Tag Archives: antennas

The Move Is Done

Well, sort of…

We are here in Klamath Falls, Oregon now. We started the move July 1st and I was making runs all July. The old place was officially vacated July 31st. August was the slow unpacking of boxes and the beginning of several furniture building projects. I have built 6 bookcases; 2 of them 40 inches tall, the other 4, 70 inches tall.

I still have a number of things to build like the DVD cabinets that will hold our 1000ish movies and TV shows. I also have a lot of storage containers to build, think apothecaries drawers. Lot’s and lot’s of them.

You can see why I haven’t posted in a while. I have made some upgrades to the shack, well the mobile, the shack is looking rather minuscule right now.

I have absolutely no bench space for shop stuff or electronics. The station is occupying a puny 1 sq.ft. space across 2 shelves, but, I actually have an HF antenna outside! The MFJ-1982LP endfed is up. The feed point is about 15 feet up on the mast my 2m roll-up J-Pole is attached to and the rest of the antenna is supported by 2 31 foot Jackite poles and 20 feet up into the Ponderosa Pine in our front yard.

So far 80 and 40 meters have been kind. The net controls have had to work me pretty hard, but I have been getting through. I have been heard as far away as Victoria BC Canada, La Jolla California, Somewhere in Wyoming, Utah, and Nevada. Not bad for 5 watts.

The power on the base, my Yaesu FT-817ND, needs a boost now that I am putting together a local NTS Net. I need to make the Local to Section hop on HF more reliably and not make control work so hard. The local net will be on one of the club repeaters.

I have also moved forward by getting involved with a local active club, the Klamath Basin Amateur Radio Association. I have already done two events and a VE session with the club since we got up here. Also in the mix is getting started with the Klamath County CERT program.  There is some early work on getting an ARES/RACES group together. All kinds of fun going on.

Once we got up here I started work on the mobile. The Baofeng UV-5RE+ was not cutting it on 2 meters. I upgraded from 5 watts with a crappy little antenna to 25 watts with a QYT KT-9800D dual band mobile radio and an ANLI DC-124H TriBand antenna.  Much better performance. Also in the mobile, I installed a Uniden BEARCAT 980SSB Single Sideband CB and a Midland MXT400 GMRS radio. There is hardly any CB traffic up here, but surprisingly, there is quite a bit of GMRS traffic.

For a 2 meter base, I have been using one of the 5 watt handhelds attached to the homebrew 2 meter twin-lead J-Pole I built a while back. Now that I am getting hooked up with CERT, I think I should pull the J-Pole out of the PVC and use it as a portable roll-up. I also need a little more juice for poor weather conditions so a 2 meter base upgrade was in order. Another QYT KT-9800D mobile radio and a Diamond X50A dual-band base antenna should work nicely for VHF/UHF. Those will be incorporated into the station by the end of the week.

As for the HF side of the station… I need to poke around for something around 100 watts, which will require an antenna upgrade too. The MFJ-1982LP is only rated to 30 watts. As long as I keep the power down I should be able to use it for a while. That will still give me a 6 db power gain over the 5 watts I am pushing now. Anything should help. The section nets are on 80 and 40 meters so I will need an antenna that covers at least 10-80 meters. 100 watts should be more than enough for my needs.

Oh, one other thing, I finally got my Skywarn ID number, now I need to find a net for Skywarn. I haven’t found anything in southeastern Oregon yet. I’ll keep looking.

Anyway, that’s the status update for now. Look for an NTS page to be added to the site soon.

73,
~Jon KK6GXG

July? Has it really been that long?

Wow, yes it has in fact been that long.

20151104_161606From a building stand point… nothing new has been going on. I am still working on the Beach 40 and the Bitx 20. The Beach 40 still needs the audio section rebuilt and the Bitx20 needs some troubleshooting . I don’t have the facilities to put up a 20 or 40 meter antenna and since both radios are QRP(p), a good antenna is vital to making any contacts.

20151121_072647From an operators perspective… ya, nothing going on there ether. I need to pull down my Frankenstein/Hill Billy mast because we are having our building painted soon. I have plans for a simpler replacement that should work out fine. I’ll post about that if and or when that happens.

