East Lincolnshire Repeater Group
Stenigot Radio
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From experience I blew the microphone ground track on my

FT847 by using hard wiring, thankfully this was an easy fix.

PTT - if you create a hard wire bridge, you then need to think

about how you are going to key the radio into transmit.

Unless you're good with circuits your only option is to go with

VOX. This does work, and it works very well. However, there

are inherent TX start up and drop off times, so you could lose

some of your outgoing and incoming data so this is not recommended.

The Interface

The best solution is to install an interface unit;  an interface

will create the bridge for you between the radio and

computer. The interface will also handle keying your radio via

the computer’s communication RS232 port. The PTT circuit

employs either a reed relay or Opto isolator, the circuit that

handles this does it in an isolated manner.

The interface also performs another function where not only

does it carry signals to and from the radio/computer, but it

does it in electrical isolation to each other. The interface

employs a 600 Ohm isolation transformer in both TX AND RX

audio lines. This allows AC audio signals “the good” to pass

freely, however they block any DC currents “the bad” from

getting into your radio. The interface also uses an

electrolytic capacitor on the microphone line as good

measure to block any stray DC currents. The other function

of the interface is to remove any chance of ground loops “the ugly”.

No RS232 Comm Port I hear you say!!!!

Most modern laptops and computers no longer have comm.

ports built into them; the easy fix is to install a USB to comm.

port adaptor lead. Install the driver that comes with the lead,

insert the lead into the USB slot and your computer should

assign a comm. number - you now have one Comm. Port.


FLDIGI and HRD have a very useful CAT function. Once setup

you can control the radio’s controls via your laptop.

However,  for novice users I strongly recommend leaving this

until you have mastered the art of digi modes.

Remember “keep it simple”.

More on CAT in a later document.

Interface Options

There are many options available to us; each option offers

varied functions. However, as I keep saying, “keep it

simple”. You can pay anywhere from £25.00 to over £300.00 for an interface.

That just about sums this document up.  If I can be of help

please feel free to ask, and if you’re in need of an interface I

can help there as well.


Alan M0AQC