iiinova — where your digital self keeps evolving

Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 23/01/2026

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!!

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 07/01/2026

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!

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 07/01/2026

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.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 06/01/2026

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.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 05/01/2026

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.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 21/12/2025

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.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 20/12/2025

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).

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 19/12/2025

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!!

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 13/12/2025

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!

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 12/12/2025

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.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 11/12/2025

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.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 10/12/2025

Stopped the battery pack powering refrigerator test after about 8 hours as the refrigerator cycles power draw on and off, and the pack is still at over 70% capacity. The refrigerator has been at ~35 degrees all day. Conclusion is that I will have no problems […] [Original post on mastodon.radio]

Screen capture of the Anker app showing over 70% remaining capacity after 8 hours of running the car refrigerator at ~ 35 Deg F today. Test was a success!

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 10/12/2025

#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...

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 08/12/2025

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.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 06/12/2025

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.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 05/12/2025

Found another ZFL-2000 amp in the lab stock - but this one is tagged as “BAD”. Will retest and if actually defective, will set aside for disassembly during next snow day. Curious to see if there is a part number / label on the back side of that 12-pin circular Mod-Amp case. #RFAmplifier #SmokeLetOut

Photo of a Mini-Circuits ZFL-2000 modular RF amplifier with a "BAD" label attached. Is it really bad (or just faking it)? Time will tell. If bad, will disassemble to see what RF amplifier module is used within.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 05/12/2025

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...

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 26/11/2025

Completed a few tests on the 2.4 GHz RF Equipment (RFE) components for the single-band Pluto transceivers. TLDR: All looks good and ready to continue evaluating controller software. Details at the qsl.net blog. #HamRadio #SDR qsl.net/n8dmt/24-ghz-pluto-rf-equip…

VSWR for the TECOM 2.4 GHz antennas showing under 1.5:1 over the 2.39 to 2.45 GHz band.

Photo of the UTE Microwave RF circulator being tested for forward insertion loss and frequency coverage. This unit covers 2-4 GHz and provides more than 20 dB of reverse isolation.

SATSAGEN measurement for the UTE Microwave circulator showing forward passband of 2 to 4 GHz.

SATSAGEN measurement of UTE Microwave circulator showing greater than 20 dB of isolation in the reverse path.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 23/11/2025

RF equipment setup complete for first low-power 2.4 GHz test using Remote SDR and Pluto SDR. Waiting for the afternoon to find/retrieve the second RaspberryPi-5 computer needed for the second transceiver controller. (Have moved multiple times with re-boxing […] [Original post on mastodon.radio]

Photo showing two Pluto SDR connected to UTC Microwave circulators and Tacoma 2.4 GHz collinear antennas. This supports simple half-duplex low-power tests of the RemoteSDR controller software.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 21/11/2025

Here is the system drawing showing the local laptop PC with headset and the remote computer & RF equipment group (Raspberry Pi 5, Pluto SDR, and transmit/receive amplifiers and filters leading to the antenna). Ideally, the remote equipment is located VERY […] [Original post on mastodon.radio]

System drawing for the PlutoX transceiver showing local laptop PC & headset, connecting via Ethernet to the remote equipment group (Raspberry Pi 5, Pluto SDR, TX/RX amplifiers, filters and antennas).

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 17/11/2025

Slow Work Day: Let’s sort ferrite! Made a quick ferrite material sorter using NanoVNA-H4 and a two-turn test loop. Ended up finding at least four material types. Now labeled in separate bags and ready for (easier) future use! #HamRadio #EMIEMC #SortAllTheParts

Close up of the two-turn test loop attached to the NanoVNA-H4 analyzer measuring S21. Normalized this as my calibration reference.

Desktop photo showing many ferrite clamp-on parts ready for test. Some are labeled with part numbers (and material types), others are not marked in any way...

Example for testing a type 31 core. Blue curve is the DUT trace. Red is a previously stored trace using a type 43 core.

Phot showing ferrite sorted into three major piles. Not precise, but better than I had before. The rectangular clamp on in the upper left (from Radio Shack long ago) was the worst of those tested today. Would need many turns through it to attenuate common mode signals. Ugh!

