Gary @N8DMT
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n8dmt.mastodon.radio.ap.brid.gy
Gary @N8DMT
@n8dmt.mastodon.radio.ap.brid.gy
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Amateur Radio Extra, Maker, Product developer, Wireless/RF/Antenna guru / electronics consultant, LabVIEW, RTL-SDR, ADALM Pluto, GNU Radio, FCC testing. Location […]

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n8dmt.mastodon.radio.ap.brid.gy
Cold WX stay-home activity: Successfully repaired my Chameleon F-Loop3 tuning capacitor (to remove intermittent shorts) and restoring TX operation on 40 meters. More evening CW fun ahead! Details and more photos at the QSL.net blog.
#hamradio #antennarepair […]

[Original post on mastodon.radio]
Photo of a CHA F-Loop3 magnetic antenna on a tripod inside a home office. Photo of the inside of the tuning loop, showing variable tuning capacitor with inserted paper insulating strips, placed there to assist in troubleshooting just which of these very-many metal plates was shorting to its neighbor when turning (or pressing sideways on) the knob. Photo of the tweaked tuning capacitor that no longer exhibits rotor-stator shorts when turning or pressing on the knob. The plastic wonder tool to the left of the box allowed precise adjustments of the plates! Success!!
January 23, 2026 at 8:31 PM
n8dmt.mastodon.radio.ap.brid.gy
Review of the Fluke 1953A counter/timer shows it is fully working as hoped (operating under local and remote control.) Verified all inputs and operations via GPIB remote control with a simple LabVIEW program. Have a few more esoteric tests to run in near […]

[Original post on mastodon.radio]
Photo of a Fluke 1953A multi-function counter on a very busy table top. Counter is under remote control and measuring a frequency of 20.123457 MHz from the TinyGTC source. Desktop photo from above showing a NI GPIB-USB-HS module connected to the rear of the Fluke 1985A counter. Coaxial cable from the TinyGTC clock output is routed to the counter's A input jack. Poor photo of the laptop screen showing the LabVIEW virtual instrument control panel controlling the Fluke counter via GPIB. The display shows mode control, time base, cycle LED, and output measurement of 20.123460 MHz. It works!
January 7, 2026 at 8:00 PM
n8dmt.mastodon.radio.ap.brid.gy
What to do with an old Ubiquiti AirView2 USB spectrum analyzer when the software won’t run on Win10 or later PC? Answer: Write a LabVIEW program to read/display the raw serial data to keep using it for 2.4 GHz spectral occupancy and channel power info. Plan to […]

[Original post on mastodon.radio]
Photo of a long 2.4 GHz antenna, thin coax, and a USB spectrum analyzer module (Ubiquiti AirVIEW2-EXT) with a wooden clamp mount. Screen capture of the LabVIEW program user interface panel showing the various settings and example captured spectrum data chart and a running channel power chart to the lower right.
January 7, 2026 at 3:56 PM
n8dmt.mastodon.radio.ap.brid.gy
Slow work day = A few moments to work on 2026 goal to make the lab a little better everyday. Today’s task is to add crimped connector shrink sleeving and a length marker to this Pasternack RG-58 C/U cable. Luckily it has a SMA on one end to slip the shrink […]

[Original post on mastodon.radio]
Photo of an unknown length of RG-58C/U cable terminated with BNC-Male and SMA-Male connectors. Two short lengths of shrink tubing are ready to be installed at the connector ends. This provides additional protection to the crimped shield connections. After photo of the measured/labeled RF cable with shrink sleeving installed at the connector ends. This 15' cable is regularly used in the home lab to connect gizmo1 to gizmo2.
January 6, 2026 at 2:37 PM
n8dmt.mastodon.radio.ap.brid.gy
Was able to measure the output 1 dB compression point for the QB-150 RF amplifier (with 12V supply). Kept it simple and just measured at 100 MHz as approximation for full frequency range from HF up to VHF band. Have been looking into how to measure across […]

