Mini EFHW transformers - power handling test

 I was asked if the mini EFHW transformers (designed by DG1JAN) can handle 10W. I guess it depends of the ambient conditions. Same as people whose KX2 overheats and they need to install side radiators. Mine never does - probably because it is rarely warmer than 85°F in my area and I don't use digital modes.

Test conditions

• Location: Parc de la Cité, grassy field
• Radiator for 18MHz mounted on Sotabeams carbon mast (6m)
• Transformer with ratio 1:54 and FairRite 5943000601 toroid.
• The rig indicates DWR 1:1.1 without tuner.
• My weather app says it is 21°C (70°F) on shade
• No wind, clear sky
• The antenna and the transformer are fully exposed to the sun
• The rig is KX2 and I shield it from the sun with my body
• Calling VVV DE VE2WLD VE2WLD with 10 seconds intervals at 10 watts CW.

Results

After 10 minutes of work (with a total of about 2 minutes interruptions), I can't detect any heath coming from the transformer.

After another 15 minutes of work without interruption, there is a hint of warmth coming from the transformer. 

The KX2 indicates internal temperature swinging from 41°C to 47°C. The right side of the rig is noticeably warm. Much warmer than the toroid.

Conclusion

The transformer handles the temperature better than my rig. 

I would use the 601 version at 10 watts in most of my activations (usually in the forest, some breeze near the summit, no extreme heath).

I would stay at 5 watts or use the 501 version (double length) toroid if the day is particularly hot.

Mini EFHW transformers

 DG1JAN has shared on GitHub some really nice designs. I went with the MicroUnUn which seems to be a nice alternative of the popular K6ARK.

It uses Amdion FT82-43 (FairRite 5943000601) toroid. The author suggests two other variations:

1. combining 5943000601 with a smaller inner toroid 5943001101  
2. using the double length FairRite 5943000501

I was hesitant about he combined toroid design - the winding was really dense inside the small toroid. So I made few units with 601 and one with 501. I made several configurations and measured the lowest SWR.

Winding	Secondary turns	Secondary / primary	Ratio
10-1-10	21	7	49:1
10-1-10	22	7.33	54:1
11-1-11	23	7.66	59:1
11-1-12	24	8	64:1
12-1-12	25	8.33	70:1
12-1-13	26	8.66	75:1
13-1-13	27	9	81:1

I did my tests in Parc de la Cité with a radiator for 18MHz and SotaBeams Carbon mast. Here are the results of the first round:

Subject	Ratio	Lowest SWR	Frequency
1	49:1	1.43	18.350
2	49:1	1.44	18.300
3	81:1	1.16	18.000
4	81:1	1.12	18.100
5	81:1	1.12	18.200

Second round of tests:

Subject	Ratio	Lowest SWR	Frequency
4	81:1	1.10	18.090
5	81:1	1.10	18.170
6	49:1	1.44	18.190
7	54:1	1.35	18.170

Third round of tests. 

Subject	Ratio	Lowest SWR	Frequency
5	81:1	1.16	18.210
7	54:1	1.38	18.170
8	64:1	1.20	18.150
9	64:1 *D	1.25	18.130

1:64* D uses the double length FairRite 5943000501

These are the indications of my RigExpert. When hooked to KX2, the values are about 0.25 better.

Antenna quests - EFHW vs Random Wire

EFHW or RW - witch one is the best ? They are both lightweight and have relatively small footprint. No wonder they are so popular for field, POTA and SOTA operations. Main advantage of RW is the freedom to jump from one band to another and thus make more QSOs in a short time. But wait, EFHW is resonant and more efficient, shouldn't it be easier to score more contacts if your signal is stronger ? In order to answer this question, I decided to make a quick test. 

Configuration

I used 6m telescopic pole and a slopper configuration for both antennas in VE-5005 park. I tested the RW first and the EFHW right after. It was on a weekend without contests and the SFI was about 110. The radiators for both had a similar length - about 31' for the EFHW and 29' for the RW. I used 10 watts and TX-500 rig in CW.

