios, but that is a low priority) input the filtered signal
line into the mic input of the transmission radio in the
base (possibly requiring a resister to
drop the
level to an acceptable
level). The transmission radio will
send to all beltpacks. The output from the receive radios in each
beltpack will feed the
headphones. The mic on the
headset will go into the mic input on the transmission radio in the
beltpack, which will then transmit on it's own frequency back to the
base receive radios. The output signal from the receive radios in the
base will be mixed together, be dropped to
line level and put back into the party
line.
From what I can see, the number of beltpacks will only be limited by the number of available frequencies.
Another low priority will be to make the wireless
base into a wired
base. Correct me if I am wrong, but from what I have read, to make a partyline
base, all I need is a 30V
transformer feeding the
power pin on the
line, and a 200ohm resister between the
ground and the signal
line. Also a 12V
LED (or lover
voltage connected through a resister to lower the
voltage) connected to the signal
line for
call signal. A 12V
call signal could also be sent down the signal
line for
call. This would obviously have to be switched so that when the
unit is not being used as a
base, the 200ohm resister does not interfere with the rest of the
system.
Also a headphone amp and mic pre-amp could be connected to the signal
line on the partyline at the
base so that a local
headset could be connected.
I'm sorry if this doesn't make much sense. If you can comment on the design, it would be most appreciated.
Tom