Radio Society of Greater Bixby

In the old days when you got your license at the FCC the test was a lot more difficult than asking a multi guess question, things like ‘Draw a 5 tube radio schematic.’ Nowadays the hardest question might be, Which tube draws the most plate current, the 50L6, 35Z5, or one of the 12 Volts?

We meet 2wice a month, 2nd and 4th Thursday, and as usual (April 9th) it’ll be at Scott’s hamburgers in downtown Bixby 7PM to 8:15PM. If you come a bit early you can get a great hamburger for dinner. After the initial Show & Tell of whatever people bring (last month it was a 1948 handy talkie – working) we’ll discuss 2 magnificent electronic designs, the five tube radio, and the single transistor TouchTone (reg PatOff) oscillator. Of course both designs grew from Ed Fleming’s diode tube; Lee DeForest’s Audion amplifying tube, the SuperHet radio receiver layout, and later, William Shockley’s 1947 point contact transistor. Edwin Armstrong was smart and helped, but I’m not sure if General Robert Sarnoff was instrumental in anything other than buidling RCA. Oh, the Pentagrid thing? A superheterodyne receiver utilizes a Local Oscillator and Mixer to convert the incoming RF to an Intermediate freq. The pentagrid conveter does it all in one tube, that first one with all the grids. Count ’em.

Early radios by Bill Halligan like the Hallicrafters S38B had only five (5) tubes, just like the one in your mother’s kitchen. (My 1960 Hammarlund HQ145X had eleven (11) tubes, and was a better radio.) The old (early 1970s) Kenwood 520 five band (6 b. in the S and SE versions) transceiver had 3 tubes, a driver and 2 finals, plus 73 transistors. Draw that schematic. OK, just list the many functions. Don’t forget the (standard) Noise Blanker circuit.

Hey, you’re going to the Green Country Hamfest right. Saturday at 400 Veterans Pkwy Claremore.

Tom NMH has switched back to his old callsign, WA5MAZ from the mid 1960s. At the Thurs 03.26 meeting he brought in two (2) Motorola handy t – well, back then they were more like lunch boxes, the one from 1958 mostly transistors (except driver and final tubes – little ones, 1W out), and the other from 1948, one year after Shockley and the other two guys invented the point contact transistor, It was all tubes, a bunch of them, like 19 little ones, mostly mounted in replaceable/fixable modules like the one shown above, part of the crystal multiplier chain that makes 146 Mc from a crystal in the 12 Mc area. Tom has used the old ‘Lunch Box’ Motorolas on the 146.91 repeater. It’s a little trick to do that since Int’l Crystal Co. doesn’t make crystals any more, and that’s another story about Tom, using a freq synthesizer chip to program not only a 12 Mc crystal, but also a PL tone. We asked him, Why don’t you just buy a Baofeng, but I guess he likes to display his talents

Kenny KJ5EKW brought in a heavy 14 VAC transformer and asked about making a power supply. The linear Astrons start with a little more voltage that comes out around 21VDC. One idea was to use the 7812 type regulator chip which can regulate with as little as 2 Volts difference. (14VAC times 1.414 yields 19.7; less 1.4 for loss in hte bridge rectifier; now 17.3; less maybe a Volt of ripple with a large (80,000 uF) filter capacitor; down to 16.3 that could be regulated to the 13.8 – 14.0 DC range.

We were going to compare RX sensitivity on Chinese H/Ts, but instead, we spent most of the hour measuring TX output and using a Spectrum Analyzer (Tiny SA on Ebay for $68) to check for spurious output. Shown above is an anomaly, second, third, and fourth harmonics that weren’t there.

Two Baofeng UV5Rs (the x3 model) measured 5.3 and 5.4 Watts out on 220. That’s good. They were bought about a year ago on EBay. Deb and Sam, DBE and BJR, both had Baofeng UV25s that output at stated ratings.

Every transmitter has a Low Pass filter on the output to restrict spurious at higher freqs. FCC spec is a 40 dB reduction. Deb DBE’s TID Radio H8 showed the second harmonic at negative 50 dB, similar to Mike KI5YX’s Japanese HT at negative 53.

Rich ZQG related a story from the beginning of WWII how Leo W0GFQ and friends were able to mass produce crystals for Army tank radios, their first contract spec 60,000 xtals in a few months from a small town (Council Bluffs) in Iowa that enabled our guys to communicate faster and more easily than the opposition using tunable radios. Their secret technique was not allowed to be kept secret back then so other Americans were later able to do the same.

