Oceania DX Phone Contest – Wyrrabalong NP 3-4 Oct 2015

The Oceania DX Contest is an amateur radio event held annually on consecutive weekends in October. The first weekend is phone (SSB) and the second is CW (morse code). The first (and last) time I participated was in 2010 as a portable station using a kite antenna. It was a lot of fun and the video has been quite popular. This year I wanted to operate for the full length of the contest, not just for a few hours. I also wanted to operate as a portable station and this meant using low power (QRP). Luckily the contest has a QRP category so I would not need to compete with much bigger stations using beams and high power. Going portable has three advantages: (1) away from city noise; (2) have space for 160m antenna; (3) can qualify a national park for WWFF.

Wyrrabalong National Park map

Wyrrabalong National Park map showing north and south sections

Location

The criteria for the location was based on: (1) must be in a national park; (2) have reasonable car access; (3) near a body of water; (4) room for antennas; (5) clear RF takeoff in all directions; (6) away from RF noise sources; (7) 24hr availability. Most of the criteria for a location can be assessed beforehand by studying internet sites. For this exercise I looked at national parks on the Central Coast of NSW and drew up a short list of possibilities within the Wyrrabalong National Park VKFF-0550. The park is coastal and divided into a large northern section and a smaller southern section. The northern section is virtually at sea level with the ocean to the east and a lake to the west. It is bisected by the Central Coast Highway running north-south. A road off the highway provides access to the park and the beach. Unfortunately the road is gated and closed at night, but I added it to my short list anyway. There did not appear to be any other accessible locations in the northern section of the park.

The southern section of the park was much more familiar as I had done the coastal walk many times. This section has ocean to the east and housing to the west and consists of a long narrow strip. The prominent features are the Crackneck Lookout providing stunning ocean views and a favourite for hang-gliders, and the Wyrrabalong TV translator tower on the southern end of the coastal walk. Of these only the Lookout is suitable. Another location was also found half way along the coastal walk next to some water tanks with access from a nearby suburban street.

Southern section of Wyrrabalong NP showing operating point

Southern section of Wyrrabalong NP

Scoping It Out

On the Saturday of the contest I packed the car and set off for the northern section of the Wyrrabalong National Park at about 3pm. The goal was to reach the location by 5pm and set up in time to start contesting at 6pm. Most of the drive was along the Sydney-Newcastle freeway then head head east through Budgewoi then south through Norah Head to the park. Upon turning off the Central Coast Highway there was a large gate into the park and a sign showing the opening hours. I checked out the carpark at the end of the road and decided that it was not that suitable. Probably the best spot would be on the beach.

Left the northern section and drove through The Entrance township to Crackneck Lookout in the southern section of the park. On the approach road there was a wedding entourage and photographer actually on the road. Proceeding on and just before the lookout there was a gate – one that I had not seen before. Seems the lookout carpark now has restricted hours which seemed odd. The views from there at night are pretty nice. As a consolation, two car spaces have been provided just before the gate about 100m down the road. After a quick scout around and a gawk at the stretch limousine I decided the spot wasn’t as suitable as I was expecting.

Now down to the third option I drove back through the gate and around to the closest road to the water tanks. The road to actually get near the water tanks is gated too but intended to be used by pedestrians to access the coastal walk. The walking distance to the park is about 200m. The area around the tanks has been cleared and was within the national park according to the GPS.  I decided this would be a good spot to operate from though I was unsure how much electrical noise would emanate from near the tanks and the nearby houses. The nearest power lines were 50m away. Maidenhead locator: QF56RO.

