Batteries for portable use.

Batteries for portable radio operation are always an interesting subject for discussion. I have been asked many times which batteries I use. My battery of choice for portable operation is the LiPo (Lithium-ion polymer ) battery.

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I find the 4 cell 5 Amp variety suits my situation very well. The operating voltage can be up to 16.5 volts with no load when fully charged. However the stated nominal operating voltage is 14.8V   Most operators would be concerned  these voltages may cause damage to sensitive 13.8v radio equipment. This is correct in some circumstances.  I operate a Yaesu Ft-857 for  SOTA activations, this is a radio designed for in vehicle operation where voltages may exceed 14.5v. The specifications for the FT-857 state the normal supply voltage is 13.8v +/- 15%. This equates to an operating voltage range of  11.73-15.87V. Even better for the FT-817 being specified at 8-16volts . Ok so I hear you say ” Your  16.5v battery is outside that range!” This is true, however by making use of a full wave bridge rectifier in circuit (I use a MDA3504, 35Amp 400piv variety) the voltage will be lowered by 1.2-1.4v. (remember silicon junction theory 101) There are two advantages, a lower voltage and polarity protection. Ensure you  wire the rectifier correctly in circuit, the Battery  wires are  connected to the “AC” input terminals on the rectifier, Do not be concerned  which battery wire connect to what “AC” terminal it makes no difference. However it is critical  the Radio positive (RED) wire is connected to the + (positive) terminal of the rectifier and the Radio negative (BLACK) wire is connected to the – (negative) terminal of the rectifier. I recommend using an in line fuse between the rectifier and radio for protection.   Once the bridge rectifier is in circuit the no load voltage is  15.1V  from a fully charged LiPo battery.  There are some heat losses via the rectifier however mine is mounted on a small heatsink and becomes luke warm  at 100w output on SSB. I would not recommend a full duty cycle mode such as SSTV or FM for long periods at this output level.

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How long does this battery last on the FT-857?  That depends on what output power is used. For my  SOTA activations I set the output to 30% , (approximately 30w) at this level I have successfully activated 3 summits of about 20 contacts each and still had plenty of power left. There are precautions with LiPo batteries, they can be easily damaged by incorrect charging and balancing. They have also been known to catch fire under certain circumstances. I have not experienced any such issues with the batteries I use, however I follow the documented procedures for this type of battery. It is always a good idea to monitor the individual cell and combined voltage when using the battery. There are many voltage monitoring devices available for purchase, I use a fairly simple unit which emits a loud screech when the cell voltage reaches a pre set level. Mine is set to sound the warning when any cell reaches 3.5Volts.

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 This setting will ensure the alarm sounds when the battery reaches less than 14 volts. The limit can be set lower, however I prefer to err on the side of caution maintaining the battery condition  since replacement cost is not cheap. There are several brands and styles of LiPo battery available, I use the Turnigy  brand,  they have a very good reputation especially with the Radio Control crowd. I prefer to use the hard case variety, they are a little more robust out in the field. There are lower voltage (12.3v) 3 cell LiPo batteries available for those who want to connect directly to the radio equipment. Hobbyking is a good source for these batteries. I tend to avoid ebay as a source of cheap batteries, usually these batteries are cheap because they are  older stock and have not been  regularly charged so have degraded over time. Dealers who have a high turnover of stock do not have this problem.

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 As can be seen here the battery voltage indicated is 16.4v and the display on the radio is 14.9v after the rectifier. Transmitting at full power (100w)  reduces the voltage to 13.2v on peaks. The LiPo battery is able to provide bursts of high current when required, in some cases up to 30 times the charge current to 150A. Charging can be easily managed with the many charges available on line. The charger I use allows an input voltage of 13.8volt perfectly suited to charging batteries whilst driving between SOTA summits.

$_57

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Radio operating at full power with 13.2volts indicated. The battery recovers quickly after transmitting making it ideal for portable operation. In comparison to Sealed lead Acid batteries the LiPo battery is about quarter the weight for the same current, perfect for lugging to the top of summits! As always ensure you read the instructions and follow the precautions for using LiPo batteries with your equipment.

Enjoy!

