This is very useful test instrument that every radio amateur should have in the shack and can be built for next to nothing. Let's look at this very handy instrument and its uses.
A passive RF field strength meter is a simple, un-powered device used to detect and compare relative radio frequency signal levels. It uses an antenna to capture RF energy, germanium diodes to rectify the AC signal into DC, and a sensitive analog micro ammeter to display the relative output level without requiring a battery.
Core Components
Antenna: A telescopic whip or tuned dipole to pick up local RF radiation.
Germanium Diodes: Low forward-voltage components (like 1N60 or OA47) used for RF rectification.
Analog Meter Movement: A highly sensitive zero-center or standard 50µA / 100µA panel meter.
Capacitor & Potentiometer: Optional bypass capacitors to filter RF and a variable resistor/potentiometer to attenuate strong signals.
Common Uses
Checking transmitter output and relative power.
Adjusting and comparing directional antenna radiation patterns.
Testing the efficiency of baluns, tuners, and antenna setups.
I decided to build two of these instruments. In this issue we will be looking at the passive RF Field Strength Meter version.
Diagram
Bill of Materials
2 x Germanium Doides (IN34, OA70, OA90, IN60, BAT43 or 85)
1 x 470 pF (471) Cap
1 x 10 K Potentiometer
1 x 50 uA Meter
2 x DC Power Posts (Red + Black)
1 x Piece of Veroboard (PCB)
1 x 500 mm Stiff Copper Wire (Antenna) or old FM Radio Antenna
1 x Instrument Cabinet
1 x Potentiometer Knob
Construction
I am not going to go into detail as the diagram provides more than enough information to construct the meter successfully.
1. Reminder: Do tune into the DMR-ZA Net this evening at 19h30 SAST
Herewith a list of different equipment / apps and images that cross transmit / receive the DMR-ZA Net on a Tuesday evening. (Click on images for larger view.)
1. ZS1I 49355 AllStar Hub Network which incorporates Echolink. (ZS1I-R)
2. DMR / DVSwitch /AllStar Bridge (TG 65522)
3. ZS1I MMDVM Digital Repeater (TG 65522) 1. Reminder: Do tune into the DMR-ZA Net this evening at 19h30 SAST 4. 145.550 Mhz Analogue Simplex RF Link Mossel Bay area.
5. DroidStar / VoxDMR Applications for DMR TG655
6. ASL3 to Mumble Bridge PC (Mumble Client) as well as Mobile Phone (Plumble Client)
7. BrandMeister - Hoseline Application (PC or Mobile Phone - Receive only.)
8. DVSwitch Mobile Application (PC or Mobile Phone)
9. Many Analog-Repeaters and Links are connected to the ZS1I Hub Network on a daily basis. Some of these analogue repeaters will be connected to the ZS1I Hub Network on a Tuesday evening and they might also be linked to other repeaters country- and world wide. So why not link up with your local analogue repeater. You might just be able to connect to the DMR-ZA Net on a Tuesday evening at 19h30 SAST.
Finally: There are an abundance of means illustrated above to connect to the DMR-ZA Net on a Tuesday evening at 19h30 SAST. The DMR-ZA Net is an open net and all radio amateurs are welcome to join / connect to the net. Brian ZS5BR is the net controller and I would like to thank him for professionally conducting the net each Tuesday evening. Highly appreciated!!
2. Would WSPR work on DMR?
No, WSPR (Weak Signal Propagation Reporter) will not work over a DMR (Digital Mobile Radio) voice/data channel. They use completely incompatible modulation schemes, bandwidths, and timing structures.
Why WSPR and DMR are Incompatible
Modulation Type: WSPR uses continuous phase 4-tone Frequency Shift Keying (FSK) at an ultra-slow 1.46 baud, designed for analog SSB audio passbands. DMR uses 4-level and 2-slot TDMA Time-Division Multiple Access with 4FSK phase modulation at 9600 baud, processed by proprietary voice codecs.
Bandwidth: A WSPR signal occupies a tiny 6 Hz slice of spectrum (inside a ~200 Hz to 2.5 kHz audio window). A DMR channel requires a strict 12.5 kHz channel spacing.
Transmission Length: WSPR transmissions are precisely timed and take nearly two full minutes (110.6 seconds) of uninterrupted carrier shifting per burst. DMR cuts transmissions into rigid 30-millisecond frames and timeslot bursts.
