I have some questions regarding the KX3 and doing SOTA. I am new to the hobby, the KX3 (should be here the 27th), and SOTA all at the same time, so please bare with me, but I am very excited to get started soon.
First, I know the KX3 comes with batteries, and I did order the charging system, but if I want to run at 10W for an hour (how long exactly), would it be suffice? If not, would one 4S1P A123 Battery Pack enable to do that? I have looked for this information, but I find a lot of different ideas and not to that specific wattage, usually only 5W.
For now, I am just a technician, but taking the general in a month or so. Is it worth trying to go out and hit someone on 10m during the day? I hear that 17m is the ideal band for SOTA though.
There is no one in my local club that does SOTA yet, but I hope I can talk someone into trying out Sugarloaf Mountain with me near Maryland for my first try. I will definitely do a back-yard dry run to make sure I am not missing anything.
Well, thanks for the advice in advance, and I can’t wait to get into activating/chasing since I am already addicted to the SWL logs.
Congrats on the new rig - the KX3 is a beauty! A 4S1P of 1.5Ah or greater capacity will run 10W for over an hour. However, you need to drop the voltage of a 4S battery. Many of us use two diodes in series to do the trick. Ideally, you should be able to take the diodes out of line to bring the voltage back up once the batteries start to sag.
10M during the day can be an excellent SOTA band depending on propagation.
I am a electronics novice, (know what a diode is and how it works), but I assume that it’s easy to install these two diodes you explained?
Thanks - sounds like I don’t have to necessarily wait for general to attempt an activation. I use an Alex Loop (SML) for now for 10m.
I don’t have a yagi 2m or handheld yet, (just a Yaesu FT-2900 in the XTerra), but I might try and snag a handheld (trade out the rubber duck for 1/2 wave).
I think I have heard that Arrow antennas were good for 2M, but can you recommend a specific one for SOTA on 2M? Thanks again for your time.
You would need to wire a connecting cable between the KX3 and battery, and you can add the diodes in that cable as well as a switch to bypass the diodes. If that’s beyond your ability, perhaps you can get some help from a local or consider a lower voltage battery than 4S.
I’m sure some others will weigh in here with their opinions before too long.
The Alex Loop is a good antenna if you need to set up quickly. Otherwise, you can do much better with a simple wire antenna and save a couple of pounds of weight as well.
I never activate on 2M for SOTA so I’m not a good one to comment. The Arrow antennas are very good - maybe a 3-element yagi?
You might also post your message to the NASOTA Yahoo Group, which you should join if you haven’t already.
In reply to N1EU:
Barry, I’m curious why you need to add the diodes in series with the battery. I know it will drop the voltage but I’m running two of the BuddiPole 4S3P battery packs and they never measure above 13.8vdc after they cool down from a charge using the BuddiPole charger. Are you using a different brand of battery and different charger? The KX3 is rated up to 15vdc on input voltage.
LiPo/LiION cells are 4.2V when fully charged so 4S = 16.8V which is above the max for just about all the rigs designed for 13.8V.
LiFePO4 are 3.6V when charged so a 4S = 14.4V which is fine.
It’s only recently the LiFePO4 has become cost effective compared with LiPO cells designed for the RC market. 817 owners were lucky in that the voltage discharge curve wasn’t an issue making cheap LiPOs a no-brainer decision for the best power/weight ratio.
In reply to MM0FMF:
Thanks for the reply Andy. I never really got around to using the LiPo/LiION cells so never had the problem. I just went straight to the LiFePO4 batteries that BuddiPole sells as they have a good reputation and everyone I’ve talked to that use them has had positive comments.
I don’t have a yagi 2m or handheld yet, (just a Yaesu FT-2900 in the
XTerra), but I might try and snag a handheld (trade out the rubber
duck for 1/2 wave).
I think I have heard that Arrow antennas were good for 2M, but can you
recommend a specific one for SOTA on 2M? Thanks again for your time.
Try a co-ax colinear, make one for basically the cost of coax and a connector (and some ferrite rings)
Just about fits on the standard fibreglass pole that people use, and you can wrap it up and stick it in your backpack. I’ve used mine with a handy, an 817 and an 857 with quite good results.
I have used an ELK antenna for sota (I replaced the supplied ‘mount’ with a pipe clip so that it fits about half way up the pole, and makes it easy to change between horizontal and vertical polarisation) It’s quite bulky though, and a bit of a faff to screw the bits together when out and about.
I’ve been looking at this design for quite some time and I intend to build one as a club project. I’m a massive colinear fan, shed loads of contacts from most summits (well maybe not Guisborough Moor) without the hassle of turning a beam.
Hello everyone.
I use Zippy Flightmax 4200 mAh 4S1P and a Turnigy ACCUCELL 6 Balanced charger.
This battery charges over 15 volts tested off the charging cycle but after a day or so it is sitting nicely around 14.6 which I use straight into my kx3 .I could probably get 2 activations of about 2 hours each rx and tx on 1 charge.
I do have a set of diodes to put in series on the positive lead but have not needed to use it.I did use the diodes with the ft 897 battery I used before that used to charge to 16 volts. The Zippy is half the weight and now my whole SOTA kit is as light as the 7 amp hour lead acid cell I used to carry up hills. Too easy now !!
I have never bothered to put batteries inside my kx3.
I checked out KC3BRW on QRZ but no email address I was going to send some photos of my kit.
73 de Ian vk5cz …
In reply to KC3BRW :
I am not that smart really lugging a 8kg pack up a summit then suffering with aches and pains for a week after .
I found old injuries from past sporting achievements I had forgotten about.
Take care in the hills .
I’ll check QRZ again tonight .
73 de Ian vk5cz …
In reply to KC3BRW:
Hi using a Zippy Flightmax 4200 mah LiFePo 4S1P battery from Hobby King. Works well and no issues with over voltage. The key for these batteries is to use a balanced charger - I use a Turnigy Accucell 6 also from Hobby King, Weight including power lead, plugs and a ferrite choke is 670 grams and will last for many typical activations. I have the internal real time clock & NiMh cells fitted as not only a back up but also to use when conditions are not favourable & I want to get the least amount of gear out as possible. This may be due to weather or operating location. Being able to operate the radio without anything hanging off it is a plus.
Cheers Tony VK3CAT #4625
In reply to N1EU:
The radio kit is relatively light its all that food and flask of coffee I take .
Gota have an apple to eat on the way down .
73 stay slim de Ian vk5cz …
In reply to VK5CZ:
First replacement for my heavy 7 Ah SLAB was LiPo Zippy 4S1P 5000 mAh. Overvoltage problem solved by either interrupting the charging process before achieving full voltage or by controlled discharging the fully charged battery to the safe voltage level. No need to fuss with the diodes in field. Second try was with similar LiPo but 3S1P 5000 mAh. The 4S1P sits at home since then. 3S1P is fully sufficient for FT 857 at 50 W and more than enough for KX3 at 10 W.
One thing to observe about LiPo’s: The RC guys need high C-value (surge current) but we do not. The cost of the LiPo depends heavily on the C value so you should select the lowest C-value available.
73, Ruda OK2QA
