Power meter for 1.2ghz
n7issham
Mike Lewis
There are a few options. Probably the easiest and lowest cost is one of the online milliwatt meters with the little OLED display. Used with appropriate attenuator(s) they work up to several GHz. Mine is accurate to around 1dB, usually better.
Here is an example of the milliwattmeter
1-8000Mhz OLED RF Power Meter -55～-5 dBm 1nW～2W Power Set RF Attenuation Value | eBay
These work quite well. Finding the optional PC software is not easy but I did and can send it to anyone in need.
You can also use this or any milli-wattmeter (I have built my own with Arduino) with a surplus RF coupler. Using a bidirectional coupler you can measure both directions without disturbing the main RF cable. Use a coax switch, or 2 meters, or swap the meter-to-coupler cables to measure forward and reverse.
Couplers:
https://www.ebay.com/itm/133921430208 is an example of one that works on 1296 at high power levels. These come in many frequency ranges and power levels. Prices are highly variable so shop wisely. This one at $55 is decent priced, you can find them for less sometimes and often for a lot more. They usually work well outside of the published frequency range but the coupling attenuation will usually be higher. That is normally desirable for high power but does mean you have to measure it at the desired frequency to get useful absolute readings. This requires another calibrated meter or known set of attenuators to compare with. https://www.ebay.com/itm/162651436894 shows a printed graph for 400Mhz to 1.4GHz. Here is an example of a (uni)directional coupler with graph etched on it. https://www.ebay.com/itm/203735461587. This one covers 950Mhz to 2GHz. Flip it around for reflected power. Like most things on eBay, patience rewards the right part at the right price. You can find bi-directional versions (aka dual directional) online but they are fewer so harder to find at a decent price. I use several of these.
Sensors:
In my Arduino RF wattmeter I use the ADL5519 dual log power sensor board with bi directional couplers to monitor every VHF antenna SWR and power. I have built several versions over time with different displays, some are embedded in VHF RF amps like my 1296 60W amp. More at K7MDL2/RF-Power-Meter-V1: RF wattmeter and Band Decoder on Arduino or PSoC5 modules with Python desktop monitoring and control app. Remote operation via USB Serial or Ethernet (new). (github.com)
This is one of several single channel log power detectors, rated to 8GHz.
https://www.ebay.com/p/3014117890
This is my preferred sensor good to about 10GHz and has 2 channels on the same chip. I use the temp sensor as a rough indication of the ambient inside my remote cabinet. It is essentially 2 8318 on a single chip with better specs especially in relation to each other.
ADL5519 RF Power Detector - sv1afn.com
When you add your own calibration for each band and coupler/attenuators you can get highly accurate results.
You can use just a voltmeter with these sensors and convert the voltage to dBm. Be sure to use the right attenuators to keep them in their operating range. These higher frequency sensors are a bit harder to use that way since their outputs ranges from about 2.2V at no signal (~60dBm or less) to 0.5VDC at 0dBm. Putting an Arduino and display on is a lot easier. Even easier is the prebuilt power meter such as the one I linked above.
One of the pics is a M5Stack Arduino in a self-contained LCD+Battery module. It is cabled to a small box with 2x 8318s inside. I created Power and SWR meter scales and a calibration screen. Later I moved the ADL5519 dual sensor and digital displays and other CPUs for better AD specs, lower noise, better ADCs, and better voltage references.
Mike Lewis
K7MDL
CN88sf and EL87sm
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Mike Lewis
I should add you can use several PCB kit couplers/detectors and LED bar graph meters such as from W6PQL
LED Bar Graph Meter (w6pql.com)
I think W1GHZ and DEMI also have similar items.
Ed Cole
I use a Bird43 meter with E-series elements that under read by 20% at
1296. A 10E or 25E element would work for you. If you can find a 10K
its rated at 10w 1100-1800 MHz. Probably cost at least $150 for meter
and one element (check e-bay).
Another method is to obtain a 1296 directional coupler which one can
take the coupled output thru attenutators (if needed) to drive a Power
detector board (ALC Detector made by W6PQL). I would not get a coupler
rated under 20-dB coupling. The power detector board uses sm resistors
to reduce drive for the diode detector. Contact Jim-W6PQL directly for
your specific needs.
You can buy the boards assembled for $20 from:
http://www.w6pql.com/parts_i_can_provide.htm
mw directional couplers for 1w with sma connectors are common to find
from mw dealers in $20-$40 rang. Maybe someone on this list, even?
I use two MECA 900-MHz cellular couplers with 40 and 50 dB coupling to
sample fwd and ref power on my 600w 1296 amp. I tested them using 10mw
with my HP432A mw power meter. the HP432A is hard to find (especially
the sensor and its cable for under $250).
GL
Ed - KL7UW
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