AFAIK, lots of Icom HF models from that era have the jumper arrangement. It is a good place to add a preselector, MW highpass filter, etc. without having to use extra RX/TX switching.
That said, I think ya' meant to post here....
https://www.hfunderground.com/board/index.php/topic,130371.0.html ;)
Deployed a 60' loop-on-ground for my nightstand radio, which is currently an ATS-20+ with aftermarket firmware.
I did not feel like building a mix 73 1:1 isolation transformer. I rembered having several 4:1 TV VHF/UHF transformers, so I have one at the antenna feedpoint for now. About the ratio, impedances will be all over the place anyway. I used the same model tranformer to connect my National NC‐125 to coax, so I knew it worked okay enough for HF and MW. It likely is down a few to maybe several dB at lower frequencies, but I have noted there is still plenty of signal down to MW for casual listening, so whatever IMO.
I tossed a "SDR protector" in line as I have not verified any ESD protection inside the ATS-20+. I tend to doubt there is any, as I know my previous ATS-20 non-plus did not have an ESD chip installed. I ended up adding diodes and a bleeder resistor to the older model.
Also added a MFJ-1020B for preselction if needed plus added gain at upper HF since LoG antennas often tend to rolloff above mid-HF.
Nightstand radio setup replaced with HTPC (older notebook) and RTL-SDR V4 connected to the bedroom 50" HDTV. Plenty of ferrites as well. Listening to a 40m amatuer QSO in the background at the moment.
After another round of radial field damage, the 31' vertical is back once again on the 10.5' mast. Using a 4:1 unun at the feedpoint and RF grounded against the mast and guy lines for now. Common-mode choke back near the house entrance, along with a SDR protector and common-mode chokes near the SDR.
I probably need to get a galvanically isolated choke in there somewhere. Anyway, I have WWVB on 60Hz with a decent copy along with various 11m and 10m signals sat the upper end of HF. Actually I spotted an area 2m repeater and multiple NOAA frequencies in VHF as well, but those are mostly just a bonus IMO.
Installed a new galvanic isolation transformer at my Airspy HF+D. Isolated 4:4 windows on 3 stacked mix 73 binocular cores. Seems okay from LW through VHF.
I might eventually add another isolation transformer at perhaps ground level below the 4:1 unun on the 31' vertical.
Multiple posts mergedFinally did an isolation transformer on a TDK N30 binocular ferrite. Just one small ferrite with isolated 4:4 windings. Seems to be doing okay for MW through VHF at my bedroom RTL-SDR V4 receiver. The TDK B62152P0008X030 is $0.32 each at Mouser. A few cents higher at Digikey and likely others.
https://www.mouser.com/ProductDetail/EPCOS-TDK/B62152A0008X030Probably posted this before, but anyway:
https://dh1tw.de/2021/06/whats-the-best-ferrite-material-for-a-common-mode-choke/Speaking of the bedroom receiver, I am am likely replace the 60' LoG. I am thinking just a vertical wire on a 10' bamboo crappie pole against a ground rod. Perhaps a cheap 9:1 receive unun, or maybe wind my own unun on a small TDK N30 toroid.
Replaced with the 4:1 TV transformer with a LDG 1:1 balun on the 60' loop-on-ground. HF seems a little better in a quick skim. The 4:1 TV transformer likely would have sufficed for a receiver with high sensitivity and dynamic range, but that antenna is feeding a RTL-SDR V4.
I still need to get around to changing the feedpoint balun on my 148' LoG to perhaps just a mix 73 isolation transformer. Right now there is a Nooelec V2 9:1 balun, which was handy in the spare parts at the time. Okay at HF, though the ratio is probably rolling off some performance at MW and under due to the loop's already low impedance at such low frequencies.
I have yet to test it, but I did just receive an inexpensive active RF distributor. 1 input to 4 outputs. Integrated battery as well.
https://www.aliexpress.us/w/wholesale-Active-RF-Splitter-Isolation-Distributor.htmlClaimed specs:
The RF signal splitter operates in a frequency range of 100kHz to 150MHz. It offers minimal insertion loss (<0.8dB), superior output-to-input isolation (>80dB), and excellent output-to-output isolation (>60dB).
Received a preamp from Aliexpress earlier this week as well. The model with the gold-colored enclosure and integrated battery.
https://www.aliexpress.us/w/wholesale-100k%2525252d6GHz-low-noise-gain-amplifier.htmlPower supply: 5V 70ma;
Frequency range: 100K-6GHz;
Ultra low noise figure, 0.4 dB NF at 1.95 GHz;
High gain at 1.95 GHz, 20 dB gain;
High linearity,+35 dBm output IP3;
High input power robustness,+22 dBm continuous wave;
I did not take measurements, but gain is likely over 20dB at HF and lower frequencies. No real comments on added noise as I am using it mostly for a MW/HF with just a RTL-SDR V4.
Without upstream attenuation it does show some overloading with my 60' LoG, but that is pretty much expected here. Radio Marti signal levels tend to be ridiculously high at my QTH. It probably would suffice better with a small vertical.
There is now a 20dB attenuator upstream from it to deal with the potential overload. I opted for a CATV attenautor, which might be YMMV on low frequencies. Actual gain numbers aside, I am more or less using the attenator and preamp combo to deal with the significant impedance mistmatch between my 60' LoG and RTL-SDR V4.
