Comments on the KX3 Extended VFO Temperature Compensation Procedure

So I am the very pleased owner of KX3 #3899, purchased used from an absolute gentleman of a ham (WB4OQX). I only just recently acquired the KXPA100 amplifier for the KX3 and sold off my FT-950, IF-2000, LP-PAN2, and LDF AT100Pro2. So far with the KX3 as a base station I’ve only run SSB, but I want to get the PKS31 and JT-65HF modes up and running.

To help out with this, I performed the Extended VFO Temperature Compensation Procedure two nights ago. I made some mistakes and performed the procedure again last night with much better results. I’m going to share my notes and observations so others can avoid my pitfalls.

Note:  I used the XG50 from Elecraft, which I assembled from a kit. I am relatively inexperienced with a soldiering iron, but I have a good soldering station (fine tip, temperature control) which made it rather painless. I highly recommend the XG50 for this. I also used a hairdryer for the heating element.

 1. On my first try, I applied the heater (hairdryer) to the radio as soon as I started data logging after removing it from the refrigerator. This was a mistake. This caused the temperature to rise too fast from the coolest point and the data gathering did not get a nice, wide spread of data points in the cooler temperatures. The second time around, I let the radio naturally equalize to room temperature (as observed before cooling it) and only then applied the heater.
2. On my first try, I kept the hair dryer too close and the temperature rose too quickly to the 52 C mark. How did I figure this out? When the procedure was complete and the data logging finished, I switched off the heater and let the radio equalize naturally back to room temperature. I watched the temperature drop and saw that the baseline frequency oscillated over 20Hz from the 550Hz. It should have been maybe 2Hz off, so I knew something was wrong.
3. On my first try, I attached the XG50 directly to the KX3. Doing so allowed the XG50 to be heated by the hair dryer due to its proximity to the KX3. I believe this affected the signal output, making it inconsistent. On my second attempt I attached the XG50 to the KX3 using a three foot coax cable which kept the XG50 well away from the heater.
After the second attempt at the procedure, I let the radio cool naturally and watched the temperature drop and saw that the frequency varied at most about 2-3Hz all the way down to room temperature from the 550Hz baseline. This was much better the the first attempt.
So now I have a reasonably temperature stable KX3, primed and ready for JT65, JT9, PSK31 and just about any digital mode I can throw at it.
Next up, my first foray into PSK31.
Posted in Equipment, KX3

EJ0M – Ireland DXpedition to Arranmore Island

Well, what a surprise. Tuning around 20m I stumbled across EJ0M operating from Arranmore Island. After a few tries, I got through at a 59. That makes the last of the British Isles I needed for the set.

Posted in Operating

Portable 13.2V 4200mAh LiFePO4 battery

It’s only recently that I have been hearing about Lithium Iron Phosphate batteries. I read about it first on a post made on the Worldwide Radio Forum. Then, a few well known portable QRPers posted about it so I gave it some investigation. LiFe (as they are called) batteries offer really amazing power density, and they are extremely safe to travel with. Doing my research, I found that these batteries are also very popular in the RC market. HobbyKing carries a whole slew of them in their stock. There are a number of varieties and configurations you can get. I’ll go over this first to describe why I purchased what I did.

LiFe batteries come in a number of configurations: 4S1P, 4S2P, 3S1P, and so forth. This naming convention indicates how many cells are in series, and then how many of those series cells are in parallel. For example, a 4S1P battery has one battery in parallel and then four in series. Well, you can’t be in parallel with yourself so it’s just really one series set of four cells. A 4S2P battery has two batteries in parallel, and four sets of these two in series. Simple enough. Only, as you add more cells to a battery pack, your opportunities for failure increase.

In a 13.2V, 4200maH 4S1P battery each cell is 3.3V and has a 4200mAh capacity. That’s very close to the standard 13.8V that most power supplies produce and well within the 9V-15V range the KX3 accepts. However, in a 13.2V  4200mAh 4S2P battery, each cell is still 3.3V but has a 2100mAh capacity. Having two of these cells in parallel is what produces the 4200mAh capacity, and then four of them in series produces the 13.2V. It is the same result, but using more components. Enough of this, on to the pictures.

photophoto (2)This is the Zippy FlightMax 4200mAh 4S1P LiFePO4 battery pack, purchased from HobbyKing. It is effectively four 3.3V 4200mAh cells wired in series with a circuit included to allow balanced charging using a charger that can accept the additional voltage inputs. It comes with some kind of generic plugs that I didn’t recognize. It didn’t really matter, as you will see in a moment.


