Tag Archives: homebrew components

Back to the radio

KK6GXG-MakingWavesTo keep domestic peace I have not been building on the Beach 40 non-stop as I might otherwise do and there is a side benefit… By taking some time away from the build I can clear out the cobwebs and refocus on the greater project to check my thinking and my work.

I still need to do testing on a few of the sections. However I have all but two sections assembled with only minor followups. I need to figure out the value of the common emitter voltage limiting resistor on the Audio Amp and I need to wined and connect the two bifilar toroids in the RF Amp.

T_R Switch
Not a literal schematic, just a rough idea

The last two sections to build are the Low Pass Filter and the T/R Switching sections. The bit that I have been burning cycles on is the T/R Switch. I want to do something that consumes the least power overall at-rest, something basic and bulletproof.

My current thinking on the T/R Switching is a pair of relays, one NO and one NC. RX on the NC and TX on the NO. This way everything is normally in the at-rest state and I only need to run one power lead from the TX momentary switch to both power leads on the relays. Since I don’t have the relays in stock I will need to go get a pair. Sounds like a trip to HSC. 🙂

Once I have the relays I will draw up a new schematic for this section and get it posted on the project page.

While not working on the Beach 40, I did do some radio stuff. I picked up some parts for stock from Jameco one day, a bag of varactor diodes, then two days later went back to pick up voltage regulators, a bag each of 5, 9, and 12 volts.

The XYL went with me to a local Radio Shack that is closing down. We picked up a bunch of zener diodes, a pair of bridge rectifiers, and some mechanical connections at 80% off. There wasn’t much left to pick through. I also found a pair of NO SPST relays which got me thinking more about the previously mentioned T/R switching circuit.

I also ordered a few bags of various op amp transistors that are frequently used in radio circuits. Purely a stock order, and I’m pleased to say the parts bins are slowly filling up and I am getting to the point I think I could actually build my next radio without going out and buying any parts. This is a good thing and I’m fairly certain my wife will agree.
Sneak Peak: I’m thinking about a Beach 20…

Also radio, not Beach 40, the beginnings of research on VFOs. I have been looking at a lot of material on VFOs without finding what I am looking for. I want something small physically, low power consumption, as close to all discrete components as possible, all readily available parts, stable, and a wide tuning range. A tall order I think.

20150603_105313
First pencil sketch, next into the lab book and beyond

A first design only slightly out of specifications is this one I worked up from a test circuit diagram from N6QWs VVC page and the NE/SA602 spec sheet. It will be my VXO-X01 build. 😉

An Experiments page has been set up to keep a log of these kinds of long-term projects. I haven’t created the page for the VFO research yet but that will be up shortly after I update the Beach 40 build page.

One other non-radio, well mostly, is the slow planned migration to Linux. I have been wanting to this for a long time but the last time I tried it wasn’t so well planned. This time I am running both Linux (Ubuntu) and Windows (8.0) side-by-side rather than one virtual. It will be a long protracted process this time but it should result in a much better transition.

That’s it for now. Trying to keep the smoke inside the parts where it belongs until next time,

73,
~Jon KK6GXG

40 Meter DSB Coming Soon

Busy weekend for me.

20150530_161129Before moving on to Beach 40 progress, I got something else in the mail. A frequency counter module I ordered off eBay for ten bucks. I am thinking about using it in a future radio project as a digital frequency display.  Not sure what project, but it beckoned to me and I figured it might work out well.

20150530_221434In a related sidebar, I have been doing some VFO research. I have been looking at several options and one that seems simple and efficient is using varactor diodes to replace the air dielectric capacitors in tuning circuits. I have some ten-turn potentiometers and found a good deal on Motorola 68ρF varactors so I bought a bag of 100.

I found N6QW’s website with some great information including a test circuit for testing the tuning abilities of various diodes and transistors. Definitely more to come on this venture after the DSB project is done.

Now, on with our regularly scheduled program…

20150529_164741In the last post I talked about skipping the Balanced Modulator/Product Detector and moving on to the Audio Amplifier.

I built the Audio Amp and got everything all tied in to the panel mount components.

20150529_165009I still haven’t tested the Audio Amp yet and I am saving that for after I get all of the sections built out.

About the time I finished up the Audio Amp the 200Ω potentiometer I was waiting on showed up. With the parts in hand, I moved on to the BM/PD.