I did spot some very minor Radio Marti breakthrough on upper HF earlier this morning, but that is likely far more related to the limited dynamic-range of the RTL-SDR V4 as dropping its own gain setting largely resolved the issue. Otherwise it appears to be working pretty much as expected. Not bad for a cheap preamp IMHO.
HFDY active loop deployed and currently feeding the KiwiSDR 2. Configured as a shielded loop. The mast is just wire tied to a fence pole in the backyard for now, so I will have to work on that later. Running RG-6QS as well as I did not feel like dealing with RG-11 today. Anyway.
Power is via a 9v linear regulated wall-wart. The HFDY preamp tends to favor 8v for optimized performance in another person's testing. I am likely somewhere in the ballpark when considering voltage drop across the feedline.
I suspect it will not outright compete with my 31' vertical for signal level and SNR, but propagation has been horrid today due to solar weather, so that is perhaps a test for later.
Moved my Kiwi back to the S9v31' vertical with the previously mentioned little to no gain hi-z preamp at the Kiwi to smooth out the impedance excursions. Huge difference in reported signal level and SNR. WWVB is also back in the waterfall.
Current local SNR measurements are 36 dB (0-30 MHz) and 26 dB (1.8-30 MHz). That puts me in the top ~30 of Kiwis at the moment. :)
http://rx.linkfanel.net/snr.htmlAdmittedly those are nighttime numbers, and as expected, daytime SNR drops considerably here.
I get the feeling a good part of the Kiwi SNR measurement requires a decent signal level.
Actually the perceived SNR of the HFDY loop seemed okay IMO. Just somewhat low signal levels.
The HFDY might fair better with my Airspy HF+D, which has far better sensitivity and dynamic range than a Kiwi.
Status could change at anytime, but my Kiwi is online at the moment.
http://21084.proxy.kiwisdr.com:8073
HFDY on my Airspy HF+D is decent so far. Noted WWVB on LW. Quick screenshot of lower MW:
(click to enlarge
I am listening to multiple frequencies with South American milsat pirates via Airspy HF+D and HFDY active loop. lol
Meanwhile despite SNR values dropping drastically due to solar weather and extremely poor propagation, the Kiwi with 31' vertical has been logging 15m FT8 traffic tonight (~0400z) from South America, Oceania, China, etc. Noted loggings at 15000-16000+ kilometers from the Marshall Island and Australia.
Not sure I call it a weak signal antenna, but anyway, the HFDY loop does appear to be helping mitigate RFI this afternoon. The noise blanker in SDRSharp barely moves the noise floor on the 40m amateur band compared to the filter's usual few dB drop for ~7MHz during afternoon hours for my 31' vertical.
Afternoon noise floors at the moment:
80m - S2-S3
40m - S2-S3
20m - ~S2
15m - ~S1
10m - <S1
Looks like I hopefully found a decent null. The null is somewhat NNW/SSE. That might affect some NA signals but probably not enough to matter for casual listening.
Part of it is down to the somewhat low gain, but that is still not bad for an inexpensive active loop.
Parts of longwave do to have moderate to considerable RFI, though again, it is a $30 antenna kit. ;)
I suspect the HFDY loop might eventually be feeding one or more of my secondary receivers.
Suspect I might be able to coax another dB or few SNR for the Kiwi. It is just temporarily hooked up near a feedline for testing. I still need to sort out the the cabling, add ferrites, etc.
Temporarily moved the Kiwi to my 148' loop-on-ground for testing. Current SNR is 40 dB (0-30 MHz), 35 dB (1.8-30 MHz). which puts me #14 on the Kiwi SNR list at the moment. That is with a cheap preamp (with output attenuation) at the receiver and a little 9:1 receiving balun at the loop feedpoint. o.0 Sadly daytime SNR will be another matter.
Prototype inverted delta loop deployed. 2x 10' bamboo fishing poles in V formation. ~10' 24ga copper wire on each side of the triangle. Bottom apex is maybe 18" above ground and fed via a 1:1 (4:4) mix 73 isolation transformer. I still need to add a choke or isolation transformer at the SDR end. Using an existing RG-6QS feedline for now.
That should be in-plane directivity at lower frequencies transitioning more to perpendicular directivity at higher frequencies. In-plane approximately NNW/SSE at the moment.
Some daytime dBFS noise floor numbers as reported by SDRSharp with default FFT and Airspy HF+D SDR....
10m: -135
15m: -133
20m: -131
40m: -122
80m: -112
160m: -125
MW high: -129
MW low: -125
JA NDB 344KHz: ~120
GN NDB 269KHz: ~120
WWV 60KHz: ~122
Those are general floor numbers. as naturally there are higher noise excursions due to narrower signal noises and usual summer static crashing.
I was able to null some wideband noise, but there are still a few spots of local daytime noise. The narrower RFI is more a few narrow spots instead of extremely wideband, so I suppose "whatever" for now.
Hopefully even lower nighttime noise numbers, especially if that RFI is solar panel installs.
Assuming the prototype works out, I have two 13' fiberglass fishing poles to build a slightly larger and probably more sturdy inverted delta loop. Not that I really another 11m antenna, but a ~36' perimeter wire would be big enough to transmit on 11m as well.
^Mutiple posts merged.
