The End Fed Half Wave Antenna and EFHW Tuners

In the SPRAT 179 (Summer 2019) article describing their Peregrino (Pilgrim) transceiver,  Joan EA3FXF and Eduardo EA3GHS recommend the use of an End Fed Half Wave (EFHW) antenna. Their circuit incorporates an EFHW tuner and an SWR indicator.  As I planned my trip to the Dominican Republic with a uBITX, I had this antenna system idea in mind.  I was attracted by the possibility of avoiding having to carry coax with me.  And it seemed that an EFHW antenna would be easier to get up in the air than a coax-fed dipole. 

When searching for schematics for EFHW tuners I came across the QRPguys tuner kits.   

https://qrpguys.com/end-fed-half-wave-sota-antenna-tuner

This looked like just what I needed, so I ordered one.  But I placed my order kind of late, and I started to worry that I might not get the tuner kit in time.  So I decided to homebrew my own (just in case!) 

As it turned out, QRPguys got the kit to me in plenty of time. It went together very quickly and is a really useful piece of gear.  My homebrew version works fine, but I prefer the QRPguys device. 

You can check out the manual here: 

https://qrpguys.com/wp-content/uploads/2019/09/efhw_40m_tuner_assy_090119.pdf

The circuits are interesting.  The EFHW antennas present an impedance not of 50-70 ohms, but of 3000-5000 ohms.   The Peregrino and the the QRPguys circuits use a matching transformer to change the high impedance to 50 ohms.  In both circuits polivaricon capacitors are used to tune for resonance. The QRPguys circuit uses an N7VE LED absorption bridge -- I found it very satisfying to put the circuit into "tune" mode and then just adjust the capacitor until the LED went out.  That means the antenna system is presenting 50 ohms to the transmitter. 

SOTA beams has a good explanation of the EFHW antenna here: http://sotabeams.co.uk/efhw/
I did use a counterpoise. 

The Experimenter

https://www.americanradiohistory.com/The_Experimenterr.htm?fbclid=IwAR2k7bmbXoRXg6rTiy411riH1WfWUvqso1lpGEn8cEEGk2JKb8FKB4OT7zo

I think I have a set of those headphones. 

Thanks to the K9YA Telegraph for alerting us to this.   

Mike WU2D on QSO Today with Eric Guth 4Z1UG

Eric Guth has a great interview with homebrew and boatanchor guru Mike WU2D.  

Listen here: 

https://www.qsotoday.com/podcasts/WU2D

Wow: "My receiver was from a Sherman tank." 

His story about getting in trouble after "borrowing" his friend's callsign was really great. 

I also liked his wise comment about how anyone who homebrews simple gear will collect some "wallpaper" from official observers and the FCC.   Mike is right:  we shouldn't get too concerned about minor transgressions. If we do, we run the risk of becoming so careful, cautious, and fearful that we never BUILD anything.  

There is a wonderful discussion of the Paraset. 

Mike coins a term that we might want to add to the SolderSmoke lexicon:  RetroQRP.  (Over to you Steve Silverman.  Your call OM.) 

Notes From the Dominican Republic on possible uBITX mods

It was really great to have the multiband and CW/SSB capabilities of the uBITX with me in the Dominican Republic.  And even with my large wooden box, the rig and all its accouterments fit into my carry on baggage (and there were no problems with airport security). (In the picture above you can see the cloth case that held the whole station, including the antenna.)  

As I used the rig, I thought about possible mods for future operations.   Here are some ideas: 

-- Filter for CW?  Definitely.  Farhan suggested switching in a more narrow 12 MHz IF filter for CW operations, but that seems like a bit too much work.  I am going to try to use an audio frequency filter.  I've ordered the active CW filter from QRPguys.  I've long been intrigued by these kinds of filters, but they didn't seem very wirthwhile with a DC receiver.  With a superhet like the uBITX they make a whole lot more sense. 

-- Sidetone volume control.   Need it, especially with fellow vacationers trying to sleep nearby.  Should be easy -- just a pot on the side-tone line.

-- Low impedance mono headphones.  Need them.  

-- An LED light for logging.  Would help. 

-- Switch to turn off the 16X2 display to save power?  I thought about this but I checked after we got back and the whole display pulls only about 20 ma.   So it probably isn't worth it to put in a switch. 

-- Internal protective cover for the uBITX board.    I used the extra space in my big wooden box to store the key, the mic, the battery, the tuner, etc.    They all bounce around a bit and could damage the uBITX board.  So I will try to build in some internal physical shielding, perhaps from a BITX plastic box. 

-- Brass contacts for my homebrew CW key.   I think brass is better than the copper foil I am currently using.  I already did this with some brass bolts from the local hardware store.  Mush improved.  Pounding brass is better than pounding copper tape. 