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 14/11/2025

Have you seen video on the DIY capacity hat for a vertical antenna whip? Link below for one ham’s approach. Have purchased some 24” zip ties and found the lab stock of copper tape. Interested to see how this works on my 17’ SS-17 whip antenna! With the cooler […] [Original post on mastodon.radio]

Photo of some 24" zip ties and multiple rolls of adhesive-backed copper tape. Planning to build a DIY capacity hat for a 17' telescoping whip antenna system.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 14/11/2025

The 3/8-24 antenna ground-isolator/connector test box is completed. This simply connects or disconnects the lower ground stake connection to the upper counterpoise / coax-feed and vertical whip assembly. It’s easy to have the ground stake connected with the […] [Original post on mastodon.radio]

Photo of the antenna ground isolator / connector box parts (plastic electrical box, wire, 3/8-24 bolts and nuts, SPST switch).

Photo of the interior wiring of the test box showing SPST switch in the middle and wires leading up and down to 3/8-24 bolts. This is intended to attach to a ground spike on the lower side and radials/coax-feed/whip on the top side.

Photo of the outside of the box (up is to the left in this photo) showing counterpoise/coax-feed/whip attachment to the left 3/8-24 socket and the connection to the ground spike (bolt connection) on the right.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 12/11/2025

I’m sure there is a project in here somewhere: Parts for an experimental ground isolator for a 3/8-24” vertical antenna mounting system. The box goes in between the ground spike and radials/coax-feed/vertical-whip. The switch will open or close the ground […] [Original post on mastodon.radio]

Photo of a 1 gang 18" Nail on PVC box, two 3/8-24 nut, two 3/8-24 bolt, a SPDT switch, a hunk of yellow wire, a lock washer and an elongated nut fitting 3/8-24 hardware. Not shown are two 3/8" wire terminals to connect the antenna mounts to the switch. Will it make any difference?

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 11/11/2025

A follow up post on the DIY RF Comb Generator. TLDR: It works even better when mounted to a small board with SMA jacks! Nice quality combs up to over 1 GHz! Details over at the qsl.net blog. #HamRadio #TestEquipment qsl.net/n8dmt/diy-rf-comb-gen-test/…

Desktop photo of the SATSAGEN / UNO / EtherKit SI5351A / comb-generator-board / TinySA-Ultra showing a nice series of RF combs up to 800 MHz.

Close up photo of the comb generator with the RF input SMA jack on the left, a 15 nF series capacitor leading to the shunt small-signal diode and the output SMA jack on the right. Board is soldered and tested but not yet cleaned after being soldered together. It works!

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 10/11/2025

DIY RF Comb Generator for less than $1.00? After evaluating the mil-spec Herotek comb generator module and Pluto SDR clock source combination, decided to try out a low cost alternative for generating combs. With an on-hand SI5351A clock source, added two […] [Original post on mastodon.radio]

Desktop photo of the comb generator setup. SATSAGEN controlled Arduino UNO controlling EtherKit SI5351A clock source, with CLK0 feeding series capacitor on proto board to shunt signal diode with clip leads attached leading to TinySA-Ultra spectrum analyzer. A large number of comb signals are displayed on the TinySA.

Close up photo of the protoboard showing a single blue capacitor in series from the CLK0 output (right) to shunt signal diode and output to spectrum monitor at left side of the blue capacitor. (Not worried about parasitics for this test.)

Close up photo of the TinySA-Ultra display showing comb pickets extending up to 500 MHz.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 08/11/2025

Finished up testing of what looked like an RF amplifier module but was really a comb generator. TLDR: It works! Now have picket-fence RF signals! Details in two posts over at the qsl.net blog site. #HamRadio #TestEquipment […] [Original post on mastodon.radio]

Photo showing Pluto SDR with HP and LP filters around 640 MHz, HP8447 RF amplifier, Herotek GCA640 comb generator with heatsink, and a TinySA-Ultra spectrum analyzer displaying a series of RF combs (pickets). A well-used HP transistorized power supply is feeding 5 VDC to the comb module. It works!