Entering the outbuilding behind the house you were greeted with an enormous Ham collection of a lifetime, and atop shelves on the far wall, dozens of 2M cavities (those round things on the top). Motorola experts would know if those stacks of radios were Maxars or Mocoms, but all the rest of us could do was look in amazement and then turn to another group of items to ask, Are these dummy loads, only to be told by an expert, No, isolators, or circulators. What’s that. There was a small stack, maybe half a dozen, of Kenwood commercial UHF mobiles. You could find familiar Ham items too such as MFJ accessories. And parts. Parts. Parts. And a scope or two. And . . . .

Tom KJ5NMH found a 1960s era HT-200 handie, a dual freq model (Motorolas in those days were often single, dual, or sometimes 4 freq variations) and took it home for a pittance (and put in a home made freq synthesizer – also PL tone synthesizer – that he designed himself.) (It’s the size of a crystal can, not quite an inch square.) Here are two boards he has made recently, the postage stamp size freq and tone generator that fits inside an H/T, and the slightly larger multi freq board for mobile rigs.

Kenny KJ5EKW and Rich WA5ZQG each found what appear to be new in box 220 rigs (Chinese) and are working on antennae for them. Paul WB5ANX was prominent among volunteers helping to make the sale successful. At the end of the morning, although many items were taken, the sale had made only a dent in the inventory.

Both Mike KI5YX and Phillip KI5PFV brought their new Baofeng DMR HTs, the new DM32 model with lots of memories and larger size. In the Amateurish (see what I did there?) pic below, Mike’s 55 dollar black and green HT is on the right. Phillip spent $67 to get the clear plastic see through model (and some extra antennas and stuff).

As advertised, Mike YX also brought along his Baofeng programming computer. Kenny KJ5EKW had his new TD Radio H3 Plus (2 of them for $80) that had somehow gotten into BRICK mode. Mike tried resetting it to factory specs (didn’t work) and then reloading the firmware. The radio (in BRICK mode) didn’t respond. Lesson learned: Careful when buying radios that offer BRICK mode. Mike put a variety of 2M and 440 freqs in the other one.

Kenny EKW won the Silver Plated door prize (see pic above) although a condition of winning was to donate two bucks to another club (RSGB does not have a Treasurer).

Deb K5DBE brought her new MeshTastic Node, an 89 dollar RAK WisMesh pocket V2 with internal battery, GPS, and small LCD display. You talk to it through an App on your phone. Deb set it up herself (with guidance from Jeff AI5ME) and has been reading texts from all over town. See the pic above – the green HT thing on the left. No PTT button, and no speaker. Your PHONE.

Next mtg is Thurs 26 Febr, 7PM at Scott’s hamburgers in downtown Bixby. Left side, way in back..

Mike KI5YX brought in a 220 J-Pole made with 3/8 in copper pipe (2/3 the length of a 2M J-Pole). The ‘U’ at the bottom was about 13 in tall, and the half wave radiator above was around 26 inches. There used to be a 220 Net on one of the 220 repeaters, but not lately.

The slightly revised meeting format allows a brief Show and Tell from each person prior to the Tech subject program. Mike held up the copper J-Pole and the rest of us had a few comments. A common concern on antennas was the advertised gain figures, often distorted by ISOTROPIC gain; ground reflection gain, or plain lies. Next mtg is on Lincoln’s BDay, Febr. 12th.

Tune in Wed and Fri on the B.A. 146.91 repeater at 7PM for the Conspiracy Net where you can talk on a variety of subjects.

Mike KI5YX: Really? That old? Tom KJ5NMH: Yeah, we weren’t even teenagers yet when this one was new. 1958. Tube finals, a 6146 driver and 6550 final, both laid down horizontal in the aluminum heat sink in back. International doesn’t make crystals any more so I added a freq synthsizer, you can see it under my fingers at the top, and a PL tone generator too. It’s also there, but so small you can’t see it in the picture. Ten (10) channels now. Big problem is there’s no hi/low power switch so it’s a hundred (110 W) and ten Watts out all the time. It’ll smoke your average mobile antenna. I got another one from the 60s that’s all transistor. Put a freq synthesizer in it too, but totally different than this one. Has a two wire serial input to the crystal socket from outside with a digital freq display.

