Assembling Glen Martin Rt-424 Roof Tower

The RT-424 is a 4.5 foot tall roof-mounted tower for rotatable antennas.

As I have heard, this looks like a nice product but the instructions leave something to be desired – something HUGE. Here are a few notes and warnings from my assembly process.

Things you MUST know:

  1. There are 28 bolts, and eight of them are shorter than the others. You must use the 8 shorter bolts in the top section to secure the thrust-bearing plate. otherwise (if you use the longer ones), it will not be possible to assemble it.
  2. If you tighten everything as you build the tower from the ground-upwards, you will not be able to align the holes to attache the thrust-bearing plate (unless you are very lucky).

Some General Observations

The pieces came well packaged, with the hardware in one of those multi-section shrinkwrap bags.

The machining appears to be well done but they did not deburr the holes on my parts. Be careful, you could get a nice cut from the sharp edges.

Some Assembly Photos and Suggestions

When assembling the tower, leave all hardware loose enough that you can move around the parts, until you are ready to put on the top thrust-bearing plate. I suggest starting by attaching two-each of the cross-braces to each of the legs using the top bolt for each brace, as shown below.


Two legs with the braces attached at the top


Next attach one of the rotor plates between each pair of legs, and then attache the lower portion of the cross-braces between the two legs.


One side lower assembly with two legs, braces, and cross-plate attached


Here is a closeup showing the attachment of the braces and the rotor plates.


Completed Corner, Outside View

Next, attach the cross-braces between the two pairs of legs Now you have the entire tower together. If you tried tightening all the hardware as you built the tower, you might now have a situation like mine shown below, where you can not possibly align the holes to attach the thrust-bearing plate.


Top Plate holes do not align with the top of the four legs.

Once everything is loose enough, install the thrust bearing plates, then tighten all the hardware starting from the top. The top plate should align nicely like this:


Now attach the feet on the bottom and your tower is ready to mount on the roof. Here is a shot of the completed 4.5 foot RT-424 tower. Good luck.



DXDUSB Next Version with Custom PC Board

After using some DXDUSB prototypes with DX Doubler SO2R boxes for several months, I finally got around to completing the PC Board layout for the next version. This one will add some power conditioning and choice of operation from +5 or +12 VDC. It also should be able to survive use in a Mobile environment where the voltage can go well above 12 VDC.

This should be a more reliable DXDUSB. For those who have asked about the availability, this version should be available in early November. Watch for updates as I assemble and test these boards. They should arrive around October 20th.


Top View of the DXDUSB PC Board layout.

Top View of the DXDUSB PC Board layout.

The board is a just under 2-inches on each side. It should fit inside a small enclosure similar to a dual-port Ethernet box. You are only seeing the wiring on one side of the board, so there is much more to it than what you see here.

I have also been considering a version that could be mounted inside the DX Doubler box. The only problem with that is that I would need to remove the DB-25 (Parallel Port) connector on the DX Doubler’s circuit board inside the enclosure. I have been considering the possibility of installing this board in place of the parallel port connector on the X Doubler product, since nearly nobody wants parallel port devices these days. Makes sense, since you can hardly find a new computer with a parallel port and the add-on boards I have seen do not seem to work well at all.


Roof Tower RT-424

I have been looking at a way to get a Yagi on my roof. No room for a big tower at my QTH, but something on the roof is within reason. I have been looking at the Glen Martin Roof Towers, particularly the smaller Glen Martin RT-424 Roof Tower. It is a 4.5 foot tall, four-legged “quad pod.” The prices on these have suddenly been reduced substantially, so I finally placed an order.

I received the package a couple days ago. Today I decided to put it together. It is a lousy day here anyway, so I will build it in the garage. The box was surprisingly small. They did a good packaging job. Just a bunch of pieces of machined aluminum, a shrink-wrapped container of hardware and a 4-page manual.

Looking at reviews on eHam, it appears to be a good quality item, with not-so-great instructions. With a couple pictures in the manual, it looks like is should be fairly easy to build.

I will post some of my findings as I put it together. Hopefully everything I need is there. I still need to find a rotor for the rooftop setup. The antenna will be a used C3S 10/15/20 meter yagi that I bought a few months ago. This will be the first yagi I have had in a station for many years, so it should be fun.