Shack at Wyrrabalong National Park

Operating chair and tent at Wyrrabalong National Park

Setup

Getting the gear to the site took three trips and then I set up the ZS6BKW antenna on the 9m squid pole with the wire oriented north-south. Next was the double-sized ZS6BKW which was awkward to set up due to the available cleared space. There was little undergrowth as the park had been burnt out recently, but there were still quite tall trees. It took some time to weave the antenna wire through and over these. I used my 10m travel mast leaving the top sections unused, and there was a pronounced bend in the mast due to the load. One antenna crossed the other one but only at about 30 degrees. They were almost parallel. A ground sheet was put down and then an operating chair which would serve as the shack for the evening. Then the KX3 and computer were installed. The chair has a small side table useful for putting things down when not seated in the chair.

Operating chair and tent at Wyrrabalong NP

Operating tent at Wyrrabalong NP

Contesting

By 6:20pm I was on the air but it was getting dark so I used a headlamp to see what I was doing, especially with the computer. The bands were all very much alive. I started on 40m by hunting and pecking my way up and down the band. After half an hour there were a bunch of VKs and a couple of ZLs in the log. Then to 15m for a couple of JAs then 20m for more JAs and a US station. My 5 Watts was cutting through though not to every caller – some of them completely ignored me. Then to 160m and even though it was still early, 2 contacts were made and then to the 80m DX window for 2 more including a ZL. Back to 40m and it was definitely the busiest band and some new stations were calling. Continued to cycle through the bands calling all I could hear that i hadn’t already worked. Occasionally I would put out some CQ calls and was sometimes rewarded with a call.

After a few hours it started to cool down quite a bit and the wind was a little cool. It was time for more shelter so I started to set up the tent. I had a new “mosquito” tent so had not put it together before. The instructions consisted of a series of numbered pictures printed on a tag attached to the tent bag. By a process of trial and error the tent was set up in about 15 minutes then the radio gear was moved inside. I could continue contesting in more comfort though I was squatting instead of sitting. I managed to work Indonesia, PNG and more US stations. VK2IM who lives nearby was worked too. His signal was so strong on 20m that the KX3 automatically switched off its preamp as a protective measure. Later it was found that he was line of sight and only 6.5km away running a linear amp and a beam. It normally takes a very strong local signal for the radio to react in this way – impressive!

Two antennas at sunrise in Wyrrabalong NP

Two antennas at sunrise in Wyrrabalong NP

Some more hours of contesting and contacts had slowed down to a snail’s pace. After an hour making no contacts I decided at 1am to close down for the night. A trip to the car was made to recharge one of the 4200 mAh LiFe batteries that had been powering the computer after its own internal battery went flat after 4 or 5 hours. The radio was still running fine on its battery of the same capacity and did not need charging. Only one battery can be charged at a time. Returned to the tent for some much needed sleep.

Morning

Arose just before dawn, took some photos and retrieved the battery from the car. By 6am I was back on the radio though with the changeover to daylight savings time, this was now known as 7am. 40m was running well and I made many contacts. After 2 hours I tried 10m and 15m and made a few DX contacts with Japan, Indonesia and Russia. This was great because contacts had now been made on all the bands available in the contest. From 10:30am to 11:30am there was a spate of SOTA activations, all on 40m. Some were CW so were not logged as contest contacts and instead recorded in the regular portable logbook. At midday the KX3 was shutting down when PTT was pressed. It was time for a run to the car to charge the battery powering the radio which had dropped to 8 volts. It looked to be bulging a bit too – oops. The charger accepted the battery and started to charge it without complaining about the voltage.

Shack inside the operating tent in Wyrrabalong NP

Shack inside the operating tent in Wyrrabalong NP

Afternoon

The break gave me an excuse to have something to eat as breakfast had pretty much been skipped. Returned to the airways at 12:45pm and set up the voice keyer on the radio to put out calls while munching away. I started to call on 7.144 which is a popular frequency for World Wide Flora and Fauna activations. There were some responses but not from the usual VKFF hunters and I could not self-spot under the contest rules. 40m and to a lesser extent 20m were the bands I was able to make contacts during the afternoon. Occasionally another SOTA station would come up and I would chase them. The most notable was Takeshi JS1UEH on 15m CW.