[Original post on mastodon.radio]
Plotted data for the QB150 powered with +12V at 100 MHz. Data shows ~ 1 dB gain compression at +22 dBm output level. Photo of test setup to measure the 1 dB compression point of the QB-150 RF amp at 100 MHz. Test oscillator output into a variable attenuator to the amp input. Amp output to 30 dB pad then into DIY RF Power Meter.
January 5, 2026 at 8:06 PM
n8dmt.mastodon.radio.ap.brid.gy
Have you noticed that some types of test equipment have gotten much smaller than the rack or half rack width instruments of the past? I am transitioning towards tiny-instruments and downsizing my home lab (having moved multiple times recently). Latest acquisition is a TinyGTC GPSDO timer counter […]
Original post on mastodon.radio
mastodon.radio
December 29, 2025 at 5:34 PM
n8dmt.mastodon.radio.ap.brid.gy
Get going with FreeDV on HF, without fears or tears - The time has come for digital voice on the HF bands by Peter Marks VK3TP. (Found this linked from Peter’s blog on blogs.radio.)
#hamradio

https://www.wia.org.au/members/armag/2025/november/documents/AR%20Issue%206-2026_pp42-48_2.pdf
December 28, 2025 at 2:37 PM
n8dmt.mastodon.radio.ap.brid.gy
@FediTree
December 27, 2025 at 2:26 PM
n8dmt.mastodon.radio.ap.brid.gy
First (easy) test of the QB-150 Amps: Does the one with the top installed work? Answer: Yes! Measured 12.6 K Ohm on the power pin to GND. Applied 12.2VDC, measured ~120 mA current draw. Tested with NanoVNA-H4 with 40 dB pad on input side and found it has ~ +24 […]

[Original post on mastodon.radio]
Desktop photo showing NanoVNA-H4 connected to QB-150 RF amplifier through a 40 dB pad on the input side, measuring S21 gain of +24.5 dBm through HF up to 100 MHz. Amp has +12.2 VDC applied. It works! Photo showing the stop frequency extended so as to measure the 3 dB gain point for the amp (~446 MHz). Amp was originally used as a HF antenna pre-amp up to about 30 MHz. Plenty of gain (and very flat) up to that point. Photo of the working amp and summary of test notes. DC resistance on power pin to and was 12.6 K Ohm. Measured with a 40 dB pad. Indicated gain of -15.47 dB gain at ~ 30 MHz. Approx 120 mA at 12.2 DC test voltage. Overall amp has ~ 24.5 dB gain down in HF bands. 3 dB point is ~ 446 MHz.
December 21, 2025 at 9:34 PM
Reposted by Gary @N8DMT
brouhaha.mastodon.social.ap.brid.gy
I'm reading a 1974 issue of _Electronics Design_, and I'm amazed by all the cool new stuff. There are a bunch of things I want to order, but unfortunately they don't give any URLs.
December 21, 2025 at 8:49 AM
n8dmt.mastodon.radio.ap.brid.gy
Repair RF Amplifier Project: With some time off ahead, dug out the box of Q-Bit QB-150 RF amplifiers. Likely these are all toast, but will test and troubleshoot to confirm. (These were pulls from a field HF antenna system that occasionally had lightning […]

[Original post on mastodon.radio]
Photo of a hand drawn schematic, four modular RF amplifiers, and miscellaneous parts ready to replace failed parts on the boards. May be nonrecoverable, but will test and debug to evaluate before scrapping the boards (keeping the nice cases).
December 20, 2025 at 8:46 PM
n8dmt.mastodon.radio.ap.brid.gy
Slow work day = time for RF fun! Remeasured the Copper Mountain Technologies R54 vector impedance probe output signal characteristics to understand if it always used a fundamental output (or if it relies on harmonics like the NanoVNA-H4). TLDR: the much more […]

[Original post on mastodon.radio]
Photo showing test signal at 3 GHz with no other signals present in the observed 1 to 6 GHz range on the TinySA-Ultra. Clean!!
December 19, 2025 at 4:12 PM
n8dmt.mastodon.radio.ap.brid.gy
Home Handyperson: Had a complaint from a family member that they were not feeling well when the dryer was running. Found multiple issues with the vent: 1) clamp was loose, vent pipe had two large slits cut into it that were leaking. Cut off the hack-job, fixed […]

