Push-To-Talk Foot Switch Adapter for KX3

Recently, I picked up an inexpensive BM-800 condenser microphone for my KX3. It works beautifully. However… I don’t like running in VOX. I get too many interruptions. So I need a PTT solution other than using the PTT button on the KX3. I’ve had this Heil FS-3 foot switch sitting in its box for over a year, just waiting and waiting for this moment to come:



The foot switch isn’t anything fancy, it just shorts to two conductors on the plug when the switch is pressed. It’s a good quality switch though, I do recommend it.

What I wanted to do was create an adapter so that I could use the foot switch to trigger PTT on the BM-800 microphone. To figure out how to do this I decided to look at the schematic for the Elecrtaft MH-3 hand microphone:



According to the schematic, the shield is the ground, the tip is the mic audio, and the rings (R1 and R2) are what control PTT. If I just shorted R1 and R2, that would cause the KX3 to TX. I didn’t care about band up and band down, so it seemed simple enough. Here’s what I came up with for a design:




I felt this was a good design to fit all situations, but I wanted to check and see what the wiring was like specifically on the cable from the BM-800. So I opened up the XLR end to see how it was wired:



As you can see here, the two pins show are wired together, and the ground is wired separately. Some testing with my Fluke made it clear that both the tip and the ring were wired together. So my design was good, and there was no need to connect the ring to anything.

I assembled the following parts:

And this is what came out as a result:

photo12Here’s a good look at the 1/4″ jack wiring (foot switch)

photo11Here’s a good look at the stereo jack wiring (BM-800)

photo10Here’s a good look at the 1/8″ 4-conductor jack (KX3)

photo14The closed container, the foot switch jack on the left and the KX3 jack on the right

photo13The closed container, the BM-800 jack on the left and the foot switch jack on the right

Does it work? You bet it does! I’ll post more pictures later of the complete setup when I get the boom and pop screen installed!

Posted in Equipment, KX3

Shengyue BM-800 Condenser Microphone

Ever since I had my FT-950, I’ve been wanting a nice station mic setup. Well, late last year I switched from the FT-950 to my KX3/KXPA100 and it took me a couple of months to figure out that the range of microphones that could be used with the KX3 were somewhat limited. The KX3 just doesn’t like dynamic microphones. It needs a microphone with a load impedance of somewhere between 600-1500 ohms. A firmware update has been released to provide up to 20dB more mic gain, which allows some microphones (dynamic maybe?) to be used with the KX3 but I suspect that if you crank the mic gain up into the higher ranges of the settings it is less than optimal. So I’ve been keeping my eye out for a good, inexpensive condenser microphone.

I don’t know what motivated me, but I found myself browsing eBay for “condenser microphone”. I was somewhat stunned by the search results. There were lots of inexpensive ( less than $50) condenser microphones that *might* suit my needs so I started look through the styles and tech specs. I skipped over all the side speaking mics, I wasn’t interested in those. Then I found this gem: New-BM-800-Black-Condenser-Microphone-Mic-with-Shockmount


A quick search for the model number showed lots of other sellers and the microphone seemed targeted towards PC and Skype users. I knew that the KX3 worked with a lot of PC compatible microphones so this looked promising. The load Independence was > 1000 ohms. That was a good sign. The connecting cable ended in a 3.5mm stereo connector. Also Good. Frequency response seemed adequate, though I’m not an audiophile enough to know one way or another. It came with a shock mount, which I wasn’t going to assume was the highest quality but that was a plus. For $33.29 shipped, it was too good of a possibility to pass up. But I wanted to know more.

I found this YouTube video where someone unboxed the mic which gave me a good idea of what it came with. He even opened up the mic itself to show some of the internals, which showed that it used a AA battery so external power wasn’t needed: https://www.youtube.com/watch?v=XrYy64TgfVM

Some more searching led me to this discussion about “cheap condenser. It seems the microphones are possibly/likely rebranded leftovers from production runs for the ISK brand, which is pretty reputable in the audio world: http://forums.acoustica.com/bbs/viewtopic.php?f=4&t=14937. You can see some of the ISK models for same in the UK at this site: http://www.micsdirect.com/isk.htm. Also, here is the ISK main site: http://www.iskmic.com/.

So I took the plunge and bought one. It arrived last Friday. Now it’s picture time.

photo01The picture on the box is NOT what was in the box. I thought that was wierd but it matched with what was in the YouTube video.

photo02I actually took everything out and then put it back in for this picture, so everything is out of their wrappers and the battery is already installed.