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 06/11/2025

Getting the lab organized a-bit more: Printed out a data sheet for a pair of Narda RF couplers. Have both couplers back in the same storage package again. What is the RF Geek equivalent of the old hammer-nail saying? When all you have are RF couplers […] [Original post on mastodon.radio]

Photo of two Narda RF couplers, one larger and one smaller, both with red plastic connector covers. The larger coupler covers 0.5 to 2 GHz and the smaller coupler covers 1 to 3.5 GHz. Both provide 20 dB loss on the coupled port. These are useful for return loss measurements in RF systems measurements.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 04/11/2025

Random RF Component Find #308: Herotek GCA640-258 RF comb generator. Was stashed in one of the garage lab boxes. Needs cleaning! This appears to be a 640 MHz input comb generator that will output multiples of that frequency up to ~ 18 GHz. Includes a […] [Original post on mastodon.radio]

Desktop photo of a small packaged RF device with SMA connectors and pins for +5V and GND connections. It is bolted onto a small gold colored metal heatsink. Per the part number, it appears to be a RF Comb Generator. Will be fun to check out and add to the lab stock.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 02/11/2025

2M FT8 Monitor: Setup the IC-705 with 16’ of RG400 coax feeding a DIY 2 Meter halo perched on top of the office closet door. Using SDR-Control on the iPad for FT8 decode. Will monitor 144.174 FT-8 to see if I can hear anything (only seeing always-there power […] [Original post on mastodon.radio]

Photo of a small DIY 2 meter halo antenna constructed using a SO-239 jack and number 14 solid copper wire.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 01/11/2025

Testing the new 33 cm Pluto SDR controlling software: Have basic RX/TX working and tested on FM mode using a local (second Pluto) SDR linear translator “repeater” controlled by GRC. Notes on using F1ATB’s Remote SDR SW over on the QSL.net website (3 postings) […] [Original post on mastodon.radio]

Desktop photo of the Remote SDR Pluto SDR with its Raspberry Pi 5 controller, along with a second Pluto SDR being controlled by GNU Radio Companion running on a laptop.

Simple GRC program providing a 33 cm 5 MHz split all-mode repeater on the Pluto SDR.

Screen capture of a browser window showing Remote SDR loop back test. Boom headset plugged into laptop: Speak into microphone and hear voice in headset. It works!

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 23/10/2025

Testing a RF Limiter with a Yaesu VX-8DR HT: Was able to find 4 RF limiter candidates for use in a 902 MHz full duplex transceiver and tested one unit’s limiting function using L2 TX Po at 446 MHz. TL:DR, the tested limiter works as hoped! More information and […] [Original post on mastodon.radio]

Desktop photo showing the Yaesu VX-8DR with antenna connection leading to RF adapter, 30 dB high power attenuator, RF adapter, 10 dB SMA attenuator, and ZX47-55 RF power sensor attached at end. Wires lead to the Arduino and 2-line display.

Desktop photo showing same line up but with the AEL MW16301 RF limiter in line next to the Yaesu radio. The limiter does not allow high power to pass through (and instead reflects it back to the source).

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 21/10/2025

Thinking about a 902 MHz transceiver based on the ADALM Pluto SDR using a set of printed circuit board filters and a RF circulator to combine the TX and RX paths together at the antenna (supporting full-duplex comms). Measured two sets of 902 MHz circulators […] [Original post on mastodon.radio]

Desktop photo of the RF circulator test setup, showing ADALM Pluto SDR (controlled by SATSAGEN) connected to a dual RF circulator through path with RF terminations on the third and fourth RF ports. A second dual-circulator is next to the one being tested.

A SATSAGEN screen capture showing through path insertion loss from 70 to 3000 MHz. There is a low-loss portion of the curve in the 900 MHz band. The through path for the transmitter also offers harmonic rejection to the second and likely third harmonic signal levels.

SATSAGEN screen capture showing reverse isolation of over 60 dB in the 900 MHz band. This offers very good reverse power (failed antenna) protection to the transmitter stage in the proposed 902 MHz transceiver.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 18/10/2025

Today’s Music Festival Attire: A green shirt with a T-Rex dinosaur with the statement “Make Billionaires Extinct”. Background is a ringed planet and stars. #MakeAStatement

Photo of a green shirt with a T-Rex dinosaur with the statement “Make Billionaires Extinct”. Background is a ringed planet and stars.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 13/10/2025

KK7B 144/902 converter LO update: Setup the HP1121A RF probe to walk down the LO lineup and found a gain stage with only +2 dB gain. The resistor to VCC is 560 Ohm instead of 100 Ohms as the other amp stages have installed. Will find a 100 Ohm resistor and […] [Original post on mastodon.radio]

Modular RF amplifier "schematic" showing RF input on the left and RF output / DC input on the right. Amp needs DC blocking capacitors for both in/out connections.

