QSOs for Sunday
In theory I am working the Sunday portion of the VHF contest. It is so quiet that even my voice keyer is tired. I spent more time on the phone today than I did making QSOs. (There are a few Q’s today but it is pretty slow.) I started drawing out ideas for another radio project.
The picture is ugly and from my camera phone but that is not really what matters.
I am thinking of building a control box with the following features:
- All for the selection of two different microphone connections (useful during a family station event or with two different types of mics like a headset/boom or headset/handmic)
- Select 1 of 4 radios as the target for the microphone and AF signals
- Select 1 of 4 radios as the target of the CW keyer source
- OPAMPs for the microphone signal going to each radio (each radio can have adjustable mic levels)
- OPAMPs for each microphone input
- Built voice keyer using a micro SDHC card (record it on the PC, play it on the DVK)
- RJ45 connectors on the back of the box (use RJ45–>8pin cables)
- header pin jumpers to allow for different pin connections for different radios
I will likely use an Arduino for the prototyping. I was looking at relays and solid-state relays but N0FP suggested using CD4066 or 74HC4066 quad bilateral CMOS switches.
Clearly I have been more focused on the project than the contest today. (Mouser & Digikey got a lot of traffic from my QTH.)
I think that we have a large Aurora event on the way, shortly after the VHF contest ends, go-figure.
73 de NG0R
QSOs for Saturday
I am working the Jan VHF contest this weekend so there are lots of contacts on 50, 144, 222, 432, 902, and 1296 today.
My son Ben (N2BEN) is also working the contest under the family station rule.
73 de NG0R
QSOs for Friday
I worked PJ4C on 17m RTTY (Bonaire)
http://www.pj4c.com/
73 de NG0R
QSOs for Thursday
I worked F5IN on 80m CW (France)
Coldest morning of the winter season so far….
Right now at 7:45am both of my electronic thermometers are reading -13F (one is -13.8F) making this morning the coldest morning of the winter season so far. The rumor is that we will only warm up to around -5F for our daytime high.
Today is a good day to work from home. (Luckily I am a full-time telecommuter.)
QSOs for Wednesday
I worked PJ4C on 40m SSB and 30m CW (Bonaire)
http://www.pj4c.com/
73 de NG0R
QSOs for Tuesday
I worked VK2DD on 15m SSB (Australia)
73 de NG0R
Class AB amps from cheap parts
Yep, it is ugly…
This morning in between conference calls (yes, working on my day off again) I was I wondering about amplifiers. Specifically about using Class AB, B, or C amps. It has been a while since I have played with push-pull amps so I pulled up some notes from the Internet to jog my memory.
I grabbed a 2n3904 (NPN) and a 2n3906 (PNP) and a couple of DC blocking capacitors with the thought that I would breadboard a sample circuit and. Then I would hook-up my signal generator, oscope, spectrum analyzer, and micro-power meter.
I decided to start simple (no diodes or bias resistors) to take some measurements. I did not remember what kind of power level that I was going to need to switch on the base of the transistors. It turns out that this particular configuration needs about -40dBm to start turning on the base. (I tested it up to +10dBm which is as high as that particular signal generator went.)
- I was seeing about +10dB of gain driven with -40dBm to +10dBm of signal source. The current draw was almost nil which is nice compared to a class A amplifier circuit.
- Looking at the my oscope it appears that it was running in Class AB as I was not seeing any distortion in the sign wave. (I would have guessed Class B from the design.)
- When I looked the spectrum analyzer the harmonics where all very low… around -40dB from the fundamental frequency.
In summary while it did not create a ton of gain, +10dB is still pretty nice when it only took two 10 cent parts and 5 minutes of work. Two of these in parallel would probably make a nice final stage for a QRSS rig running 150-400mW range.
73 de NG0R
QSOs for Monday
I had to get up at 2am for a conference call on my day off so I decided to try to work a little overnight DX.
I was able to work PJ4C on 40m CW, 80m SSB, and 160m CW (Bonaire)
I have not worked a lot of 160m contacts in quite a while, but this was the hardest Q on that band that I can remember. The noise level was incredible and we really struggled to get the Q completed. –But they are in log and it shows up online!
73 de NG0R
Arduino + DDS 60 = Sweep Generator
I am still bonding with the code from the Internet but I was able to make a small tweak and it is now sweep generator running from 1Mhz to 60Mhz. I need to increase the step rate or it will finish about the time I retire but the general principle worked.
I think that there are more efficient ways to handle writing out the data word groups to the AD9851 but I will need to better understand this before I can look at those kinds of things. (crawl, walk, run, fall.)
73 de NG0R