The weather got quite hot in the afternoon and peaked at 34 degrees in the shade. I was glad to have the tent for protection from the sun. The wind kicked up too and was nearly at the point of blowing things away like the chair sitting outside the tent. During the afternoon I noticed that the UTC time and time to contest end was advanced by one hour. The clock on the computer was showing the correct daylight savings time. I decided to continue on and fix it up later. At about 5pm the long path to EU opened on 20m and many contacts were made. This dried up by 6pm and it was back to 40m. At 6pm the logger reported end of contest, but there was still an hour to go. I set the clock on the computer back by an hour and this fixed the problem. With only one hour left and darkness approaching I started to pack up and just left the voice keyer calling on 40m. The 160m antenna was pulled down first as it would not been needed at all and would take some time to roll up. Responses to calls were very infrequent by 6:30pm so the main activity was packing up the tent. QRT happened at 6:45pm, 15 minutes before the contest end and it took another 20 minutes to collect everything and transport it to the car over multiple trips. The timing worked out well with sunset at 7pm, the same as the contest end time and no need to use lights.

Path to local station VK2IM

Path to local station VK2IM

Log Processing

After the contest the log needed to be massaged and submitted. Entries in the log after the changeover to daylight savings had to be manually edited to take off an hour except for the last few contacts after 6pm (0700z). There was no easy way to do this other than manually. The author was contacted and could not shed any light on why the UTC time was incorrect after the switch to AEDST. Cabrillo format can be generated by the software and directly emailed to the contest manager. ADI format can be generated as well and after some editing to include National Park information, callsigns, locator, etc, the log can be imported into my station log running in Log4OM. When logging I always put in the exact frequency in the comment field. This must be extracted and put into the frequency field, and any SOTA or WWFF reference must be extracted from the comment field and new fields created for those. After importing the contest log, the non-contest QSOs can be added manually in Log4OM. Then the log is exported in ADI format for submission to WWFF to claim the national park activation. SOTA chaser contacts are also exported in CSV format and submitted to the SOTA database. There is also upload to eQSL as well, and it is all handled through Log4OM.

Contest contact and multiplier accumulation over time

Contest contact and multiplier accumulation over time

Statistics

The chart on the right shows for each hour the number of contacts made in red and the number of multipliers made in green. Contest contacts made per band are summarised below:

Band   QSOs Mult  Pts  Inv 
160 m    6    3   120   0 
 80 m   12    7   120   0 
 40 m   92   15   460   0 
 20 m   36   31    35   1 
 15 m   13   12    26   0 
 10 m    6    4    18   0 
 
 QSOs/Multiplier:   2.3

Highlights

At the end of the contest I had logged 165 stations plus another 15 non-contest stations (5 CW). I had worked 3 other national parks and 23 SOTA stations. All this using 5W except for the JS1UEH on 15m using 10W. Contacts were made on all 6 bands from 160m to 10m. Local station VK2IM was worked on 5 bands – all but 160m.

As a QRP station I found making contacts to be a very active process of chasing up and down the bands looking for callers and also switching bands regularly. Its not enough to just call away on one frequency and continuously log contacts like the high power stations do. I found myself calling CQ only a small percentage of the time. Often a higher powered deaf station would take over the frequency so one would be forced to QSY. However, this can happen regardless of output power.

It’ll be interesting to see how my contest score compares to other QRP stations.

Thanks to all contest stations and hunters. Great to get you in the log!