DXDUSB – DX Doubler USB Interface Update

DXDUSB Development Status

I have had some requests to provide DXDUSB prototypes to  couple people. The latest prototype (Protot3) is still very rough. I have a couple in ongoing testing and they seem to be working well. However, these are very rough – assembly is hand soldered wires attached to the Arduino board. While I am happy to make a few of these available for testing, I can not sell them as a final product. I would not want anyone trying this out and having problems during an important Contest or other operating event.

I am in the process of designing a PC Board that will be used in the initial version that should be solid enough to make it available to anyone that is interested. It will probably be late September before these are available.

How it Works

The DXDUSB uses a USB-to-Serial interface with the FTDI chipset. This is known to work with N1MM+ software. The converter plugs in to a USB Port on the PC and into the DXDUSB chassis with a standard RJ-45 Ethernet connector. N1MM+ is configured to use the OTRSP protocol to communicate with the DXDUSB. CW Keying and PTT signals are also provided. An Arduino micro computer board converts the signals from the USB–>Serial converter into signals that are compatible with the 25-pin LPT connector on the rear panel of the DX Doubler box.

There is no special software or software driver needed. The only driver used is the standard FTDI driver. So installation and setup is simple.


A USB Interface for the DX Doubler – The Last DXDUSB Prototypes

I have been working on a USB-only interface for the Top Ten Devices DX Doubler for some time. I recently completed the 3rd generation prototype. This is still a prototype – it uses a very small Arduino board with attached wires, but it is shoved into a nice small Ethernet drop-box enclosue.

This version has been in testing for several months. I have tested one, and a friend, K7SV, has also been testing one. He is a much more active and accomplished SO2R operator than I, so his feedback has been very helpful and much appreciated – thanks Lar.

At this point, I feel this is a viable design and it seems to be reliable. The only issue known is that I have to recycle the 5 volt power on mine after a week or two of inactivity in my shack. Not sure why, and I know Lar has not had this problem. I am wondering if my PC is shutting-down the port.Recycling the power once always resolves the issue.

There a a couple photos of the latest prototype below.



This version uses a tethered DB25 connector that attaches to the DX Doubler box. The USB connector you see is for 5v power ONLY – this seemed like an easy way to power the device, but I am still experimenting with other power options. I need a version that uses 12vdc for my shack. I also plan to make the final unit capable of working with supplies of up to 15vdc, so it can be used in nearly any station, Home or Mobile. Notice the attached snap-on ferrite. I put these on nearly all of the peripheral devices in my shack, and especially in my Mobile. I have not had any indication that this is needed to combat RFI, so it is only a precaution. My antennas are too close to my rig, so I do not want to push my luck.

The RJ45 port seen in the lower photo is for connection a USB to Serial interface. This is the actual port that is used for communication between the DX Doubler and the PC. There is a standard USB–>Serial cable that is made for connecting to Cisco routers. I have opted to use this cable, which is available at Amazon for under $ 14. It uses the popular (though somewhat expensive) FTDI chip, which is known to be compatible with the N1MM+ software I use. With this cable connected, I can utilize all of the DX Doubler functions, including computer-generated PTT and CW keying. This design has been setup for use with N1MM+ Logger software. It should be compatible with other software that can use the DX Doubler but I have not yet found any testers to configure and verify this. I am in the early stage of trying the DXDUSB with WRITELOG software, another popular contesting application.

I have now turned my attention to designing a printed circuit board version, that will be enclosed in a small chassis, and could possibly be embedded inside the DX Doubler chassis as well. more on this later. I have received a couple inquiries about providing this as a product. That is my plan if there is enough interest. Sorry, but I am not yet ready to ship these in any quantity. I may be able to send a couple out for testing, but delivery time would be at least 2-3 weeks. Any additional feedback or questions would be welcomed.




VA QSO Party 2016 – Two for the Road

I went mobile again for the 2016 Virginia QSO Party, using the callsign KT4KA. I use that callsign so as not to confuse everyone when calling CQ (with my normal “3”call). The goal this year was to beat last year, and hopefully win the Mobile all-Band category. No matter what happens, this is always enjoyable. It is a challenge assembling a usable HF Mobile station, and I get to see some parts of the State that I don’t often visit. Following is a summary of this year’s event, and some photos of the equipment.

