Entries tagged with “bitx20”.

Look at this crew ;]

Burt Nate Homer Roy Jim Dave Vern and John at the last weekly tech party to he held at Verns. Another fun and productive meeting!

The only thing consistent is a constant state of change
What a great tech party. We’ve had a great year!
All things must change, and so with the Wednesday Night Tech party. Vern announced that there is a health issue in his family and he is needed at home.
We all appreciate the marvelous host that Vern has been since the establishment of the BiTX20 builders group and the ensuing Solder Social which grew into the Tech party.
Thank you, Vern! We wish you all the best and pray for a full recovery.
Burt and Nate studying intensely!

Burt and Nate checking out the data ... note all the cool digital toys surrounding them. Click the picture for a closer view.

The Tech Party needs a new facility. Perhaps two? Vern says he can probably host one meeting a month after a bit. Which got me to thinking, what if we did three tech parties a month, one at Verns, then one near the east side and one near the west side? Perhaps a ‘triangle’ with Vern to the North and spots to the Southwest and Southeast. That way everyone will have one tech party per month that is ‘closer’ to them.
Before we got the BiTX project going I had started doing the Technet from guest locations – Local amateurs homes, restaurants, parks, etc. So moving around isn’t a new concept to the technet, shouldn’t be a problem for the tech party, don’t you think?
This is a large metropolitan area and so there will never be any one location that is more convenient than another. There will always be someone excluded because of distance. This way I think more people will have a chance to participate.
SO, if you have an idea for a facility please email n4lgh@147120.com or leave a comment on this article. This coming Wednesday we’ll probably take the night off – if we haven’t secured a facility by then everyone is invited to my place in Winter Garden until we find locations more convenient to everyone else.
This past Wednesday was a lot of social but we got some great discovery done in the microprocessor world. I gave Nate a couple of PIC chips to play with on his new proto board and encouraged him to pick up a PIC programmer. There was some really god discussion on the various development kits available for the PIC, AVR and STMicro uP’s.

Coming along nicely! the crystal filter is installed, but needs to be tested, as is the audio amp. Go Vern!

The BiTX project is coming along nicely for most. More of us are conquering the VFO, although we will need to do a session on the VFO circuit again to learn to recalculate the other capacitors in the system to accommodate different values of variable capacitors.
I found this awesome calculator online. Can someone get this figured down to C code? This is nice –
Most of the guys have populated the crystal filter and audio amplifier portions of the board but haven’t tested them yet. Jim has almost the entire board stuffed, he’ll be mounting it in a chassis soon! This is going to get exciting when we start putting these things in enclosures and getting them on the air!
The next meeting, wherever we are, will be spent mostly on testing. We’ll have the IFR to run them on and several of us will have lab power supplies to run them with. It will be a hoot, ya’all come on out now, ya hear? ;]
Tracy N4LGH


Jims Coverage

Jim used a larger value variable capacitor, so his VFO has more frequency coverage ...

Well, mostly conquered
Jim has a capacitor that is way more than 50 PF. So it’s time to learn series and parallel capacitance, resonant circuits and probably something else. No, I’m not going to dive into it here, admitingly I have to learn that myself! However, there do seem to be some calculators out and about that should help.

As you can see in the picture his VFO covers a lot more than just the 20 meter band. For some that may be just fine. What it does, though, is limit the ‘resolution’ of your tuning dial. The radio does have a nice fine tune adjustment to compensate for that.

This is the disk!

This is the SD 'disk' that we used to update the Flash (U-Boot) on the NGW100. It's an older card that the older U-Boot could handle.

Another big breakthrough at the Party was the flashing of Das U-Boot. Yah, we have flashing Das U-Boot! Dave sucessfully formatted an SD card the way the NGW100 likes, we moved the Atmel Flash Upgrade Utility to the SD card, and told U-Boot to load the image. It was cool! Took seconds flat and now reports U-Boot 2010.8.

This is important to anyone who has an NGW100 as this upgrades the ‘bootloader’ in the board to be able to read 2GB cards. The U-Boot bootloader that ships preloaded in the card won’t read the cards with large blocks. We’ve been stuck with older cards, usually 64 and 128 MB. Dave had one card that was 1GB with the small block setup. That’s the card we ended up using to load the flash image.

Vern, Ralph and Roy

Vern, Ralph and Roy doing what we do at the Tech Party!


We had quite the group for the first Wednesday of the month. Remember there are several other groups that meet the first Wednesday of the month so the Technet and Tech Party are usually kind of light. We did great this week though!

Remember EVERYONE is invited to our group – you don’t have to be involved in any of our current projects to attend. The social value of this group is immeasurable! From time to time the group leader does focus the attention of the group to a specific point, but other than that this is definitely a multitasking group.

