First I want to promote some excellent papers on rig interfacing and grounding produced by Jim Brown K9YC. There is a wealth of information there, produced by a very talented and experienced engineer.
Now…on to the topic of interfacing PC headset to ham rigs…
Heil Headsets get a lot of support and advertising in the amateur community. But they are expensive. The W2SZ VHF/UHF contest group that I belong to uses mostly Heil headsets, so I have a lot of experience with them. The problem is that a lot of them are broken. We only use them two weekends a year for about 36 hours but they fail in a variety of ways.
I don’t own a Heil headset (I’m too cheap), but wanted a more reliable headset for my own use on the mountain. In this case, reliable means I can bring several for a reasonable price. So, this led to a series of experiments with PC headsets that are available for prices that range from about $13 to $50.
PC headsets and Heil headsets operate differently. Heil headsets use a dynamic microphone and cannot tolerate any DC current through the microphone. PC headsets require a DC bias voltage to operate their electret microphone.
All PC headsets have the ring terminal for bias…that is the key to this design.
The box below takes 8 volts from the ICOM microphone connector and uses it to power the PC headset. The circuit has…
3.5 mm (1/8th inch phone) jack for the microphone
0.47 uFd series cap on the microphone, pass audio and block DC
2.2K resistor to pass DC from the 8V pin to the ring terminal
1/4 inch phone jack for rig keying
Cable and ICOM microphone plug
It was important to ensure the Heil headset doesn’t see any DC if plugged into the microphone jack of this adapter. The design put bias on the ring terminal to feed the PC headset. But, the Heil microphone connector does not have a ring terminal so it simply grounds the bias voltage… so, no bias gets to the Heil. The dynamic microphone in the Heil couples audio through the series cap.
Here’s another design. This one has two 3.5 mm connectors, one jack, one plug plus a battery. The battery supplies power to the PC headset without the need for power from the transceiver. This also supplies power to the ring terminal and block DC to the microphone on the tip terminal. This took about 5 minutes, the components are under the tape.
One of our W2SZ members, Tom Price KC2PSC, designed of a PC board to implement this idea.
RJ-45 connector for rig microphone interface
Converts to 3.5 mm microphone and line out
Converts 1/4 inch phone for rig keying
Includes option for battery
There are a number of web sites that discuss the same thing
As many of you may know, I QSY’d to Florida last summer and now live in a large retirement community. With the move I find myself in an area tailored for the elderly – single-story homes with wide doorways; age minimum of 55 years old; small lots with few trees; landscape and lawn-care services; and the omnipresent golf carts. The biggest industry besides the care and feeding of golf clubs is health care. While I do not consider myself elderly at least for another 10 years or so, it is nice to know what lies ahead.
The Villages, FL is probably the largest planned retirement city in the country. The city’s goal is to make retirement as enjoyable and comfortable as possible for residents, free from those annoying things you had to put up with during your working career up north. That “freedom” factor is often embodied in fine print on one’s deed that is called Covenants, Conditions, and Restrictions (CC&Rs). Hams are familiar with the term since those who live in apartments or condominiums have to contend with “no outside physical structures for non-commercial antennas, or related paraphernalia attached thereto to one’s domicile”, or similar gobbledygook that means no towers and antennas.
So why in the world does a guy who had two towers, stacked beams, contested regularly on 160 – 10 meters running the legal limit in power, and has worked them all (DXCC and states) pull up stakes for such a place? I’m still asking myself that question, although I must admit being able to cycle, run and swim in January and February is pretty cool. I’m still in good shape for tower climbing if I find a big station off the reservation that needs some help.
But take heart. Life’s changes mean new challenges and ham radio is no different. Thanks to technology and ham radio ingenuity, there are ways to coexist with Big Brother and still enjoy the hobby. Before I made the commitment to make the move, I checked out the local radio club’s site at K4VRC.COM that contains some useful and clever stealth antenna configurations one can implement. A number of local hams have an “ugly” flagpole made of PVC pipe that encases a vertical antenna. The base hardware is disguised with a fake rock or a nice flower bed while the lush lawns hide a radial field. It didn’t take me long to settle on a Hustler 6BTV vertical for my flagpole antenna. The 6BTV is attractive because it requires no top hat capacitive loading that would not work inside PVC pipe. It is about 24 feet in height which fits in with the CC&R limit of 22 feet for flagpoles. (The two feet that stick out are part of the 80-meter coil and are hard to see.)
I’ve been operating about four months now with the vertical and have had some success with it. I managed to work 500 stations during the ARRL CW DX contest in February and several hundred more during a couple of the RTTY DX contests. I find my hamming has a familiarity that hearkens back to when I got started. As a newly minted General in the 1960s I was confined to low wire dipoles; the Heathkit DX-20/DX-40/DX-60 line of transmitters; and a Hammarlund HQ-100 receiver. I was happy working the states and especially the counties, the latter being “retired” at ~3035 confirmed.
