Efhw kit


W3BNO
 

I received the EFHW kit I ordered today and was happily surprised. I was expecting a PC board and maybe a BNC connector. Boy was I surprised to get several toroidal, an assortment of capacitors and some #18 enameled wire. I stock toroidal, capacitors and magnet wire in an assortment of sizes so I would have been able to complete my 49/1 transformer no problem, but now I don't have to pull the parts. What a great kit for the very small price of 15 bucks including shipping. Needless to say I'm thrilled. Thanks guys for another fantastic kit.
John Fitzer W3BNO


Johnny AC0BQ
 

Your Welcome John
Bryan did a good job on the design.
73 
Johnny ACØBQ 

On Mon, May 2, 2022 at 7:36 PM W3BNO <Jfitzer1053@...> wrote:
I received the EFHW kit I ordered today and was happily surprised. I was expecting a PC board and maybe a BNC connector. Boy was I surprised to get several toroidal, an assortment of capacitors and some #18 enameled wire. I stock toroidal, capacitors and magnet wire in an assortment of sizes so I would have been able to complete my 49/1 transformer no problem, but now I don't have to pull the parts. What a great kit for the very small price of 15 bucks including shipping. Needless to say I'm thrilled. Thanks guys for another fantastic kit.
John Fitzer W3BNO





--
Check out the 4SQRP website at 4sqrp.com


David Todd <ac9xh@...>
 

Johnny ac0bq,

I read the manual and Pretty sweet!!!. love the design and the ability to use a different core to run 100 watts and the designer went overkill on the caps.Thats his words. That shows care and pride in their work

For the price, everyone should order at least 2 or three ,being able to orientate many efhw to be switchable with a coax switch to be like a giant beam,.covering N,S,,,,E,W,,,,and in between.

73
David
ac9xh


Larry Ryan
 

I just opened my kit. Wow! Just what I needed to experiment with EFHW antennas. I just completed QRPGUYS 40-10m EFHW Tuner. It didn't work exactly as I expected but I have a 40M end fed working. My goal is to build a no-tune version using the materials in the kit.

My question: When I make my 49:1 transformer, the included example uses 3 primary and 21 secondary windings. Why not 2 and 14? I've seen that in other articles. I would rather do that but there may be a big price to my laziness. Can anyone tell me the difference?  My goal is a 40m that I will use with my Bayou Jumper. 

Thanks, Larry W7DGP


W3BNO
 

The 49/1 transformers that use 2 primary and 14 secondary turns are generally wound on ft 140 43 cores. On a ft 140 43 that results in a primary reactance of approximately 188 ohms. Two turns on the ft 82 43 core supplied in the kit would only yield approximately 90 ohms, while 3 turns would yield 188 ohms which will require 21 secondary turns to achieve the required 49/1 ratio. Keep in mind that the 188 ohms reactance is still a little low at 7 MHz, but this is a good compromise between efficiency and the higher leakage reactance that would occur with 4 primary turns and 28 secondary turns. I have seen one design that uses a ft 50 43 core but I really don't see how it would have reasonable efficiency. All I can say for this ft50 43 design is that even poor inefficient antennas will work thanks to the magic of RF.
JOHN W3BNO


On May 5, 2022, at 7:02 PM, Larry Ryan <llryan@...> wrote:

I just opened my kit. Wow! Just what I needed to experiment with EFHW antennas. I just completed QRPGUYS 40-10m EFHW Tuner. It didn't work exactly as I expected but I have a 40M end fed working. My goal is to build a no-tune version using the materials in the kit.

My question: When I make my 49:1 transformer, the included example uses 3 primary and 21 secondary windings. Why not 2 and 14? I've seen that in other articles. I would rather do that but there may be a big price to my laziness. Can anyone tell me the difference?  My goal is a 40m that I will use with my Bayou Jumper. 

Thanks, Larry W7DGP


Larry Ryan
 

Thank you John!  I learned something today: Core specs include the OD which in this case, my core is .82 in (measures 13/16"). A core of 1.4 in OD being larger has a larger XL with 2 turns. Makes sense.  One example I have is a FT240-43 core with 2T/14T using #14 wire. 

I'll replicate the example shown in the K0EMT doc: FT82-43 toroid with 3T/21T turns ratio. Not my first toroid winding but my first "no tune" EFHW.

