Let's Build A Field Strength Meter
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- Опубліковано 24 лют 2015
- I follow Richard's, KB3VZL, February 2015 QST (page 71) article about building a field strength meter into a DVM. He built the circuit to fit inside a Harbor Freight digital volt meter. You can get these free at Harbor Freight if you have the right coupons.
I also use my new ISO-TIP battery powered soldering iron.
www.iso-tip.com
Three capacitors, two diodes and a pot is all that is needed. Build this on a small perf board and it fits easily inside the meter.
Parts:
0.05 uF Cap
470 pF Cap
0.01 Cap
1N34 Diodes, you need 2
50K trim pot
hunk of perf board
switch
connector for antenna
I don't believe I have ever seen a circuit built on an upside down perf board! Whatever works right!
What a fantastic simple project for a "ham in waiting for the ULS to get updated". Thanx, Randy. Am enjoying learning from your experience.
I have made it with 1n4148 diode, and set the meter on 200milivolts range, its working fine, Cool Project. Thanx sooo much.
Thanks Randy for another handy project and the tips on getting the meter. This mod should work with other meters even an old analog. Nice that the switch lets one use it as a field strength meter or multimeter. Good job.
Thanks, Randy, that's a great way to use an old meter that we have lying around. After a while they tend to breed like rabbits - I must have collected eight or ten of them over the years, both analog and digital, most now in various stages of disrepair. BTW, you probably know that the Iso-tip soldering iron isn't new. I had two of them back in the mid 1980s. Mine were made by Whal and were powered by nicad batteries, but neither lasted long as I recall. The tips kept breaking, especially when dropped, and the batteries had too little capacity. Maybe they're using nimh cells now. They were, however, good for field repairs if care were taken in their storage and charging.
I have an endfed wire antenna that I use on several of the lower bands. Transmitting 100 watts max output, so of course there is a bit of RF in the shack at times. A field strength meter is very useful in sniffing the RF and helping to know how to arrange cables, power leads, installing ferrites, counterpoise, etc. in order to keep RF away from keyboard, mouse, etc. It may be a little "old school" but I simply placed a germanium diode across the terminals of a Simpson model 374 microammeter. No antenna lead necessary- it is plenty sensitive. Just move the meter around to hunt the RF hot spots. Very handy indeed. (And no batteries required, haha...)
Inspiring. Thanks for another great lecture.
What a great job, Randy! I love what you're doing, helping keep ham radio a hands on hobby. So many new hams today can't build anything and know very little about electronics.
Nice project. Time to dig through the parts bin.
great video, this will be my first Electronic project. Exciting!
Great as usual...gotta love the "lava light"...
Thanks Randy well done ! I built one and it works great much more sensitive than my old heathkit field strenghth meter picks up my 1 watt two meter HT at a distance of 25 feet with a 19 inch whip on both . I did not have 1N34 diodes but did have two 1N295 germanium Diodes I don't know what the difference is but they worked fine I am thinking that just about any of the germanium glass diodes will work ok . I also eliminated the 50 K pot shown in the QST article just put a 100 k resistor there across the .01 cap figuring the meter has several Voltage ranges and in this case would not be required . 73 Bob W9RAS
Randy, great job! I'm planning on making a FSM, and your video was the first to pop up. I like the design of adding this into the HF meter. Very cool!
Very cool project!
Hi folks, don't knock Randy for putting those parts through the opposite side of the board, it does have its advantage, because the printed circuit HOLES are copper, and RF can jump to each of these because they are so close causing interference from stray RF signals outside the meter, and adding a miniature DPDP switch to disconnect both the + and the -- will keep the user from electrical shock when measuring high voltages.Thanks Randy, great job.
Randy, love all your videos. New ham (KK6VZD) in Yuba City just breaking into playing with building electronic projects. Yours was easy for a beginner and it was a kick to see it actually function when I finished it. SInce the only toggle switch I could find was a double pole I used the extra pole to add an LED to the top to indicate when the circuitry is engaged. Only question I have is what to set the 50K pot to, not in your video or the original article. I think I ended up adjusting mine to 10k. Next step: put together another FSM from different plans using analog meter.
I have one of the original's from qst and it uses an analog 1ma ge meter. Its pretty sensitive. Good that this one uses germanium 1n34 diodes for best sensitivity. i'm going to build one inside this same box with the analog meter, but it will add a little .96inch digital display. I'll use an i2C circuit and probably an arduino nano. So it will be an analog/digital hybrid.
A very nice little project Randy. Thanks!
good project, but need more tests! and check exact frequency field that this small circuit can detect, THanks
Good idea to install it into a DVM. Project for tonight! 73 VA7GTE