This year I decided to take my newest radio, the Yaesu FTDX-3000 with me. It was not exactly made for the road, but I love the receiver in it, and it is much better on the low Bands than my other radio, the made-for-mobile Icom-7000. I also planned to use my two-radio controller, the DX Doubler in the setup. that did not exactly work out, but so it goes.

The map below shoes my route this year, as reported by the APRS system.


Day one – I started near Richmond and headed out toward skyline drive, making stops in the following Counties/Cities: Richmond City, Louisa, Orange, Rockingham, Harrisonburg, Shenandoah, Warren, and Fauquier

When I got to the entrance to Skyline Drive, I was told that it was closed due to snow at the high elevations. Not exactly what I had in mind, but I was in the higher elevations and was able to add on many VHF QSOs from that area. Nowhere near what I could have had on the Skyline, but that’s life.

Day two – I started in the Falls Church area, and worked my way to the west, toward my home in the Warrenton area. Stops were made in: Falls Church City, Fairfax, Fairfax City, Manassas Park City, Manassas City, Prince William, Loudon, and Culpeper.

Here is a shot of the Mobile antennas in the parking lot of The Stone House at the Manassas Battlefield Park. You can easily see the Hi-Q Antennas 4/80 HF screwdriver antenna. That did most of the work for me in VAQP this year, with 40m and 80m being the big Bands. there is a smaller antenna on the passenger side roof for 2m and 440 MHz.

KT4KA Mobile, 80m through 432 MHz.

KT4KA Mobile, 80m through 432 MHz.

The next photo is a shot of the Mobile station from inside the Ford F-150. You can see the Laptop, FTDX-3000 in the middle, and the Head unit of the IC-7000 on the left. The cell phone that is barely visible is showing the VAQP Spotting network hosted by QSOPARTY.COM. That is the brainchild of John, KX4O and it has become a widely used spotting system by FARA members and recently by many others. he software was, or course, N1MM Logger+. If you work contests and you are not using N1MM, you need to see what you are missing.



In the later hours, here is how it looked:


Overall it was a very enjoyable weekend. Band conditions were not good on Saturday, with VA stations barely able to hear each other on HF. I attempted to compensate by working more CW contacts, with the usual breakthrough ability of CW. I found a number of stations in several other Call areas that were willing to work me many times. Overall score was better than last year despite the Saturday doldrums. We will see how it all works out. The FTDX-3000 will be joining me on the road again next year. I just love the rig. I need to do some improvement on the antenna switching setup. I also plan to take a complete SO2R setup next year, with the DX Doubler.


It Really is all About Antennas

As I try to continually improve my Station, I keep coming back to the antennas. I have a couple very nice Radios, but I am still not very competitive in Contests, especially DX contests. I have always used mainly wire antennas and generally if I can hear them, I can work them. Now I know the problem is that I can not hear enough of them!

I had an opportunity to work a Contest from a world-class Contest station (NR4M) recently. The contest was the ARRL International DX CW. I won’t go into the details of the antenna system there (you can search on NR4M), but let’s  just say they have about 65 acres worth of antennas like I will probably never see anywhere else.

I had access to all kinds of antennas on all the HF Bands. One antenna group that really impressed me was on 80 meters. I heard all kinds of DX during the weekend and I even managed to work China on 80 meters. That will not be happening at my Home QTH any time soon. I was using two antennas at the time, in Diversity Mode on a K3. This was quite a new experience. The diversity did just enough to bring the China station’s signal out of the noise enough for me to work him.

So the lesson learned here is that if I really want to improve my station and get to the next level, I have to do something about the antennas. First project is going to be getting a yagi on the roof. I will always use wire antennas, and I will be trying to improve them as well. I  recently installed a Beverage antenna for the first time. At a length of about 300′, it is not very long, but I am hoping it will improve my hearing ability on the Low Bands.

Of course another thing I could do is raise my Power to the KW level. I do not plan to do that, mainly due to the small lot I am on and the close proximity of my antennas to the Shack. I think going QRO would result in an RFI nightmare.