-- I installed an additional stage of microphone amplification but I have this stage running even on receive.  But I checked and the amount of current pulled by this stag is so small that it is not even worth changing the power supply line. 

--  Reduce output to below 5 watts on CW.   To make the rig "QRP Compliant."  

In the pictures you can also see my homebrew straight key, the QRPguys EFHW tuner, my mic (the original SolderSmoke podcast mic!), the 3 amp-hour LiPo battery, the additional stage of mic amplification.   The little relay that you see just above the mic amp allows for the keying of an external amplifier. 

Aeronautical Mobile Contact from the Dominican Republic

767

On the morning of January 9, 2020, I was up early, sitting alone out in my open-air tropical hamshack on Bahia Rincon on the Samana peninsula of the Dominican Republic.   I had been looking at the stars. As the sky brightened I was listening to band noise from a still-dead 20 meter band on my uBITX.  

Skies were partly cloudy.  The Big Dipper hung upside down in front of me.  I had also seen Corvus, Scorpio, Andromeda, and Leo.  There were a few meteors and one bright satellite.  

But 20 was quiet... until, suddenly,  BOOM! A very loud and clear SSB signal came through.  It was KX4WE/Aeronautical Mobile.  Mike was in a 767.  I called him and he came back right away, giving me a 57 report. He gave his position as 170 miles Northwest of San Juan, Puerto Rico.  He was heading to Port-o-Spain, Trinidad from Miami.  We had a quick QSO -- it reminded me a lot of my contacts with the MIR space station from Santo Domingo in the mid-1990s.  Suddenly Mike's signal dropped very significantly.  I figured that he had moved further south and was no longer line-of-site with me. I had some hills to my south and they were now attenuating Mike's signal.  I could hear him working M0NKL.  We were Mike's only two contacts on 20. 

I realized later that had I looked up, I might have seen the lights of the plane.  Below is the track of the aircraft.  He was at 35,000 feet when he passed over the DR. 

This contact was a lot of fun. Thanks Mike! 

Contacts from the Dominican Republic

Below I have my log from the Dominican Republic.  A few noteworthy contacts highlighted in yellow.  The first contact was actually on 30 meters,  My guess is that the 20 meter EFHW and the counterpoise got close to half wave on 30. 

AE7KI's was a famiiar voice. Terry transmits from Tennessee but his voice is from down under.  I recognized him before I heard the callsign.  

F6HKA was a familiar call.  I checked -- he was a Straight Key Night contact from one year ago.  Great to meet up with Bert again. 

The Aeronautical Mobile contact was icing on the cake.  More on this tomorrow...

Thanks to all who contacted me or tried. 


In the Dominican Republic 30 December 2019 – 11 Jan 2020

4Jan2020 

30 meter CW HK1ANP Fred.  I was in Bavaro.  30 meters on an 20 meter EFHW!

All subsequent DR contacts on 20 meters from Samana near Las Galeras

6Jan2020

0922 CW EW1I Alex in Belarus.

0959 SSB KG4ZEC. A net on 14.300

1657 CW KB3WAV Md

1701 SSB AE7KI Terry – old friend from Tennessee and Australia.

7 Jan 2020

0917 CW F6HKA Bert near Limoges 14.050 SKCC 60693

1500 CW KN4ZQ Dave in Palmyra Va. Me 599

1523 NO CONTACT but close,  CW KC2OHL

1800 CW KC5F Steve – he answered my  CQ   NC SKCC 21092T

8 Jan

CW N3JB John in Va. Me 599

CW W9YXX Bob in Ind. Me 569

1749 CW W8TK Tom in Tuscon Az.

9 Jan

0700 SSB KX4WC/AM Me 57 767 170 miles NW of San Juan

0840 SSB KI5PZE Miguel, Lake City Fla. In Spanish.

0908 SSB W1FDY Jack in SE Va. Me 58 

The point of the Pen shows where we were in Samana. Bavaro is on the Eastern tip if the island.

N2CQR Portable with uBITX in the Dominican Republic (video)

More to follow... 

KK4DAS Michigan Mighty Mite Heard by WEB SDRs -- CBLA Mobilized!

Dean KK4DAS continues to do great things with his Michigan Mighty Mite.  He has been calling CQ on the Color Burst Liberation Army (CBLA) frequency of 3579 kHz.  I think I was the first one to hear him, but since that memorable moment he has been picked up by multiple Web SDR receivers, including the one at Penn State (PETE JULIANO'S ALMA MATER!)  (screen shot above, listen by clicking URL below).  He has also been heard by Web SDRs in Concord Mass,  Newport News Va, and Cleveland, Ohio.  FB Dean.  

So come on folks -- this is a mobilization call for the CBLA!  Get those MMMs on the air.  Send us reports and recordings from Web SDRs or the RBN. 