151004WyrrabalongContactMap

Map of contacts made from Wyrrabalong NP VKFF-0550

Equipment

  • Elecraft KX3 transceiver
  • Computer headset/microphone
  • Two LiFePO4 4200 mAh batteries
  • 7200 mAh SLA battery
  • Hi-Mound MK-706 CW paddle
  • Lenovo S10-3 netbook computer
  • VK Contest Log (VKCL) v3.12a software
  • ZS6BKW inverted-Vee doublet (28m long) on 9m mast
  • Double size ZS6BKW inverted-Vee doublet (56m long) on 9m travel mast
  • Headlamp
  • Turnigy Accucell 6 charger

Popran NP for the Remembrance Day Contest 15-16 Aug 2015

Popran National Park  VKFF-417  (-33.38463,151.188109) QF56OO

On the entry to one of the three areas of the Popran NP lies the Ironbark picnic area. With a picnic table, isolation from powerlines and a nearby parking area it provides a great location for radio activities. On this occasion it was the Remembrance Day Contest colloquially known as the “RD”, the biggest contest event on the Australian calendar. Operating in the park allowed qualification as a WWFF award as well as entry into the contest, and all stations contacted qualify as “Hunters” for the park in the WWFF scheme.

Popran National Park site for RD 2015

Popran National Park site for RD 2015

Ironbark Picnic Area, Ironbark Rd, Glenworth Valley, NSW

The park is easy enough to find as it is not far from the M1 freeway north of Sydney as the crow flies, however one must travel a circuitous route via Central Mangrove by vehicle. The road goes no more than 100m into the park where one finds the Ironbark picnic area. A major shortcut between Peats Ridge Rd and Ironbark Rd is available, but only if travelling on foot, a route known as the Pipeline Trail. There are a number of trails leading from the carpark, however a barrier prevents only pedestrians and horse riders from continuing.

Arrival

With the contest start time of 0300z (1pm) I arrived half an hour before for setup. The 9m squid pole was set up against a metal post marking the boundary of the carpark and the ZS6BKW inverted-Vee doublet raised in an east-west direction. The nearby picnic table was filled with radio gear and a netbook for logging. There was time for a bite to eat before kick-off, but not much opportunity for listening to the pre-event broadcast.

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Power

For this contest I had decided to enter as a low power station transmitting at 5 Watts since the availability of juice to run the radio was limited. Batteries on hand were two Lithium Iron Phosphate units with 4200 mAh capacity and a 7200 mAh Gel cell. These would have to power the radio as well as the netbook computer for the duration of the event. Local recharging was available in the vehicle, but could only handle one battery at a time. As a backup, operations could be conducted from the vehicle as there is no restriction on WWFF activities being conducted in this way. As it turned out, the backup was not required.

Radio and logger in Popran NP

Radio and logger in Popran NP

Contesting

40m SSB was the focus at the start of the contest. After 20 mins a spot from Glenn VK6HAD on Isongerup Peak VK6/SW-003 came up on SOTAwatch so I switched to 20m and was able to work him, but only received a 3×1 report off the end of my east-west antenna. Glad to get him in the log. Returned to 40m SSB for the hour and then switched to CW and there were plenty of contacts to be had.

A spot came up from Takeshi JS1UEH on 15m and I could hear him very weakly. I tried to call but there was no reply even after jacking up the power to 10W. Nick VK2AOH called him too. I’d missed Takeshi’s 17m activation, but afterwards he went to 10m . I listened there but heard nothing. Propagation conditions seemed below average. Shortly afterwards a spot appeared for Compton VK2HRX at Bulgo Hill VK2/IL-017 on 40m SSB, but I was too late as he had already flown to 20m. I couldn’t hear him on that band – he was only 120km away yet too far for ground wave.

After all that SOTA chasing I settled back in for more contesting on 40m SSB and CW. Tried 20m SSB and there were a few stations there, but I was not able to work many of them. There did not seem to be anyone on 20m CW. Later on a spot came up from Mike 2E0YYY at Gun G/SP-013 on 20m and he was too weak to attempt a contact – my antenna was pointing the wrong way anyway. There were other SOTA activations that I missed completely being focused on the contest. One that wasn’t came from John VK6NU at Mt William VK6/SW-042 as the sun sank low in the sky. I worked him on 20m SSB as a SOTA contact and only found out later he was giving out RD contest numbers as well. D’oh! Only a 4×1 report but glad to have him in the paper log even when not in the computerised RD log.

