The small SWL beam (1...30 MHz)

[13dka]

That would suggest using a 1kOhm pot in parallel with a 1 kOhm resistor, at least for experimentation. As a general SW reception antenna the almost one hemisphere wide beam is a good decision with many advantages tho, making the beam narrower is probably getting us very quickly into the "diminishing returns" zone.

Since it's really cozy up here (a day earlier than predicted) I'll probably be sleeping at the dike tonight and running tests, this time with the preamp.

Edit: The new balun is ready for pickup, so is a short SMA->SMA 5mm coax piece to make a separate CM choke, and 2 90° SMA adapters. Getting close to perver..err...perfection.

[Andrew (grayhat)]

a pot may be ok to experiment, but won't be ok for a "final" loop, also, changing the resistor value will result in an impedance mismatch, not a big issue, but may affect LNA performance; also, if the target is LW/MW the same idea will work, but increasing the loop diameter (side) and then readjusting the resistor value (use the NEC optimizer) since the resistor value and height also depend from loop size

[13dka]

Out at the dike again, but condx are really bad or something is wrong, but I'm on 15 MHz and if I turn the antenna to the south I can fade the thunderstorm crackling in and out, cool stuff

[Andrew (grayhat)]

Out at the dike again, but condx are really bad or something is wrong, but I'm on 15 MHz and if I turn the antenna to the south I can fade the thunderstorm crackling in and out, cool stuff

is the resistor pack ok ? I wonder if it may be damaged (resistor cracked) ... ok, probably I'm just a pessimist

[13dka]

Looks like we have a really bad radio blackout, local kiwisdr has nothing on 18 MHz either, I only hear south American stations on 20m...dammit.

Edit: A=24 right now, probably the right time to explore the FM band then

[Andrew (grayhat)]

Looks like we have a really bad radio blackout, local kiwisdr has nothing on 18 MHz either, I only hear south American stations on 20m...dammit.

Edit: A=24 right now, probably the right time to explore the FM band then

well; there's little one can do if propagation doesn't collaborate, at least until someone won't come out with a rig having a knob labeled "propagation" on the front panel

as for FM, that may be an idea at least the LNA has its upper limit around 150MHz and the SDL shows gain in the FM band

[13dka]

Worst. Propagation. Ever. I usually don't go to the dike when the web SDRs confirm bad space weather indicators but last night I had to escape my 3000°C cozy attic apartment, so no choice.

I was really worried the antenna is broken, or the LNA, but all SDRs up here had the same absence of stations...well, almost. Of course I had residue signals where they didn't but I never had a day when I couldn't hear WWV and 20m was lacking signals above 14.250 and most of the Americas. The absence of enhancement by sun activity has never been a problem at "the dike", but during a blackout there is no trick or loophole making that not suck. Well, at least at this high latitudes - this morning I heard Italian and Spanish stations working DX just fine, but then again I heard some of the VK they worked too.

As for what I've learned about the antenna:

- The LNA doesn't seem to like it on MW and below. Not sure what's going on there, on LW it decreases the SNR with full gain, this is back to normal when reducing gain. (I can switch the power bank to 3.xV output, then the LNA decreases the gain to maybe 10dB or less.) On MW this seemed to happen too, but then it looked like it decreases the SNR only when the station is on the backside of the antenna, in other words it looks like there is some interaction between the LNA and the antenna, more gain = more directionality. Strange. This may also have to do with me being lazy - I just connected the LNA directly to the balun and maybe it's not a good idea to leave that much space and an LNA between the balun and the choke. I'll have another involuntary opportunity to check that tonight.

- Having incredibly faint residue signals from RNZ on 15720 and this morning on 9700 kHz gave me an opportunity to play with height: Going from 4m down to 1.50 (feedpoint) had no effect whatsoever on RNZ and at best a suprisingly little effect (I can't hear it on the audio recording) on the one clearly readable VK station this morning (VK3KJ). With the latter I also tried rotating again and got the impression that the signal came from W and not SW as expected, IOW the directionality was there, and since the signal dropped in N/S/E directions and the center was W, I guessed that's the path the signal took and was quite happy about the antenna letting me come to this conclusion.

- Obviously, the condx improved only a little in the morning but I still managed to hear faintly (some words readable) the Australia VOLMET on 11387kHz and Auckland VOLMET on 8828. Unfortunately I didn't bother with laying down the LoG due to the unrewarding conditions but the fact that I heard these stations makes me very confident that the amplified SDL is just as good if not better than the big LoG.

- Despite no appreciable tropo enhancement, I had a blast on FM! With so much gain to boot and 2 nice flat-ish lobes I could really hear through the entire radio horizon and a little beyond , I heard more southern Denmark stations than with the vertical, I got really great signals from all the 2m and 70cm repeaters around, I heard surprisingly far up and down the coast on the VHF marine band, and picked up an unknown to me zombie satellite on 136.695 MHz ("Shinsei MS-F2"). Seems that's quite the right RX antenna for a wideband SDR!

[Andrew (grayhat)]

the fact that the LNA isn't working as expected down to MW/LW is strange, judging from the NEC model, the antenna gain "down there" should be quite low and the backside even lower, so it's really strange

as for height, I think it should be tested with better propagation when any signal change will be more evident

one thing to try may be leaving the preamp as is but moving the chokes at the vertical section of the coax

as for FM band and up, the antenna has positive gain there, so your test is quite interesting, even the sat signal one

[13dka]

the fact that the LNA isn't working as expected down to MW/LW is strange, judging from the NEC model, the antenna gain "down there" should be quite low and the backside even lower, so it's really strange

I'll take the other one next time (I have 2 of those) to make sure the LNA isn't just defective in some way (I tried the antenna with that one at home, and it seemed to work better than at the dike yesterday).

as for height, I think it should be tested with better propagation when any signal change will be more evident

Hm... my thinking was that if the station is so grassroots barely there, any drop in level will be super evident because the station has absolutely no spare level left, it would just disappear. But that could be wrong and you could be right - if that little residue signal was just diffusely scattered all over the place from a lot of angles, and the antenna would react different when the signal has a more defined approach path. However, the VK station had a pretty defined approach and the antenna didn't mind the height change either But that may just say that the elevation of the signal was steep enough to fit the lobe independent of height..

one thing to try may be leaving the preamp as is but moving the chokes at the vertical section of the coax

I'll try that if putting the choke between balun and LNA doesn't do anything.

as for FM band and up, the antenna has positive gain there, so your test is quite interesting, even the sat signal one. Hepburn index page was black for my neck of the woods, at best "unsettled" conditions.

Hard to put that into relation tho, my reference antenna for FM out there would be the 10m monopole or diople in L-config and that's surprisingly good on FM/2/70. But I had the impression that the SDL at only 3 or 4m height was better. I heard 2 ATIS stations I never heard before, and my benchmark FM stations were both like local stations.

[Andrew (grayhat)]

check the shinsei orbits !

https://www.n2yo.com/satellite/?s=5485