Low Aspect Ratio Sailplane
Are there Advantages for this style of sailplane?
ICOM IC-718 PA 2N2904 Transistor Replacement
Just this past holiday season, I was able to complete a transistor replacement for my ICOM IC-718 Transceiver. Outlined in the posting are my considerations on how the process went.
More details to the complete process found here.
Small circuits are interesting and don’t take long to build.
In order to experience a new construction technique with what they call manhattan construction. I built a crystal Tester.
It is a simple two transistor circuit that has a socket for crystals and the output goes through a 50pf to 90pf trim cap that I added that was not specified.
This circuit was found at a site with a good article on testers.
Crystal Testing Circuits
By G3PTO John Reynolds in England.
I used the simpler circuit that was in the article as I was using it as an example for Manhattan Construction as a first attempt at this style of circuit building. I ended up with only ones small solder bridge and with some voltage checks, I found it. The circuit worked straight off and a bit of an adjustment of the output trim cap to peak and I was in business.
This season the DX-88 antenna broke at the base again, this time the post at the insulating bell broke off. I guess it was time I gave the antenna another good overhaul. In this image, the cylinder that contains the mast conductor ring at the top of the insulator broke off at the base just above the bell portion.
I had to rebuild this device using CA glue and very fine powder micro-balloons that are made of glass. Fortunately this was successful and I managed to assemble the antenna again. In the meantime I will go through the whole antenna and give it a good tightening and moderate cleaning. Some moisture was observed in the lower long tubular capacitors for 40 M and 80 M.
Over the holiday season I was offered the opportunity to buy a Yaesu FT-7 radio and I accepted. For the last number of months I have been experiencing the advantages and disadvantages of QRP operations and this is THE rig for just this practice. I have been working 15, 20 and 40 meter bands on power outputs in the range of 5 to 15 watts on the voice peaks.
Full Review Here
For those of us struggling with 60Hz hum from wall adapters, here is a nice device that flattens out that hum to near Zero.
Construction Project Here
This project worked right away and needed only some minor adjustment to voltages.
Dead quiet when using the wall adapter, and this was a welcome addition to my small amp projects like the Guitar Pedal and the Headphone amp.
Aviation Headset Interface for Amateur Radios V2.0
I had completed version number two some time ago with the help of a nice aluminum chassis, a Hammond 1590B case that is popular with the Guitar Pedal and the Box Mod enthusiasts. In my case it’s not an amp or a current booster but a passive audio exchange for Aviation Headphones that uses a microphone for amateur radio communications.
The reference for this is right out of the ARRL Handbook 2013 edition, Pages 24.34 and 24.35, schematics by K5ALQ, transformer based and K0IZ, restive-attenuator based circuit that is what I chose for this project.
I am pleased with the level of RF shielding and I am happy with the performance with other headset brands. That was the big payoff. Plus the changes that I made are to R3 resistor where I used a 10K pot that ranges through the resistances needed for different types of microphones. I changed the resistor R5 which was a fixed resistor to a 5K pot that allows some adaptability to just about any aviation microphone going. The switch is an option that will allow for some tweaking for DX by switching in or out C4 Capacitor or R5 5K pot. In this way good adaptability to a bunch of aviation headsets is possible. Fits in the hand well and is easily to use with a keyboard.
Further write up here
DIY MOSFET Headphone Amplifier
This project works really well and is based on two MOSFET per channel. A MPF102 in each input and a IRF510 in each output.
The chassis is the main heatsink for the power MOSFET’s
Continued as a build HERE.
Tested this amp with my Lightspeed QFR Aviation headset that is a 300 ohm headphone and they had plenty of headroom. The source for this sound was my Q5 Blackberry, Driving this headphone without the amp does not even cut it.
Full volume both the source and the Amp has no noticeable clip and is about all the volume I can take for a period of time. I finally dialed back the volumes to about 30%
Happy to hear good sound with major passive attenuation from a aviation headset no least.
I have had the opportunity to work on a TJ4A 4 Band HF Transceiver from a local ham. These are kits from a maker called Youkits and I am impressed with some details and not impressed with others. The problems with this rig began with a failing Push To Talk condition that stopped the keyer from making the rig TX. Later, the mic PTT failed as well and the rig would go into full transmit when turned on. As well the mic audio would then come out the speaker. After that it stopped turning on altogether with no power in any stage of the radio.
The repair is outlined on the main page for this Rig.
I completed my first Guitar Pedal based on a popular circuit called the Trotsky Drive. It is a single transistor Overdrive circuit to boost the output of the guitar signal into the clipping region for some distortion. The circuit initially uses a Vintage Transistor from Russia called a KT312 which is a NPN transistor. I did not have this transistor but I did have a 2N3566 button head transistor that works very nicely. I tried some traditional 2N2222 but was not impressed, so I left the 2N3566 in. I have a transistor base that you can take out and plug in other transistors to experiment. Initially I struggled with the wiring for the pedal switch as I was wiring it backwards to the jacks but one I got that sorted out the rest was successful. Certainly my pedal is less refined than the ones found in this site, but for a first attempt at a pedal project I was happy.
Complete Build Details
Trotsky Drive Overdrive Pedal