MX-P50M HF AMPLIFIER REVIEW.

There comes a time after climbing some tough summits when you decide to look at the weight of your backpack. I had  recently walked 20Km to activate a summit in the Snowy Mountains, towards the end of the walk my backpack just felt too heavy. I had stopped on several occasions to rest and I remember thinking “I have to lighten this pack!” The radio I use for SOTA activations is a Yaesu FT-857, it weighs in at 2.5Kg. A great radio which covers all bands and produces 100w output. I also have a Yaesu FT-817, by comparison it weighs only 900 grams without battery pack. I hardly ever take this radio on SOTA activations since I prefer to run about 30watts output and the 817 is lucky to produce 5 watts! I had thought about building a lightweight amplifier to boost the output of the 817 to around 30watts. I looked for suitable components on ebay and this is where I discovered the MX-P50M amplifier. It was advertised specifically to suit the FT 817  and produce an output of 50 watts at a mere 500grams.  My first thoughts were, “this might be one of those dodgy cheap amps, best to be avoided !” With that I decided to move on and continue looking for parts to build my own amp. I found many parts and kits available to build a small amplifier however I was curious about the little amp I had seen. I decided to do a Google search on the amplifier, I found only one positive report on eham and no other information, no circuits nor operation manual. For the asking price ($226 delivered) I decided to purchase a unit, thinking if it did turn out to be dodgy, I would simply use the components to construct a better amp. It took only a week for the amp to arrive from China. The amp ships with a DC cable, an FT-817 control cable and nothing else. No instructions, specifications or circuit!

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Setting up the amp is relative easy, simply connect the supplied control cable to the FT-817 accessory connector and the DC cable to a 13.8v supply. Then connect the coax output from the radio to the input of the amp. The output of the amp connects to your antenna.  The amp has a manual band change switch, so check the band switch is set to the correct position before transmitting.  Not having any specifications, I had no idea what power level could be expected. I connected a power meter and dummy load in line and decided to test initially on 40M.

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Applying 3 watts AM carrier from the FT-817 produced 30Watts indicated on the meter.

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On SSB a whistle into the mic produced 50watts indicated. So far so good, I proceeded to try the other bands and was delighted to find I could produce 45watts PEP at 28.5 Mhz and 50 Watts PEP on 3.585Mhz, Note the voltage reading of 13.3v.

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Here you can see the full output from the FT-817 producing a healthy 50watts PEP on the 30M band. I conducted tests at a higher input voltage (14.5v) and found the amp can produce more power output if required. I did find some specifications for the encapsulated  RF device inside the amplifier stating it can accept input voltages up to 24v to produce 100w output. I am not going to try it, the results could be catastrophic!

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The MRF 186 encapsulated RF device as used it the amplifier. Also an internal view of the amp, showing the filter layout and circuit arrangement.

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Having tested the amplifier into a dummy load it was time to put the amp “on the air” I started with 40Metres and called CQ with 5 watts only. Vin, VK3FMOL replied and reported a 5×4 signal received at his location. I asked Vin to check my signal strength again this time with the amp on line. My signal report was now 5×8, but more importantly Vin said my audio level had increased quite a lot to the point where I was readable above the noise.  At that point Scott VK7NWT broke in to provide his report. He had been listening and was happy to report the same, an increase from S4 to S9 with a large increase in received audio level. Scott also reported he had tuned across my signal whilst I had been talking with Vin and could find no evidence of splatter or bleed over, thanks Scott. Seems like this test had a few people interested because Ray VK3NBL was next to call in and report he had no particular signal increase but a noticeable audio level increase. Ray had also been looking at one of these amps, but like me was dubious about the quality. As it turns out I had contacts with four or five others whilst using the amp and all the reports were similar, a noticeable increase in audio level and no change in quality with some reporting a signal strength increase also. During the tests I noted the amplifier remained cool to the touch and the current drain was around 6.5 amps on voice peaks.  I have been asked several times if this amplifier can be used with radios other than the FT-817. The answer is yes provided you can supply the correct RX/TX control lines into the amplifier. The amplifier is supplied with a connecting lead and attached plug suited for direct connection to the FT-817 Accessory socket. I have taken the time to check which connections are made to the FT-817 and they are as follows. The Black or in some cases Blue control wire from the amplifier is connected to ground or GND (-VE)  on the radio and the Red control wire from the amplifier is connected to TX GND from the radio. So to operate the amplifier in transmit mode it is a simple matter of shorting the two control wires from the amplifier together when transmitting and open circuit them when receiving.

