You can, but the better compromise if you can do it is the longest possible radiating element with the least amount of added inductance in the coil.
Reason being, a very short radiating element, even when tuned to resonance with a lot of coil will have, among other things, a very low radiation resistance. In the field this will have two results that will make you tear your hair out: one, an extremely narrow bandwidth, which will make adjustments to resonance extremely touchy and two a high swr even at resonance. So you may still only be able to get it to 2:1 at resonance, depending on how short your element actually is. And even so, the performance will be significantly reduced due to the low radiation resistance. I do a lot of /p with my Buddipole and have found this through experimentation. For example, with its stock 5 1/2' whips, it's only enjoyable to deploy on 10,12 and 15. On 17 and 20, it gets really touchy to adjust and the 2:1 bandwidth just barely covers the CW portion once tuned. Also, raising the antenna on my 19' mast raises the resonance enough to really be annoying to get it setup on 20 meters. 30 and 40 meters, forget it lol.... So I ordered the longer 9' whips for mine and that all but solves the problem. on 20 meters, for example, only a few turns of each coil is needed, but the SWR at resonance is commonly 1.2:1 or even 1:1 depending on where I deploy out in the woods. It's reasonable to tune on 30 meters (and haven't tried 40 yet). On 10, 12, 15 it can go to full length and no coils are required at all. There the bandwidth is very wide with a low SWR across almost the entire 15 meter band for example. When I really need to "boom in" somewhere with my 10 watts, I setup a resonant antenna with the long whips and just accept having to adjust the antenna when I change bands. When I'm lazy, I just use a 100' wire inverted V centered on my 19' mast and just use the tuners in my rigs (all my K's have the antenna tuners in them). That works pretty good, especially on the higher bands, but not quite as good as resonant setups... Anyway, just my experience since I operate /p almost 100% of the time now, out in the mountains here in northern NM. At 10,000' I'm almost a SOTA operation lol... 73, LS W5QD John Pitz wrote > Hello All, > > Please excuse the amateurishness of this question, but could you get one > of these whips for a low band such as 40M and use it on say 20M if you > don't extend it fully? > > John Pitz > KD8CIV -- View this message in context: http://elecraft.365791.n2.nabble.com/Strong-recommendation-MFJ-18xx-series-single-band-whips-for-KX3-etc-tp7615498p7615512.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