VA QSO Party 2016

I plan to go mobile again this year for the VA QSO Party in March. This is an enjoyable contest with lots of activity. You will probably see every County and City in the State activated at some point over the weekend. I will be using the callsign KT4KA/M so as not to confuse people by using my normal “3” call KG3V.

I try to do something a little different every year for this Contest. This year I am going to attempt to take a complete SO2R (single operator 2 radio) station in my pickup truck. I have an ICOM IC-7000 permanently in the pickup and I will be adding my SO2R Controller box, the DX Doubler, and my FTDX-3000 for the HF Bands. Plan is to use the IC-7000 for mainly VHF/UHF. The SO2R controller allows me to work HF continuously and still hear anything that pops up on VHF/UHF.

I am still in the process of building the station. I had to completely rewire my HF antenna, a Screwdriver antenna from HiQ Antennas. All of my connections had corroded after 3 years of use with little maintenance. I also had to buy a new door mount for the VHF/UHF antenna as the feedline for mine had gotten cut in half by the door hinge.

Had one setback today. My homebrew USB interface for the DX Doubler was not working and it turns out the Arduino board (a Pro Mini) had died. So I replaced that and all seems to be working again. Still not sure what happened to the Arduino, but this was a $3 board. more proof that you get what you pay for, I guess.

If you are not a regular in VAQP, give it a try.

Arduino Pro Mini – A Great Tiny Micro Controller

If you have been working with Arduino boards, you may already know about this great little board. The Arduino Pro Mini is about 1.7″ X 0.7″ in size. It has the normal 14 Digital I/O lines and several analog inputs as well. The one thing you need to know is that you must have a Pro Mini Programming Cable for this board. These cables convert USB to Serial I/O and provide a 6-pin header that connects to the Pro Mini when you are downloading or debugging.

Spark Fun is the designer of the Pro Min. There are also some “knock-offs” out there that are even less costly. if you look around, you can find these Pro Mini Arduino boards for under $ 5.00. These are great for an embedded project. I am using one to design a USB interface for my DX Doubler 2-Radio Controller box. It almost fits inside a D-sub connector backshell. I am using a small Ethernet port box to house mine. It makes for a nice small platform for various Micro Controller projects.

There are a few things to be careful of with this board. There are 3.3V and 5V boards, so you need the right voltage on your Programming Cable. The programming cable is also not cheap, but you only need one and they have a genuine FTDI chip, so they are reliable and very flexible using the FTDI driver and configuration software. Beware of cheap FTDI imitations. If you buy one, there is no guarantee that your FTDI driver software will work. There are also different pin-outs and different clock speed version available.

Pro Mini boards come with headers for the programming cable and the I/O pins. Some sell them already installed, others make you solder them in if you want them. They are easy to install, so this is no big deal. My one minor complaint is that this board has no mounting holes. That makes it a challenge to put into a chassis, but the board is so lightweight that you can use a cable tie or some double-sided tape to put it wherever you want to mount it.

I mentioned varying pinouts. If you are just using the Pro Mini on the bench, the only issue is that you may need to reverse the programming Cable on some versions. If you are planning to put an Arduino Pro Mini on a circuit board, you need to be careful to use the correct pinout for the devices you buy. I am currently using PCB123 to layout a PC Board and attempting to build a footprint that will be compatible with both pinout versions I have seen. This will let me keep my costs down by purchasing whatever version is the cheapest when I am ordering.

The pro Mini is a great little board. Buy a few and have some fun. You might be surprised at what you can do with them.





ARRL Triple Play Award – One Worth Having

I just saw on the ARRL LOTW Web Page that they have processed my application for the ARRL Triple Play Award. I do enjoy Contesting but otherwise I do not spend much time chasing awards. The Triple Play Award, if you don’t know, is for confirmed contacts with all 50 States on CW, Phone, and Digital modes. I like to bug other Hams to get on the Air and make some contacts. This shows I am at least making an effort to use the Bands and try the various modes. I will be glad to have this award hanging on my Wall. Congratulations to the other 1,747 Hams who have received the Triple Play award.

ARRL Triple Play Announcement