Jim, Nate and Bert

Jim, Nate and Bert working on Jims VFO - conquored for the most part, it's on frequency but covers more than the 20 meter band because he used a larger variable capacitor. What we need to do next is calculate the new capacitors to set his bandwidth.

Ejhngofarten nkne hbgrlop

Roy and hbgrlop being entertained by some of the technical magic that happens at every Tech party!

Jims VFO

Jims VFO with Vern and Dave in the back

Let the knowledge flow

It is absolutely the best thing in the world to have a room full of Elmers an aspiring techs. Here is Jims VFO showing the large range of coverage he has, with Vern and Dave in the background digging in to their projects.

Jims VFO

Here's Nate working on Jims VFO. Note the neat setup Nate made with some protoboards and a neat 'laptop' type case he found at Skycraft. This week his creation sported individual switches for each of the power busses, 12, 5 and 3.3v regulators and a lot of spirit for the next run of mods!

Here is a closer view of Jims setup and the frequency. Also note the power supply showing 80 mA current at 13.8v. Keep in mind the entire circuit is not powered, just the VFO and display.
See you next week!
Come out to next weeks Tech Party! Log in to the net on 147.120 Wednesday at 8pm if you can’t make it in person. There’s always something good going on and now n then there’s munchies! Never be afraid to bring munchies – you become an instant hero of the 147120 Tech Crew ;]

We have been having a difficulty with the VFO section of our BiTX20’s … I’m scratching my head and wondering why we’re off frequency but with the right spread. Enter Mario …

DUH, I never checked the values; we had discussed that there were no 560 PF NP0 caps in the kit, but I totally forgot. Mario asked, ‘where did you get the caps?’ Well, the builders had used the 56pf caps in the kit and it makes sense why none of them were on frequency.

We are making an order for 560 pf caps, but they will not be NP0. They will be very close, but we can’t find NP0 caps. It’s fine tho, the ones we are looking at have less than a decimal of a PF over a huge temperature range.

If you’d like to get in on that buy please contact Dave KC4ZVW or myself in the next few days and we’ll get you in on the pile.

I feel stupid, sorry I didn’t look at that, but at least we know where to get replacements.

Tracy N4LGH

This weeks Solder Social was a great learning experience!

Yeah, I’ve started calling our BiTX20 building group the Sewing Circle with Soldering Irons. A Soldering Circle! What’s the difference? A bunch of old bitties sitting ’round gossiping and trying to make ourselves sound important to one another. It’s a hoot!

We saw firsthand what a couple of picofarads can do to / for a filter. The BiTX20 transceiver front end has a nice bandpass filter that doubles as the front end filter for the receiver and the driver filter to the 5W PA. It’s a fairly important part of the circuit because if it’s not tuned well, performance will suffer on both receive and transmit.

First off, the documentation is a little contradictory to the markings on the board. In the photos of the board layout, the filter capacitors are marked 68pf. They are also 68pf in the supplied schematic. BUT, on the board itself, and in the written text, it calls for 33pf. In the text it states one could use either a 33 or 47 pf. We figured it was because of the tuning range of the inductors.

Some of us had already built the filter with 39 pf caps that appear to have been substituted for unavailable 33’s or 47’s. Maybe it was in the middle of the range?

Contemplating the filter

Dave KC4ZVW had his Filter / Amp assembly ready first so we applied power and checked voltages per the instructions – everything was within tenths of volts, fantastic!

Next we went about setting up the Tracking Generator and Spectrum Analyzer. Thanks to Tom KD4WOV for helping us get that set up. I’ve never done that on a filter before.

Wow, what a mess! It had huge insertion loss and a lousy pattern. But after fiddling with the caps a bit Dave found a nice compromise between pattern and insertion loss.

At last, a decent pattern with low insertion loss!

Mario KU5E had used 33pf capacitors and came up with completely different results. He ended up removing the 33’s and putting in the 39’s. What a difference! We spent quite some time fiddling with the pattern and insertion loss with the 33’s and were never able to get less than 15dB of pure wasted signal.

As usual, Vern Ki4SDY was an excellent host and generously provided some caffeinated beverages, although I’m not sure this group really needed any stimulants ;]

Best we could get with the 33pf caps!

Now this is a good pattern!

Once I finally figured out how to take a picture of the spectrum analyzer screen these shots came out pretty well. Next week I’m going to bring my desktop tripod so that I don’t have so many blurry shots. These screens sure tell the story. We were able to get these tuned to with a dB or so insertion loss.

Overall the filter looks like it has better than 20 dB overall rejection, with less than 3dB insertion loss in about a 100 kHz passband. We don’t think we have this filter optimized – I will likely try several values there. Perhaps a variable?

a higher resolution shot of the pattern

Everyone is invited to our weekly Solder Social at Verns barber shop in Longwood, near the intersection of Ronald Regan Blvd and Church Street. Vern is the second door east on Church.