Antenna positioning in Popran NP

Antenna positioning in Popran NP

Second antenna

After one more contact I decided it was time to prepare for 160m. A second squid pole was set up and the 56m long double-sized ZS6BKW hoisted aloft perpendicular to the other antenna. This antenna covers 160m-20m and was oriented north-south-ish (the light blue one in the diagram). There was a certain amount of consternation sorting out which antenna wire would be the higher one where they crossed, and also sorting out the best tie-off points for the ends. I used the travel squid pole for the second antenna and it collapsed a couple of times. The pole was flexing so much with only half the antenna load on it that the antenna kept flying off the top as well, so in the end I put gaffa tape around the top section. One end of the first antenna had to be relocated to maintain separation between the antenna wires. What should have been a quick job took about half an hour, but it was complete before dark and high enough to not be an obstruction in the carpark.

The longer antenna is a better performer on 80m and it wasn’t long before 80m became the band of choice for contacts in the contest. A couple of hours on 80m before 160m contacts were snared, the first being with Alan VK4SN the contest manager on CW. Band noise was low so that gave my low power signal a chance. I spent most of the evening on 80m and 160m jumping between SSB and CW with only occasional forays on 40m. On SSB especially I would call certain stations and they would not respond, so I learnt the calls to avoid on account of my low power. Some stations were obviously running 400W and did not necessarily have good “ears”. On 80m I mostly ran without the receive preamp as it saves a little bit of juice.

Computing

In the early evening, the internal battery for the Netbook ran low so it was recharged using the car charger connected to a 7200 mAh SLA battery. After a few hours the charging battery went flat so had to be transferred to the car for a recharge of its own. Then later on a 4200 mAh LiFe battery was used to recharge the computer. The computer was going through batteries much faster than the radio, but its screen was on most of the time albeit at a very low brightness setting. Windows 10 had been installed a few days beforehand and there were no stability issues arising. The logging software used was VK Contest Log (VKCL) v3.12a. As I log each contact, I put the frequency in kHz in the comment field and then a name, lighthouse number, SOTA summit code or National Park code. It is useful to have the frequency for transferring to my station log, and during the contest it can be a useful reference when looking for stations that you haven’t worked. In this contest I did not use it much because there was plenty of activity right across the band. It would be good to automate the recording of the frequency, but that is beyond the capabilities of the VKCL software, and for me it is more important to have logging software that automates the contest rules.

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Triple points

During the period from 1am to 6am local (1500z-2000z) any contacts made earn triple points. This provides a huge incentive for stations to keep going in the wee small hours when they should otherwise be resting. I was bitten by this bug too and kept operating until I ran out of steam at 3am. There was actually still plenty of activity and I made contacts on 160m, 80m and 40m. One golden contact with VK2GGC on 160m CW earnt 12 points. Seems the 160m CW ops are not nightowls as I expected there would have been more. Point allocation is 1 for SSB and 2 for CW, then doubled for 160m. Any 160m CW contact is prized. I did hope to work WA or New Zealand on 160m but it didn’t happen. I did make it to VK5, VK7 and northern VK4 on 5 Watts so can’t complain.

Resumption

Morning was a slow start. I must have woken before 7am and then fallen asleep again. In the end I got up around 7:45am. All the gear on the picnic table had to be restored and I was back in the contest. First in the log was Andrew VK1DA on 80m CW, also a QRP operator. There was no activity observed on 160m and very little on 80m. Everything from then on was 40m and above. There was plenty of activity on both SSB and CW with just about every slot between 7065 and 7160 kHz being utilised by contest operators and lighthouse operators for ILLW if it wasn’t being used for the Sunday morning WIA broadcast. With so much activity I found it more productive to hunt and peck for contacts on SSB rather than call on my own frequency. There were times when I’d call and call and not elicit a response, obviously due to my low power.

