It's a simple PCB design that has pads for SMA edge connectors at each end, a ground plane around the whole board, and pads for placing SMT components in arbitrary combinations to build up filters, attenuators, and amps for RF … var AFS_Server="www"; Dummy loads like this are used on base station setups, or test benches when you want to measure power output without actually broadcasting your signal. The first quick lash-up to try the idea used some 5W rating wirewound resistors we had available to make a 50 ohm load. Some of them being of gigantic measurements, some of them are even drowned. A transceiver can be tested and configured without radiating a radio wave by using a dummy load. It could be used as a Dummy Load too but you need to connect a 50ohm Resistor Load terminator with suitable power ratings to the output terminal of the attenuator. Create an account in a few clicks or log in to continue. Resources listed under Dummy Load category belongs to Technical Reference main collection, and get reviewed and rated by amateur radio operators. The home of ALL things Radio - CB, 11m DX, Amateur, PMR446, PLD, Network and Data. Or you can do the simpler thing -- find an RF ammeter. Special flange mounting RF metal film resistors like the Florida RF 32-1037 make an ideal resistor for a dummy load. Works a treat. T he 50 Ohm dummy load is an indispensable accessory for any radio transmitter. A dummy load is used at the output of a transmitter for testing purposes. This would make an ideal terminating resistor for HF use for the Terminated Inverted U antenna to work at the UK legal limit of 400W even for higher duty modes such as RTTY or FT8. It’s used to allow full power output while testing or experimenting without radiating a radio frequency signal. Since I didn’t have one, a hunt was on to source the parts to build a dummy load. This all came from the picture i put up and a joke after the post lol. The photo of the plot shows the return loss from 3 MHz to 50 MHz. If the power output is 1 W, the peak RF voltage will be 10 V. The detector output will then be about 9.5 V and the signal to the power meter is −10 dBm. Contact Chris Moulding, G4HYG via Email address hidden from spambots for more details, comments or feedback. The answer is yes. Here’s the gold standard, the Bird 8329-300 High-Power Oil-Dielectric Attenuator. The final values shown in the schematic diagram were proved after calculation and test. Welcome to the Charlie Tango DX Group. First, everyone who puts a signal on the air should have, and use, a dummy load.With older equipment, there was a lot more knob-fiddling … Since I developed the Terminated Inverted U antenna I have had many questions mainly asking where to source a high power 390 or 400 ohm resistor to run the antenna at the legal power limit for amateur radio transmitting of 400W in the UK. The prototype in the photo had 50V ceramic capacitors and thin PVC insulated wire as they were available. I used a metal alloy box which was a bit small but a bit of ingenuity made it fit. StevieG, Alan - Mirror Man and Swadeyboy like this post, Victor and Alan - Mirror Man like this post, Alan - Mirror Man and Tristar like this post, NUBSTER and Alan - Mirror Man like this post, NUBSTER, Victor and Alan - Mirror Man like this post. Elecraft DL1 Dummy Load Kits are a great addition to any ham shack. These dummy load attenuators can get very pricey. This is an BNC-type attenuator. var AFS_Page="DetectName"; I'm uncertain, if not perplexed by the last couple of responses to this posting, but will do my best to resolve or at least understand them. RF Powermeter / dummy load By Guy, de ON6MU rev1.2. This particular BNC attenuator is a 50 in/out with an attenuation of 3dB, but the attenuators are available in other impedances, connector types and Production versions will use high temperature wire and 2kV ceramic capacitors. I calculated that if I added capacitance to ground from the resistor junctions it was possible include the inductance of the wirewound resistors as components of a low pass filter. No muss, no fuss. High power dummy loads are expensive diy with a bit of water and a halve teaspoon of salt ! ... On this webpage I show a method to make a resistive termination or dummy load that uses the inductance in wirewound resistors in a lossy low pass filter to extend the frequency range to cover the full HF radio spectrum. Probably many times! The circuit