Highly recommended with this battery, I also purchased the Turnigy Accucell 6 balanced charger. It is capable of balanced charging batteries with up to six cells in series. It does not have an internal AC to DC converter so you need a DC power supply.



photo (3)The first thing I did when I got the battery pack on my bench was to remove the useless connectors that came with the battery and attach some Anderson power poles. This was a little tricky because the cables used are thick with fine strands. I’d guess they were 8 gauge. After I stripped off a length of shielding, I clipped small sections of the exposed strands until I had enough to manage to slip into a 30-amp power pole connector and crimp. Out of pure luck, I stripped exactly the amount of shield to make a flush fit with the power pole housing. I still added some 3/4″ heat shrink tubing over the connections (not pictured) for good measure.

photo (1)The charger unit came with alligator clips on all the ends for power connection. The wire on the bottom of the picture connects to the charger on the left side… and I guess the alligator clips are supposed to connect to DC terminals to charge. The charger output goes to the right (connected in the picture) and to some kind of small molex connector. Another cable with a molex connector goes to yet more alligator clips. Suffice to say all the alligator clips were removed and replaced with still more Anderson power poles. The alligator clips went into my parts drawer.

photo (4)Finally, I was ready to charge the battery. I used my recently acquired Powerwerx SS-30DV switching power supply to charge it, as it has convenient front panel power pole connections. This will be the power supply that I travel with for portable operations. A separate review of this will come soon. The power supply will connect to the charger, which will connect to the battery. Also from the battery the five-pin balancing circuit connector (see picture three) will connect to the charger so that it can monitor the voltage of each of the four cells in the battery. It’s pretty slick.

I let it charge, it took about two hours at a 2A rate, which is what the battery pack is rated for. Then I did a power balancing charge. That took only a few minutes. The real test was attaching it to my KX3. The KX3 fired right up and I was able to transmit SSB at 12W, which it will only do when connected to external power greater than 12V.

I’m in business!

Posted in Equipment, KX3, Portable, QRP

Powerwerx DC Inline Watt Meter for… half price!

I’m in the market for a watt meter and power analyzer to take portable with me for my KX3. Since I plan on operating primarily from an LiFePO4 battery pack, I’d like to be able to monitor the voltage, amperage and how many amp-hours have been used. The nicest unit I could find was the Powerwerx DC Inline Watt Meter and Power Analyzer:

WattMeter-PP_lrgThe problem is that Powerwerx wants just under $60 for it. That’s a little much for my budget. The Watt’s Up meter from HRO is about $50, but still a little pricey. I found myself looking at the picture for the Powerwerx Watt meter and something looked familiar. The brand on the picture is Turnigy, and the model is 130A. Now, Turnigy is a brand I recognize from RC forums (radio controlled) for car, plane and boat enthusiasts. If you’re looking for efficient, light and portable power, they are the people to go to. I had found my Lithium Iron Phosphate battery on HobbyKing along with a Turnigy charger, so I did a search for the make and model… and this is what I found:  Turnigy 130A Watt Meter and Power Analyzer


This is the exact same watt meter as the one sold by Powerwerx, minus the power poles. The Anderson Power Poles are easy to add, so I wasn’t terribly worried about it. But the kicker is the price of $23.95. Less than HALF of what PowerWerx or HRO wants for anything like it. It isn’t in stock in any of HobbyKing’s USA warehouses, so I had to order it from their international warehouse… but international registered air mail was only $5.99. So for $29.94 and a few powerpoles I will have a full feature watt meter and power analyzer.

It might be a week or two for delivery. It may not even arrive in time for my Colorado trip, but I can live without it. I’ll post more information and pictures when it actually arrives.



Posted in Equipment, KX3, Portable

Preparing for Colorado Portable QRP

In two weeks my wife and I will be travelling to Colorado. We’ll be spending most of our time in Steamboat Springs, but before we arrive there we will be visiting Black Canyon of the Gunnison River National Park


I am preparing my portable QRP kit and I plan to activate in the national park during our visit. Looking at the map of the part for the best high point to set up, I think I’m going to try this location:


The road ends on the blue marker, and it’s another 1000 feet to the red marker. The red marker is close to 8800′ up, so I should get some good signal out from there. I have no idea who I’ll make contact with at 10W, but I’ll find out.

