Forgot this one: That may be true and I may have to try this more thoroughly but while I messed around with resistor values I noticed the massive increase in output (mostly QRM) of the antenna with one wire not yet attached to the resistor, that's why I ran this through 4NEC. If the preamp likes this arrangement there's no reason why the Belka shouldn't like the output of the preamp. The passive version of the loop works like the YouLoop with the Belka - almost not at all. With the preamp the Belka seems to be happy with the antenna of course. If the antenna would be adapted to the Belka's high impedance input, the little bugger could be attached directly to the antenna, which would be a cool RDF device. Edit: Maybe not that cool having the antenna pointing at the Belka's display.Andrew (grayhat) wrote: ↑Tue Jul 26, 2022 1:44 pm it's easy to see that w/o the resistor in place, the resistive part of impedance becomes very low while the reactive one raises, this in turn causes losses and may probably cause problems if using the SDL with an external preamp or with a receiver which doesn't "like" too much impedance mismatch (like the Belka), so while running some experiments will be cool, I doubt that there will be real benefit in adding a switch to change the antenna config
Like I wrote, I wouldn't want to bother. TBH the only thing I like less than putting up antennas is packing them up again (collapsing the mast, coiling up antenna wires and the coax in a way that it can be conveniently deployed again next time...), so I want that all to require the least possible amount of steps/moves.Andrew (grayhat) wrote: ↑Wed Jul 27, 2022 3:32 pm
Yes, that's another possible way to arrange the loop, I just wonder if the additional complexity when it comes to deploying or dismantling the antenna, for portable use, may be worth
Too bad it didn't work out. A rhombic was always an antenna type I'd like to try and a mini version would be so cool. I didn't mean to discourage you trying to improve the design further though, of course a narrower beam also has benefits and if the would be easy to reconfigure for that - the more options the merrier.Andrew (grayhat) wrote: ↑Wed Jul 27, 2022 3:32 pm I've been fiddling a lot with NEC model variations but had no real improvement, the only thing I didn't try (yet ) is flipping the loop horizontally so, in practice, turning it into a "mini rhombic" antenna, I think I'll give the idea a spin, just for curiosity
I tend to forget that because the closest FM transmitter is 20km away here and has pretty moderate power. When I was still living in the city I had not only a whole bunch of much closer FM stations but also a 100kW AM transmitter (Moorfleet 972kHz) giving all of the cheaper radios I had back then some frontend headaches. Today my very helpful test "enemies" are RRI, CRI and Vo Turkey and if they wouldn't be there I couldn't really assess radios at the dike. Speaking of which - as much as I regret having paid major €€€ for the ML-200, the preamp coming with it has no IP issues with those at all, not even when the 20m loop is up in a tree.Andrew (grayhat) wrote: ↑Wed Jul 27, 2022 3:32 pm In own experience, here in EU the FM stations are the culprit for a lot of IMD issues, and if you consider that the LANA HF works up to 150MHz, it's more than possible that some FM signals overload it causing the issue; as a note, I had to buy an FM bandstop filter time ago since some of the SDR units I was testing shown "ghost" images due to overloading from FM stations <deep sigh>
Andrew (grayhat) wrote: ↑Wed Jul 27, 2022 7:31 am Nay, I don't think it's a miracle, just a small loop with some tweaks
"Miracle" is a big word, even though the shape of the installation as shown above looks like a miracle is just what you'd ask from that thing. But it's definitely something I was dreaming of for a long time - a small, simple and very hassle-free unidirectional antenna for shortwave, whereas the relative independency from ground quality/conductivity and surprisingly low height requirements are a small miracle to me TBH, as much as I don't like to use that word.
Yes, that may help of course, provided there is a sufficient size to the artificial ground plane. Being quite the opposite of an almost "isotropic"Andrew (grayhat) wrote: ↑Wed Jul 27, 2022 3:32 pm As for physical height vs "electrical" one, my bet is that installing the SDL on a terrace at the 23rd floor and on a 3m pole will still give a pattern similar to the one of the antenna sitting at 3m from ground, at least if we consider that the floor of that terrace usually contains metallic net and/or metal bars, so the antenna will "see" it as the ground (plane)
SML it may be even very deaf to all the RFI racket from the floors below.
That's very nice, thank you! But I'm just such a great businessman as you are, so we are discussing all this in public instead of keeping that in private and have a container full of those antennas made in China to sell. I admire the spirit of making knowledge public for DIY and further development (and commercial exploitation) in ham radio and open software development but taking the cardioid loop design and removing the complications it has (ground rod, custom preamp) is a big achievement IMO. If this proves to be as good as I hope for*, this should have your callsign/name attached to it.Andrew (grayhat) wrote: ↑Wed Jul 27, 2022 7:31 am oh, by the way, I never meant to "make money" or whatever with this antenna, it's just an idea, but if you think you may earn something, absolutely go for it, the design is public and free, anyone willing to can use and abuse it
* I need to compare it with other "low flying" antennas, particularly SMLs and at less ideal locations than the dike and document the findings. Almost any contraption is good at the dike and LoGs work magic there - but how does that compare when the ground is only average?