Monday, 13 August 2018

Adding 60m to the SBX-11

As I had an unused channel position and spare set of red coils for the SBX-11which cover the frequency range 4.00 to 5.66 MHz , I decided to add crystals for the 5.400 MHz 60m spot frequency to allow operation on the 60M band .

Calculation for the crystals for the SBX-11 is as follows -

  • Determine the centre frequency of the of the channel - 5.400 MHz
  • Subtract 1.5 KHz from the centre frequency to get the supressed carrier fequency . 
  •  5.400 MKz - 1.5 KHz = 5.3985 MHz  
  • Add 456.5 KHz to the suppressed carrier frequency
  • 5.3985 MHz   + 0.4565 MHz = 5.855 MHz 

The SBX-11 uses 2 x HC-6/U crystals which are difficult to find, so I ordered some smaller HC-49/U crystals from in the Czech Republic  using the following spec -

Frequency         5.855 MHz / fund.
CL:                    32 pF
Package:            HC-49/U
Adjustment:      ± 15 ppm at 25C
Stability:           ± 30 ppm in OTR -30/+50 CC

cost for two crystals , VAT and shipping came in at about €26 and the crystals arrived about 2 weeks later .

Rather than solder the smaller HC-49/U crystals in to the SBX-11 I decided to use some old HC-6/U crystals to make adapters.  Using a hot air gun it was possible to desolder the case on a HC-6/U crystal , remove the old quartz crystal and solder the HC-49/U in its place .

The old casing was then soldered back over the new crystal .

SBX-11 crystal slots showing red coils in place and empty crystal positions
Orange coils - 5.66 to 8.00 MHz are used with an 40M crystal
Brown coils - 2.82 to 4.00 MHz are used with an 80M crystal
White coils - 1.6 to 2.00 MHz are used with a 160M crystal

 new HC-49/U crystals in HC-6/U cases in place
Crystal cover in place

The new crystals were adjusted for correct frequency using the crystal trimmers while measuring the frequency at the Tx HFO and Rx HFO test points using a frequency counter connected via a 10pF capacitor .  Alignment carried out as per section VI of the SBX-11 service manual 

Update the label with the new channel frequency .

Initial on-air testing indicates that I am getting out > 6w and the receiver is sensitive .
more testing to follow .

Monday, 20 November 2017

New DMR gateway for Galway

Steve EI5DD  is currently testing a new multimode digital gateway in Galway city . 
for more information see

EI2GCD is a 24/7 multimode digital voice gateway based in Galway City, Co. Galway. The Gateway coverage includes the City of Galway and surrounding areas such as Barna, Headford, Oranmore.
Operating Frequency 144.850 MHz

The frequency is 144.850 MHz, Color Code 1, Slot 2. The DMR node is connected using the MMDVM DMR Gateway link to access to the Brandmeister Server 2721 in Waterford.
  • The default gateway connection is to DMR TG 2722 Ireland Call but is user selectable.
  • There is a Timeout of 180 secs (3 minutes) after which your QSO will time-out.
  • Please leave approximately 3 Seconds between overs to allow components of the Network to reset.
The Gateway is connected to IE YSF Ireland which is also Bridged to DMR TG 2724 and CQ-IRL Wires-X Gateway. Pressing the Dx button on the fusion radio will allow selection of other YSF Reflectors.

Monday, 30 January 2017

60m test , 100w vs 2w

I had a contact with Michael EI3GYB on 60m yesterday at about 14.30 where we did a test to compare the received signal strength at my end as Michael reduced his power from 100w down to 2w .  The intent was to compare a 100w transmission with the 15w EIRP allowed under WRC-15 .   Received signal strength was less at 15w than at 100w but still very readable . Even at 2w I could still receive him clearly .  The codan 9780  does not have a proper S meter but the video below shows the effect of reducing power on the received signal. 
The band was very quiet at the time so results could be different under noisy conditions, but it does show that the 15w EIRP limit is not so much of a limitation  .

60m test 100w vs 2w

Friday, 19 August 2016

New enclosure for the MST400 40m SSB transceiver

Last year I completed an MST400 MK1 SSB transceiver from - see post here

This worked well but I was not happy with the plastic box I used for the enclosure .  Sometime later I cam across a nice metal box on eBay and decided it would be more suitable for my MST400 .

Here is the finished product in the new enclosure -

Sunday, 24 January 2016

Trio TS-120S PLL unlock fault

I recently acquired a Trio TS-120s HF transceiver with an intermittent fault - when powered up the PLL would fail to lock , resulting in no TR or RX and no digital display - just two dots.

PLL Unlocked

Once the set warmed up the PLL would eventually lock , first on 14MHz then  on the other bands.  Once the set had been switched off for a while the PLL would return to the unlocked state on power up .

I checked the PLL board for cold solder joints but nothing obvious was found.