OK, what now? Why, more antennas, of course. The back of my house has a peak about 20 feet up that I figured would be a good spot for a pole bolted in place to support a dipole. I have a tree on the front corner of my property that is 30+ feet tall, fine for one end of a multi-band dipole. Back in the early 80s when the WARC bands were new, I built a tri-band dipole for 30, 17, and 12 meters. This simple antenna worked well since there were few beams and even fewer amplifiers on these bands so everyone was on an equal footing. I decided to go with a 40/17/12 meter combination to give me another option for 40 meters. I hung the antenna between the tree and pole on the back of the house, the 40-meter dipole resting just a foot or two above the roof. The 17 and 12-meter antennas were made with insulated wire and run across the roof to tie-off points on the side of the house in a tilted inverted Vee configuration. Other hams in The Villages have run similar antennas across their roofs and found them to work OK with a tuner. (Such antennas are also hard to see even for the neighborhood vigilante.)
The new antenna allowed me to cover the entire 40-meter band without a tuner. The 12 and 17-meter antennas, however, did not perform as well as I had hoped. Propagation was a factor but I also noticed that the wires worked their way under the roof shingles and I did not want them pulled up when the antenna flexed on windy days. Time to figure out a new scheme, especially when the XYL complained about the dipole being visible from the street.
I studied the pole on the back of my house where the dipole was secured and had an idea. Why not mount the center insulator on the pole and feed the antenna ends to the ground as a series of inverted Vee antennas? This approach was desirable for two reasons: (1) it was hidden from the street view; and (2) I could orient the inverted Vees to the Northeast to favor Europe. I found that I could secure the ends of the 12-meter antenna off the ends of the soffit at the back peak of the house. The 17-meter inverted Vee hangs off one end over a lower roof and is tied off to a bush on the corner of the Lanai, and the other end is tied off to a hook on the other side of the roof. The 40-meter antenna runs from a small tree at the back of the property on one side and to a stake that supports a rope to my flagpole on the other side. The coax is taped along the pole and runs across the roof to a row of hooks along the soffit to the front of the house and into the shack. A check of the view from the street shows only the pole to be visible. As for the ends of the antennas, well, I love black Dacron rope.
The figure below shows the antenna from its pole mount. The center feed point is visible at the top of the pole. The top dipole is the 40-meter antenna, followed by the 17-meter antenna and finally the 12-meter that is tied off at the peak roof line. The 40-meter antenna is forward-most, meaning it is the most Northeasterly of the three.
Triband antenna installed at K2TE
The tri-band inverted Vee antenna is a very simple design and it works. Some pruning may be necessary to tune the antennas due to interaction with each other or nearby objects. I’ve been able to work stations on 17 meters as propagation allows, but nothing much on 12 meters for the same reason. (Zack, W1VT has designed a WARC tri-band dipole that uses ladder line for matching to a conventional wire dipole strung between trees. Unfortunately, I do not have the trees to try this.)
So here I am with a capability to operate 80 – 10 meters again. I’m limited to 100 watts for the time being. Adding my AL-1200 beast in line is not an option since my 6BTV is about six feet from the rig. Besides, 1.5 KW into the antenna will be like unleashing an EMP on the neighbors as well as myself. When I sit back and ponder my setup, I find myself back to the future with simple antennas like I started out with. Ahh, but this is the 21st century and technology comes to the rescue.
In a previous article, I wrote about jumping into 3D printing for fun and home-brewing. I decided I wanted to try printing a custom case for my Raspberry Pi 2 Model B that I found on Thingiverse. I chose one that had VESA mounting tabs with 75mm spacing in order to mount to the back of an older LCD monitor I had laying around. I am doing this to create a dedicated computer for running my M3D 3D printer.
Custom Cases for Raspberry Pi found on Thingiverse.com
I’m printing the case you see above on the left. There are other upper case options for mounting mini-fans should you need to provide extra cooling for your Raspberry Pi. And if you are handy with one of the many 3D modeling software packages out there, you can mod this case (or any case) to fit your specific needs.
PRINTING THE CASE LOWER
I acquired a spool of black PLA filament (Hatchbox) from Amazon.
While not specifically branded by M3D, I wanted to try other sources because the Hatchbox brand was less expensive on the order of 2.8:1 than the M3D branded filament. I was taking a chance because I am learning that getting the temperature right for a brand not tested by the printer manufacturer can be tricky. I did have issues of the print starting to lift off the print bed (M3D is non-heated). But I recovered from that by tacking down the corner with a hot glue gun. Maybe this would have printed better on a heated print bed or if I would have controlled the surrounding temperature better.
Almost completed lower Raspberry Pi caseCompleted Raspberry Pi case lower
Back of case showing “raft” before removal and cleanup
Cleaned up lower ready for test fit
Fits like a glove!
PRINTING THE CASE UPPER
Given the experience I had with printing with the Hatchbox filament, I wanted to see how printing the case upper would be using the M3D filament. I just chose one of the other M3D filaments to contrast the black lower. The printer’s program calculated this to be a 14 hr print. But, the output is looking good for far–no lifting of corners or warping.
About 12 hours later… DONE!
Print completed for the RasPi case upper
After removing the raft and cleaning up stray flashing (inside)
After removing the raft and cleaning up stray flashing (outside)
Fits great! Just need to figure out the case screws.
As mentioned earlier, I wanted to print the case version with the VESA mounting tabs on the back of a monitor. In this case, they needed to be 75mm spacing. Aligned nicely!
This was a fun project. While not a perfect printing experience, it was good enough for a first major print project. Lessons learned will be turned back into the printing experience and improved upon on subsequent projects.
After mounting this Raspberry Pi w/case to the back of the monitor, the next mini-project is to get the Raspberry Pi working with the 3D printer. There appears to be groundwork already done in this area, and I will follow the path already paved.
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