KX1 internal battery using NiZn cells

Hi all,

Nickel Zinc rechargeable batteries are not common, however HobbyKing sell them. I decided to get a batch and have a look at them in the KX1.

NiZn batteries are not for everyone. Firstly, the capacity is lower at 1500mAh than the typical NiMH battery at 2400mAh. The plus side is that the NiZN carry a higher voltage. It is at 1.85V at the top of the cycle and then slowly decreases throughout the cycle, but remaining well above NiMH, and even Alkaline batteries that start at just under 1.6V and decline to 1.1V over the cycle. NiMH spend most of their cycle flat at 1.2V.

For a radio like a FT-817 that linearly regulates the voltage, there is no point using AA cells with higher voltage, as the regulator literally burns the excess voltage as heat. The 1.2V of NiMH are fine in that application. The KX1 is a different matter.

The KX1 has a capacity for 6 internal AA cells. Using NiMH cells, these would deliver only about 7.2V for most of the cycle, which is below the recommended minimum voltage required by Elecraft. The rig still works – although I have not extensively tested it. The power levels generated are very low – perhaps only good for QRPp levels of 500mW or less. I am quite happy with QRP operating, but I don’t see a pressing need to go to QRPp at this stage.

The NiZn cells represent an opportunity to mix things up with a higher voltage that the KX1 can then use to generate more RF power. It won’t give me more operating time, but it will give me more punch. Here’s a look at 6 NiZn cells installed inside the KX1 AA battery holder:

Turnigy AA NiZn cells in the KX1 internal battery holder

Turnigy AA NiZn cells in the KX1 internal battery holder

The cells come charged, and showed 1.85V per cell and a total of 11.1V installed. I used the cells for several hours in the field, and I came back with the six cells developing 10.4V across them. The KX1 would develop low 1W to 2.5W depending on the band and (reasonable) antenna configuration. This was only a little down from what power it was developing with a 12.2V external supply.

The 1500mAh capacity would mean that these NiZn cells will deliver many hours, perhaps more than 20 hours, of operating time in the field. The low RX current draw of the KX1 is certainly a great factor here, especially compared to a all mode rig like the FT-817. This kind of setup would be really useful for multiday remote area activations, where the radio part of the gear needs to be kept to an absolute minimum for weight reasons – for example when South West Tasmania or Fiordland in New Zealand are part of the Summits on the Air program.

Regards, Wayne VK3WAM

Mt Buller and 4 other summits CW only

Hi all,

After building a “random” wire antenna, it was time to take the new configuration on activations and see how it works in the real world. I decided to leave the FT-817 at home and go cold turkey on real CW only activations, with no capacity to fall back on SSB to ensure I got four contacts.

I don’t have a great deal of spare time these days, so I thought about going up on a Sunday afternoon and pull a flexi time off day on the Monday. If I’m going to jump in the deep end CW only, this is a way to do it when there are fewer SOTA chasers available during the week.

VK3-VE123

This is an unnamed summit accessible from Timbertop saddle on the Howqua Track. Three Chain Track heads off to the west. I was able to get the Prius up part of this and called stumps (a cricket term meaning the end of play) about 1.5km from the summit. From there, I headed on foot.

The track would be easy going in a proper 4wd.

For this activation, I still took a bit of a safety net, with the end-fed antenna on board and I took up the 7m squid pole. I decided to employ the “random” wire on the 7m squid pole.

The KX1 was able to tune on 20/30/40 with a very dodgy tune on 80 for interests sake. The rig reports the power after the tune. Compared to home, I was using a set of 18650 LiIon cells which develop 12.6V fully charged, but quickly drop down to mid 11’s. At this voltage, 2.5W would be the best I could hope for. Practical KX1 activations are lower powered than FT-817 activations where 5W is easily obtainable.

Power is lost across the tuner, depending on how difficult the match is. I was developing 2.2W on 20, about 1.7W on 30 and about 1.3W on 40. The tuner was effectively losing about 3dB on 40, but less on the other bands. SWR was 1.5 or less.

