Discussion in 'Antennas, Feedlines, Towers & Rotors' started by AI5DH, Aug 1, 2018.
Thanks for clarifying.
No problem - I just snagged G4RCG and a little earlier HA8FK. 20-meter cw. Cans and filter on, but I didn't have close my eyes to hear them.
I'll stop posting dx since I think the point is made. The guy on the other end (and propagation) is doing all the work.
For instance, G4RCG is running 500 watts to a 3-element yagi up at 65 feet. Working a nearby 7-lander, so I'm right in his path.
Gotta' grab some zzzz's for FD tomorrow!
If we assume that Signal plus Noise to Noise Ratio (S+N/N) and Minimum Discernible Signal (MDS) are reasonable quantitative parameters, it would be instructive to know what your particular results are.
My request to you is: Do you have any good performance SDR waterfalls that you might have that you would care to share ?
You bring up a good point - depending on how sensitive the waterfall is, I'm not sure you would see it, and could present a trap for a dx'er waiting for something visual rather than spinning and grinning across the noise floor like I do where low level sigs just pop out. Guess it's time for me to pick up a waterfall rig just for kicks.
Moral: don't wait for a waterfall spike with the loop. Spin-n-grin slowly once in awhile.
Adopted a rectangular format:
In my space-restricted environment, I found that using the real-estate for a rectangular (2:1 ratio between sides) format rather than square allowed me to push the loop antenna wires just a few feet further away from the house, and more centered amongst neighbors backyards.
This quieted things down even a little further. Problem is that the transformer box is now in the middle of the yard. So I changed the feedpoint to the other side near a neighboring fence, but now have a dilemna: Do I make this huge end-run of coax around the loop back to the shack?
Gambled on putting a slit in the yard for the coax and foot-tamping it down, which then runs straight under the rectangular loop wire at a perpendicular angle to the feedpoint on the other side where the transformer box won't be an eyesore or get water sprinkled upon.
To my ears it doesn't seem to be affected. Just being paranoid, in addition to the 9:1 physical feedpoint isolation, I also have the line choked as usual.
Pleased with the results. Like any antenna, just a few feet can make a difference. Mostly away from neighbor qrm, and puts the antenna pattern just a bit more out in the open as compared to the square.
Waterfall rig - I DO have one!
I forgot - my Yeasu FTDX-1200 has a waterfall. Kinda frustrating since it mutes as I tune, and the sweep isn't real-time. Got tired of pushing the scope button manually.
But I can confirm that unless you spin-n-grin, you'll miss a lot with the waterfall. Maybe guys with better waterfall rigs can do better with their displays.
Clean armchair cw copy is almost indistinguishable from the noise floor - at least on the Yaesu 1200 display. Same with ssb. You wouldn't know armchair clean copy of ssb was possible, if you relied solely on the waterfall display.
This is one of the mind-blowers. Unless you put boots on the ground with your own wire, you might even find that rigs that aren't at the top of Sherwoods list a great candidate for the log.
Agree.....I've got high performance RFSpace SDR's that I've buffer connected to the pre first mixer section (just after the switchable preamp) on my Icom's as pan-adapters.
Even so, my hearing and grey matter are still good enough to discern sigs even though the visual doesn't quite show much....some minor 'peaks' above the floor.
For my purposes, I prefer to know quantitatively what I see in dBm rather than 'S' units.
Being in a suburban residential environment, excessive noise floor issues are a challenge to get rid of here.
The easiest addition if you haven't already done so is a CMC on a jumper near the rig.
Thing is, if you do 160m monitoring you can't play around. You won't know any difference with say an inline MFJ choke. Even with a loop on ground. Especially at the low end on 160m.
Sadly, the now discontinued rx-only myantennas CMC-0510-R (0.5 - 10 mhz) is the only choke that I've ever witnessed just hammer down on common mode - despite using a 9:1 isolated xfmr at the feedpoint. Even beats his other offerings intended for tx. Like opening and closing a window on 160!
Maybe if we *beg* him to offer them again. Tempted to gold-plate mine, or put it on ebay for $10K.
Wondering what was being used in that MyAntennas CMC choke.
Do you have any info on the innards of that choke?
10 turns of coax around a FT240-43 or FT240-31 toroid will give you lots of RFI choking. If you feel you need more choking then do it twice.
Usually a lot cheaper than some companies "secret" choke and likely more effective.
Well, Balun Designs has one with new core material for the low bands - and you can pump 5kw into it / on ground loop *accidentally* - the model 1116D I believe.
So that's *likely* to work better than the FT-240's. Check it out.
No secret to the myantennas either. Just make sure your resistive is higher than your reactive. Homebrew, spread your cables apart and don't put too many into one core. Standard winding procedures. Use low-freq cores. Cut one open and duplicate it. No harder than cutting up an MFJ.
I think the real trick no matter what is you can specialize with an rx-only to be highly resistive from 0.5 - 10mhz much easier than a tx-capable version of 5Kw. Now that the cmc-0510-r is discontinued, maybe Balun Designs can make an rx-only version too that goes and works that well down low.