ICOM-7851 musings

A friend has been having some issues with his new, rather gorgeous, ICOM flag ship radio, the IC-7851. CAT issues, com port issue, cw keying issues, STEPir tracking issues. This post is really to act as a record, and perhaps help anyone else with similar problems. All related to configuration, possible conflicts and other such annoying gremlins.

So, after removing the icom usb drivers, unplugging the usb cable, and reinstalling the drivers, then reconnecting the usb cable, the radio and computer seemed happy. COM7 and COM8 showed up in device manager. However, there does seem to be an issue where upon reboot, sometimes the USB devices will not be recognised. This issue is to be monitored and some more work perhaps required figuring out what is happening.

Moving on, we managed to get the radio talking to HRD and Logger32, at 19200 baud, 8n1, no handshaking, on COM7.

We then looked at CW keying over the USB cable, instead of running a separate cable and related serial interface. The IC-7851 presents two com ports as mentioned above, COM7 seemingly the CAT control, COM8 the keying port perhaps. Another friend did mention that COM8 might be second RX, but not entirely sure on that. Anyway, COM8 was used in the keying config of Logger32, and the 7851 was configured to use USB2 DTR as its CW keying source. All worked great, with CW and break-in selected on the radio.

We then looked into getting the STEPir auto tracking the vfo frequency. The STEPir control box is quite an old version, pre-dating the current SDA100’s. After much head scratching, we decided to use the remote (ci-v) port on the radio. The TIP of the 3.5mm jack, going to PIN9 (ttl rx) of the 9way d-type female that plugs into the STEPir box, and the RING to pin5 (gnd). A quick solder job and it was all working. Note: the pin out of the STEPir 9 way is not standard serial, certain pins are there to be connected to different makes of radios.

3.5mm mono – 9way d-type female – CI-V to STEPir

It has been noted that the STEPir will only track when the vfo on the radio is adjusted, and not when Logger32 tells the radio to move frequency. The IC-7851 needs to have CI-V transceive turned on.

Some configuration settings recorded here as a record.


current IC-7851 settings

MB7TR – SSTV repeater

We have a new local SSTV repeater, and as far as I know one of only two in the country. Classed as a ‘regenerative node’ it will relay/repeat a received image.

MB7TR is situated in Cwmbran, and maintained by MW0RPB (Peter). It operates on 144.500MHz using FM and outputs in the Martin1 sstv mode.

To get it to repeat your transmitted image, which incidentally can be transmitted in any SSTV mode, you need to do the following, all on 144.500MHz in FM :

  1. TX your CW ident (good practice)
  2. TX a 1750Hz tone burst for around 1-2 seconds and key off
  3. Listen and wait for MB7TR to reply with its CWid – this signifies it is ready to repeat
  4. TX your SSTV image
  5. Sit back and wait for your image to be repeated out

You can use your SSTV software of choice, MMSSTV being mine. It is working great, after a few teething problems Peter has ironed out all the gremlins. Give it a try, you never know who might reply !!

SSTV from the ISS

An SSTV image from a pass of the ISS @ 14:23z today as part of the “Expedition 55 Interkosmos” mission. I didn’t get set up in time so only managed to get the end of the last transmitted image. ISS was over north France at the time, at about 250 miles up. 145.800MHz +- some doppler. SunSDR2 Pro and the X510n vertical. 30dB over 9 signal.

The next pass at 15:50z ish was going right overhead, so I was all set up for this one. The first image (with the green noise) was received over the middle of the Atlantic (amazing 800-1000 miles away?), the second when overhead here in S.Wales and the third when passing over the east side of Poland.

The last pass of today, around 17:30z resulted in the following two images. Signal strength on the last was around S5-S7 with qsb. 

Most of the time signals were around s9+10 or so, with very little qsb. I did notice some flutter/phasing/qsb on the final image as can be seen by the noise lines over the image.

Anyway that is all for now. I will put any new images below.

73 Richie.

The (call)sign of things to come?

So, I decided to have a dabble on JT65 last night, had a listen to the bands and opted for 17m.

The frequency was quite busy but I found a spot where I could call some CQ’s. 7X3WPL came back to me, but as you can see he failed to give me a report. In fact, he ended the contact with a 73 and then started calling CQ.