Photo showing test setup for measuring RF signal level through the LO source and multiple / filter chain. HP1121A RF probe is connected to TinySA-Ultra spectrum analyzer through a DC block. Sorta-short ground lead ties probe to circuit ground for measurement. Setup is not too precise, but good for relative measurements. (Does amp have gain, output greater than input?)

Photo of KK7B 144/902 converter schematic with mark up for probed RF levels at input and output of RF amplifiers. All amplifiers on board are the same with a capital A marking on them (model # unknown). DC levels are marked on top side of amps on schematic and pointed out difference on amp marked "Mar-6". That feed resistor is 560 Ohm (and not 330 as indicated on schematic). Other modular amps all have 100 Ohm feed.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 12/10/2025

A few additional thoughts on the KK7B 144/902 translator boards: 1) Add connectors to the RX and TX filter chains on a bare board and use it as a Pluto SDR front-end on 902 MHz. With pi5 & Langstone SW + RX LNA, TX PA and T/R switch yields low-cost 902 […] [Original post on mastodon.radio]

Bare circuit board with printed RF Filters for 902 MHz (separate TX and RX paths).

Photo of Mini-Circuits RF Mixers showing 4 SBL-1X circuit boards with mounted mixers and a tube of surface mount RMS-25MH mixers (tiny!).

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 11/10/2025

The converter’s oscillator/multiplier stage basically works (although a-bit low on power level). Board draws ~208 mA at +12V which seems reasonable for the number of active devices installed. Frequency looks good at 758 MHz monitored at the tacked-on BNC jack […] [Original post on mastodon.radio]

Broad band capture of the local oscillator output spectrum as measured on the TinySA-Ultra. Will be monitoring the spurious output level once the desired 758 MHz output is corrected to be closer to +7 dBm.

Closer in spectrum capture for the 758 MHz local oscillator signal. Seems close to be on frequency (and verified that tweaking the trim-cap adjusts the frequency. Will leave frequency set alone for the moment and focus on optimizing 1) LO power level and 2) LO spurious/multiplier quality. Have some work to do on both as next step.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 11/10/2025

Ran across an unfinished late-80’s project that would benefit from some time to poke around on: SHF Systems 144/902 MHz linear translator boards (3). Two boards are bare and a third has the oscillator built up that might be checked out with current test gear […] [Original post on mastodon.radio]

Photo of KK7B 144 to 902 Transporter boards and documentation. Two boards are bare and one has the oscillator section built up. Will it work?

Close up photo of the KK7B 144 to 902 MHz transporter oscillator section. Curious to see if this fires up (and if not, how much effort to get this stage working. Need to look for some amps and mixers to fill out the rest of the board's stages.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 10/10/2025

Further investigation of the EtherKit Si5351A shows it is a useful (square wave) signal source from 4 Hz up to 200 MHz when controlled by SATSAGEN. This is a versatile clock source that will add value here in the home lab. Monitored source output with the […] [Original post on mastodon.radio]

Desktop photo showing an Arduino UNO controlling an Etherkit Si5351A clock source with output to a 5 dB pad, a DC block, a 2-way splitter with the RF sensor connected to one port, and the second port leading to a 10.7 dB coupler feeding the TinySA-Ultra spectrum analyzer, and the through line leading to an RTL-SDR USB stick at the top of the image. The RF power meter is reading -5.7 dBm, 26 Deg C.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 06/10/2025

Getting a little closer to demonstrating a low cost RF scaler analyzer based on SATSAGEN PC software. Have Si5351A clock as transmit source through VHF RF filter demo path to Pluto SDR receiver. This is a little squirrelly setup-wise at the moment, but […] [Original post on mastodon.radio]

Desktop photo of the (almost) low cost RF scaler setup, showing EtherKit Si5351 clock source feeding into a 2-way splitter with TinySA-Ultra analyzer showing sweeping RF source. Left side of splitter is coax leading to a VHF bandpass filter, then into Pluto SDR receiver port. Arduino UNO is driving Si5351 source via commands from SATSAGEN PC software.

Poor quality photo showing SATSAGEN PC software running on Win10 ham computer. Spectrum Analyzer with Tracking function is running and sweeping RF source from 100 to 200 MHz. In-line bandpass filter is tuned to the 2 Meter (144-148 MHz) band. The filter shape can be seen on the scalar analyzer display. It works!