There’s no real risk of a CW pile up on a SOTA activation in VK at this stage. I had a range of contacts from local to DX and across all three bands.

One thing cropped up. The KX1 paddles are a little loose in their socket. I would tighten the hand screw to help, but even so, there would be some movement on the paddle base and this affected my keying. Ian VK5CZ got the worst of it, so much so I noticed after I got home that he suggested going down to 12wpm. Slower keying would not have helped in this case, it would have actually made it worse.

I found the solution to this problem would be to hold the base of the paddles with my thumb of my non keying hand. This seemed to make keying much more reliable, with only the occasional missed formed character.

Its not the same as my touch keyer, which does not lose a beat. However, the touch keyer needs its own battery and is liable to be turned on in a backpack. This can flatten it over time (takes several days). I think I will learn to live with the KX1’s paddles.

The activation was at dusk, so it was too dark to take photos of the setup. It was a nice sunset to look at though.

Mt Timbertop VK3/VE-073

It was back to Timbertop saddle where I slept. Next morning, I took the walking track from here which goes up the mountain. This track has been upgraded from going straight up to a track that does some zig zagging. Makes the track more pleasant to walk on. In a few places, walkers are trying to use the closed track, but I don’t think it would save them much time – apart from being harder.

There are some great views looking west.

Northwest from Mt Timbertop's slops showing Mansfield

Northwest from Mt Timbertop’s slops

The summit is reached quite comfortably. This climb is easy if one is fit. If you are not, you need only take your time. A walking pole is of great assistance.

The summit itself has some snow gums (Timbertop suggests there should be some timber on top). I decided to put the KX1 in a tree so that the base of the wire is not near the ground. This seems to help 40, but does not necessarily help, perhaps hinders on 30.

Summit area of Mt Timbertop

Summit area of Mt Timbertop

For this activation, the 7m squid pole was left in the car and my 4.7m squid pole was brought along instead. This pole, discussed in this post, is very lightweight. 20m and 30m worked fine, but I found I had better tuning results on 40m if I tuned for near the top of the band, around 7.28 to 7.3 In VK, operating CW here is fine, although somewhat unusual. To get some contacts, I operated down the bottom of the band, but with SWR around two. The power was around 0.8W verses 1.2W at the top of the band.

I was wondering if the squid pole would be strong enough at my chosen mounting point about midway on the second highest segment. The squidpole looks like it does fine at this point for the sloping wire of the antenna. I’m not sure about mounting my HW end fed on it because that wire is much heavier.

Mt Buller VK3/VE-008

Most local readers would be aware that Mt Buller is the location of a significant winter ski resort and has also developed into a summer mountain bike park. The development of this mountain means that there is a sealed road most of the way to the top, then a short gravel road. There is only a 50m vertical climb to the top. I operated a little down from the actual summit, about 30m horizontal or so from the top.

I operated with the lightweight setup again on this summit. The KX1 was reporting about 11.4V from the battery. It seems it takes about 0.5V off the input voltage. I tried this at home with really fat cables on a 13.V supply and the KX1 reported 13.0V. I tried it at home with same thinner supply cable and it still reported 13.0V (alternating a little to 12.9V)

The setup is shown below. The lightweight squid pole can be wedged in some rock with tension on the cable holding it in place. It was windy up there – the picture shows some wind load on the cable.

VK3WAM station at Mt Bullder Vk3/VE-008

VK3WAM station at Mt Bullder Vk3/VE-008

The KX1 developed about 2W on 20, 1.6W on 30 and 1.1W on 40. 40 needed to be at the top of the band for an acceptable SWR. Down the bottom was a SWR of well over 2 and a power of only 0.7W.

All contacts at this summit were on 40. Peter VK3PF tried his hand at some CW, which was certainly good enough to read his reports, with some initial confusion on his call sign. Given that he, along with Gerard VK2IO had not done CW for extended periods, SOTA is having an impact on use of this mode. Perhaps motivated by wanting to work the summit and knowing that CW was needed to active this, helped them dust off those long unused keys!

