Gary @N8DMT

Amateur Radio Extra, Maker, Product developer, Wireless/RF/Antenna guru / electronics consultant, LabVIEW, RTL-SDR, ADALM Pluto, GNU Radio, FCC testing. Location: EN52, Chicagoland https:/www.qsl.net/n8dmt

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n8dmt_at_mastodon.radio@momostr.pink

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Last Notes

2026-03-12 11:48:27 UTC

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To find where a file is in the search results, right-click on the file and select Open File Location which brings up a new window showing the file location/path. They degraded the search tool and effectively killed off the ability to easily find specific individual files in these latest windows versions… #Microslop

2026-03-11 14:43:49 UTC

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Have been looking for one of those mugs for some time. Congrats! (The search continues here…)

2026-03-10 22:40:54 UTC

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Nice! The included mount will certainly make use far easier than without. Covers a nice frequency range too. :radio_tower:

2026-03-05 21:28:52 UTC

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Mag-Loop Antenna Tuning Indicator Project - Collected a few plastic caps, dug out the #30 wire-wrap wire, and tested LEDs for brightness using DVM diode-check function. Found some really bright RED LEDs to try in next version (super bright using IC-705 20% TX power level). Plan to make a few versions using different number of loop turns. Maybe red cap for higher power (less turns) and white for lower power (more turns)? Still thinking about how to best attach to loop. #HamRadio #DIY #MagLoop
https://mastodon.radio/system/media_attachments/files/116/178/666/181/003/478/original/d75578a957cf6c69.jpeg
https://mastodon.radio/system/media_attachments/files/116/178/670/860/140/840/original/e61a1860bb84df31.jpeg

2026-03-02 00:43:28 UTC

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Turns out that adding ferrite to a loop antenna “dampens the loop RF flow”, i.e., degrades the antenna efficiency. Doh! But, taking out the ferrite and just coupling a small three turn loop to the mag-loop’s main loop does not degrade the antenna much (if at all). This version built with a few turns around a water bottle cap and close coupled to the loop works pretty well down on 40m. Will continue testing and optimizing, then write up as blog post thereafter.
#HamRadio #DIYSuccess #MagLoop
https://mastodon.radio/system/media_attachments/files/116/156/796/359/121/181/original/1c089d39b120d95b.jpeg

2026-03-02 00:22:13 UTC

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How does that old story go? If it appears to work well on 10 meters, it must work on all the bands right? As it turns out, the same indicator seems to attenuate the RX signals down on 20 meters by more than 10 dB. Removing the indicator returns signal strengths to normal. More experimentation ahead (will try a few other core materials and vary the number of loop turns feeding the LED)! #DIYFail #HamRadio #MagLoopAntenna

2026-03-02 00:08:23 UTC

Today’s distraction from the news: Build a DIY LED tuning indicator for the magnetic loop antenna. Searched for information on the AlexTune LED indicator which just attaches to the PL259 loop connector. No joy on finding details/schematic on that. Instead found a video by VK3YE on a simple clamp-on ferrite core with a couple of turns of wire through it connected to a LED indicator. Works great! #ChameleonMagLoop #HamRadio
https://mastodon.radio/system/media_attachments/files/116/156/106/831/400/957/original/825d2d7aa576fa95.jpeg

2025-10-15 16:23:29 UTC

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Did you open the case and see if it had sets of crystals for TX/RX frequency control? It reminds me of a Wilson Mark II that I had in the distant past…

2025-09-19 20:54:15 UTC

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Very nice! And has both remote and local control! Really miss remote (LabVIEW / GPIB) control for most gear here in the home lab… Thanks & 73

2025-08-05 16:09:30 UTC

TIL: TinySA-Ultra has a quick screenshot shortcut on the front panel. To use this function:
1) Check AUTO NAME on STORAGE menu
2) Set the DATE TIME on CONFIG menu
3) Be sure to have a microSD card inserted
4) Using a small plastic pointer (i.e., PalmPilot extra stylus you’ve been saving all these years), press the small green text/outline SD card symbol just above the battery indicator
5) Presto: Screen captured to card in .bmp format with date/time file name
#HamRadio #TestEquipment
https://mastodon.radio/system/media_attachments/files/114/976/986/439/025/030/original/a3fe4cd13cbf8531.jpeg
https://mastodon.radio/system/media_attachments/files/114/976/991/859/189/552/original/5233128787b74277.jpg

2025-06-08 12:19:18 UTC

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Really like your 435B-K13 — have many uses for one of those here. Keeping an eye out for one of those (from someone who does not appreciate what this instrument does). Will be powering up my Telk scope and charging batteries later today.

