Radio Society of Greater Bixby

Jim K5LE won the prize for most miles traveled from his QTH 8 miles North of Pryor OK, choosing a 12V 2A wall plug over a 1A USB charger. Brad WA5PSA chose the USB charger for bringing the most meters. Scott’s hamburgers welcomed us into the back ‘Party’ room set up with rows of deluxe wood grain Flea MKt tables and chairs where we displayed several LifePo batteries; some other items to be measured, and a Xiegu G90 20W HF rig brought by Deb K5DBE and Sam KJ5BJR.

Several digital Voltmeters agreed the 100Ah LifePo featured was right around 13.35V right then, (they tend to vary from 13 to 13.5 just sitting there depending on remaining charge). An old Radio Shack analog meter (with a needle and a scale) said 12.5 which is why you use a digital to determine max charge at 14.4 Volts.

One of Brad PSA’s digital meters wasn’t acting right, possibly due to a weak battery. An old faded red digital from Harbor Freight, bought back when they were 4 bucks instead of the current $7, showed 13.4 and then while you watched, 13.45; 13.5; 13.6; 13.7, and back down. It’ll be dissected (with a hammer) and brought to the next mtg for inspection.

We never did get around to calibrating all the meters against a stable Voltage (the LifePo), a known resistor of 1k; 12mA current or the 120V line., instead discussing towers, rotors, wind load, and how well the Xiegu G90 performs for it’s modest $465 price. Bring your meter to the next (Thurs 28 Aug) mtg and have it judged against others.

Where: Scott’s hamburgers in downtown Bixby, 08.28.2025, from 7-8 PM. Be early if you want to eat.

Yes, that’s right, there are two (2) kinds of Meters, analog and digital. Shown above is the Radio Shack lookalike to the Simpson 260 VOM which I bought in 1968 because it was cheaper than a Simpson, and said it was more sensitive, 100k Ohms per Volt rather than 20k.

Voltmeters such as this analog by Radio Shack are made by inserting a large resistor in series with the delicate, in this case, 10 microamp movement. That’s 0.000 010 Amps. For the 10 Volt scale the resistor is (100k Ohms per Volt) one Megohm. 1,000,000 Ohms. Hey, what’s the color code for a 1 Meg resistor. Nevermind, in this case it’s a 1% tolerance with the value printed right on it in English. There’s a bunch of 1% resistors in there, selected one at a time by the function switch.

Digital meters are another animal. It’s complicated and more than this article can explain. The good news is they’ve gotten really cheap for fairly good ones, and tend to be more accurate than analog. When you want to charge a LiFePo to 14.4 Volts without going over 14.6 because the BMS will disconnect, a digital meter is the thing to have. Let’s compare our meters Thursday.

We meet twice a month, 2nd and 4th Thursdays at Scott’s Hamburgers in downtown Bixby, a couple blocks from 151 and Memorial. Go a few blocks East and some South until you see the ARCH pictured above, and then half a block West (toward the setting sun).

Order at the counter if you like and then head left and into the back room. Program starts promptly at 7PM so come early to order and eat. The club features No Dues, No Business Meeting, and a tech program every month.