Performance on 20m

• EFHW got 8 RBN hits with signal strengths 7-38 dB
• RW got 9 RBN hits with signal strengths 8-26 dB

Clearly, the EFHW preforms better, but the RW is not bad either!

Multibands

The random wire allows me to switch bands almost instantly. And even with this short radiator, I can use 30 meters comfortably (9 RBN hits with 3-27 dB). I even worked a local ham on 10m that day.

The EFHW would need a longer radiator for 30m and changing the bands takes much longer.

Best of both

I was ready to trade the extra decibels of the EFHW for the instant band-hopping of the RW. But then I had an idea - it is possible to use the 17-20 linked EFHW radiator as random wire for 30 and 15 meters ! This way, I can cover all my favorite day bands with only one radiator and minimal effort of changing the transformer.

Antenna quests - Random Wire

Advantages

• Multiband
• Short feedline or no feedline at all
• Only two contact points when deployed as a slopper
• Lightweight
• The tuner is able to compensate the deviations from the optimal deployment configuration

Disadvantages

• Non-resonant antenna (needs tuner)
• Needs counterpoise
• Too long for vertical deployment
• Impedance higher than 50Ω, needs a transformer

Deployment

Telescopic mast (6m), slopper configuration

[mast] ------ radiator ------ [transformer] --- coax (10') --- [tuner] --- coax (3') --- [rig]

Transformer

The goal here is to bring the impedance as close to 50Ω as possible for the differends bands and leave the tuner do the rest. So 9:1 transformer is OK.

Tuner

I am suing ATU-10, because the popular Elecraft and MAT equivalents are no longer available. ZM-2 would have been another nice alternative but I found out about it when the ATU-10 was already on the way.

Test 1

I was told that for this type of antenna, the length of the coax is a variable to take in consideration (it is part of the radiator). My initial test was with 3m RG316 coax, 9m radiator wire, 7.5m counterpose lying on the ground and a homebrew 9:1 transformer. It had a good SWR on 40, 30, 20, 15, but not on 17. I was even able to work a local ham on 10M SSB with this setup :)

Test 2

The second test was combination of EFHW and RW

1. For 17 and 20 meters band, I used linked radiator and 81:1 transformer.
2. For 30 and 15 meters band, I used the same radiator with the tuner and the 9:1 transformer and 9.5m counterpoise lying on the ground (my backup EFHW radiator).

I am very pleased with the result. The SWR on 30m was 1:1.16 and on 15 it was 1:1.04 This will probably be my main POTA setup.

Test 3

Trying to trim the radiator so that the tuner can find an acceptable match on 30-20-17 bands. The coax from the 9:1 transformer to the tuner was 10' RG316 and the coax from the tune to the rig was 3' RG316.  The theoretical sweet spots are supposed to be somewhere around 29', 35.5' and 41' Knowing that the setup and the coax length affect these numbers, I  got a long piece if wire ans stared cutting down. The table shows the SWR values of the tuner; the radio 9TX-500) had more optimistic values (about 0.4 lower).

L (m)	L (ft)	30M	20M	17M	15M
13.0	42.7	1.34	1.30	1.30	3.00
12.6	41.3	1.17	1.60	2.09	2.20
12.3	40.4	1.23	1.90
12.0	39.4	1.23	1.77
11.6	38.1	1.02	1.77	1.47
11.3	37.1	1.09	1.61	1.17	1.61
11.0	36.1	1.38	1.42	1.19	1.07
10.6	34.8	1.11	1.22	1.29	1.01
10.3	33.8	1.14	1.09	1.52	1.02
10.0	32.8	1.01	1.17	1.85	1.15
9.5	31.2	1.05	1.91	2.20	1.10
9.0	29.5	1.15	3.30	2.60	1.00
8.6	28.2	1.46	2.70	2.80	1.07
8.3	27.2	2.00	5.00	3.00
8.0	26.2	2.50	1.85	2.66

The best results were somewhere around 10.6m (34.8') of radiator length. I am surprised that the 29' zone did not work. Either the tuner is not so capable or I should have used smaller cutting steps.