Listen to Dean's MMM as received at the Penn State Web SDR: 

http://soldersmoke.com/KK4DAS MMM.wav

It sounds great!  And nice CW Dean!  

Santa Came to SolderSmoke! From Australia!

Oh wow!  Santa Claus made a really long distance DX trip to SolderSmoke's East Coast HQ last night.   His chief Elf this time was Peter VK2EMU who crafted the AMAZING Morse key you see in these pictures.  This is truly a work of art.  I will indeed put it on the air with a homebrew transmitter.  And we will keep on soldersmoking.  

Thanks very much Peter.  This was really great.  

Merry Christmas to all!  

Dean KK4DAS Puts Michigan Mighty Mite on the air! And is heard in Falls Church, Virginia! (video)

QRZ.com says we are 5.9 miles away.   The U.S. Postal Service almost prevented this from happening -- they objected to my just putting the crystal in an envelope and mailing it.  Dean's wife had to pay postage due.   

The rig didn't work at first, but Pete N6QW provided sage advice and tribal knowledge.  Adjustments were made and Dean experienced the Joy of Oscillation.  Then, he connected an antenna and was heard at the SolderSmoke East Coast HQ. 

Obviously the beret was the key to Dean's success: 

This was a lot of fun.   And it is a reminder of the power of the MMM.   Dust off those Mighty Mites!  Call CQ and see if you can be picked up by the Reverse Beacon Network.  Let us know if you succeed.   

Getting ready

Done!  Dean's MMM

SolderSmoke Podcast #216 Is Available: BITXs, Paesano, Paraset, ET2, Antuino, Mailbag

Bill's uBITX with HB keys and the mic that used to be the podcast mic! 

SolderSmoke Podcast #216 is available 

21 December 2019

HAPPY HOLIDAYS TO ALL! 

http://soldersmoke.com/soldersmoke216.mp3

Pete's Bench 

Sprat Article

BITX 40 Fun

ZL2BMI Rig

Paraset.   Three tubes!  Almost an ET-3!

Bill's Bench

ET-2 Adventure over,  Rig on the wall

Final QSO count. 20   3 "random" 

Last QSO with AA8OZ

Lessons learned:  100 mW not the problem. Crystal Control cramps your style. 

N0WVA regen amazingly effective.

Tried for the Sunrise Net.  Walter sent me some crystals.  

On to the uBITX. 

Accidentally wiped out calibration and BFO settings. 

Had to do recalibration and reset BFO. 

Learned a lot about the rig. 

How they did CW and how they do it now. Shift TX?  Or shift RX?  Or just shift BFO on RX? 

How all the signals end up as upper sideband.  Only one BFO freq.  Very cool. 

TalentCell 12 V Lithium Ion 3 AmpHour battery. Size of a deck of cards. 

Inspired by Peregrino -- I ordered EFHW Tuner from QRP Guys. 

Homebrew Straight Keys

Antuino upgrade 

SMT soldering. 

Back to Arduino Nano and the IDE.  

A very cool tool. 

Antuino filter analysis.

Version 6 of uBITX out. 

The "Watt Meter" DC power meter.  Very useful.  8 bucks.  LINK:

https://www.ebay.com/itm/Digital-DC-combo-Meter-LCD-Watt-Power-Volt-Amp-RC-Battery-charging-Analyzer-M/152339793114?fbclid=IwAR0u9SlZi2Dm6zOJyZt4fDTu7w_pjBIEYD_FiNfLymxtQUbMjcNHjfB17P0

SPRAT, balloons and hardcore homebrew hydrogen. 

MAILBAG

VK3HN's AM receiver.  I ordered 6kHz 455 kHz filters from Australia. 

Dean's MMM

Peter VK2EMU   Hertz not hertz. 

Ben KC9DLM LTSpice YouTube Videos

Steve Silverman  Electroluminescent Receiver Kit

Lyndon N0LFX back to listening.  FB OM

Steve M0KOV built a pill bottle variometer.  Did you get the regen going? 

Anthony VU3JVX   FB HB uBitx.  

Allison KB1GMX  Great to hear from her

Leif WB9IWT -- helped me trouble shoot my uBITX (BFO was low)

Mike EI0CL  old buddy from Azores days.  Recognized his voice on 20.  Great QSO.  

YouTube LTSpice Tutorials

For those who want to get started in circuit simulation, or to improve your use of the LTSpice program:

https://www.youtube.com/playlist?list=PLT84nve2j1g_wgGcm0Bv3K4RSl2Jdjsey

And this one for the inductor:

https://www.youtube.com/watch?v=65fNDRows90&feature=youtu.be

Thanks to Ben  KC9DLM for alerting us to this.