In the last two hours of the contest Andrew VK1NAM had activated a SOTA summit Booroomba Rocks VK1/AC-026. I chased him on 10m and 6m not expecting signals. Eventually he came onto 40m and I was able to find him after calling on various frequencies. There was less than half an hour to go and Andrew closed, but I continued on his spotted frequency. There weren’t many SOTA chasers around as I’m sure the RD Contest had forced them to go to ground. Under the RD rules you can’t use a public cluster below 50 MHz so that ruled me out from spotting my National Park activation on ParksnPeaks or on the DX Cluster. Still, I was able to catch a few regular chasers by riding the shirt tails of Andrew’s SOTA activation.

Conclusion

RD Contest scoring statistics for VK2IO

RD Contest scoring statistics for VK2IO

I closed out the contest on 40m CW having spent most of the last hour on 40m SSB. In my RD log I had 271 contacts, 96 on CW and 175 on SSB. There were 2 additional SOTA contacts on 20m SSB with VK6 so 273 total for the parks activation and 122 unique callsigns. Breakdown was 22 on 160m, 103 on 80m, 141 on 40m and 7 on 20m.

The bar graph from VKCL shows the rate at which contacts were made with red being the contact count and green being the points for each hour of the contest. Most productive time points-wise (green bar) was between 1500z and 1700z (1 to 3am) – those triple points really make a difference. Also the 160m contacts between 0900z and 1100z (7pm and 9pm) made the score kick along too.

Highest contact rate was in the first hour 0300z and the first hour after resumption 2200z. Lowest rate was in the hour when I was setting up the second antenna at 0700z. Note to self: set up all antennas before the contest starts!

Mt Olive

After all the contesting gear was packed away there was time to explore the park before my next appointment. I decided to walk up to Mt Olive which is only about 800m from the carpark. In terms of elevation it is only about 20m higher, but one must first go down hill before climbing up. The summit is a fairly flat rocky platform with loads of trees. It overlooks the Glenworth Valley to the east and one can see (but not hear) the M1 motorway in the distance. A very pretty spot for very little effort. There are other trails in the park and an attraction called the Emerald Pool, but one would require a few hours to explore them. While I was operating, a number of parties did enter or emerge from the park so there are certainly visitors, and a lot of them seemed to travel on foot to the carpark. Some may have been deterred by the access road as it helps to have some ground clearance even though the national parks say that it is suitable for 2WD.

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Highlights

  • Qualified the Popran national park with 122 different callsigns logged
  • RD Contest was fun!
  • Comparing two antennas in the field
  • QRP really can go the distance (mostly)
  • Powering a computer a bigger challenge than powering a radio

Equipment

  • Elecraft KX3 @ 5W
  • Two LiFePO4 4200 mAh batteries
  • 7200 mAh SLA battery
  • Hi-Mound MK-706 CW paddle
  • Lenovo S10-3 netbook computer
  • ZS6BKW inverted-Vee doublet (28m long) on 9m mast
  • Double size ZS6BKW inverted-Vee doublet (56m long) on 9m mast
  • Headlamp
  • Turnigy Accucell 6 charger

Thanks for all the contacts!

150815PopranContactMap

Map of CW(green) and SSB(red) contacts from Popran NP VKFF-0417

 

Fixing Elecraft MH3 Microphone

I’ve enjoyed 2 years trouble-free service with the Elecraft KX3 transceiver using the original microphone. However, after about 50 SOTA activations I found the MH3 microphone randomly keying itself. Luckily, the PTT on the microphone can be disabled from one of the menus and then the XMIT button on the bottom left of the radio’s front panel can be used to key the transmitter on and off. Several more SOTA activations followed using this method. Problem is that it occupies two hands making logging and answering calls slower than it should be. Yes you can use VOX, but in the variable weather environment on a summit, this is not an attractive solution. Something had to be done about it. A new microphone shipped from the USA costs north of A$100 so that was ruled out. Repairing it myself seemed the only option.