From an experimenters view point…  I have been kind of busy lately. Many of the newer radio projects I have been looking at use micro-controllers and embedded Linux systems. All of which I am totally fine with. There are so many other applications besides radio that I can employ these technologies. The only impediment is getting some play time in with these technologies and getting familiar with there capabilities, use, and programming.

arduinoEarlier this year I picked up some Arduino hardware. I haven’t had much time to work with it yet as the Day Job has been keeping me hopping as well as a lot of stuff in the personal life, nothing bad, just a lot of changes and preparations.

Many projects are done with the Arduino and various shields. Some require a little more direction in the form of an embedded system with a true OS. Enter Raspberry Pi and Raspbian.

rpi3bLast week I added a RPi 3B to the hardware pile and began working with it. Along with the Pi I picked up a copy of Exploring Raspberry Pi: Interfacing to the real world with embedded Linux From Wiley written by Derek Molloy.

Linux doesn’t worry me at all. Many moons ago I was a Solaris 7/8 admin as well as a RedHat 7 admin. The problem is that well over a decade has gone by since I actively worked on those systems. I have been in a Windows only environment for so long my Unix brain has turned to mush. So now I’m re-learning the Unix command line and re-acquainting myself with the Linux directory structure along with some all new unique elements of embedded systems and the Raspbian OS in particular.

With all of the projects piling up and now adding a lot of general computer stuff to the pile, Arduino Sketches, Python, C/C++, and picking up where I left off with Perl, it almost feels like I should go back to school and get credit for all of this work. I could pick up a CS degree with everything on my “tech to learn” plate right now. Add in all of the projects and an engineering degree (EE or ME) isn’t far behind. Thoughts for another time.

Radio specific plans are to read and build along with Crystal Sets to Sideband by Frank W. Harris W0IYE, and then get back to Experimental Methods in RF Design and do the same. I don’t expect to do a lot of operating other than 2 meter until we have the facilities to put up a real antenna, and there is no solid timeline for that.

Life outside radio has taken all of my time lately and I am just now slowly getting back to things. Most of it is general electronics/computer experimentation and adding to the knowledge pool right now.

So in conclusion, no I haven’t been busy, I’ve been too busy.

:-/

hamverseryP.S. Today’s post is brought to you by Hamversary. On this day in 2013 I received my license grant about a week after I walked into the Saratoga Fire Station a non-ham. Since then I have worked my way up to Extra Class, begun teaching license preparation classes to prospective hams, and I have been a Volunteer Examiner for 42 exam sessions, most of them at the Saratoga Fire Station.

I have learned so much in so many ways in this short period of time. Thank you Amateur Radio.

73,
~Jon KK6GXG 

Another month gone by

foto001mdOkay, it’s now March 11th, and I have done just about NOTHING radio related except attending VE testing sessions since what, December?

Not entirely true I suppose. I pulled down the 70cm and 40m antennas from the Hillbilly mast rig, and I have done some poking around at the 40m DSB project, though I haven’t done any real work on it.  Also the VE sessions have been a saving grace in many ways. One, I am still “participating” in the community. Two, we have been engaging is some interesting discussions in the back of the room while waiting for exams to grade. Three, I did reach a milestone in so much as I sat my 25th session this last Saturday. That at least, is something I can honestly say I am proud of.

There are so many projects I want to get going on, I just can’t justify the time right now.  The family is working towards a relocation up to northwest 7 land, and I am really looking forward to the move. There is just so much swinging in the breeze right now, making any plans or starting any projects is just not a good idea.

We are heading up north in May to look at some property. We are hoping that this trip will provide a target for relocating by the end of September at which point, all hell’s gonna break loose and I’m going to be a very busy man.

I have no idea what I will be able to do radio-wise between now and then. I do know I am itching to do something though. I will just have to see what opportunities present themselves in the meantime.

73,
~Jon KK6GXG

Holy Hanna!

20151121_072647February is half over and I haven’t posted at all this year so far!