uses the inductance in the resistors and the capacitors as a low pass filter with a cutoff frequency around 30 MHz. Dummy-loads are easy and relatively inexpensive to build yourself, using one or more suitable resistors. Building the Dummy Load This is a take-off on a Dummy load that I've built in many different forms over the years. Using the resistors in series on their own the impedance match was OK up to 4 MHz but became too inductive above that. Which works great. Unlike an antenna, which Join today and claim your own unique World Famous CT Call-sign, New Member and Call sign Request (Issued). RF dummy load using wirewound resistors by Chris Moulding, G4HYG. Power measurements require a dummy load. High quality panel mount wirewound resistors are available at low prices compared to thick film resistors. As the radio frequency power is converted to heat, interference is avoided. But more importantly is making sure you are using an exact 50 ohm test variable that won't change like an antenna system might. For special designs the manufactures can produce different custom Z inputs/outputs. Optionally you can also use an oscilloscope to measure the RF voltage at the Dummy Load (not shown, also dangerous voltages are present!). If four resistors are used the ratio between the three capacitor values should be the same. Here is a nifty way to re-purpose a useless low pass filter into a useful 50 ohm RF dummy load. This would need a resistor rating of 750 W to absorb the power at the worst case antenna match. It is submerged in oil to allow somewhat extended operation during tuning or … I do have one at… You choose the RF connector; type N or UHF female are the most common and flexible. This device has a maximum dissipation rating of 250W and an SWR of less than 1.15:1 from LF up to more than 2GHz. The dummy load display case. var AFS_Url="DetectUrl"; Attach the transmitter through the tap to a dummy load where the output voltage can be read directly using a di- ode detector and DVM as shown in Fig- ure 6. If an accurate 50Ω dummy load is available in the shack, we can measure RF power by measuring the RF voltage developed across the load. On this webpage I show a method to make a resistive termination or dummy load that uses the inductance in wirewound resistors in a lossy low pass filter to extend the frequency range to cover the full HF radio spectrum. This dummy load consists of 20 1K 1% 1W resistors connected in parallel to make a 50-ohm 20W QRP dummy load. // -->. If your club has never tried a club build, this would be a good first project for several reasons. The Build: I have already seen a bunch of examples on how to build a dummy load with an abundance of same value 1/2 W resistors. We welcome all radio enthusiasts of all knowledge levels. This wattmeter is based up on a dummy load of 50 ohm which can handle 50W. This is about the size of your typical old school home radiator and is rated for “2kW continuous.” It’s $2923 in the Bird Online Store, but can often be … A search on the Farnell™ website found a Bourns™ 50 ohm 150 watt terminator 6 mm x 9 mm x 1 mm thick at a very reasonable price. Figure 1. Useful range is from DC to 150MHz. up to 12 watts. The basic design for this dummy load comes from the RF Biscuit project by @georg ottinger. The metal box helps with any heat build up. 2x 100ohm 100watt panel mount resistors wired in parallel. You’ll need 30 dummy load resistors — 1.5k-ohm, metal film, 2-watt resistors soldered in parallel. So if you are playing around with radio transceivers an RF load is a nice addition to your set of tools. You’ll need a small 3/8-inch rubber grommet, to serve as a vent, as well as about two feet of #18 tinned solid wire. For starters, it's a safe way to test your transmitter without worrying about QRM'ing the bands, and you know it's a perfect match for the transmitter. A simple RF attenuator is shown in the photo below. The prototype worked OK at 100W for a short test but the 50V capacitors would soon fail at higher power levels. This RF-power meter combined with build-in dummy load is made to measure power levels starting from a few milliwatt up to 50 watts (or more if suitable components are used and an avalanche sinterglass diode). Those examples to my eyes looked like a complete mess. It's possible to buy 100W thick film resistors but the price goes up faster than the power rating. (If not only for me but maybe others