Amplifiers at the workbench
I decided to go back and revisit a simple Class AB amplifier circuit based upon an NPN and PNP bipolar junction transistor that I worked on a couple of weeks ago. I am not sure what happened but I lost the magic and was not able to reproduce the gain in the circuit. <sigh>
After a bunch of messing around I grabbed a prototype Class A amplifier circuit board that I built back in February 2010. (It is even on an etched board)
The circuit is not very efficient since I am using about 190mA of current @ 12vdc. It is very much a Class A circuit with small signal parts but it has some gain. (The extra resistors are tweaks that I made 20 months ago to tweak the bias.)
When time permits I will need to come back and design a new set of gain stages that are more efficient. Class A is a simple but expensive way to generator power. I need to think about Class B or Class C stages.
73 de NG0R
QSOs for Saturday
I worked VP6T on 12m SSB (Pitcairn Island)
I also worked HK0NA on 17m CW (Malpelo Island)
http://hk0na.com/
73 de NG0R
QSOs for Friday
I worked HK0NA on 10m and 12m SSB (Malpelo Island)
http://hk0na.com/
73 de NG0R
QSOs for Thursday
I worked HK0NA on 17m SSB (Malpelo Island)
http://hk0na.com/
73 de NG0R
QSOs for Wednesday
I worked VP8DNT on 20m SSB (Falkland Islands)
I also worked HK0NA on 20m SSB (Malpelo Island)
http://hk0na.com/
73 de NG0R
QSOs for Tuesday
I worked T32AU on 30m CW (East Kiribati)
I also worked VP6T on 30m CW (Pitcairn Island)
73 de NG0R
QSOs for Monday
I worked TI2CC on 40m CW (Costa Rica)
73 de NG0R
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