In truth, I haven’t done squat so far this year with regard to radio stuff. Well almost nothing, I have made it to three VE sessing so far this year. The next one is this Saturday.

I really wish I had more to report but I basically had to shut down all of my radio projects because I just don’t have the time right now.

One radio related project I can report is a partial disassembly of the Hillbilly Radio Tower. I pulled the 70 cm and 40 m antennas down leaving only the 2 m antenna in place.

The 70 cm was working fine, I just don’t use it that often and I needed to pull the 40 m down anyway, so I opted to clean up the cabling on the back porch.

The 40 m had to come down, or be adjusted. It was tilted from the high winds of the last storm that blew through. It was still useable, just leaning about 30 degrees off vertical. After cleaning up the mast the 2 m is hardly noticeable, which is a good thing.

Other than the antennas, nothing going on or planned for the near future. I will make an attempt to get back before another 2 months goes by.

73,
~Jon KK6GXG

Antennas & More

20150507_192446Today was a good antenna day. I finally got the PVC cover on the 40 meter helically-wound antenna I started back in April. I have been using the antenna without the cover as a test antenna next to the bench but it’s time to get it up on the roofline for some actual use.

By “actual use” I am referring to the Beach 40 project that is back in motion now that I have a VXO that pulls more than 1.8 kHz of selectivity. Yay 148 kHz selectivity! Now all I need to do is get the Tx/Rx switching working for the transceiver to be operational.

20140430_131323Another antenna project completed today is the 2 meter twin-lead J-Pole. This one was also waiting for a PVC cover so it could be mounted on a pole. The original design was intended as a portable antenna but the twin-lead J-Pole on any frequency above 50 MHz lends itself well to mounted vertical use, it just needs a housing to keep it in the vertical position.

This little antenna works really well. On numerous occasions I have been unable to ping the local repeaters with my HT with the stock or aftermarket antennas for handhelds. If I attach the twin-lead J-Pole I can actually get out and participate in the nets. With this antenna up in the air at roofline I should have no problems working any of the local repeaters including the packet and Winlink towers.

Speaking of which, I want to get into digital modes once I get the antennas up in the air. I’m not quite up to building a TNC from scratch so I need to save up a hundred and fifty bucks to get digital rolling. Soon…

20151111_145644The other antenna project today was a new-start. When the 2 and 40 meter antennas go up I also plan on attaching a 70 cm half-wave vertical with counterpoise. This one is an experiment. I originally planned on building a 70 cm full-wave twin-lead J-Pole, and I likely still will, but I wanted to see if I could make a vertical with counterpoise that works well. I may even mod this one into a full-wave vertical with half-wave counterpoise radials. Dunno. Like I said, this is an experiment.

Another near-term antenna project, as-of-yet not started, is an aviation band twin-lead J-Pole set up like the 2 meter one. Being a pilot and mechanic, at some point I would like to have either a hangar at a local airport or a small strip at home to work on restorations, so it would make sense to have an AvBand radio in the shop. I have a Vertex Standard (Yaesu) HT for aviation VHF, it just needs an external antenna. I also have a few old radios salvaged from aircraft that would never make it back into an aircraft, but may be suitable for base station operations.

I have a number of other antenna experiment/projects in various configurations, in particular 2 m and 70 cm yagi and/or helical beam antennas suitable for satellite and moon bounce communication. But these are for the future. I also want to build some highly directional antennas for radio orienteering and high-gain narrow-beam antennas for really low power communications.

As for the “More” in the title, once I finish the 40 m transceiver I plan on building a 20 and 10 meter versions. I also have an idea for simple low power beacon transmitters I want to play with. I also want to get set up for QRSS, WSPR, and APRS.

Lots to do. One step at a time.

Till next time, 73,
~Jon KK6GXG

40 Meter DSB Coming Soon

Busy weekend for me.

20150530_161129Before moving on to Beach 40 progress, I got something else in the mail. A frequency counter module I ordered off eBay for ten bucks. I am thinking about using it in a future radio project as a digital frequency display.  Not sure what project, but it beckoned to me and I figured it might work out well.

