2M Rx ( blue) Zares 70cm Transmitter , Basic Stamp Inside W2FS Controller ( 70 cms audio level pot ~ 47K)
A DTMF Controlled ICom IC-R75 Communications Receiver .
This is something I have always had a desire to do and I did
start the project using the old reliable IC R71 receiver which will
run on 13.8 v DC .. Since I was not at all sure of the computer connection for
this receiver ,I began to experiment with opto couplers across the
frequency and mode controls keypad . the
optocouplers were to be driven by the latched output of a DTMF
decoder . thus I had a scheme to remotely control the receiver on a
solar powered , low HF noise hilltop location a long way from the
built up area via a 2 m command frequency and listen to the HF
audio output on 70cms.
This is the hilltop farm site of our local 2m Linear repeater (
whose audio has to be heard to be believed ) and sounds just like a simplex
contact . The HF noise here at this site is purely atmospheric. We
are so far from any houses there is just no way local man made nearfield
noise contaminates the site . Its a perfect site for an HF receiver .
2M Rx ( blue) Zares 70cm Transmitter , Basic
Stamp
Inside W2FS Controller ( 70 cms audio
level pot ~ 47K)
I also had in the shack an Icom R75 receiver , which can be driven using an external computer control via a two wire system , the rear of the receiver has a 3.5mm mono jack plug for application of the bidirectional data and while perving on the net , with great luck I came across the article by John Hansen W2FS in QST for May 1998 titled " An Inexpensive Remote base station Controller Using the Basic Stamp" http://www.coastalchip.com/ This was the answer to my prayer ....dump the R71 receiver project and press the R75 into operation !. John had written the software to enable a Basic Stamp microprocessor to control an Icom 706 HF rig remotely via DTMF generated on a hand held radio . Download and Read the Article, it is very informative The beauty about the Icom radios is that all the rigs use the same basic control commands and what works on a 706 will most probably work on any computer controlled Icom ...within reason . So I studied up control codes, commands adresses etc for icom radios , There is an extremely informative german website http://plicht.de/ekki/civ/civ-p4301-r75.html which is a must read for anyone contemplating external control of icom equipment .
The PC Boards for the project are available ex stock from "Far Circuits" in USA , http://www.farcircuits.net/ so I ordered 4 pre etched and drilled PC boards at US$6 each ,plus postage down under , and Fred had them here in no time at all. Meanwhile I had ordered the Basic Stanp BS2 itself not cheap NZ$ 70 , educational programming kit locally, more $$$ ( which you do not need for this project as you can program the Stamp via your RS232 port on your computer straight into the W2FS remote base PC Board, ) and sourced the DTMF decoder equivalent ZARLINK CT8880 IC from a source in Australia . While waiting for all these parts I downloaded the Zipped Stamp Basic control program from the "net " source http://www.arrl.org/files/qst-binaries/ and studied it as closely as I could . also downloading the free programming software from the Parallax website . http://www.parallax.com/tabid/441/Default.aspx
When the parts were all here I assembled the pcboard connected all the audio in , out cables, required plugs switches sockets etc , I plugged the controller board into the Rs232 port switched the controller on and loaded the 706 controller software into the Stamp , connected it all up to the 2m radio ( control frequency) 70 cms radio my received HF audio output , IC-706 data connection and them tried different commands as described in the QST Article , Bingo it worked on the 706 so I swapped over to the data port on the R75 and bingo that worked as well ....jackpot!!
We now have the makings of a handheld controlled remote HF
receiver ( the 706 may have been a more versitile unit to place up
the hill as it has wide receive frequency coverage ), however the site is
solar powered and the 706 has a couple of undesirable features , like high
standing receive current and it would require modification to
remotely turn it on and off. We dont need to transmit from there as that can be
done from home where electrical supply is not limited ,and ambient local noise
is not a concern,
The original software is written to readout the frequency and modes of the
radio if interogated in CW ,This works well, but Im not a cw man so
I popped the UT 102 speech synthesiser into the R-75 so It
would speak the frequencies when commanded . There was some simple
basic commands added to the existing code to do this I "remed"
out the morse routine and dropped in the line of basic call subroutine ,
to command the speech synthesiser to read out frequency and operation mode
when the morse subrountine was called .
speech:
SEROUT 8,813,[$FE,$FE,$48,$E0,$13,$00,$FD]
(' to set speech synthesiser to talk)
RETURN
This did all I really wanted to as far as knowing frequency and modes the
receiver was on , however there was another extremely useful piece of
information I found in the Icom command codes !
