8-BAND HORIZONTAL LOOP
( UNDER CONSTRUCTION - ALMOST FINISHED )
The antenna described on this page was built by Everett Sharp, N4CY (ex-N8CNP).
I have not personally built or used this antenna as it is described here. I have used a similar antenna fed with Openwire Feedline and as you will see on another page in my web, I have declared it to be my favorite all band antenna. Well this one might just replace it as my favorite - if I can ever find space to build and try it.
SWR Across the HF Bands
*Everett initially tried a 2.5:1 (125 Ohm) commercial balun by Balun Designs. The results are shown below in light blue. Then he replaced it with his 4:1 home-brew balun which improved all bands (except 80m) considerably. 80m is still very good.
Measurements were taken with a RigExpert AA-170.
SWR measured in the Shack:
SWR measured with 50 ft. of RG8X, using A RigExpert AA-170:
Common Mode Current can easily skew SWR curves. Transmission Lines transform SWR values.
Measuring at the feedpoint would be a better method but Everett is 72 years old, so I doubt he will climb a ladder. The AA-170 does not have an OSL feature. [DJ0IP]
In order to determine this, short of buying an analyzer that can zero out the coax, we can measure using different lengths of coax. When doing so, we will look for changes in the apparent resonant frequency (i.e. point of minimum SWR on each band), as well as any significant changes in the magnitude of SWR. [DJ0IP]
SWR Comparison with different lengths of Coax:
Comparing these two graphs strongly suggest that there is very little Common Mode Current at work here. When just a little CMC is present, what you see when changing coax lengths is a change in the apparent resonant frequency and also better looking bandwidth. That did not occur here, which IMO indicates that there won't be problems with CMC. [DJ0IP]
If the SWR level were significantly affected due to transmission line transformation, then the level indicated on the band(s) affected would be quite different from one graph to the next. This is not the case. Therefore it is a fair assumption that the values shown here are very close to what we would find at the feedpoint. [DJ0IP]
I don't know why the 4:1 balun worked out better than the 2.5:1 baln on my loop. I am feeding the loop in a corner, which should be 100 Ohms - more or less. On another installation, the results might be different. [N8CNP]
Hopefully Everett has found repeatable results. If so, this antenna is going to make a lot of people very happy. My personal experience using the openwire-fed version of this antenna has been overwhelmingly good - as you can read on some of the other pages here on my web site.
The openwire fed version was best fed with a good symmetrical tuner. I used a high-power ANNECKE SYMMETRICAL KOPPLER, which is an improved version of the old Johnson Viking Kilowatt Matchbox. These were terribly expensive and next to impossible to find.
The coax-fed version shown here would be a very welcome addition to anyone's antenna farm and most likely will not require a tuner, or if it does, then any general purpose tuner will do the job.
IF ANYONE ELSE TRIES THIS ANTENNA, PLEASE SHARE YOUR RESULTS WITH US! TNX.