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 02/10/2025

Exploring lower cost alternatives in measuring RF filter frequency response… Added a RTL-SDR to my SATSAGEN controlled scalar network analyzer setup just to see if how well it might work. TLDR: It works pretty well! Isolation between TX/RX is improved with […] [Original post on mastodon.radio]

Photo of a RTL-SDR receiver stick testing a Mini-Circuits low pass RF filter with a Pluto SDR as a transmit source.

Screen capture of SATSAGEN running on the Ham Win11 PC, with the software controlling the RTL-SDR receiver and Pluto SDR transmit source. A frequency sweep is running from 70 to 1200 MHz. The plot shows the reference line at 0 dB and the classic low-pass filter shape below that the Mini-Circuits SLP-300 filter provides (attenuating frequencies above the pass band up to 300 MHz).

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 24/09/2025

Have seen some recent posts about high frequency scope probes and thought I’d share a short post examining the frequency response of a Agilent/HP 1121A RF probe. This probe is stated to have a 3 dB bandwidth of 500 MHz. I found that my unit works to over 650 […] [Original post on mastodon.radio]

Desktop photo of the test setup showing NanoVNA-H4 VNA, BNC-T with load on port 1, RF probe connected to BNC-T second port. VNA port 2 cable routed to HP1121A probe output with a SMA DC block in that path. VNA shows a blue trace with a reasonably flat S21 response curve.

Close up photo of the NanoVNA-H4 S21 response curve showing 2.5 dB/division response. The blue line stays within 1 division up to over 650 MHz. More photos at the qsl.net website.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 23/09/2025

Si5351 Phase Noise Checks: Looked at the Etherkit eval board 14 MHz clock phase noise at 1 KHz and 10 KHz offsets using the TinySA-Ultra phase noise measurement function. Also measured my Wenzel 100 MHz sine-wave +13 dBm output test oscillator as a comparison […] [Original post on mastodon.radio]

Desktop photo showing Arduino UNO, Si5351A clock board, 10 dB pad, and TinySA-Ultra spectrum analyzer. SA is displaying close in phase noise of the clock zero output.

Screen shot of theSi5351A's 1 KHz offset phase noise shows approximately 84 dB down from the carrier.

Desktop photo of the Wenzel 100 MHz test oscillator connected to a TinySA spectrum analyzer via a 20 dB attenuator. SA is displaying close in phase noise of the Wenzel test oscillator.

Screen shot of the test oscillator's 1 KHz offset phase noise shows approximately 83 dB down from the 100 MHz carrier.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 22/09/2025

Set up Digilent Analog Discovery 3 w/ Waveforms SW to monitor the Arduino UNO to Si5351A clock generator interactions. Will investigate the existing UNO’s programming with the Si5351A board and then create a LabVIEW VI to mimic that process using another I2C […] [Original post on mastodon.radio]

Desktop photo of the Arduino UNO wired to the Si5351A clock generator evaluation board with three wires (GND, SDA, SDC) routed from the Digilent Analog Discovery 3 breakout cable. Monitor wires are connected to the clock board's headers, allowing control from UNO and monitor from AD3 to happen at the same time.

Screen capture of the Digilent Waveforms software showing I2C capture and decode on the Win11 ham PC. Lots of messages are shown, with some longer and some very short. More leaning ahead!

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 21/09/2025

Looking at a couple of I2C interfaces to connect a EtherKit Si5351A eval board to the Win11 PC with LabVIEW. First is a JOVA TIMS-0102 packaged module that looks good outside (but with LOTS of hand-soldered surface mount joints inside). Next is a Dimax SUB-20 […] [Original post on mastodon.radio]

Photo of the Jova Solutions TIMS-0102 interface module with the lid removed. Simple USB interface module with both I2C and SPI interfaces via DB front panel connectors. Unknown if this works or not...

Close up photo of the Microchip PIC18F452 controller and an associated FTDI interface. Soldering appears to be 100% hand soldered. Was surprised to see this quality inside a commercially produced product. Wonder if it works? Will test to see...

Photo of a Dimax SUB-20 USB to multiple-I/O types interface board. This covers the desired I2C interface for my Si5351A square wave generator project. Wonder if it works? Will test to see...