1000x1000If you visited the ISK website, you won’t find this model there, but you’ll see lots of models that look too similar to be coincidence.

photo2The mic takes a singe AA battery for power.

photo1Another interior picture of the mic. The upper part doesn’t come apart easily so I didn’t try.

photo03A close up of the cable ends, which goes from XLR to 3.5mm stereo.

photo04A close up of the shock mount. It’s actually better than I thought it would be.
NOTE: The shock mount uses a 3/8″ mount, not a 5/8″ mount. You cannot use this with a Heil mic boom without an adapter.

So it *looks* good,  but how did it work? I contacted a friend who lives about 1.4 miles aware and we met on 28.360MHz for some testing. I performed before tests using the Elecraft MH-3 microphone and after tests with the BM-800. Of course, with the BM-800 mic I had to use the PTT button on the KX3, but my friend reported the audio with the BM-800 was better than that with the MH-3. He said the audio was excellent and the basses in my voice came through better.

Okay, so that’s one opinion, but it was enough to tell me that this microphone is good enough, and it looks like it will work well with the KX3. Deep, deep down I had always lusted after the Heil PR-781, but from everything I read it wouldn’t work (that well) with the KX3. Now I have something that looks similar (I know, I’m petty) and does work with the KX3. Now I just need a mic boom and I think I’m set.

Now I have something to connect to my homemade PTT foot switch adapter.


Posted in Equipment, KX3

Review: PAE-Kx31 heat sink for the KX3 from WA4PSC

The KX3 is amazing QRP radio, probably the best in it’s class. One of the more remarkable features is it’s built in PSK/RTTY mode. Recently, the fact that when running 5-10 watts for prolonged transmit times causes the KX3 to heat up to a point where the temperature monitor will force you to scale back your power. While this is very annoying, it’s necessary  in order to protect the KX3.

In the KX3 online discussions, a number of aftermarket heat sinks have been developed for the KX3. After reviewing the various designs, I took the plunge and placed a pre-order for the PAE-Kx31 from Pro Audio Engineering. More than just a chunk of aluminum on the back of the Kx3, this promised to have several features that I wanted:

  • Fins for better passive heat transfer
  • No sharp edges to snack in a backpack, clothing, or myself
  • Anodized instead of powder coated
  • The ability to continue to use my SideKX end plates and SideKX LEXAN cover

I got word last week that the item had shipped and it arrived Friday (April 18th). Excited as I was, I couldn’t perform the installation until Sunday. Here is the step by step with pictures along the way.

IMG_0040The package contents included the heat sink, four replacement screws to accommodate the additional thickness of the heat sink base plate, an installation guide, and a small package of thermal grease.

IMG_0041 The heat sink in more detail.

IMG_0045The small packet which contained the four screws and the thermal grease packet.

IMG_0046The heat sink measures just a bit over seven inches long.

IMG_0047The heat sink is about one and a half inches high.

IMG_0048The heat sink is about five-eighths of an inch thick. Note there is a notch on this end of the heat ink base plate. This is to accommodate the lip of the SideKX LEXAN cover.


IMG_0043The instruction guide is well detailed.

IMG_0053The one provided screw that is longer must go in the hold closest to the DC power supply.

IMG_0054You can see the size difference, accommodating the thickness of the base plate.

IMG_0055Removing the factory heat sink plate, you can see the original screws in the front row and the provided replacements behind them. Sadly, this means my brass ID plate from Arkay Engravers will have to find a new location.

IMG_0056With the original plate removed, the new heat sink is ready to go on. There are instructions for three different installations. I performed the first, which is a simple replacement of the original plate with the new heat sink. I did not use the thermal paste.

IMG_0058You may have to open your case and re-seat the locking nuts that the middle two screws attach to.

IMG_0057You can see these two screw holes next to the battery pack. When I removed the original screws, the nuts fell out of place and I had to fish them out. I attached these two screws first, and then attached the two on the end last.

IMG_0059Here the nuts are in place with the heat sink attached.

IMG_0060Behold, the heat sink is attached!

IMG_0061You will notice, the anodized black is an excellent match to the black of the KX3. It’s an excellent detail that was attended to.

IMG_0062Sitting on the legs, the heat sink doesn’t add any perceptible bulk to the KX3. The rounded radial fins help reduce that impression.

IMG_0064Also important, the SideKX LEXAN cover fits perfectly. That little notch on one end of the plate was thoughtfully included.

All in all, I think this is a very fine product. Howard Hoyt (WA4PSC) paid a lot of attention to the details of this aftermarket heat sink and I think it was worth every penny!

Coming soon, I’ll do a key-down time vs temperature chart comparing operation with the new heat sink versus with the stock plate.

Posted in Equipment, KX3

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



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