also.). Dummy Loads Test your transmitter the proper way—with a dummy load from DX Engineering! Testing four Arcol HS50 100 ohm 50 W wirewound resistors in series on our HP network analyser showed that the inductance affected the required impedance match at higher frequencies as expected. The new resistor low pass filter design works so well that we are going to manufacture it instead of the 50W thick film resistor unit for the same price. If you change the resistor value or type you will have to change the capacitor values to match the resistance and inductance of the resistors used in the low pass filter. RF dummy load using wirewound resistors by Chris Moulding, G4HYG. We offer fan-cooled, air-cooled, and oil-filled dummy loads (also known as dummy antennas) from the most-trusted brands in ham radio, including Ameritron, Diamond, MFJ Enterprises, Palstar, and Vectronics. [size=46]Just warning beware this style and specification dummy load from a reprital cb shop or ebay seller go for about £25/£35 so when my mate and I saw them for £15 on ebay new and aUK seller thought we'll get a couple, they turned up guess what ,from China ,so my mate decided to test his one before use, well it wasn't even 50ohms like its suppose to be and was suppose to handle 30w it could only handle 5w when I checked mine it wasn't even connected inside so basically if we never check we would damaged our equipment, so if it looks a bargain beware [/size]. The roles of RF attenuators, terminations, matching pads and loads are important in radio communications test and measurement, as well as in equipment interconnection. Elecraft DL-1, MFJ-261) to submersion in non-conductive oil baths (e.g. As admin cant be bothered to put my contribution to making a dummy load which I ask for to be put in this section. My Pulse Width Modulated AM transmitter project required dummy loads to match the load impedance of the RF power stage (50 ohms) and the Pulse Width Modulator (12 to 16 ohms). Hi all, I've come across several occasions where someone requires a RF Dummy load for checking/testing their radios. The QRPGuys Dummy Load/Power Meter is a 50 Ω, 12W rated terminated load that is useful tool when setting up or diagnosing most low power transmitters. MOTOROLA 58C9860F01 Dummy Load Termination 500W 50 Ohm DC - 1GHz RF RM250-100 4.5 out of 5 stars (5) 5 product ratings - MOTOROLA 58C9860F01 Dummy Load Termination 500W 50 Ohm DC - 1GHz RF … Using 1.5mm sq electrical cable. The need in this question is merely for a DC load, so kettles, bathroom heaters, light bulbs etc suffice here, where they would not for RF. var AFS_Account="00037964"; Gary WA7KKP Salt water dummy load. The Minty Load DIY Version The minty load is basically a QRP+ dummy load with a RF detector circuit that allows a standard Voltmeter to be used to measure RF power out, ideal for anyone adjusting homebrew QRP Transmitters. Back to main Cross Country Wireless web pages. This allows RF power up to 30 MHz to flow through the resistors and be dissipated as heat. Victor if you look at one of my post in the Antenna section its says " Admin please feel to post this in the Information section but give the video maker Gary (Offplanet)the credit" the reason I ask Admin to do it was when I posted the Q code list Lee put it in the info section so I thought it was up to Admin to do it ,but also I got a bit of a impression that some thought I was talking cr*p and was more interested in making ones with diodes and heatsinks which cost money ,my info cost next to nothing and was use by radio operators (not just hams)years ago in fact it's common physics and not really electrical or radio . Further tests running a constant 100W carrier into the resistor low pass filter circuit for ten minutes showed that the resistors were dissipating the power evenly and that the temperature rise indicated that the diecast box used would be suitable for running at the full rated power of 200W. I made my own 50ohm dummy load using readily available parts from CPC. RF dummy loads from Pasternack are available in two categories, feed-thru and RF load. How many times have you been told that you can't use wirewound resistors at RF? Well this was my attempt at building a dummy load. With the use of an inexpensive 11 Megohm multimeter, and a little math, you can measure the power output into the 50 ohm load. A dummy load is an indispensible tool for the novice as well as expert ham.