I miss making blog posts about building kits. I think the last major one I did was about building the Tut80, and before that, the Norcal 2N2/40. It’s been a while since those posts, so I’m looking forward to posting about the building and operating of Etherkit’s new CC-40 QRP CW transceiver. Many of the blogs I follow are updated on a much more regular basis than mine, and I enjoy reading them, so although I don’t think I’ll be able to offer the content that many of my favorite blogs do, I can at least pass along my rambling ham radio thoughts while I wait for the beta kit of the Etherkit CC-40 to arrive at the AA7EE QTH.
The current antenna here is an inverted vee cut for 40M. The center is supported by a 32 foot fiberglass windsock mast that I bought from The Mast Company. It’s mounted on the balcony of my house, which is about 15 feet above ground, putting the center of the dipole at about 47 feet. 75 feet of JSC Mini RG-8/U type 3060 connects the dipole to my Z11 tuner, which is sitting right next to the FT-817. It’s cut for 40, so works great there. It also works on 15 – not sure how well as I haven’t had many QSO’s on 15 yet.
So far so good – a 40M dipole is expected to work on both 40 and 15, so no surprises there. Lately though, with the sunspots becoming postively more sociable, I’ve been wanting to be QRV on other HF bands too. At some point soon I will most likely try feeding a dipole with balanced line for all HF band coverage but right now I don’t want to mess with the coax-fed 40M dipole as it’s working great on 40, and I want it to remain that way for giving the CC-40 it’s on-air testing.
So what to do? I know that I can use the Z11 tuner (which is located next to the rig) to present an acceptable impedance to the rig so that it will transmit on any HF band, but I also know that on bands other than 40 and 15, the mismatch at the center of the dipole will be great, incurring losses in the coax. In other words, only a bozo who doesn’t know his antenna theory would try to load up a coax-fed 40M dipole on bands other than 40 and 15 with an antenna tuner located at the rig.
So I tried it.
And it gets out.
Amongst the QSO’s I’ve had with this “unwise and inadvisable” antenna (my quote marks) are FG5FR on 30M and LU4FLJ on 12M. On 30M this morning, I QSO’ed with AB7KT who was running the same power as me – 5 watts (not sure what his antenna was). He gave me a 579 and I gave him a 559. Also on 30M, WB7NZI was running 83W (odd figure) to a dipole. He gave me a 559 and I gave him a 589. KD0V was running 100W to a 3 ele beam at 50 feet. He gave me a 579 and I gave him a 589. Remember that there is 5W coming out of my transmitter (not sure what the erp is). There are many other examples, but I have had successful QSO’s on 40, 30, 20, 15 and 12 – all on an antenna system that my understanding of antennas dictates should only work well on 40 and 15.
Does anyone reading this know how I could model or otherwise calculate the theoretical losses for such an antenna on bands other than 40 and 15? I’d love to know what the theoretical losses are on this system on bands other than the one for which it was designed, because going on just signal reports alone, the losses don’t seem to be that great. Although I haven’t had QSO’s on 80 or 10 with it, I have seen my spots on the Reverse Beacon Network, and the SNR figures are quite encouraging.