N3SDO/B 10 meter Beacon Ellwood City Pennsylvania

If you hear this beacon, please Email your reception report. Send to my callsign @yahoo.com Thanks!

( I'm trying to NOT make it easy for spambots )

73 DE N3SDO

28.219 Mhz, 5 watts into a homebrew end fed 1/2 wave vertical antenna. In a valley at 880 ft elevation surrounded by large hills 1100 ft - 1400 ft elevation ASL a few miles away.

This beacon project began when a coworker gifted me a Uniden HR2600 10 meter radio from an estate sale. The previous owner had tinkered the final output transistor and succeeded in completely killing the transmit in the process. I tested it and thought the final was fried. During the Covid19 lockdown, I got bored so I fixed it. After removing the final transistor, it tested ok. !??!! Turns out I needed to rebuild 2 of the transmit inductors. It's now capable of the full 25w of output. I reduced the RF bias down as low as it would go towards class C to reduce the current draw and heat, and reduced the drive level to 5 watts output. If operated on AM or SSB with the output biased this low, it would be a splatter generator, but for CW, its just fine. I installed a PIC microcontroller based keyer inside the radio, for a nifty little ruggedized one piece beacon unit.

So who will hear it? The band is pretty dead, still in the sunspot minimum in August of 2020. So I thought about trying out different antennas on this little beacon radio. I drive 15 miles to / from work and thought it would be fun to do some antenna experimentation.

The rig

Uniden HR2600 repaired and tuned down to 5 watts CW to avoid getting really hot operating with a 24/7 duty cycle.

The controller

A PIC based single board micro-controller was dropped off as a sample by a sales rep 4+ years ago. It sat unused and unloved in a drawer in the lab, deserving a purpose.

Now it sends CW all over the world.

The power source

We had some 12v 10a AC to DC switching power bricks at work that were being scrapped. Rather then hitting the dumpster, I converted a couple to 13.8v by changing a feedback resistor in the voltage regulator circuit.

The antenna

A ham's favorite thing to tinker with! The current antenna is an end fed 1/2 wave mounted on a 10 foot pole. The original was a 5/8 on a ground capacitance plate with the fed end about 1 foot off the dirt. Signals are improved in local testing over the 5/8.

The prototype feed for the 1/2 wave, a ringo inspired 1 turn loop between ground and the antenna with a sliding feed point. Turned out to be too flimsy.

Here is the same amount of wire wound into a coil for better mechanical stability.

A side view of the antenna with the test feedpoint alligator clip. Now replaced with a bolted clamp.

Another view of the 1/2 wave end fed matching coil. I squeezed the turns together to center it on frequency.

I have done a couple of YouTube videos.
Search : N3SDO.

One of my better videos.

Modifying the USB Simple Spectrum analyzer to get FM modulation from the tracking generator/VFO.

There are a number of videos on tinkering with this spectrum analyzer and repairing and testing duplexers and Hamtronics repeater boards.

Half wave vs 5/8 wave antenna comparison.

This pattern chart shows that the 5/8 should outperform a 1/2 wave antenna. My local testing shows the 1/2 wave at 10ft elevation is better then a 5/8 at 1 ft.

I changed the antenna as of 9/25/2020 to experiment and see which one works better. Currently an end fed 1/2 wave is being used on a 10 foot pole on my workshop building. In my local testing, the 1/2 wave outperforms the 5/8 wave, but it also has an 8 foot feed point height advantage, but the 1/2 wave does not require a ground plane like a 5/8 does. Previously a 20+ year old 22 ft 5/8 wave (.625 wl) CB antenna bought as scrap from a metal recycler, was being used at 1 foot off the ground. No radials were used, just a large 2 ft x 5 ft aluminum plate as a grounding capacitor, and 2 or 3 turns of a bug-catcher type coil in series to match the impedance. Previously I had tried a 3 foot magnetic CB on the roof of the workshop, SWR was ok, but it barely worked, local testing proved very disappointing, and the 5/8 beat it considerably!

I have ideas about a variation on a magnetic loop antenna, but instead of being a loop, being a dipole shape, using coax, shorted at the far ends, and having the matching capacitor in the center between the center conductors. A sort of spin on the skirted monopole.

Small loop antenna

My current prototype is about 6 feet diameter and will tune down down to about 60m, but won't quite make it to 80m. The performance with WSPR is below that of my 40m OCF dipole at 30' (10m) but is quite respectable for being what it is!

The Prototype 2M dia loop

Here is a 6' (2m) ish diameter saggy loop made from an 18 ft piece of damaged coax that the jacket was cut through in several places and could not be used outdoors. Its suspended from the ceiling by a couple of cup hooks and loop fed in the far corner near the wall. The pattern is East-West but favors the East.

My motorized capacitor

The cap was a $5 hamfest find, and the worm drive was recovered from a junked tape backup autoloader. The motor and reduction drive were salvaged from the wheel drive from a motorized floor sweeping robot.

The Bookcase loop idea...?

Can I make a loop around the rear of a book case and make the tuning capacitor into a Fake Book on the bottom shelf?

I have also had ideas of putting the loop on the back of an interior door. That would permit changing loop orientation by opening and closing the door...

And here is your favorite disclaimer. This web page is a work in progress. More to come.

Can I build a nice morse iambic key out of wood, ball bearings salvaged from some old PC fans, and some stainless 4x40 screws?

Here is what I made.

The base and key mechanism is oak, adjustable magnetic repulsion provides the tension, and stainless screws provide the electrical contact. The key switches pivot on 4 ball bearings. The wonderful things you can build with a Dremel and some leftover parts and some wood.

A first coat of sealer on the apple wood finger paddles prior to shaping. Look at that grain!

Doing some fine tuning of the bearing fitment with my home made carving knives.

Working out the geometry of the mechanics.

Here is the finished result.

The recycled Bakelite tuning knob and the rectangular booster amp on the back of the VFO with the brass SMA connector along with the buttons and A/B switch just adds to the Jules Verne coolness factor for me.

The wood key next to the DDS VFO for my Heath SB-104.

I like the SteamPunk effect the brass and wood gives the VFO. The frequency and status is shown on the LCD, but the camera flash washed it out.

Yes the paddles are asymmetrical, I tried to keep some of the live edge on the Apple wood, and it works well the way my fingers contact the paddles.

Speaking of SteamPunk...

I had some old meters, and a huge heatsink and some big azz resistors and some high current Mosfets > MOOSEFETS! So I set about constructing an electronic load for testing power supplies and doing AH drain tests on batteries.

The load has 2 independent variable electronic load circuits with 1 Ohm 50 watt resistors and high power mosfets in series, then the resistor + mosfet circuits are then in parallel. x3 on circuit 1, x2 on circuit 2.

Each circuit is variable and switchable, and the 2nd circuit uses a push button on the top right to engage the load for generating transient loads to simulate a transceiver in transmit mode.

The PCB with the OP-Amp is not shown in the photos, it controls the fets in a voltage control to constant current configuration, and adds a variable voltage threshold to disconnect the load for battery AH testing without draining the battery down too far.

It also functions as a multiple circuit switchable load center since I had a bunch more connections on the terminal strip to use up.