The operating spot gave a good look down the steep NW face of Mt Buller. Apparently some people have tried skiing down here. There was a sign nearby with two sets of double black diamonds reminding skiers that the area was unpatrolled.

NW face of Mt Buller

NW face of Mt Buller

Mt Stirling VK3/VE-011

From Mt Buller, there is a road that goes to Howqua gap, but I was not prepared to drive down that in a Prius. Instead I drove down the mountain and then up the Stirling Rd. Mt Stirling is surrounded by a circuit road, but this does not approach the summit closely. I decided to use the River Spur track. Its a walk of a little over 3km, with a climb of about 400m up to the summit. It can be accessed by using the southern side of the Circuit Rd – the first track heading up is Bluff Spur track (over 4km) with River Spur track being the second track heading up.

The summit is above the tree line. I used the trig point to mount the squid pole.

Operating at Mt Stirling VK3/VE-011

Operating at Mt Stirling VK3/VE-011

The trend of 20 and 30 tuning quickly and 40 being better at the top of the band continued here. The battery voltage was reported about 11V, and power levels were 2W, 1.5W and 1.1W on 20, 30 and 40 respectively.

Even though the KX1 is only developing 6dB less power, with the tuner, on this configuration on 40, it is enough to get contacts. The setup is very lightweight and very fast to put up and take down. If I was to take the larger squid pole, with the end fed on a FT-817, that might give me another 12dB with everything, but it is significantly more gear to take. The nicest thing about the KX1 is it is a complete station, with the antenna. I’m using it with an external battery, but it does have the capacity to put some internal AA batteries inside.

I was able to activate with a mix of 20 and 30 contacts. I saw later on SOTA spots that N7SP was trying to get me on 20, but looking at messages others try to send using SOTA spots is not always easy on summit.

Most of these mountains have great views on top and Mt Stirling is no exception. Here’s a view back to Mt Buller:

Mt Buller from Mt Stirling

Mt Buller from Mt Stirling

And a look north towards Mt Buffalo and Mt Cobbler (right of centre)

Mt Cobbler from Mt Stirling

Mt Cobbler from Mt Stirling

Mt Winstanley VK3/VE-036

The last summit on the menu was Mt Winstanley. This summit is to the north west of Stirling, so I used Circuit Rd and then No 3 rd to access it. Here’s a screenshot of the tracklog:

Tracklog of access to Winstanley

Tracklog of access to Winstanley

There is a track going along the ridge – and this is shown in opencyclemap. It is not in the Forest Explorer or the OziExplorer maps that I have. I used the track for the last 500m. Opencyclemap does not show RazorBack Trail correctly, but this track departs near the junction of No 3 Rd and Circuit Rd. Going up RazorBack and taking the walking track, I presume, from there is likely the easiest route to access this summit.

Spot the station – including the squid pole – in this photo:

Operating at Mt Winstanley

Operating at Mt Winstanley

The KX1 reported a battery voltage of 10.7V. This would be around 11.2V out of the battery. This would be a little less than half a cycle on these batteries. They are fake Ultrafires, branded for 2400mAh capacity, but actually give about 1200mAh. It would appear that the KX1 drew about 500mAh to 550mAh, for around 7 hours of operating, including lots of CQ calls.

At this lower voltage level, I was getting about 1.8W on 20, 1.4W on 30, and 1.1W on 40. Interestingly, 30 did not like the KX1 a metre and half off the ground, I got a much lower SWR on the ground – power levels were similar. 40m liked the rig off the ground, but again, tuning was better at the top of the band, where tunes were getting an SWR of 1.1 and power of 1.1W, compared to SWRs of 3 or higher and power of less than 0.7W on the ground.