2025-02-16 02:27:26 UTC

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Long time ago, but think annoying the family with the clacking late at night was a contributor to funding the radio upgrade to the IC-735! :radio_base:

2025-02-16 01:50:52 UTC

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Bought in the early 90’s an Icom IC-720 HF radio that had lived on a Florida sailboat. Was “thought to be working when last used”. Found corrosion on metal frame /shields inside, and discovered at least 10 copper PCB traces in shielded modules had totally disappeared/dissolved. Had months of fun fixing that radio (and sold soon to upgrade to a IC-735). Saltwater!!

2025-02-13 18:16:41 UTC

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How about alligators? Any better?

2025-01-28 15:35:25 UTC

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Have similar formable cable here but not insulated outer surface. Don’t the turns short out when wrapped around the core? (Have constructed a similar cable several times in the past — just without the cores (was OK with shield currents).

2025-01-22 21:22:15 UTC

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Roger that. Keeping things simple in social media… (And thanks for the nice videos!)

2025-01-22 20:37:23 UTC

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Missed another key characteristic: broad banded (typically 2-3, sometimes 4+ octaves).

2025-01-22 20:27:16 UTC

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I call them cavity-backed spirals, with the cavity behind the antenna aperture playing a big part in the lower freq drop off. Their circular polarization and ability to be flush mounted is an important characteristic in their use in electronic warfare applications. Have a couple in the lab here for when CP is needed. Have fun & 73…

2024-12-28 21:21:10 UTC

Here’s the first real measurement with the TinySA-Ultra, capturing power levels and spectrum of a 100 MHz Sine OCXO that I use for my Pluto SDR up/down converter setup. Fundamental power at 100 MHz is ~ +13 dBm (enough to split and then comfortably drive two paths of Level 7 mixers). Second harmonic is ~ -26 dBm (~39 dBc) and third is ~ -41 dBm (~54 dBc). Still getting used to slower sweep speeds, but this is working quite well. Next step is to fire up the PC SW to yield better screen captures.
https://mastodon.radio/system/media_attachments/files/113/732/521/617/738/310/original/8a06311d9aca20ed.jpg
https://mastodon.radio/system/media_attachments/files/113/732/521/999/411/487/original/c698f2f32df2ea3f.jpg

2024-12-10 21:12:49 UTC

One of the major RF test equipment suppliers (Rohde & Schwarz) has published a FREE 129 page technical note on making common measurements using a spectrum analyzer. While focused on using R&S equipment, many measurements are also applicable for those with other brands (even lower cost home lab equipment like TinySA-Ultra, etc.). Includes background theory and how-to-measure step-by-step walk throughs. A fun read for geeks!
Measuring with Modern Spectrum Analyzers
https://scdn.rohde-schwarz.com/ur/pws/dl_downloads/dl_application/application_notes/1ma201_1/1MA201_9e_spectrum_analyzers_meas.pdf

2024-09-18 16:42:08 UTC

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Might also consider the “Someone Steals Them” factor and how you would feel coming out of the store to find them missing? That points me to more middle of the road products…

2024-08-04 17:25:01 UTC

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Happy to see approximately 10 dB return loss in your video. My slightly smaller LPAs are similar RL from 800-8000 and use hardline from feed to SMA-M. Generally hook directly to PLUTO SDR with a long USB cable to laptop when chasing emitters. (Use SATSAGEN and/or SDR-Angel on PC for monitoring/decode.)

2024-08-04 16:57:09 UTC

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Do you have two of them, supporting determination of K (and calibrated field measurements thereafter)? Have similar small LPA in lab here, but without hand grip. That’s a nice feature!