20150527_153801The BM/PD build went well. with no real surprises.  The diode ring ended up being laid out in an actual ring configuration with the RF transformer being mounted right in the middle.

The one thing I don’t like about this layout is the really long lead from one side of the diode ring all the way around to the other side of the board to the potentiometer. I don’t know if I can come up with a better layout in a future rendition but for now it should be fine.

20150530_214234One of the first things I started with today was building the interconnect cables out of RG174 coaxial cable and SMA connectors. I considered MMX connectors since they just push on rather than thread on but they are way expensive. I have seen a number of builders use coax interconnects for modularized construction and it makes separation for experimentation much easier.

20150530_220849One cable I made was actually an antenna, a test antenna at least. For testing transmission sections giving them something to radiate out of. By using a receiver near the transmitting device I should be able to copy the transmission. It’s the one on the right if you hadn’t guessed.

20150531_110751Cables, of any kind,  are one of those things that can seem fairly easy to do, but when they go bad, they can go epicly bad and it can be hard to detect. The only preventative effort I know of is to take your time, use a light touch, don’t force things, and pay attention to detail.

I made 4 interconnects, 1 antenna, and one single end cable for connecting to the antenna outlet. It took a coupe of hours, but all of them are solid mechanically, and test to be solid electrically.

20150530_221209After getting the cables done, I hooked up the antenna and one of the interconnects but I still haven’t done any of testing beyond the Local Oscillator.

I have a lot of testing to do but I’m almost done with the modules so I wanted to plug away and finish up the modules.

20150531_143223The last thing I worked on before turning off the soldering iron was the three stage RF Amplifier.

The pic is the first stage, a buffer stage. I started the board with a configuration in mind but by the time I got to the third stage I had shifted a few things around.

20150531_150232One thing I wanted to point out is the spacing of the stages. In this pic I have most of the second stage done and the pads for the third stage laid down. The gaps between stages are for the addition, if needed, of shielding between the stages. This amp is fairly low power so I don’t think it will need the shielding, But I wanted to make the option available.

20150531_161643The third stage saw several pads moved and things reconfigured a little. The yellow leads are the RX Amp Bypass (short lead) and Amplified RF (long lead) lines going to the relay circuit which after a lot of thought this evening will be replaced with cable ports and the relay section will be moved off this board entirely onto it’s own module.

The other bit on the RF Amp board that still needs work are the two bifilar toroids that still need to be wound and installed. It sounds like a lot of work still to be done, but it is getting very close to First Contact.

Thats all for this post. May the magic smoke remain contained in all your circuits.

73,
~Jon KK6GXG

The AADE L/C Meter IIB

If you don’t work with RF electronics the need for an L/C meter may not be readily apparent. If you work with RF, you have likely found capacitors and inductors in the junk pile and played hobb trying to figure out the value, unless of course they were marked.

My first homebrew toroid inductor. Aint she purdy?
My first homebrew toroid inductor. Aint she purdy?

If you wind your own inductors or make your own capacitors the need for an L/C meter is a no-brainer. I bought a cheap Chinese manufactured meter and it was no bueno. No redeeming qualities what-so-ever.

Within the Amateure Radio world AADE (Almost All Digital Electronics)  and the L/C Meter IIB has earned an almost legendary reputation for being just the piece of equipment the homebrew ameture needs.

20150518_173544Being a homebrew ameture and a recycler of electronic components, I decided to buy the L/C Meter IIB kit and build it. The kit itself is very straight forward. Assembly is well documented and easy to follow.

I have been generating a lot of solder smoke lately so I may have an advantage here in assembly speed but I went from shipping box to functioning test equipment in about 4 hours.

20150518_194352Starting with full parts inventory I went right into construction. The parts list is only one sheet and it is very detailed. After checking in all of the parts and tagging them to the parts sheet I fired up the soldering iron  and started melting metal. Filling the printed circuit board didn’t take long at all.

Th20150518_212344e only hiccough was technician error. I got all of the components soldered in, mounted the board in the back of the case, mounted the LCD, and plugged in the battery. When I turned on the power switch I got nothing. I knew from reading the instructions fancy that that a common oversight is that the contrast pot should be turned fully clockwise. When I went to check the pot I noticed something missing, I forgot to install the IC’s in the sockets. Doh!

20150518_215451
A great product that supports a US, family owned and operated business AADE L/C Meter IIB

After installing the IC’s I checked the pot and VoilĂ ! A working L/C meter.