Tapping on the boards when the PLL was unlocked made no difference , so I tried gently heating the boards using a hairdryer , this helped pinpoint the problem - the PLL came in to lock whenever the area near the back right hand side of the AF board was warmed up .
I didn't expect that a fault on the AF board would prevent the PLL from locking , but underneath the AF board is the carrier board which produces a ~8MHz signal which is fed to the PLL board .

Testing J19 CAR signal

I attached a frequency counter to Pin2 of J19 on the PLL board and a volt meter to TP1 on the PLL board .  When the PLL was unlocked there was no 8MHz signal reaching the PLL board . When the CAR board was gently heated  the 8MHz signal appeared and the PLL locked .

An article on indicated that there was a common fault where the  carrier board would fail to oscillate due to the Q1 transistor going low gain, so I removed the AF board to gain access to the CAR board to replace Q1 .

AF Board

AF board removed 

CAR board removed

I removed Q1 ( 2SC460)  and tested it on a transistor tester - the device was ok , but the gain (hfe) was very low at around 29 . It should be about 100 for this device.

Original Q1 - low gain

After warming the faulty transistor the hfe came up slightly to 36

Original Q1 warmed up

This additional gain was probably enough to get the oscillator to start up once the transistor warmed up.  I tested the new replacement transistor prior to installing it - it had a hfe of 107

Replacement Q1 

After re-installing the CAR and AF boards I powered on the set - the PLL locked immediately on all bands !

PLL Locked

Sunday, 6 September 2015

Codan 9780 HF Transceiver

I recently acquired a used Codan 9780 HF transceiver. This is a commercial HF SSB transceiver that provides 15 user programmable channels in the 2.25 to 30MHz range.  Power output is 125w of USB or LSB.

Codan 9780

The radio was purchased without a microphone and I thought it would be straightforward to find a suitable replacement microphone, however a search online only found original replacement microphones at AU$ 389  - way more than I was prepared to pay.

I found the schematic of the Codan keypad microphone on the blog - this is a very useful blog with lots of information on Codan 9xxx series radios , including how to enable programming of channels from the control panel.
The microphone schematic is here .
The schematic indicated that it would be possible to connect a normal dynamic microphone to the radio , leaving out the custom keypad controller.  I had an old Pama dynamic CB microphone that looked suitable , so the next problem was to find a suitable microphone plug. Unfortunately the 9780 has a very custom 7 pin connector - I wasn't able to find a suitable connector at a reasonable price , but I found an eBay seller in Australia that had a replacement Codan microphone cable and plug for AU$ 65.  This was ordered and it arrived about 2 weeks later .  Mic plug shown below.

9780 mic plug

I found the pinout of the MIC socket in the Codan 9360 reference manual available here .
Note - this pinout is viewed from the perspective of the radio front panel, not from the microphone plug.

Microphone socket pinout

It was necessary to link pins 1 and 7 together in order to route the received audio to the front panel speaker.  This is illustrated in the microphone schematic .

On connecting the microphone I found I was still not getting any audio out of the front panel speaker , so I plugged in an external speaker into the LS jack on the back .  This worked.

On removing the front panel and testing the speaker I found that it was open circuit .  The speaker is a 66mm diameter mylar speaker  - maplin had a suitable replacement ( code VC86T)  . 

front panel speaker
Once this was replaced I tried the radio out and made a number of contacts on 80m , 60m and 40m and received good audio reports.  

Having only 15 channels is a limitation, but I plan to use it mainly on 60m where we only have access to 5 spot frequencies in Ireland.

Sunday, 2 August 2015

TS-120v repair - part 2

I spent some time today continuing my attempts to repair the TS-120v I described in part 1 here .

The radio is now usable on SSB on 80/40/20M however it still has no output on 15M and 10M , other faults are a non-functioning S meter and no output on CW.

One of the common faults that can cause a none-functioning S meter is the relay on the IF board.
There is a well written article on the replacement of this relay on the Kenwood TS120_130 yahoo group  - "TS130v Omron relay removal/replacement" Based on this I ordered 2 NF4EB-12v relays - these are a drop in replacement for the original Omron LZN4 which is now obsolete.
It seems that the Matsushita NF4EB relays are also obsolete , so it was hard to find a source for them.
I eventually found an ebay seller in China  that had them in stock for $6 each - see ebay item 381034198000

Omron LZN4 on left. Replacement NF4EB on right

IF board removed from the transceiver

I replaced the relay using the instructions in the link above.  It was fairly straightforward however I needed to use solder braid and liquid flux to cleanly desolder the 15 pins.

IF board fitted back into TS-120v with new relay (orange)

After replacing the IF board and carrying out an on-air test I now have a working S meter.

working S meter

Next I need to fix the CW problem and the lack of output on 15/10M