20150530_221434In a related sidebar, I have been doing some VFO research. I have been looking at several options and one that seems simple and efficient is using varactor diodes to replace the air dielectric capacitors in tuning circuits. I have some ten-turn potentiometers and found a good deal on Motorola 68ρF varactors so I bought a bag of 100.

I found N6QW’s website with some great information including a test circuit for testing the tuning abilities of various diodes and transistors. Definitely more to come on this venture after the DSB project is done.

Now, on with our regularly scheduled program…

20150529_164741In the last post I talked about skipping the Balanced Modulator/Product Detector and moving on to the Audio Amplifier.

I built the Audio Amp and got everything all tied in to the panel mount components.

20150529_165009I still haven’t tested the Audio Amp yet and I am saving that for after I get all of the sections built out.

About the time I finished up the Audio Amp the 200Ω potentiometer I was waiting on showed up. With the parts in hand, I moved on to the BM/PD.

20150527_153801The BM/PD build went well. with no real surprises.  The diode ring ended up being laid out in an actual ring configuration with the RF transformer being mounted right in the middle.

The one thing I don’t like about this layout is the really long lead from one side of the diode ring all the way around to the other side of the board to the potentiometer. I don’t know if I can come up with a better layout in a future rendition but for now it should be fine.

20150530_214234One of the first things I started with today was building the interconnect cables out of RG174 coaxial cable and SMA connectors. I considered MMX connectors since they just push on rather than thread on but they are way expensive. I have seen a number of builders use coax interconnects for modularized construction and it makes separation for experimentation much easier.

20150530_220849One cable I made was actually an antenna, a test antenna at least. For testing transmission sections giving them something to radiate out of. By using a receiver near the transmitting device I should be able to copy the transmission. It’s the one on the right if you hadn’t guessed.

20150531_110751Cables, of any kind,  are one of those things that can seem fairly easy to do, but when they go bad, they can go epicly bad and it can be hard to detect. The only preventative effort I know of is to take your time, use a light touch, don’t force things, and pay attention to detail.

I made 4 interconnects, 1 antenna, and one single end cable for connecting to the antenna outlet. It took a coupe of hours, but all of them are solid mechanically, and test to be solid electrically.

20150530_221209After getting the cables done, I hooked up the antenna and one of the interconnects but I still haven’t done any of testing beyond the Local Oscillator.

I have a lot of testing to do but I’m almost done with the modules so I wanted to plug away and finish up the modules.

20150531_143223The last thing I worked on before turning off the soldering iron was the three stage RF Amplifier.

The pic is the first stage, a buffer stage. I started the board with a configuration in mind but by the time I got to the third stage I had shifted a few things around.

20150531_150232One thing I wanted to point out is the spacing of the stages. In this pic I have most of the second stage done and the pads for the third stage laid down. The gaps between stages are for the addition, if needed, of shielding between the stages. This amp is fairly low power so I don’t think it will need the shielding, But I wanted to make the option available.

20150531_161643The third stage saw several pads moved and things reconfigured a little. The yellow leads are the RX Amp Bypass (short lead) and Amplified RF (long lead) lines going to the relay circuit which after a lot of thought this evening will be replaced with cable ports and the relay section will be moved off this board entirely onto it’s own module.

The other bit on the RF Amp board that still needs work are the two bifilar toroids that still need to be wound and installed. It sounds like a lot of work still to be done, but it is getting very close to First Contact.

Thats all for this post. May the magic smoke remain contained in all your circuits.

73,
~Jon KK6GXG

Marker Generator and more

20150507_190019Picking up where I left off in the last post, I got the drill bits and finished the 40 meter Helically Wound Vertical antenna. I will get a project page up soon.

Now when I say “finished”, what I mean is the antenna is useable. I still need to seal and cover it but I wanted to get it all tuned up first. As far a receiving goes, the vertical is out performing the dipole strung in the house just sitting on the floor leaning up against the wall next the operating station, so it’s looking good.

I need to finish the tuning with a transmitter on it. Since the only transmitter I have for 40 meters is a CW 250mW transmitter I am holding off on that.