Can I improve the performance of this antenna – undoubtedly yes, but why bother. If I want something better on 40, I’ll carry the half wave end fed, with its matchbox. If I improve this “random” wire antenna for 40, it will come at cost of lower convenience, because the improvement would need to be a 1/4 wavelength counterpoise for 40m. As it stands, the two counterpoises do a good enough job for the very lightweight and portable objectives of this wire antenna. 40m is an important band for local contacts, but I think 30m will rise in importance as nearby states become more accustomed to SOTA. I think, in time, that 30m will be an important band for SOTA in VK.

Regards, Wayne VK3WAM

Preparing the KX1 for SOTA battle

Hi all,

Elecraft KX1

A few months ago I picked up a KX1 from a EDMRC club member who was selling. The unit came built and fully equipped, with the inbuilt ATU, the 30 and 80 band board and the keyer. The KX1 is a CW only rig but designed especially for portable use. With my mountain goat status out of the way, I wanted a CW specific and more light weight setup.

Rik VK3EQ (VK3KAN) had shown me a very lightweight squid pole at the 2013 Gippstech. I was quite interested in this because it packs up to 60cm in length. It has a 4.7m length when extended. Perhaps the top segment is too light duty to hold anything but a vertical wire, but the next segment down should handle at least a lightweight inverted V configured wire.

Random length wire antenna

Elecraft recommend that the KX1 ATU unit be used with “random length” wire, so long as the wire is not 1/2 wave length on the desired band. Note the reason for this is that the internal tuner is not always able to match the high half wave impedance.

I decided I wanted something serviceable on 20/30/40. After looking around at various web sites, such as this one, I settled on a 41 foot or 12.5m wire length. This is more than 1/4 wave length on all these bands, and around 5/8th wave length on 20. Should be a good “Aussie allrounder” but performing best on 20.

I bought some cheap speaker wire from a hardware store for construction and separated the two wires, but keeping the insulation. I stripped back some insulation at one end and doubled back to crimp a BNC pin. I then made two lengths of wire from the spare speaker wire for a counterpoise. One is 1/4 wave length for 20, the other quarter wave length for 30. 40 misses out, but at least both the counterpoises are 1/8th wave length or longer for that band. I crimped one exposed end of each of these to the shield on the BNC connector.

To give some mechanical security to the BNC connector, I taped about 7 or so cm of the three wires together, starting at the crimp. At least at this early stage, it seems to work well. We’ll see how it goes in the field.

The idea with this antenna is that there is no feedline. The antenna begins at the BNC connector – it is literally being fed right out the radio. The other end of the wire could be put up a tree and/or having the other end or middle of the wire on the squid pole. The counterpoise wires go on the ground.

"Random wire" BNC connector with 12.5m wire and 20/30 counterpoise

“Random wire” BNC connector

Mounting the wire on the squid pole

For the squid pole, I cut a small wood mount piece with a 1.5mm hole for a wire to use to wind the antenna wire around. I drilled a 3.5mm hole to mount the piece on the squid pole. This ends up about half way on the second highest segment. The top segment would be too weak for this kind of work, I think even only the bottom half of the top segment would be strong enough even for a vertical only wire.

It sits on quite nicely.

Wire mounting on lightweight squid pole

Wire mounting on lightweight squid pole

The wood mount is quite small:

Size of wood mount compared to my hand: it is about a finger width

Size of wood mount compared to my hand

The piece is small enough to be packed up in the squid pole case cap. The squid pole itself is small enough to go inside most larger packs, and even 40l hybrid type packs.

A basic test suggests that the squid pole will be able to keep the wire up in the field. We’ll see. If need be, I just need to make the hole a little bigger and it will mount a little lower on the pole.

Testing with the KX1

My initial test was at home. My house is two story, but the upper story can look down on the lower story. I draped the wire from upstairs to down, with the two counter poises on the floor upstairs. Not the best setup, and looking forward to trying it in the field.

The KX1 was able to tune the antenna on all bands, although the result was emergency use only marginal on 80. SWRs were 1 to 1.1 on 40 and 20 and around 1.5 on 30. The KX1 also shows realised power from the tune – which is quite interesting. The 20 match was showing full power (about 4 watts), with the 30 match around 2.8 watts and the 40 match about 2 watts.