73 and tnx, Larry W7DGP


W3BNO
 

I built the EFHW kit yesterday and had an opportunity to test it out today utilizing my EFHW wire that I use on 20 meters as a vertical in conjunction with a Tentenna 49/1 unun which is resonant at 14.00 MHz. The 4states unun showed resonance at 14.314 MHz. approximately 2% higher in freq. I expected this as I wound the secondary with a total of 20 turns which offers a bit less end loading and a ratio of 45/1. This configuration offers a bit less end loading while at the same time providing a slightly better match for antennas with a slightly reduced end resistance such as that of antennas which are physically shorter such as trap EFHW wires. I also tested the unun using my 15 meter EFHW wire which is resonant at 21.450 with the Tentenna unun and it was resonant at 22.2 MHz. again slightly higher in frequency. I will add that at resonance both antennas had an SWR of approximately 1.1/1 so the 4states unun defiantly works very well. I need to add, that I didn't install any capacitor in the primary as mine worked better without it. I now plan to build and tune a 15 and 20 meter qrp trap vert to use portable with my ATS4 transceiver. All I can say is another fantastic kit from 4states qrp. Just one more remark, now that I have tested the unun and confirmed it works, I gave the toroid a coat of Qdope to hold the windings in place and offer some physical protection. 
John W3BNO

On May 6, 2022, at 1:26 PM, Larry Ryan <llryan@...> wrote:

Thank you John!  I learned something today: Core specs include the OD which in this case, my core is .82 in (measures 13/16"). A core of 1.4 in OD being larger has a larger XL with 2 turns. Makes sense.  One example I have is a FT240-43 core with 2T/14T using #14 wire. 

I'll replicate the example shown in the K0EMT doc: FT82-43 toroid with 3T/21T turns ratio. Not my first toroid winding but my first "no tune" EFHW.

73 and tnx, Larry W7DGP


W3BNO
 

An update on my EFHW transformer kit project. I completed and tuned my 15/20 meter trap vertical today. I built the trap using a 68pf mica cap and used DIZes calculator to find the number of turns required using a T50-6 core. I tuned the trap to 20.950 MHZ , just below the 15 meter band using my nano vna on the SWR curve. I used #26 AWG, as this is what I had in the junk box. The SWR is below 1.4/1 across the entire 20 meter CW band and below 1.3/1 across the entire 15 meter CW band. I don't plan to put the transformer in a case but I did coat the transformer with a liberal amount of Q dope. I think this will provide adequate protection for my usage. I have a suggestion for the club kit team, maybe a kit of PC boards, mica caps toroids and heat shrink for members to make QRP traps. The QRPGUYS have such a kit, but maybe we should also now that we have a very effective EFHW matching kit. Just a thought.
John W3BNO 


On May 7, 2022, at 1:30 PM, W3BNO <Jfitzer1053@...> wrote:

I built the EFHW kit yesterday and had an opportunity to test it out today utilizing my EFHW wire that I use on 20 meters as a vertical in conjunction with a Tentenna 49/1 unun which is resonant at 14.00 MHz. The 4states unun showed resonance at 14.314 MHz. approximately 2% higher in freq. I expected this as I wound the secondary with a total of 20 turns which offers a bit less end loading and a ratio of 45/1. This configuration offers a bit less end loading while at the same time providing a slightly better match for antennas with a slightly reduced end resistance such as that of antennas which are physically shorter such as trap EFHW wires. I also tested the unun using my 15 meter EFHW wire which is resonant at 21.450 with the Tentenna unun and it was resonant at 22.2 MHz. again slightly higher in frequency. I will add that at resonance both antennas had an SWR of approximately 1.1/1 so the 4states unun defiantly works very well. I need to add, that I didn't install any capacitor in the primary as mine worked better without it. I now plan to build and tune a 15 and 20 meter qrp trap vert to use portable with my ATS4 transceiver. All I can say is another fantastic kit from 4states qrp. Just one more remark, now that I have tested the unun and confirmed it works, I gave the toroid a coat of Qdope to hold the windings in place and offer some physical protection. 
John W3BNO

On May 6, 2022, at 1:26 PM, Larry Ryan <llryan@...> wrote:

Thank you John!  I learned something today: Core specs include the OD which in this case, my core is .82 in (measures 13/16"). A core of 1.4 in OD being larger has a larger XL with 2 turns. Makes sense.  One example I have is a FT240-43 core with 2T/14T using #14 wire. 

I'll replicate the example shown in the K0EMT doc: FT82-43 toroid with 3T/21T turns ratio. Not my first toroid winding but my first "no tune" EFHW.

73 and tnx, Larry W7DGP