Some people have asked if there is a way to use the FT-817 CAT control and the connection for the linear amplifier simultaneously. Well in fact one of those people was John Schultz who not only asked the question but provided the answer via a file he found on the net from a SK Charles Socci K1DNR. I have provided that file for download here:simultaneous-use-of-cat-control-and-linear-amplifier-on-yaesu-ft-857d Thanks John for sending me the file and thanks to Charley K1DNR.

Recently my amplifier destroyed the in line fuse every time it was connected to the DC supply. A quick investigation revealed there is an 18v Zener diode used as a form of protection circuit. This diode had gone short circuit causing the fuse to blow. I replaced the Zener with a suitable type and have not had any problems since. There was no apparent reason the the diode to become faulty, unless I inadvertently reversed the DC connection polarity. Maybe I had a seniors moment hi hi!

 In conclusion I can recommend this amplifier to anyone looking to boost their FT-817  output to around 40 watts. I will continue to run  30 watts as usual. For me this amplifier will now accompany the FT-817 on my future SOTA activations. My FT-857 will be installed in the vehicle which will lighten the backpack by 1.1Kg. A good saving!

  

MT.TUMANANG VK2SM/-049

Mt. Tumanang VK2SM/-049.

One evening whilst looking for summits in my local region (Snowy Mountains) to activate, I noticed Mt. Tumanang appeared under the VK2/SM group on SOTA mapping. Although Mt. Tumanang is on the outskirts of the Snowy Mountains region and a long way from Tumut, I decided to attempt an activation. Not being familiar with the roads around that area, I decided to call Rod VK2TWR to ask if he knew which roads would allow access to the summit. Rod was very interested, he suggested a co-activation and access would be easy from the Anembo Rd. A few days later Rod and I met in Cooma where we left his vehicle parked safely at McDonalds, with local knowledge and an eager passenger on board we set off for the hills! From Cooma we drove along the Monaro Hwy for 62km to Michelago. At Michelago we took Burra Road over the railway crossing until turning right into Tinderry Road. After following Tinderry Road 26km, we met the intersection with Jerangle Road at Jingera. From Jingera we travelled the Jerangle Road for 5km until reaching Anembo, then turned right off Jerangle Road into Anembo road. Following Anembo road for 6km we met the junction of Bald Peak Road.

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The junction of Bald Peak Road and Anembo road.

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We stopped at the junction for smoko prior to turning left into Bald Peak road and entering the Tallagandra National Park. Once on Bald peak road we drove for about 700m before reaching another Tallagandra National Park sign and the Tumanang trail on the left. Note: Logging trucks use Bald peak road regularly, caution is required!

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The Tumanang track appears to be little travelled, we encountered trees blocking the track in a few locations, fortunately I had the  chainsaw on board! Rod decided to take video whilst I cut the trees saving his energy for the climb 🙂

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The track requires 4wd in places along the way, there are two creek crossings, the first  requires a bit of negotiation since there is a steep departure angle. At 9km in we met the Crowbilly Creek.

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Crowbilly Creek crossing, a steady flow about 400mm deep on the day.

After crossing Crobilly creek the track started to climb for 4km to the summit. The track winds around the edge of the summit as it climbs passing the summit on the right. We drove past the summit to  a point where the track turns toward the right. There is enough room to park at this point. Across the road is the start of a saddle up to the summit about 300m. An easy 20 minute walk.

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I placed a few rocks on a tree stump to mark the trail to the summit.

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The trig marker at the summit. Both Rod and I had enough chasers calling to allow the minimum 4 contacts each to claim the activation. A good day was had by all and we both agreed to return next year to re-activate the summit.