Hope to see you all there next week!

Last nights build meeting was great! We’re officially batting 1000 on the FLL kits! Jims took some rework on the solder connections to the chip socket, but we were all functional before we left.

We were amazed at the accuracy of these little buggers. One of the units was within 3 Hz at 10 MHz! We were able to accurately read frequencies up to 60 MHz. It was fairly sensitive from 20 MHz and down but we needed to pump up the output of the signal generator as we went up in frequency. But it was very accurate right up to the point where it couldn’t lock any longer.


The next part of the build is the bandpass filter and amplifier for the receiver. Some of us have elected to start on the Power Supply section of the PA so that we have a source of 12v for testing. Since there are provisions on the PA board for ac operation most of us are taking advantage of that.

Anyone is welcome at the build party! We have a couple extra ‘seats’ and truly enjoy sharing at this meeting. I would have to say we’ve had the most pleasant and productive build sessions I’ve been to in decades.

Each week we share sources of parts, play ‘show n tell’ with ‘stuff’ we’ve acquired, and generally just chat away in between questions comments and statements about the project. We discuss the circuit, the nuances of the mechanical construction and even ponder programming code.

All in all, it’s a great meeting and I can’t wait ’till the next one. See you all then!!

Tracy N4LGH

Meeting #1

This was held on 30th of Nov 2009.

Talked about tools needed to assemble the project, soldering and the assembly instuctions that we are going to use.

I mentioned that the discussion list was on YahooGroups which can be found from here.

Learning about tools


Other pictures


David — KC4ZVW

KC4ZVW, Dave, commented on my last post and ask some basic questions that started me thinking. Does it work? It leads me to why I am building the BitX20. I have a strong desire to learn electronics. This project allows immediate feedback on each section that is completed.

Crystal Radio

When I completed the audio amp, I needed to find an input source to check it out. Travis, my son, and I built a crystal radio with an audio amplifier circuit. This Fox Delta design is made to learn with and has the ability to separate the audio amp from the crystal radio. I fed the signal into my BitX and it worked. I have already received the local AM station through my Bitx. DAVE, it works.

Then I built the Mic Amplifier. By jumping a signal and powering the audio amp section I was able to hear my own voice through my small amplifier setup. Yes it does squeal when you get the mic near the speaker just like the real audio setups, and yes I played with all the feedback noise I could create. That worked too.

I have completed all soldering on the radio. A radio is an oscillator that allows us to throw electromagnetic waves through the air and catch them at a different location. This radio has two oscillators. One is a carrier oscillator that is a 11.00001 Mhz, and the other is a variable oscillator, VFO, that is close to 3.0 Mhz. When combined, the frequency that adds up is near 14. Mhz, the 20m Band! Well , there’s a problem Dave. First, I have both signals oscillating and measurable although the VFO is only variable by 3.5 Khz. Not enough to qualify as a VFO. On this radio I will need a couple of hundred Khz to cover a portion of 20m phone band. I soldered in a different variable resistor and air variable capacitor and the oscillations stopped. I will go back on that change. Second, I am unable to find the 14. Mhz signal. I have unbalanced the modulator to let the carrier signal through to the mixer near the VFO and where I feel it should be, it ain’t.  There I is. Stuck again.

Dave, does it work? Wonderfully! I am learning radio theory, trouble shooting, soldersmoking, and burning my fingers. LIFE IS GOOD. Oh… the radio, well I’m sure it will work when I am done. 73


Bitx20A Alignment in Progess

Bitx20A Alignment in Progess

Hello, I have been graciously allowed to post some thoughts about my ongoing relationship with a Bitx20A.

Where to begin… my name is Robin and I am a homebrewer. It all began when I found out you could build your own and learn about how a radio really works. No more black boxes with multiple-multifunction knobs and buttons for me. I was completely innocent, without a clue of the power this would have over me. Before I knew it I was a frequent-flyer at SkyCraft. Late night sessions at the dining room table with smoke wafting about as I ponder the perplexities of mixed oscillator signals filtered through polycrystalline mineral wafers. I still remember the joy of hearing the audible oscillations of my first Colpitts, but I digress. Consider the consequences, it is not for the faint of heart. If this is the path you choose, know what lies ahead. Capacitors that disintegrate before your eyes, signals that disappear after just a small tweak, and the frustration of “dang, I followed the directions and it don’t work”. I warned you!

That said, I will post a few photos and discuss my Bitx20 from time to time. I want to thank Tracy for his inspiration on the Tech Net and David for his Web expertise that allows me to be here. 73