Antenna quests - End Fed Half Wave (EFHW)

Advantages

• Resonant antenna
• No need of radials/counterpoise
• Short feedline
• Only two contact points when deployed as a slopper
• Lightweight

Disadvantages

• Monoband (unless linked or trapped)
• Too long for vertical deployment
• High impedance, needs a transformer
• Resonance is affected by small deviations from the optimal deployment configuration

Deployment

Telescopic mast (6m), slopper configuration

[mast] ------ radiator ------ [transformer] --- coax --- [rig]

Transformer

For some reason, the classic 49:1 did not work for my setup for the 20m band. It gave me about 80Ω impedance and the lowest possible SWR was 1:1.7. I changed the transformer to 81:1 (3 primary, 9 secondary turns) and it helped a lot. The impedance went very close to 50Ω and the SWR was less than 1:1.2 for the entire CW portion of the band. malen, VE6VID who have me the parts to build the transformer commented that this higher ratio transformer works better for 10-20m bands and the lower ratio transformer works best for 40-80m bands.

Further experimenting

Try to do a linked radiator for 17 & 20m

Morse code prosigns, abbreviations, Q-codes and slang

 We use a few codes, abbreviations and prosigns to speed up the Morse code exchange and avoid sending frequently used lengthy words. The complete lists are huge and only a few of them are still in use today. Here is what I usually hear and use:

 PROSIGNS (these are sent together without spacing between the letters)

[AS] - "Wait please, I will be back shortly"

[AR] - "End of the current message"

[BK] - "Break. I have finished sending, now it is your turn." In a long conversation, people use K instead because it is shorter.

[BT] - just a separator between logical parts of the message

[CQ]  - originates from the French C'est qui? which means "Who is there?".

DE - another french word, means "From"

K - "Any station please reply."

[KN] - the opposite of K. "I expect an answer from the above mentioned station. If it is not you, stay down and wait your turn."

[SK] - "That was my last message for you, end of the conversation"

ABBREVIATIONS

ABT - "About"

AGN? - "Again, please", "Please repeat"

BTU - "Back to you"  I have finished sending, now it is your turn."

FB - "Fine business"  Your code is clean and I was able to understand it easily.

FER - "For"

GD, GM, GA or GE - "Good day", "Good morning", "Good afternoon", "Good evening".

HPE - "I hope to" 

IOTA - Islands on the Air

CUL - "See you later"

CUAGN - "See you again"

MNI - "Many"

OM - "Old man". Used for all male ham radio operators, regardless of their age. 

POTA - Parks on the Air

RR - "Roger, roger" I was able to decode it correctly.

RX - receiving radio signal

SOTA - Summits on the air

SK - "Straight key"

SK - it could also mean "Silent key" - a deceased morse code operator. 

SKCC - Straight key Century Club

SRI - "Sorry" 

TNX - "Thanks"

TU - "Thank you"

TX - sending radio signal

VY - "Very"

YL - "Young lady". Used for all female ham radio operators, regardless of their age.

XYL - "Ex young lady". The wife of a radio opeator.

WX - "The weather"

73 - Equivalent to "Best regards", "My best wishes", "I wish you all the best", "Cheers"

88 - "Love and kisses". Typically, a male operator sends 73 to all male operators and 88 to all female operators.

44 - used by World Wide Flora and Fauna activators and hunters instead of 73 or 88

 Q-CODES

QTH - "The locations of my station" 

QRL? - "Is the frequency in use?"

QRP - "Low power". Typically 5W for CW and 10W for SSB.

QRO - "High power station". Typically 100W or above.

QRS? - "Would you like me to send slower?"

QRS - "Could you please send slower?", "Slow speed Morse code" 

QRQ - "High speed Morse code"

QRZ? - "Who is calling me?" or "Who is the next station that wants to contact me?" 