[Original post on mastodon.radio]
Before photo showing one of the two slits cut into the vent (apparently to make it easier to install). Hose clamp was loose as well. Could feel leaking air on the bottom side as well. After photo with a leak-free repair. Hose cut back, properly slid over the pipe and fastened a-bit back from the edge as it should be. Could not feel any leaking air with the dryer running afterwards. Repair complete!
December 13, 2025 at 5:14 PM
n8dmt.mastodon.radio.ap.brid.gy
Ten Meters is just opening up here in EN52 Chicagoland, and seeing some single and double hop skip to the southeast. Going to be an interesting day!
#hamradio #10meters #magneticloop
Screen photo of iPad running SDR-Control to an IC-705 connected to an indoor magnetic loop antenna. Photo shows example of both single and double hop skip received via FT8.
December 12, 2025 at 2:34 PM
n8dmt.mastodon.radio.ap.brid.gy
Made some progress on the low-cost noise figure & gain measurement setup, and have it running pretty well at 440 MHz. Have pages of notes and pictures to put together a how-to post or web page. Still need to check calibration at other frequencies, but […]

[Original post on mastodon.radio]
Desktop photo of the low-cost DIY noise figure measurement system, with RTL-SDR, RF-Amp noise source, Arduino relay controller, and a few RF cables.
December 11, 2025 at 8:55 PM
n8dmt.mastodon.radio.ap.brid.gy
#patchtuesday yields #waitwedneday: Started a “how long will it run” test with the BougeRV cooler powered by a new Anker Solix C300X DC power pack. With 12V @ 50W consumed during cool down, the run time estimate is almost 6 hours. With cool down completed, the […]

[Original post on mastodon.radio]
Photo of the C300X DC power pack on top of a car refrigerator, all wired up and ready to start the run-time test. Screen shot from the Anker app showing ~50W power draw and an estimated run time of over 5 hours...
December 10, 2025 at 1:22 PM
n8dmt.mastodon.radio.ap.brid.gy
Finished a first draft for my qsl.net web page documenting a low-cost DIY RF Noise Source suitable for making noise figure measurements under automatic program control (with SATSAGEN software). Still have a few more updates to the web page, but completed […]

[Original post on mastodon.radio]
Photo showing DIY RF Noise Source consisting of a Mini-Circuits ZFL-500 RF amplifier and three 5 dB pads (one on input and two on output) connected via a SMA adapter to the input of a TinySA-Ultra RF Spectrum Analyzer. This setup measures excess noise ratio (ENR) needed to use the source as part of a noise figure measurement system.
December 8, 2025 at 1:13 AM
n8dmt.mastodon.radio.ap.brid.gy
US Coast Guard aircraft executing a search just south of Key West Florida. Additional assets joining in now.
Screen capture from adsbexchange showing a grid search pattern.
December 6, 2025 at 1:22 PM
n8dmt.mastodon.radio.ap.brid.gy
What is inside a Mini-Circuits ZFL-2000 RF Amplifier? Had a few minutes to take a quick look inside one of these RF Amps. Didn’t learn much, and was surprised to see a fully-cased (pins) amplifier module inside. Would take a lot more effort to disassemble […]

[Original post on mastodon.radio]
Photo of a Mini-Circuits ZFL-2000 RF amplifier module with SMA female connectors on each side. Power and GND pins are on the side adjacent to the RF connectors. Photo inside of the RF Amp, showing a small printed wiring board connecting the SMA jacks and power/GND pins to the module within. Disassembly would require removing the SMA jacks, unsoldering the center pins, removing the four screws and extracting the module/PWB from the case. Too much work just to see what module is used...
December 5, 2025 at 1:59 PM
Reposted by Gary @N8DMT
kb9ens.mastodon.radio.ap.brid.gy
4 General upgrades and 3 new Technicians. Not bad for an after Thanksgiving session. #HamRadio.
A plastic sign that says amateur radio test last Saturday of month from 10:00 through 12:00
November 29, 2025 at 7:57 PM
n8dmt.mastodon.radio.ap.brid.gy
Looking over Black Friday announcements from HRO and DX Engineering yields an interesting takeaway: today’s “super-specials” look a lot like last year’s everyday prices for many items. Anyone else seeing this too? #hamradio #blackfriday
November 28, 2025 at 4:12 PM