So this station did not give me a signal report (look at the times), and he then went about calling CQ. I double checked back through the call/band history and could not see his call sign. Unless there was some serious QSB or some sporadic propagation openings he was not on that frequency calling cq prior to me.

So, this morning, I checked QRZ, and unsurprisingly there was a QSL waiting for my approval from 7X3WPL.

Now, as I am only a year or so on the air with this callsign, I would have liked to have had that QSO confirmed and add Algeria to my country’s worked, but no, I refuse to add something that has been so obviously made incomplete. Why bother even operating and trying to make contacts if you cant even be bothered to send a report ?  Obviously it could be, and probably is, an operating mistake but to then call CQ as well ? As it happens according to QRZ he gave me a -14 report.

Is this a sign of things to come, with more and more automation, and the 59 73 mentality ? I read about the up and runs where the last you hear from a station is R-02.

Please for the love of god, if you are operating a slow as hell mode (5-6 mins per qso) then at least send a report and see the qso through to completion. I am slowly getting fed up of wasting my time.


3d printing – a dipole centre and a balun

So, after seeing some of the creations from a few friends, my brother and I decided to go 50/50 on a 3d printer.  I really needed a small dipole centre and balun combo, capable of 100w tops, so I decided to go about making one.

Some designs in TinkerCad, a few tweaks here, a few there, and the case was complete, together with a number of different plates enabling custom, so239 and bnc connections. The case would eventually house a 1:1 guanella current balun, using a fair-rite type 31 core.


The case went through a number of iterations, and prints. The above design was the finalised version (hopefully, lol).  The T clip you see in the design enables the dipole centre to be attached to a painters pole or slid down a fibre mast.

I am only printing in PLA at the moment, so the balun will not stand up to 365 days a year outdoor use.


Anyway, the printer is nearly finished cooking another, so i’ll sign off here.




Another 2M tape measure yagi

Last year the Cwmbran and District Amateur Radio Society staged a fox hunt and a number of us built 3 element tape measure yagis using measurements provided by a fellow club member, Pete MW0RPB.  This year I decided to rebuild mine, and rework the dimensions using a great yagi design program from John Drew – Yagi Calculator. I used jubilee/pipe clips, some plastic conduit, conduit saddle clamps and a bunch of screws. It should be noted that for these calculations the dimensions of the elements were 21mm wide and 0.5mm thick, with non metal boom.

fullyagi yagi_construction

Design frequency was 145.000 MHz the centre of the band.

Reflector length 1007.6mm tip to tip, solid, at 0mm boom position (the start position)
Driven length 972.7mm tip to tip, with a 10mm gap, at 414mm boom position
Director1 length 904.5mm tip to tip, solid, at 568.6mm boom position

Note: The driven is tip to tip measurement, this includes the 10mm gap at the centre. The boom positions should be marked on the boom from one end, starting at 0mm then 414mm and finally 568.6mm.

A hair pin match was made from some 2.5mm bare copper wire (from twin and earth mains). The dimensions for this 85mm long and 25mm wide. The paint/covering on the tape measure was scratched off/filed and tinned heavily.


The coax feeder was cut to and odd half wave length (* velocity factor) of the design frequency, 0.66 being the VF for RG58. The number 5 being an odd number of half wavelengths long, you can pick any odd number for this to give you your length of coax. Have a read of this if you are interested in why this is done.

feeder length (meters) = ( (150 / 145.000) * 0.66 ) * 5

An RF choke was added at the end of the conduit using some of the feeder, so make sure you pick an odd wavelength long enough to include enough for the choke.

rf_choke swr_curve

The results speak for themselves, what a cracking antenna, see the swr plot above (thanks George for the lend of the Sark-110).  I had a QSO on 5w with a station 37 mile away from Magor, on the ‘white horse hill’. The 3 ele giving 6.9dBi gain.

Have fun making yours !


Upgrades !

I decided to add another two directors to make a 5 element yagi. I found some 22mm alkathene that would slide over the conduite and allow me to extend the boom.  The 5 ele giving 9.9dBi gain.

Director2 length 894.6mm tip to tip, solid, at 940.7mm boom position
Director3 length 885.5mm tip to tip, solid, at 1115.2mm boom position