At $100 a kit that looks as simple as this one does you may be tempted to buy a cheaper factory assembled meter. I would strongly advise against it. A comparable factory manufactured meter will set you back at least twice what the L/C Meter IIB will, probably more.

LC meter
Save yourself the time, trouble, and expense of having to return this piece of junk, don’t buy it in the first place

I purchased a cheap meter for $38, paid $6 for shipping and another $8 to return it. Sure, it looks nice but it is complete garbage.

And if you need something else to push you over the fence on this purchasing decision, buying from AADE supports a family run US business that takes pride in the work they do. Now that’s a bargain at any price.

Solder smoke is filling the air as I continue work on the 40 meter Beach 40 DSB transceiver so check the build page for updates. I will be making an update tomorrow!

73 for now,
~Jon KK6GXG

All Aboard the Project Train

Sometimes it is indeed a project train, not just a project; occasionally a train wreck, but it’s early so we’ll hope for the best.

Now that I have built several receivers and a transmitter for 40 meters, I probably should have an antenna that does more than pick up all the RF noise around the shack. The antenna, and I use the word loosely, is nothing more than a dipole of 26 AWG insulated wire strung around the house. While it might work well if the wire was straightened out on a hill top, or even in a backyard, elevated 15 feet or more above ground, in its current incarnation, in a word, it sucks.

Next up on the project block, an antenna, sort of…

I have been looking at several small footprint antenna options like spiral coils that look like those God’s Eye yarn and popsicle stick things you may have made as a kid,  the one in the movies from the 40s when the resistance spy transmitting Nazi secrets and the SS storms in. It looks like a X and has thin wire wound around it.
288And Small Loop antennas that look more like old direction finding antennas on aircraft. And by the way, according to the formulas and general information, for 40 meters, not so small, 10′ diameter.

Now there are lots of variations and tons of experimental configurations to run with, and I do want to play with many of the possible configurations, but I need a stable, small, portable option for the immediate future. Something I could mount on the car, throw up on a pole, or stand up on the back porch, all without much effort. I also need to keep the cost down.

Scan from the 1975 ARRL Handbook, page 606.
Scan from the 1975 ARRL Handbook, page 606.

Enter the Helically-Wound Short Vertical. I ordered some 14 AWG lacquered copper magnet wire and a 72″ long 5/8″ diameter fiberglass rod, I need to learn to make these so I also ordered a How-To book on making composite fishing rods, and I’m in $20 so far. I have all of the hardware items including the 12″ spike for the top. What I don’t have is the variable inductor, or a tuner.

Whooooo Whooooo! Here comes the train.

RollspuleLets start with the one I haven’t done any research on yet, the variable inductor. The mechanics are fairly simple, rotate the coil and the follower moves up and down the coil creating a tap point. As long as the coil is perfectly cylindrical, the follower makes good contact, and smoothly moves down its axis rod, no sweat. he he he, no sweat I only need the one variable inductor according to the diagram so I really need to find out what value I need. I already have several small value iron-core variable inductors so I may not need to make this one, but if I do, it will be a homebrew. These things are a high-dollar item otherwise.

Moving on to the antenna matching unit. I have plans for one that is fairly simple and straightforward, I even have most of the parts on hand. What I don’t have is the variable capacitors. Sensing a theme here? Variable…

cav-167-205-71_lgBA funny coinky-dink on capacitors; while I was doing research on the Small Loop antennas I came across several websites that went into some lengthy discussions on making variable caps. Turns out, they aren’t that hard to make, I even have nearly all of the materials to make several. Not only are they fairly easy to make, but the formulas for calculating the capacitance based on the area of the plates, number of plates, and the distance between the plates is also fairly straight forward.

So lets see where we are now…
I have three receiver and one transmitter for 40 meters. There is an antenna for them, but it sucks particularly in this location. My next project is to build another transmitter, But I will need a better antenna first…

  1. Antenna
  2. Resonator for antenna (variable inductor)
  3. Antenna tuner
  4. Variable capacitors for the tuner

Now, after these are done I can move on to the new transmitter. As a side note, with the next transmitter project I wanted to pump up the power all the way to a couple of watts, not just miliwatting it. I also want to include SSB (Single SideBand, voice) as well as CW so I can incorporate digital modes into the shack. For all of this the antenna really needs to be better than what I am using.

That’s all for now, 73,
~Jon KK6GXG