Initial checks

The mic cable was exercised along its length to find the position of the problem. It turned out that PTT was being keyed by flexing the cable near the microphone itself. Plugging the mic cable into the KX3’s CW key jack and pressing the PTT I found that operation was normal and unaffected by cable flexing.

Schematic

The full schematic of the MH3 is available from Elecraft here. There are four terminals on the 3.5mm plug. The tip and sleeve are for the electret microphone and the 1st and 2nd rings are for the PTT and up/down buttons. The two sets of terminals are electrically isolated from each other.

With the intermittent nature of the fault, it seemed as though there was a short between two conductors when the cable was flexed. A multimeter was placed across each combination of the terminals of the plug in turn and conductivity measured. It revealed a short between the 1st ring and the sleeve. These are on separate circuits.

Fault finding

The microphone was opened up by removing three screws from the back. Inside there is a circuit board mounted on the back half containing a switch and some resistors. Two wires run to the electret element on the front half of the mic through a ferrite core. There are 4 wires from the cable soldered directly into the board. Connections are:

Plug pin
Signal
Colour
PCB label
Tip Mic out white 3
Ring 1 PTT/Down/Up green PTT
Ring 2 PTT common yellow 4
Sleeve Mic shield black 5

Looking at the board, there did not appear to be any shorts and the wiring looked normal. I removed the switch from the board by undoing the screw and then undoing 3 more screws allowed the board itself to be freed. It was held in tight by friction with the plastic standoffs so it needed to be assisted by levering with a screwdriver. With the board free, the cable can be easily removed from the back of the mic housing.

The rubber strain relief can then be slid down the cable after separating it from the metal clip. The metal clip is clamped around the cable and is loosened by prizing the two ends apart with a screwdriver. It can then be slid down the cable as well. The cable sheath can then be opened up starting at the end with the bare wires by carefully slicing along it with a sharp knife. Be careful not to strip the insulation off any of the wires within. I did this in sections of about 3cm at a time and then pulled the wires through the opening.

MH3 cable with sheath stripped aback

MH3 cable with sheath stripped aback

MH3 internal connections

MH3 internal connections

Inspecting the wires after extracting from the outer sheath there was a narrow section on the green wire where the insulation had been sliced through. The red and black wires are unused. In the red wire there was also a gash so it seems there was a fault with the original wires. The exposed copper of the green wire was shorting to the uninsulated copper shield wire when the cord was flexed. The copper shield wire is wrapped around the white wire and after reaching the end of the sheath the shield wire is insulated with a black covering.

With the wires extracted, I tested the mic with the radio. Flexing the cable caused no assertion of PTT any more. Looked like the problem had been licked!

Repair

The copper of the green wire was in good shape and not nicked so the opening was wrapped in green insulating tape. The stripped cable sheath was rewrapped around the white/shield and unused wires and insulation tape wrapped around that. There was no need to shorten and resolder wires as there’s plenty of room inside the housing for extra cabling.

MH3 cable with white/shield/red/black inside sheath

MH3 cable with white/shield/red/black inside sheath

MH3 with altered cable anchored to housing

MH3 with altered cable anchored to housing

The metal clip is slid back up the cable and clamped down 1 cm from where the slicing stopped. The strain relief is repositioned over it and the board screwed back into the housing along with the PTT switch. The end of the cable can then be bunched up inside the back of the mic and the strain relief anchored back into the mic housing taking care to align the positioning pin to prevent rotation of the cable. Reattach the front housing of the mic and you’re done!

Results

My MH3 has a slightly shortened cable, but is now fully functional again. The repair took less than an hour and saved me 100 bucks. If your mic plays up I’d highly recommend having a go at fixing it yourself.

Fixed MH3 with slightly shortened cable

Fixed MH3 with slightly shortened cable