I’ll be posting with some of the gear I’m taking with me in the next two weeks as well as the dates and potential times of the operating.

Posted in KX3, Portable, QRP

KX3: Battery Low warning when using NiMH

A small tidbit I gleaned from the KX3 Yahoo group that I don’t want to lose:

Using NiMH batteries, you might see a  ’battery low’ message when powered up, even if you know your batteries are good. The battery low default threshhold is set for alkalines and you need to adjust it for NiMH battieres. The default is 10.0V and you should set it down to 8.4v for NiMH.

Posted in KX3

Thirteen Colonies Clean Sweep!

I’m rather tickled about this. I had this waiting for me in the mail yesterday… the 13 Colonies award. They recognized my clean sweep and also the bonus Pennsylvania station.

I’m also going to be sending out for the individual special event station QSL cards once my new QSL cards come in.

2013 13 Colonies Award

Posted in Operating

The KX3 experience

So my XYL loves me, I mean really loves me. She ‘approved’ my purchase of an Elecraft KX3. Not only that, but I found a used one on eHam for about 3/4 of what the kit price would have been. The seller was a true gentleman and it was a smooth transaction all the way. The assembled KX3 came with the digital cable kit, the roofing filters, and the hand microphone. Yes, with the KX3 the hand microphone is an option.

I ordered the internal ATU from Elecraft an it came quickly. It installed inside the KX3 like a dream. There didn’t seem to be space inside but apparently there was. It is an 8 inductor / 8 capacitor transmatch. Simply amazing.KX3_ATU

So now with my new KX3 I popped in eight of the Sanyo Eneloop batteries and tuned to the CW region of 20m. It only took but a moment and the KX3 was decoding CW.

This is going to go into my portable go-bag. I’ve already got an LNR end-fed 10/20/40 trail-ready wire antenna, but I want more. Somehow, I just know I’m going to need a backup to that antenna in case it doesn’t work. Until then, this is simply the most awesome radio I’ve ever seen in my life and I can’t wait to play with it. The XYL and I are planning a trip to Colorado in the fall, and we’ll be up around 7000 feet with 9000 foot peaks around us.

If I can’t hear Japan from up there, I’ll be disappointed. If you work Summits On The Air, I’ll have that info posted here before I go.


Posted in Equipment, KX3

First 17m Contact

A couple of weeks ago I purchased an LDG AT-100ProII tuner. It is a 10:1 SWR tuner, capable up to 125W. It has taken me a little while to get used to it, but I’m liking it. Two days after I purchased it and set it up, I worked a contact on 17m. I never had 17m capability before now so I was really excited. However, the contact faded a bit at the end and I wasn’t sure if he put it in his book or not. I had it in mine.

Then, yesterday, I saw this on LoTW:



Posted in Operating

Elecraft KX3 Portable Operating Tips

This was shamelessly ripped from the KX3 reflector, originally posted by N6KR and saved here for future reference:

Battery Operation:  To conserve battery power, use 5.0 watts or less when running from a 12-V source, and 3.0 watts or less when running from an 8-10 V source (including internal batteries). At these levels, the KX3 automatically switches the power amplifier to a more efficient setting. You can tell that power-saving mode is in effect by a decimal point after the ‘W’ in the power value (e.g., “5.0 W.”). To reduce supply current in receive mode, use headphones rather than the internal speaker, and if lighting conditions permit, turn off the LCD backlight (Menu: BKLIGHT).

Oscillator Isolation:  The KX3, like other radios with a quadrature direct-conversion architecture, uses a VFO (local oscillator) running at or very close to the operating frequency. If you have another radio on the same band as the KX3, and the antennas are close together, the other radio may be able to hear the KX3′s oscillator when they’re both tuned to the same frequency.

To prevent this, the KX3 includes an isolation amplifier that keeps the oscillator from radiating back through the mixer. Normally this amplifier is turned off to save about 15 mA of receive-mode current drain. To turn on the isolation amp, set MENU:RX ISO to ON. This has no effect on performance.

Posted in Portable, QRP



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