Re: Looking for Completely Functional Dual-Band 20/(17/15/10/6) Meter QRP Rig with SSB/PSK #bitx20help


Jerry Gaffke
 

David, I suggest you look into the EFHW-4010 rather than just tell us
about some other end-fed you had trouble with.

I have the EFHW-8010 and have measured an EFHW-4010.  
SWR is as reported in the QST review posted on the myantennas.com website,
looking good on all major ham bands and reasonable on the WARC bands.
The SWR goes quite high between bands, showing it really is tuned and not just a 50 ohm resistor as some antennas are.
For packing, an EFHW has the advantage that not much coax is needed, the end of the antenna is near the operating position.
Those few feet of coax are all that are needed with regards to a counterpoise, as the antenna is near resonance.
An end-fed half-wave can be resonant at all multiples of the fundamental, not just odd multiples as the dipole is.
Radiation patterns on an end-fed are about the same as a dipole.
An end-fed doesn't need much support in the middle of the antenna wire, where a dipole has all that coax weighing it down.
The trick with an end-fed is getting the matching unit correct across many bands, and I think the EFHW* antennas do this.

We had a discussion here previously about some of the digital modes where automatic bandswitching was required.
That fell into a long discussion of how best to build an auto-tuner.
The EFHW-8010 seems a much more elegant solution.

Of course, a trapped 4 element beam with rotator would have a better radiation pattern.
If they could get that down to something that fits into a backpack sidepocket, that would be magical!

Once the weather clears, I might try setting up a 40 meter moxon with vertical polarization, 
supported from a single point at the middle of the top element so I can easily turn it.
Common mode chokes should allow the coax to be routed conveniently down from the
middle of the side element to the middle of the bottom element, then to the ground.
If done with wire and telescoping fiberglass poles, that might actually be packable.

Jerry, KE7ER


On Sun, Feb 25, 2018 at 11:25 am, N8DAH wrote:
One thing I would suggest is be careful with "magic" antenna's if its to good to be true it normally is. I once bought a par-end fed good for 10-40 with no tuner.....it was the biggest waste of 75$ I have ever spent swr on 40m was well over 4:1. Building a antenna like the trapped 40/20 from qrpkits.com is a much better option for small low weight Ant.

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