Next mtg is 4th Thurs at Scott’s hamburgers in downtown Bixby. More on how antennas work (input impedances) and what controls gain (G5RV and OCFed not included).

Right as you went in the door at the Henryetta Hamfest Saturday, Jason W5HP had this nice looking Yaesu 950 HF and 6M rig for which he was asking $500, not much more than a new Xiegu G90 that doesn’t have even a quarter as many buttons and knobs and runs only 20W.

Some other interesting items included a gold plated D-104 microphone (they also had a regular chrome D-104). There was also a Yaesu 991A put back in the box marked 1 kilobuck. Wonder if you could get it for less.

They had a whole box of Vibroplex paddles. You could probably buy one and then suggest to friends that you know code really well. (Change the subject really quick after that.)

They had 28 tables and not all of them were in use. With increasing awareness and growing Ham population in the Tulsa area, this one is going to get more popular, and it’s only 42 miles from Bixby.

The Henryetta club website is (Crossroads club) CARCradio dot org.

Larry W5LQF answered the most Jeopardy game questions Thursday night and took home a 1995 Radio Amateur’s Handbook prize. Sam KJ5BJR came in 2nd and won the 1972 edition (which has a bunch of Vacuum Tube specs in the appendix). Questions (or answers) included What’s the ARL callsign, W1AW, and What’s the color code for a (very conservative) 33k resistor, Orange Orange Orange. Note: Sam BJR and XYL Debbie K5DBE brought with them a new 10W H/T and 50W dual band radio they’d won at the TARC Christmas meeting two days before.

Kenny EKW’s Kenwood 7400 2M rig puts out 28W on high and 5W low power. Internal dissipation (Volts x Amps less RF output) changes from 38 Watts to 37 Watts (i. e. It gets just as hot on low power as it does on high.) We measured both input Volts and Amps and RF output Watts of an old Kenwood G-707 dual band to find it uses just over 5 Amps at full 27 Watts out on 2M, and also 5+ Amps putting out 22 Watts on UHF (and also the smae 5 Amps with only 14 Watts out on 462.5625 (that’s FRS Ch 1). No, we’re not going to use it there, just checking. At lower power levels it gets much less efficient, like a 2 Amp draw at 3W out.

Note: This Tx efficiency thing is not just some esoteric bit of information, but real life physics of like, How Many Watt Hours do I need to run my Yaesu 857 at 15 Watts of FT8 mode for six hours at 25% duty cycle in a portable operation (battery powered). Answ: A lot more than 15% of 20A (full power) with those parameters.

Before the digital rigs (mid to late 1980s and 90s) an HF rig in receive mode might use half an Amp or less. The early Kenwood 520 (had 73 transistors) with the tube heaters turned off (there was a switch to do just that) ran only 340 mA in Rx mode. My digital Kenwood 440 with a hundred memories and general coverage receiver takes 1600 mA in receive. That heavily impacts efficiency if you’re thinking POTA this weekend with a LifePo battery, and reducing power output to only 15W of FT8 mode doesn’t save as much as you’d think. Put these specs on paper (FM or 100% duty cycle mode): 100W uses 17.5 A, 50W uses 12 A, 25W takes 9.5 A, and 10W still takes 6.5 Amps. You could subtract the 2.4 A at zero output to get exact Tx efficiency, but you get the idea, a quarter of full output (17.5A) takes over half as much battery power. (Figure your duty cycle, maybe 10 to 20 % and the number of hours you want to work. Note: A brief stint might be accomplished with a much smaller LifePo than those car battery size hundred Ampere hour things bc you can use them down to near zero without severe damage, unlike a lead acid.)

Heisenberg, Schrodinger and Ohm are in a car. They get pulled over. Heisenberg is driving and the cop asks him, “Do you know how fast you were going?”

“No, but I know exactly where I am” Heisenberg replies. The cop says, “You were doing 55 in a 35.” Heisenberg throws up his hands and shouts, “Great! Now I’m lost!”

The cop thinks this is suspicious and orders him to pop open the trunk. He checks it out and says, “Do you know you have a dead cat back here?”

“We do now, darn you!” shouts Schrodinger. The cop moves to arrest them. Ohm resists.

Photo by Kevin KC0KJK.