QRT - "I am turning off the station". If it comes from a portable operator, it means he is done for the day, he will pack up his gear and head back home or enjoy the rest of his outdoor time with his family :) 

QRM - man-made interference that generates radio-frequency noise and makes it harder or impossible to hear the other stations.

QRN - natural atmosferic radio-frequency noise that interferes with the signal

QSO - a radio contact

HAM SLANG

DX - a remote station or contact with a remote station. The other side of the ocean or the other side of the continent is far enough to be considered a DX

FIELD DAY - the special day of the year when the typically indoor operators operate outdoor

FIST - when someone is sending with a straight key and his rhythm is "unique" or difficult to decode

HAM RADIO - amateur radio

HAM - a radio amateur

HAMFEST - a convention of amateur radio enthusiasts, often combining a trade show, flea market, and various other activities of interest to amateur radio operators

LID - a poor operator.

PILEUP - when many stations try to call one staton at the same time, Their signals overlap and it is hard to distinguish what they say. Imagine a group of people yelling at you their names simultaneously. Or a pack of reporters trying desperately to get the attention of a VIP.

RIG - radio transmitter

TO WORK - to have a radio exchange with. Exemple: I have worked Australia with this antenna.

Standard Morse exchange

Here is what the standard Morse code radio exchange looks like:

Morse code message	Translation
CQ CQ DE VE2WLD K	Who is there? My callsign is VE2WLD. Any station please reply.
VE2WLD DE KG2MM [KN]	Hey VE2WLD! It is KG2MM. Please reply if you hear me.
KG2MM DE VE2WLD [BT] GM ES TU FER UR CALL RST 599 [BT] QTH MONTREAL [BT] NAME IS GEORGE GEORGE [BT] HW CPI? KG2MM DE VE2WLD [KN]	Hey KG2MM, it is VE2WLD. Good morning and thank you for your call Your signal is easily readable and comes strong here my station is located in Montreal my name is George how do you hear me? This message to KG2MM is from VE2WLD and I am waiting for a reply from him.
VE2WLD DE KG2MM [BT] FB GEORGE ES TNX FER RPRT RST 459 IN JACKSONVILLE, FL OP MIKE MIKE SO HW? [BK]	For VE2WLD from KG2MM. Good job, Georgi, I understood everything you have just sent. Thanks for your report. Your signal is readable and fairly strong in Jacksonville, Florida my name is Mike how do you hear me? Break
[BK] FB MIKE WX IS SUNNY 20 C RIG IS DISCOVERY TX-500 PWR 10W ANT VERTICAL HW? [BK]	Break Good job, Mike. I understood everything you have just sent. The weather is sunny, 20°C My radio is DISCOVERY TX-500 the power I am using is 10 watts the antenna is vertical how do you hear me? Break
[BK] MOSTLY OK POWER? WX STORM ES 60F RIG IS YAESU FT-891 PWR 1TTW ANT IS 4 BAND DIPOLE HW? [BK]	Break Mostly OK. Please repeat your power level again, I didn't hear it well. The weather is storm and 60°F My radio is YAESU FT-891 the power I use now is 100 watts my antenna is 4 band dipole how do you hear me? Break
[BK] PWR IS 10W 10W 10W TNX FER NICE QSO MIKE ES HPE CU AGN 73 KG2MM DE VE2WLD [SK]	Break The power is 10 watts Thanks for the nice contact Mike and I hope to see you again. Best regards This was the last message to KG2MM from VE2WLD
VE2WLD DE KG2MM R R TU ES CUL OM 73 VE2WLD DE KG2MM [SK]	To VE2WLD from KG2MM I was able to hear it this time. Thank you and see you again my friend. Cheers! This was the last message to VE2WLD from KG2MM
II	Bye !
II	Bye !

Sometimes, the exchange drags on and people chat about all kinds of stuff. It is called rag-chewing :)

In other cases, the message is fast and short - the participants only exchange their callsigns and signal reports. Mainly for contests when the goal is to make as many contacts as possible, but also when the conditions are not good and the quality of the signal makes it difficult to have a meaningful conversation.