I would expect better results in the field when this antenna is setup properly, with the random wire fully extended and the counterpoises at a greater distance from the wire and fully extended on the ground themselves. We’ll see, but none-the-less, early results look promising.

The whole system weighs less than 1kg, including the squid pole. It is my most light weight setup yet. If not for the squid pole, it could even get close to the station you can carry around in a pocket (or two).

I’m keen to give this a go on a SOTA summit or two over the next few weeks. Perhaps the FT-817 and the bigger squid pole and end-fed will come along as a safety net to make sure if this falls over, I’ll still be able to activate.

73 de Wayne VK3WAM

POSTSCRIPT: First activation with this setup can be read here.

Designing a 20/40 band CW rig – Part 1

Hi all,

I have been spending some time working on the design of a ultra portable CW rig. I’ve been spending time looking at various kit designs from Steve KD1JV, Ramsey Kits, You Kits, the Elecraft KX1 and others. Some rigs are quite simple, others have a more sophisticated approach.

Goals

In setting down to design a rig, I was wanting something that would work well in a SOTA activation context. I would want the rig to do the following:

  • I did not want to be limited to a narrow band of frequencies around a crystal, but wanted the whole band to be available.
  • The power output needed to be around 5W – full QRP. 500mW CW can be tough going in VK. One attraction with SOTA activations is working the DX chasers, so 5W is nice, while keeping the QRP endorsement intact.
  • I’d like to keep open the option of some digital modes, even if the rig would not do these directly itself.
  • The rig would need RIT.
  • If possible, to switch bands without needing to use external switches.
  • Deliver near 5W from a 12V source, safe for 12.6V – a three series LiPo cell, usable down to 9V.
  • Do all of this in a kit that would cost less than US$200, good, $150 better, $100 best – but no promises!

Overall rig design

The rig could basically be broken down into a number of sub-sections.

  1. Power – a cut-off for low input voltage, and regulators for 5V and 3.3V
  2. Audio frequency – RX audio and sidetone
  3. TX – SSB rigs mix up, but this being a CW rig, I only need to switch an oscillator output and amplify up to 5W. I also need to impedance match for 50ohms at the RF connector
  4. Oscillator – Given my tune the whole band requirement – I’m going to need a PLL and VCO or equivalent circuit, such as a DDS.
  5. RX – Taking the RF connector, I need to either use a relay to switch away the TX, or a transistor switch. I then feed a mixer to an intermediate frequency for filtering, and then can feed a second mixer to audio frequency
  6. Control – Need to use an embedded controller – I am familiar with the PIC line, so I’ll use something there. This will need to set dividers for the PLL or DDS, take button input from the user for tuning, band selection, RIT, provide a keyer facility (I won’t be using a straight key) – with the ability to configure at least the wpm send rate

I’ll go through these in greater detail over a number of posts. I have been influenced by some of Steve KD1JV’s ideas, but also want to do some of my own things. I have already mentioned that I want internal band selection. I also want a volume control, with the rig able to drive at least a 16 ohm speaker, along with low impedance head/ear phones – like the ones supplied with mobile/cell phones. I also want it to be capable of driving 200 ohm headphones.

Above, I floated ideas of how to switch TX/RX. A relay could be used, but if full break-in is going to be supported, relays are a pain. Relays are good for things like band switching – ’cause you don’t switch band 100 times a minute, but to keep the power down, they will need to be latching.

At time of writing this post, I have most of the sub-section circuits designed and thrashed through simulations and a bit of bread boarding. I’ll hopefully put up some posts over the next few days or so looking at TX, the audio section and some of the RX.

This design is going to be largely SMT, but to keep things sane, I’ll use 0805 or larger size components. I could make it thru-hole, but the physical size would be much larger, and it would be significantly more expensive.

73 de Wayne VK3WAM

Continued in Designing a 20/40 band CW rig – Part 2