Archive for the ‘Homebrew’ Category

8640-jr Update #1

March 30, 2015

Well, I ran into a road block this afternoon that took some time to sort out. I built the FET VFO and Follower (for isolation) portions of the VFO…but could not get it to oscillate. After checking wiring and voltages, I pulled another 2N4416A from the junk box and checked it with my M-Cubed semiconductor checker. I noticed that it showed the DRAIN and SOURCE pins reversed from what the datasheet indicated. I rebuilt the two stages using the info that the M-Cubed checker showed me and the VFO worked. I got these 2N4416A’s from a reputable USA company but now wonder if maybe they were clones from an overseas location. Bottom line…never assume anything, always check and measure everything.

Have the BUFFER AMP to build and then do some tweaking and final measurements. This project is a joint effort of Todd, VE7BPO and myself for an article for the Michigan QRP Club’s quarterly publication called “The 5 Watter” (T5W). Todd suggested this article during the winter months and it has been a fun adventure so far.  I sort of got side tracked this last month and just now am getting back on track with the project.  The original 8640-jr project was done by Wes, W7ZOI…it is a three band VFO that develops a 13 to 30 MHz signal which is then ran through a couple of dividers to result in 3.5, 7 and 14 MHz VFO signal source or can be configured to run from 3.4 to 31 MHz as a signal generator.

Always fun to snuff solder fumes and figure out why things don’t work the first time as planned <smile>.

8640-jr VFO

March 29, 2015

Started assembling a 8640-jr VFO tonight. Should have done this a month ago but been rather busy with no-related bench stuff lately. Built and tested the +6 volt strip and now onto the oscillator and buffer stages.

Located and sorted the parts for the entire project…now just need to build it, then test and measure the three stages. This is for a T5W article that VE7BPO inspired a couple of months ago.

Update on CW Decoder

January 25, 2015

Received the 4×20 (4 lines, 20 characters per line) LCDs. This made using the CW Decoder so much more enjoyable to use. I changed the code a bit to put the WPM rate and my call sign on the first line and then three lines of cw.

I need to take a picture of the setup now as it is easier to read the CW as it is displayed and then post it here on the blog.

Hello to Fred, KD8IXP. He is a local ham who is always bugging me about updating my blog. He just received two PIXIE transceiver boards, and has promised me to get on the air with one of them so I can hear what it sounds like. I will report back on this when he finally fulfills his promise!!!

Arduino Stuff

January 20, 2015

Been doing some Arduino stuff on the workbench. I saw an article that used an Arduino for a CW Decoder. Built it but it didn’t show anything on the LCD. After some checking, realized that the schematic I was using and the software I had loaded onto the Aruduino didn’t match as far as LCD wiring. After some experimenting with various pin-out configurations, I ended up with a working cw decoder.

CW Decoder-5

I also built up a breadboard for future Arduino experiments and prototyping. I have three books that I bought this last year that deals with Arduino projects and Ham Radio. This breadboard will be perfect for doing most of the experiments detailed in each of the three books.


I am also doing a VFO/Sig Gen project with Todd, VE7BPO.  All of the project will be detailed in the Michigan QRP Club’s quarterly publication called the T5W. Todd is doing most of the work, and my part will only be the VFO section. It is based on a project done by Wes, W7ZOI in 2009. Called the 8640 –JR (a humorous namesake after the famous HP 8640 signal generator) this signal generator uses only 1 VFO but covers three ranges by applying HC74 series CMOS logic for frequency division.

That is it for now. Stay tuned for solder fume snuffing while the temps are chilly and the ground is white!

72/73…Mike, WB8ICN

Time to Relearn a Few Things!

June 25, 2014

Been trying to use LTSpice with the binuaral receiver project. What I have learned is I am quite stupid when it comes to modelling a stage and understanding what is going on (using LTSpice). I have pestered a very patient friend from down under and I decided this morning that I should be able to answer some of the questions I have been throwing his way.

So, for the near future, I need to get a better handle on understanding and using LTSpice … then I can go back to modelling what I am doing before snuffing solder fumes. There is enough tutorial info out there on the web about LTSpice and how to make the best use of it…and I need to learn (relearn???…now I am wondering how much of it I learned the first time) LTSpice from a homebrewers point of view and how to make it a useful tool for  me.

This is rather embarrassing to admit, but it is the truth and I really want to be able to use it (LTSpice) the way others have come to use  it and learn from it.

Mark, again thanks for some really important “learns learned”!

P.S. – I can now model a VXO with some success!