20150508_121409In the mean time I put together a Marker Signal Generator. The design takes an 8 MHz crystal and divides the signal down several time ending up with the desired 1 kHz signal with many harmonics to mark out a tuning dial in 1 kHz increments.

20150508_150243It was fun to build and I leaned a little about some ICs I had never used and some of the basics of working with multiple devices in a single package.

When I came to function, I was very disappointed. The oscillator was anything but stable and we very dependant on an extremely stable input voltage. The onboard diode voltage regulations stunk so I tuned down the power supply from 12 volts to the 5 the ICs need.

20150508_153648At this point I was finally able to calm down the oscillator and get close to 1 kHz I was hoping for. A millivolt up or down and the frequency was out. Not a particularly useable device as it sits but it does give me some ideas for using out of band crystals to generate a signal.

As always, this is the whole point, to experiment and learn about RF design by doing, not just reading and modeling on a computer.

The big news, and the reason I missed a post last week is that I have been doing some research on finding my next big build project. The winning design was the Beach 40 by VK3YE. I have been scouring the web looking for a simple phone (voice) transmitter. I was hoping for SSB (Single SideBand) but the Beach 40 DSB (Double SideBand Suppressed Carrier) is simple and straightforward as is.

IMG_20150513_125237Being me, I had to make some modifications to the design and tweak a few things. One of the great things about this design s that it uses discrete components rather than ICs.

At one point Peter (VK3YE) recommends changing the audio amplifier to one that uses the LM386 chip rather than discrete components because the output is rather low. Since one of the main reasons I chose this project was to keep to available discrete components I went out in search of a different audio amp.

Enter Arv Evans K7HKL and his Discrete Component AF Amplifier paper. By the way, at least via email, Arv is a really nice guy. Thanks for the help Arv!

20150513_170104Now with the circuits mostly settled and parts enroute, Digi-Key arrived a day early! 🙂 I sat down tonight and began kitting the parts for each of the transceiver subsections beginning with the Super VXO. I am only installing one crystal set right now but the plan is to set it up for several banks of crystals. I also had some ideas as to using the banks for multiple bands as well as sections of a single band, but that’s for later.

20150513_202942I also kitted the Local Oscillator/Buffer and the Balanced Modulator/Product Detector sections. There are a few bits that will need some refinement, mostly inductors, but these will be addressed as needed.

And speaking of inductors, since I sent back that crappy one I am still in need of one. I will be ordering one tomorrow because I wont get far in this build without one. The goal is to have this radio up and running before Field Day June 27-28.

Look for a project page soon.

Till next time, 73,
~Jon KK6GXG

More 40 Meter Antenna Fun

20150430_155550Ya know that little voice, sounds like Han Solo in the back of your head “I got a bad feeling…” Yah, that one. Listen to it.

If you look at the image of the antenna base you may notice no screws holding the OS-239 in the bottom of the conduit angle. Now I didn’t leave it all up to gravity. I wound cotton twine around the threads a bunch to keep the connector centered in the hole and was hoping that because the epoxy was pretty thick it would hold down the connector.

20150430_163553Not exactly what I had hopped for. The string did act as a great fiber reinforcement to the epoxy though. Took me the better part of an hour to dig it all out and clear the threads this morning. I know things had gone wrong last night when I did the pour. Thats when I took this picture.

20150430_163541I figured trying to get the epoxy out of the conduit, off all of the components and try again would consume more time than just cleaning the mostly set up epoxy in the morning. Not to mention use up twice as much of a valuable resource. I was right on that one.

I had hoped to use a polyester resin but the can I had was older than I thought so I ended up using some West Systems T-88 structural epoxy, which was also a bit on the stale side so it was very thick. I had hoped that the thickness would be my saving grace on the SO-239. I had also hoped that a lot of the epoxy would filter down the PVC pipe with the antenna but not much of that happened either.

20150501_131622All in all things didn’t work out so bad. After some scaping, thread chasing, cutting and sanding a little gouging as well unfortunatly I managed to come out with a servicable antenna base and connector that is permanently sealed.