The R8500 and R75 radios are the only icom radios that have
a software "on" and "off " function.....
Yahoo!! I dont have to solder an optocoupler across the
"ON-OFF" button to remotely turn the R75 off and on so I delved
into the basic stamp code again and inserted this line
'======================MAIN EVENT LOOP===========================
Gateopen:
HIGH 13
GOTO switch
'======================switch r 75 on ======================================
switch:
SEROUT 8,813, [$FE,$FE,$48,$E0,$18,$01,$FD]
' ( turn radio on
!! )
GOTO main
-----------------------------------------------------------------------------------
"" heaps of lines of code in between here ""
GOSUB morse
NEXT
RETURN
shutdown:
GOSUB id
SEROUT 8,813,[$FE,$FE,$48,$E0,$18,$00,$FD]
( turn radio off !!)
GOTO gateway
iddrop:
OUT7 = 1
PAUSE 100
OUT7 = 0
PAUSE 100
OUT7 = 1
GOSUB id
GOTO main
speech:
SEROUT 8,813,[$FE,$FE,$48,$E0,$13,$00,$FD] '
(to set speech synthesiser to talk)
RETURN
'=======================ROUTINE TO TRANSMIT MORSE=======================
'This routine is based upon Application Note #8 in the Basic Stamp 1
'manual
------------------------------------------------------------------------------
Now I can turn the Receiver off and on remotely ! change frequency,
mode have it all read back to me ,,,,, all with software !!
I dont have to worry too much about power budget as the
controller unit which draws milliamps , has a time out function so that if
you drop dead using the remote receiver or your handheld batterries go
flat it will turn everything off after a user "defined by
software " period of time go to standby and it works a
treat
.
Icom R-75 in Repeater shed . Blue unit is 145 Mhz
Receiver, 70 Cms hand held underneath charge meters
Now I am no programmer and the scruffy code i have inserted could no doubt be tidied , but it works you could add all sorts of commands to this code if you wanted to. I can now drive around in the middle of town not worrying about the crap sig to noise of the mobile HF transceiver as i can talk from my Vehicle to my friends on HF , and hear them coming back loud and clear at the remote HF site via the 70 cm backlink and the beauty of the icom 706 in the vehicle is i can have an HF SSB / 432 NMFB split to achieve this !!
What I have found with the system is sometimes the remote command unit must fall over when decoding DTMF multipath , If you find that it is not responding how it should . just leave the system for 5 mins or so and the stamp will clear itself and continue on as it should , Ive not had a situation where I could not get in and obtain control..
Looking towards Rotorua city 10Kms
away
Looking out west over lake Rotorua
we are so far from anywhere it takes 30Mins to get there from town with 4WD
Looking north east out to Maketu ( sea) looking East out to Mnt Tarawera
Well how well does it go ? after putting up the G5RV antenna and
connecting it to the receiver and listening on 10 m, we can hear the low
level background noise eminating from the little Zares 70 cms
synthesised transceiver ! so thats going to have to be quelled , hopefully a few
turns around ferrite toroids with the antenna coax and power supply
will help minimize that . Then when the sun comes out full shine and
the SLA batteries are fully charged, the bloody solar panel regulator makes its
presence felt by causing a whine on the received audio ( PWM
unit) I think this may be DC power induced as when I switch in
the R 75 preamp on 10m , the sig to noise improves but the whine
doesnt increase ! , need some good DC filtering me thinks
. You do however notice the improved signal when compare to my almost
identicle home set up ( G5RV and R-75 Rx ) on the same signals , my
background semi rural location still has a higher local background noise so
very weak signals , readable on the remote site are almost uncopyable on
the home set up . Well at least the guys in town with
their very high local noise level on 80 and 40 m will still be able
to work some good DX !!
The source code is a ZIP File 706stamp.zip and is at http://www.arrl.org/files/qst-binaries/ scroll down near the bottom to find MAY 1998
Cheers Mike ZL1BTB