Signal Level Loss in Binuaral Project

June 11, 2014

Well, the signal level loss was not as bad as I first thought…but the ability to discern AF is not what I was hoping for. With a -40 dBm input signal level, the AF (in headphones) is just barely noticeable. Actually, from -35dBm input and lower, the AF is nearly useable.

I have post the signal level loss with a -3dBm input signal level to show the loss for the RF portion of the receiver to be about -7dBm (from input to product detector).

sig levels - input amp and product detector

Binaural Receiver Difficulties

June 9, 2014

The RF Amp is working, but I am losing a lot of the signal before it gets to the Product Detector. The RF Amp is giving at least 25 dBm of gain…but from the collector to the Product Detector I am losing almost 20 dBm…so something is amiss with the RF portion of this project.

I need to measure each section to map out the loss and then figure out why…or just call it quits for now and move on to another project. I was thinking of using a NE602 for the front end and use the output pins (5 & 6) for the input to the Product Detector. I built a DC receiver a few years ago that used the NE602 and it worked rather nicely. I found the project and wondering if I want to just “jerry-rig” up the idea to see if it works. Since I am deaf in one ear, a binaural receiver isn’t of much use to me…but i did want to play around with the crystal resonator LO and that is what got me started on this project in the first place.

Am quite happy with the LO part of the circuit and I can duplicate it for both 80 and 40 meters…so may build up a couple  LO circuits to have on-hand for bench work.  Nice to have a steady sig gen with only a few parts!

Have to think about all of this for a day or two and then decide what I am going to do. But that is where I am for now. I can make the receiver work…but it is about as deaf as I am and that is really no good to anyone .

Hello to Fred…glad your happy with my more frequent updates!!!

Binuaral Receiver Update

May 28, 2014

Finally made some time to work on the Binuaral Receiver today. Finished installing the parts for the RF Phase Shift and Product Detector sections and now am ready to install the LO/Product Detector interface transformer. The transformer is a trifilar wound torroid “roid”. I don’t care too much about winding them, or tinning the leads…but do like them as I can make each into a value that is needed and not have to order a particular inductor for each project.

I was checking the LO output with the DSA815-TG spectrum analyzer earlier today. Noticed that the second and third harmonics are only down about -15 to -17 dBm from the fundamental frequency. I may have to build either a LPF or BPF if this project turns into a transceiver instead of just a receiver.

Anyway, time to eat and get to Bible study (Wednesday night activity at our church), so will have to finish the install of the transformer either tonight or tomorrow after I get back from a group hike along the Waterloo Trail near here.

Recovering from FDIM/Hamvention

May 21, 2014

Have about recovered from the trip to Dayton. Rained the entire time except Sunday and Monday (the day we came home) and quite cool. But, if you don’t have to like the weather to enjoy it at Dayton. We stay at the KOA campground every year and love the friendships we have made the there.

As far as what goodies I bought…some 2.5″x3.0″ prototyping boards at a dollar a piece (good deal), an interface for my MFJ-259B so I can plot my sweeps on the PC, and finally broke down and bought the DSA815-TG spectrum analyzer. I have been struggling about buying one for over a year…so made the plunge. I have been playing with it for a few days now and makes me wonder how I ever got along without it! I put it next to my DS1052E scope and was able to remove several pieces of older test equipment that I won’t need anymore on the bench. Also picked up a hiking pack for three to four day trips on the trails.

I hope to get back to the Binuaral Receiver in a day or two. I am anxious to use the new SA on it and see how clean the crystal resonator really is. If it is clean, I will use those prototyping boards and make both 40 meter and a 80 meter resonators for the work bench.

Binuaral Receiver Update

May 10, 2014

Tinned the pads for the next two sections (actually four: LPF, RF Amp, RF Phase Shift, and Product Detector).  I also laid down and tinned the three pads for the LO/Product Detector interface transformer.  Have the RF Input section (LPF and RF Amp) done and most of the RF Phase Shift section done.

I have also been doing a wood working project for the wife (five shelf bookcase) for her scrapbooking/circut hobby.  That and made a pedestal block set for the fifth wheel landing legs and stabilizer jacks for our stay at the KOA campground near Dayton.  I can’t say enough good things about this campground.  We used to stay there for family outings when I was stationed there at Wright-Patterson AFB before I retired in ’98, and now stay there for FDIM/Hamvention.  The campground hosts go out of their way to make the week we spend there for FDIM/Hamvention one of the best camping trips of the year!

The weather is supposed to be nice tomorrow (Saturday), so will spend most of the day outside getting the RV ready and some yard chores.  Sunday through Wednesday is forecasting rain showers so may have extra time available for the workbench, though I doubt I will finish this project before we leave for Dayton.