View looking from the access track

View looking from the access track

Approaching Mt.Tumanang

Approaching Mt.Tumanang

 

 

Snowy Mountains 30 points in one day

I have been travelling the Snowy Mountains Highway and the Tantangara road for many years. Having no previous involvement in SOTA I had not really paid any attention to the summits in the area apart from noticing they were there.  Things are certainly a lot different now days. I seem to find myself looking at every ridge and summit trying to work out if they could be SOTA summits. SOTA is very addictive!  Referring to the VK2/SM  SOTA mapping page there are three summits which can be accessed from the Tantangara Road.  VK2/SM- 027 Mt Nungar, VK2/ SM-033 Blackfellows Hill and VK2/SM-036

I set myself a challenge to try and activate all three in one day. Starting with the hardest first and finishing on the easiest.

VK2/SM-027 Mt.Nungar.

The Tantangara road starts from the Snowy Mountains Highway 71Km from Cooma and 111KM from Tumut.

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The road is unsealed and can be quite potholed, however it has recently been graded.

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Starting out early I arrived at the Tantangara Road around 7:00Am on a cool but clear day. I drove along the road passing SM-036 and Blackfellows Hill, under the power lines several times until reaching the Tantangara Trail at 13Km from the Snowy Mountains Highway. I decided to leave the vehicle here since there is enough space to safely park off the road.

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From here I walked along the Tantangara road for a further 200m where I discovered a walking trail to the right heading towards the summit. My GPS indicated this location as: 35Deg 49.504S and 148Deg 38.820E. This location is 1353 MASL which leaves only 357 vertical metres to the summit! Hi Hi

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The track winds up and across the ridge through a mix of wooded area and ground cover, there is a large cleared area on the way up which is a good place to rest. Nearing the summit a small amount of easy rock climbing/ negotiating was required. I managed to arrive at the summit after a leisurely 1 hour 40 min. stroll!

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There are two trig markers at the summit, the original laying on the ground and the replacement made of pipe.  View towards Mt. Jagungal in the distance.

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A green canister at the summit, it contains visitors log entries. I was happy to make an addition to log right under VK2TWR and VK3PF.

 

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VK2/SM-033 Black Fellows Hill

After descending from Mt. Nungar, I walked back to my vehicle and drove along the Tantangara Road back towards the Snowy Mountains Highway. At 6.3Km on the trip meter (6.7Km in from the Snowy Mountains Highway) I met the trail to “Wares Yard Camp Ground” on my right. Following this trail for 500m I arrived at the camp ground and car park.

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Wares Yard Camp Ground. I parked near the gate at the start of the trail.

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The start of the trail heading up to Black fellows Hill.

I followed the bridle/MTB trail from the gate in a southerly direction towards a saddle after crossing a small creek. At the saddle the trail turns towards the northwest and climbs towards the summit to the north. As I approached the top of the ridge before turning toward the summit I discovered an old wooden trig, it is about 1KM from the summit. I continued towards the summit and set up near the highest point. I looked for a trig but could not find one.

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The shack setup at the summit. Tree stumps make very useful squid pole supports. After activating I descended back down the trail to the car park. Even though this summit is a fairly easy walk about an hour, My legs were starting to let me know I had done enough for the day, so now it was time to head for Tantangara Road and SM-036.

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A view of Mt.Nungar from near the summit.

VK2/SM-036

Travelling along the Tantangara Road for 1.6Km from the Wares Yard Camp Ground (5.1Km in from the Snowy Mountains Highway) I saw a track to my left at the top of the ridge heading toward SM-036. There is a yellow road safety sign at the track indicating “S” bends approaching.

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This track heads toward the North following the power lines after crossing under the power lines there is a 4wd track heading toward the ridge. I drove to a spot near the summit and walked the rest of the way. There are no trig points here and the summit is about 150m from the top of the track. I operated from the top of the track near some rocks and a fallen tree which is inside the activation zone.

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View from the summit and the fallen tree.

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After activation I headed back down to the vehicle and drove back to Tantangara Road and home to Tumut. The day was great and 30 points certainly made it all worth while. My legs were tired and I was please I had tackled the hardest summit first up especially when I was rewarded with the easy SM-036 at the end of the day.