20150501_131150I double checked the connector with some feed cabling and all is well with that too. It won’t win any beauty contests and I’m okay with that. As long as it functions well and gives me a good match, that’s all that counts. I won’t be able to test it out until I get the last bits of the antenna finished.

If you look at the image at the top of the post you will see the steel whip is the same diameter as the fiberglass rod. I found some eighth inch bar stock in my materials along with a smaller brass rod so I shifted the plan slightly. I thought the whip should be of a diameter closer to the copper magnet wire of the antenna so the change made sense.

20150501_131901With the last few pieces cut all I need to do is drill, tap, and thread the antenna together then attach the wire to the spike and I can start finding resonance.

I should have the tap and die in the next few days so I should have a working, if not finished, antenna by the end of next week. This project seems to be taking a really long time to complete, and in a way it is. But I decided not to rush things along wouldn’t know it from the goo leak. I also have been doing a lot of day job stuff along the way so time has been divided.

That’s all for now, 73,
~Jon KK6GXG

40 Meter Antenna: Thought Process

I picked up some hardware to connect the antenna bits together into one cohesive unit. Sometimes with hardware you have to just go to the store and look around for solutions to a specific problem or situation.

20150426_122414With this project I wanted to keep things as simple as possible and use off-the-shelf materials that are easily found and relatively cheap. One of the pieces I wanted was a simple piece of hardware I have seen many times. I have even bought it and used it, a three or four-inch long nut.  We used to use them for connecting CB antennas to rigid mounts with a nylon spacer block on the bottom and a bolt. The same basic format used to connect the spring mount base for mobile use. The intended use in this project is to connect the steel spike at the top of the antenna to the fiberglass body.

I remember buying these at Orchards Supply and Ace Hardware. I never had a problem finding one back in the 80s. Yesterday I went to OSH and Home Depot and the employees looked at me like I was from mars. They had these little 1-1.5 inch versions for connecting all-thread, which is what I am looking for, just longer. No clue. Nothing registered on their faces, even with the smaller version in my hand.

20150426_122018Anyway, the next closest thing was turnbuckle bodies. The “solid” bodies were aluminum and the open body type looked like nickel plate and galvanized. I ended up buying an open body style, but it really brought about several issues. First and foremost are the mechanical issues. The contact points on both ends are fairly small, less than half an inch. Even with the fiberglass rod and the steel spike screwed down all the way and touching there is still only a half inch of contact on either end.  These things are intended for stresses in tension not in bending which s what they will be exposed to in this application.

The next issue is the left-hand thread of one end of the turnbuckle. I was willing to deal with this I even started looking for a LH die to thread the fiberglass and this is where I decided to take a step back, reevaluate, and take stock of my options.

20150426_121813At this point the base end has been worked out. The right-angle conduit box is the base and will have 12 inches of half-inch PVC conduit inserted in the port that is parallel to the box. The wound fiberglass rod will be inserted through the PVC pipe into the base. I will cut off all but an eight-inch of the other port which will be the outside housing of the SO-239 which will be inserted from the inside of the box.

Once the antenna coil is soldered to the SO-239 on the inside of the box I will fill the box and the PVC pipe with polyester resin making the base a single solid weatherproof piece. The reason for the PVC pipe being 12 inches long  is to provide a solid place for mounting standoffs to be attached. All done with off the shelf hardware and materials with only one minor modification and no special tools.

Now back to the top end and mounting the steel spike to the fiberglass rod. The most direct method is using the all-thread nut I originally wanted to use. Since it is not available, and a sufficient replacement in size, complexity, and structural strength does not appear to be an off the shelf item, at least around here, I guess I need to make one.

I thought of welding nuts together and other welded configurations but they all require more work than what is really the simplest solution. Drill a piece of half-inch bar stock and tap it for 5/16″ 18 threads per inch. I already picked up the die, now I just need the tap and drill.

This solution does require a couple of tools, tap and die along with their respective handles, the right size drill (an F), and a little machining. This operation isn’t really a big deal. If you have a bench top drill press it will make things easier, but it can be done by hand with a bench vice.