Decoding: Standard WSPR decoders (like WSJT-X) look for specific FSK tone sequences and timing relative to UTC seconds. Passing a WSPR audio tone through a DMR digital voice codec will completely distort and destroy the weak signals, turning them into noise or data errors.
3. Ham Radio Etiquette: Do's And Don'ts On Digital Modes [2026]
Amateur radio, minding the gap refers to the crucial practice of leaving a short, deliberate pause (typically 3 to 4 seconds) between transmissions (Overs). This is essential for digital voice and data networks to properly reset, synchronize, and pass traffic without causing system-wide dropouts.
Here is exactly why we mind the gap:
Network Synchronization: For digital voice modes like DMR and C4FM/Wires-X, data travels via servers, nodes, and internet gateways. The gap gives the network’s VoIP protocol time to release the digital stream, clear buffers, and allow other stations to key up.
Preventing "Clipping": If you press your Push-to-Talk (PTT) button and immediately start speaking, the first syllable or two of your transmission is often swallowed by the digital handshaking process. Waiting a second prevents your voice from being clipped.
Allowing Break-Ins: Leaving a pause between your overs gives other operators a chance to break in. This is especially vital in emergencies when another user needs to pass priority traffic.
Avoiding "Time-Out" Timers: Many digital repeaters and network nodes have strict time-out timers (e.g., 3 minutes). Taking a breather resets these timers, preventing the repeater from dropping your transmission mid-sentence.
Thanks to Chris M9UCW For The Thumbnail Image.
Thumbnail Image For Illustration Purposes Only
73 de Mark 2E1CEQ Ham Radio Gadgets YouTube Channel Please Like And Subscribe
4. The Internet Re-Invented - - - - Internet Killer?
In this video, I build a Reticulum RNode and prove that completely different radios — LoRa and Wi-Fi — can communicate through a hardware-agnostic networking stack. Reticulum routes traffic above the radio layer, automatically bridging dissimilar frequencies, interfaces, and modulation types. I then run it over Wi-Fi HaLow Haven nodes to create a long-range, encrypted IP mesh with no traditional infrastructure. Finally, I push it further by running ATAK across the network, demonstrating a fully open-source, decentralized communication stack in action.
"Ham" started as an insult — and the frequencies amateurs were handed were dismissed as useless. So how did they end up crossing oceans, building their own satellite, and talking to astronauts?
This is the strange — and completely true — history of ham (amateur) radio, told as one story: from an invisible prediction on paper to a hobbyist satellite in orbit.
You'll meet James Clerk Maxwell and Heinrich Hertz (who thought his own discovery was useless), follow Marconi's first signal across the Atlantic, and finally find out where the nickname "ham" really comes from — and why the famous "three friends" story is a myth. You'll see how the "useless" short waves turned out to bend around the world off the ionosphere, how amateurs made the first two-way transatlantic contact in 1923, built OSCAR 1 — the world's first non-governmental satellite — and went on to talk with astronauts in space. Plus India's own proud amateur-radio story: Gooptu, Bose, the Amateur Radio Society of India, and a Prime Minister with the callsign VU2RG
00:00 Ham was an insult? 00:35 The invisible waves (Maxwell & Hertz) 01:22 Marconi crosses the Atlantic 01:47 The first home radio builders 02:30 Radio's first traffic jam 02:50 Why they're called "hams" 03:30 The band the experts called useless 03:53 The ionosphere changes everything 04:15 Relay: the birth of the ARRL 04:36 First two-way Atlantic contact (1923) 05:23 Hobbyists build a satellite (OSCAR 1) 05:48 Ham radio reaches space 06:16 India's amateur radio story 07:06 The real pattern of the story
This guy (ZS1I) is getting like the YouTube video posters with his
"What's in the Box?" I received several requests to please continue
with the series "What's in the Box?" From all accounts these postings
were of great interest to some of the readers of the previous Blog. I will oblige in this regard and will from time to time post
images and information of what is in the boxes I receive. I am also
looking at providing a review of equipment, components, modules etc. I
have not yet decided in which format to publish these reviews. It will
either be done on this blog or via a YouTube channel. Now I must say I
do not regularly buy items via the Internet. So do not expect many
posts in this regard. Some of the equipment in the boxes is not new so
do not expect the latest amateur radio state of the art equipment to be
unboxed.
Lets get cracking in unboxing this item: (Click on images for larger view.)
