Discussion in 'Amateur Radio News' started by KB7TBT, Mar 23, 2021.
Ham Radio - A 6 meter cage dipole using window line.
I dont understand the purpose of the cage if it is only used at the lower 400 kHz of the band which includes all the common modes in use. FM is way up the band and in its own world.
My own 6M antennas have always been home brew including long boom yagis with at least a 500 kHz 2:1 VSWR bandwidth and the radios and amps are quite happy with it.
A solution looking for the problem.
I watched the video and thought if was interesting, he demonstrated that the cage dipole in this case did indeed have a broader bandwidth and would cover most, if not the whole band. His single wire dipole covered 2.6 MHz with a low SWR of 1.54, and the "cage" covered 4.6 MHz with the lowest SWR at 1.42. He was explicit about why he didn't personally retune it (has he was really only working the lower portion). Unless I'm missing something, the guy made a video explaining a concept, with examples, that he tested with a VNA as a demonstration. I'm new, maybe teaching people about RF concepts is out of vogue?
Thanks a lot for the video James! I found it very interesting and helpful. I am new to the hobby and I have been searching for homebrew/diy videos just like this. Great job explaining everything and showing exactly what you did. I really hope you do more videos like this and I am now following your blog too.
There is no need for a snotty comment, especially from a newbie who is totally unfamiliar with the item in discussion.
Ive nothing against new hams either, Ive mentored many over the decades.
Personally I just dont see the needs for repetitive YT videos when a Google will already provide far more info going back to the beginnings of radio.
Plus what wasnt mentioned is that the VSWR will change dramatically when wet, snow, and ice covered. I hope some dont blow their TX finals by not realizing this.
And yes Ive used the cage on 80 and 40M in the past to cover the CW and SSB/AM portions of the band.
Ham since 1955
Agreed, I should have left my editorial comment out of my reply. Although in fairness, you don't know what I may, or may not know about cage dipoles (not that it's relevant).
Cage dipole ABSOLUTELY had increased bandwidth compared to a single wire dipole. Well demonstrated in the video.
Hopefully, however, viewers don't get the impression that the increased bandwidth is useful on 6 meters where the activity is scrunched right around the low end and a simple dipole has way, way more bandwidth than needed.
The only ham bands that suffer from limited bandwidth of a single wire dipole are 160 and 80 meters. On those bands a cage can be useful if you can tolerate the weight and other physical difficulties in keeping it up.
The authors point was that the "Cage" dipole variant increases overall performance of a single wire dipole. In which he proves out with the tests he performed against a single wire dipole. More or less...
The take away point of the the cage dipole is that it generally nets you 1.7 times more bandwidth than the single wire dipole.
As my thoughts on the deployment of the cage dipole using window line. I totally dislike the idea. The added weight of the wire insulation is uncalled for and serves as a extra wind load.
There are better ways to deploy a cage dipole variant.
I guess though that for the experimental version displayed and intended build use for the author that stated that he is engaged in a perpetual camping trip. It serves up something. I could see that the man handling repeatedly might in this form of construction tend to be easier than perfect examples of the cage that I have witnessed being considered and constructed.
A rather complicated solution, too.
It seems to me that a very similar result could be had using 1/2 inch aluminum tubing, copper pipe, or even EMT conduit. A single 10 foot piece of tubing would provide more than enough material. A center insulator could be fabricated from PVC plumbing fixtures or a scrap of Corian or similar countertop material.