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 18/09/2025

Si5351 CLK1 Output: Adding two low pass and one high pass filters cleans this right up. Spurious are now > 50 dBc! #HamRadio #TestEquipment #Si5351

Photo of test setup with three blue SMA filters added to the CLK1 output to remove harmonics and sub-signal junk. All spurious are now more than 50 dBc.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 18/09/2025

EtherKit Si5351A (Rev C) Mystery Solved: Root cause for the board’s +3.3VDC rail short to ground was the presence of J10 installed on the CCA. This shorts out the supply due to the use of the ECS-250-8-30B crystal which has GND connections on non-crystal […] [Original post on mastodon.radio]

Screen capture of the ECS-250-8-30B package showing non-crystal package corners are connected to package ground.

Screen capture of Rev C schematic showing J10 (Osc Power) connecting X1 Pin 4 to +3.3VDC board power. J10 must be removed to use a ECS crystal on board and installed if a crystal oscillator is used instead. My board has a crystal and had J10 factory installed. This shorted out the +3.3VDC regulator. (Am sure it was not happy, but did not SMOKE.)

Quick photo showing EtherKit Si5351A board supplying 14 MHz output on CLK0 output.

Quick photo showing EtherKit Si5351 supplying 175 MHz on CLK1 output. Simple example program used for this test.

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 18/09/2025

After having this EtherKit Si5351 for a few years (and knowing that I was never able to make it work), finally got around to troubleshooting it today. Found that the +3.3VDC rail was shorted to ground (with the regulator working with all jumpers removed/cut) […] [Original post on mastodon.radio]

EtherKit photo of the Si5351 board. A blue CCA with multiple pin headers and surface mount parts installed.

Photo of the EtherKit Si5351 oscillator board on top of a printout of the schematic. Only a couple dozen parts on this simple surface mount board. Board has a short from +3.3VDC to GND at the X1 oscillator component.

Photo of the EtherKit Si5351 oscillator showing installed SMA jacks on right side. Hoping to get this running and make some use of it after being stored for a rainy day troubleshooting session (which happened today - and it was not even raining here). J10 jumper is cut to isolate X1 power from the +3.3VDC power bus. Getting closer to working!

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 15/09/2025

Looking at a hand-me-down circuit board that appears to be a RF detector function on a small double-sided circuit board. It has parts soldered onto it, but the main IC (marked C14 9CZ) is a mystery. Any guesses? Once IC is identified, can proceed with adding […] [Original post on mastodon.radio]

Photo of a small copper clad circuit board prototype circuit above a hand drawn schematic based on the circuit card. Circuit appears to be a RF detector with a SMA jack feeding a 50 Ohm resistor stack, then a resistor divider feeding Pin 1 of an unknown 8 pin small IC with marking of C14 9CZ on it. Connections from the board feed to a 9-pin D-Sub jack on the board.

Photo of the layout of the board which appears to be cut into copper cladding with some sort of mill. There are numerous via connections from top to bottom layers that do not have (and need to have) wires soldering them together. The gold SMA-jack is on the left and the 9-pin D-Sub connector is at the right. There are two resistors on the back side (not shown).

Close up photo of an unknown 8 pin IC with laser marking of C14 9CZ in two rows on it. The DC supply bypass parts are to the left of the photo. Open via holes are present (missing their solder-through connections). Can you identify this IC? Have looked for over an hour with no success. Mastery Part!

Photo of a diode from divided RF input to V+ with third leg to GND connection. Suspect this is a reverse/over-voltage protection part...

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Gary @N8DMT @n8dmt.mastodon.radio.ap.brid.gy · 10/09/2025

Slow Work Day = RF Power Meter updates. Added a SMA jack to the Mini-Circuit ZX47-55 analog output voltage line on the stand alone RF Power Meter. This supports adding a monitor scope to view real time power level changes, AM modulation, and RF switch […] [Original post on mastodon.radio]

Photo of the stand alone RF Power Meter with a SMA-Jack coax pigtail soldered onto the Arduino's A1 analog input. This allows connection of a scope or meter onto the raw detached RF power output voltage. First test in this image.

Close up photo of the coax pig tail connected to the A0 input and two GND pins on the Arduino LCD shield.

Photo of the completed "added jack" configuration showing the SMA connection secured off to the left of the LCD display. This modification supports using a scope to view detected RF levels in real-time (not the 1 Hz power number reading on the LCD display). Useful for AM and Pulse demodulation tests!

Screen capture from Waveforms SW showing scope display of ZX47-55 detector output with an AM modulated signal applied. Log detection yields a different demodulated waveform compared to a typical linear detector...

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