The remaining decision is material for the threaded block. I know I have aluminum and I think I have both steel and brass that are the right size, or at least useable.  I am leaning towards the steel or brass. Aluminum and steel don’t play well together when there is the potential for moisture penetration between the surfaces making galvanic corrosion an issue as well as heat dissipation and mechanical contact issues.

More to come on this subject soon.

73,
~Jon KK6GXG

40 Meter Antenna

With the direct conversion receiver now working and tuned into the 40 meter band, it’s time to get to work on a better choice of antenna. The dipole would be great if it were in the proper environment, but this indoor, RF noisy environment is not conducive to picking up much.

Since tuning the receiver to the band I have been picking up both voice and cw transmissions but they are deep in the band noise. The other issue is portability. While the dipole can be pulled down and packed up for field use, it won’t work well in a mobile environment and would be a chore at home to pull down and put back up. So a whip makes the most sense for now. If the whip works at home I can wind up the dipole and keep it in the ready for field use.

Right now my focus is on getting the receiver, antenna, and any needed matching equipment in place. Once that is all together I can turn my attention to filters, amplifiers, and a transmitter.

Scan from the 1975 ARRL Handbook, page 606.
Scan from the 1975 ARRL Handbook, page 606.

The antenna is a helically wound vertical that I mentioned in a previous post All Aboard the Project Train. I ordered a six foot fiberglass safety flag whip for the core and a fresh 1.5 pound spool of 14 AWG copper magnet wire to get the project going.

Yesterday I started the antenna construction by unrolling the 66.5 feet of copper wire and marking it every five feet, mostly so I didn’t lose my count. After dinner I started winding the coil onto the fiberglass in a tight coil. The picture in the header for this post is the fiberglass with about 30 feet wound on.

20150422_093128
66.5′ of 14 AWG copper wound onto a6′ x 3/8″ fiberglass rod

After winding the rest of the wire onto the fiberglass I threaded a dentists tool in between the wire wraps up the full length of the rod to create the uniform spacing for the coil.

On reflection at this point I think I might have opted for an 8 or 10 foot rod. For most applications it might be a better choice but neither would fit well indoors so 6 foot it is. I may build another antenna like this if it works well and try different lengths and diameters for different applications. A 10 foot whip would be better with a 1/2″ core and any longer would need 3/4″ or 1″ to remain stable unless it were placed inside a tube and filled with epoxy resin, another option. I haven’t tested any of these, I’m just spitballing with the structural integrity issue and weather resistance.

20150421_220832Now that the coil is done, the most difficult and time consuming part I think, it is time to move on to the spike and the base.

The plan for the spike is to pick up a small piece of 3/8″ copper tubing about 4″ long and use a coax crimping tool to mechanically center and attach a 1/4″ steel rod to about 2″ then sweat solder it together. After the spike is properly affixed, scoot the coil up a bit and solder the copper wire to the tube, add some epoxy inside the tube and scoot it back onto the fiberglass rod. This should give plenty of mechanical stability to both the spike and the rod as well as a good electrical contact. To help prevent galvanic corrosion I will coat the steel/copper interface with a few coats of lacquer.

The base is where I am going to have to think some more. The diagram calls for a variable inductor at the base of the antenna. I don’t think I will need this because I am planning on using an adapted Z-Match antenna tuning unit from chapter 23 of QRP Basics but that is for the next project.

OLYMPUS DIGITAL CAMERAIn the mean time I am thinking about using a PVC/ABS 90º conduit fitting with an access panel, cutting off and sealing up the right angle (on the bottom of the image), inserting the bottom of the antenna with the wire sticking up out of the box a little and filling the cavity with epoxy resin, leaving enough room to install an exterior lug fitting to attach the wire to on the inside.  For mechanical stability and to provide a secure mounting point I was thinking about using 6″ of conduit around the antenna and filling that with epoxy resin as well.

I hope to get the spike done this week and the base over the weekend. While out and about getting the final parts for the antenna I will be hitting HSC for the parts for the Z-Match. Another busy week for radio. 🙂

73,
~Jon KK6GXG