Archive for May, 2014

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.

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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.

Started RF Input and Product Detector Layout

May 8, 2014

Started the layout of the RF input and Product Detector today on paper…and just finished gluing down the pads for these next two stages.  I normally draw the layout on paper and then use it as a template to glue down the pads on the PCB. This time, after doing the layout on paper, I used a black marker and did the template on the PCB and then glued down the pads. A bit more organized and less stressful to say the least.  Here is the schematic for these next two stages:

input amp and product detector

 

 

 

 

 

 

I will also do the LO to product detector interface transformer when I do these two stages. Have to let the pads sit for at least an hour or else they have a tendency to pop-off the PCB when I tin the pads.

Binaural Receiver Update

May 7, 2014

Swapped out the experimental variable cap I was using for tuning and installed a salvaged 27 to 267pf variable cap.  Also made some voltage measurements for my data book.  The tuning range is 6.99 MHz to 7.199 Mhz with the LO signal level ranging from 3.6 to 2.3 dBm.  All voltage measurements are in Vrms.  Removing the inductor moved the tuning range up about 40 KHz…but I have left it in circuit as I am only interested in the CW portion of the band.

Ceramic Resonator Osc-1-jpg

Binaural Receiver for 40 Meters

May 5, 2014

Started a new project.  It is taken from the the Lo-Key magazine, number 121, March 2014. It is published by the VK QRP Club from down under, and the article is by Peter Parker, VK3YE.  Actually it started out wanting to play with a ceramic resonator oscillator and this receiver had one.  So I built the oscillator first…it worked first time and I am quite happy with the results thus far. It was to be for 40 meters…but found that it will oscillate on both 40 and 80 meters, so thinking I may end up with a dual-band binaural receiver. Will have to build a second LPF for the input…and I need to look into the RF Shifting network to see if it is frequency sensitive.

Here is the schematic:

Ceramic Resonator Osc-jpg

 

 

 

 

 

 

 

 

 

The range of tuning is from 6.978 MHz to 7.295 MHz. I am only interested in 7.0 to 7.18 MHz…primarily the CW portion of the 40 meter band. The tuning capacitor needed turned out to be only 250 to 30 pf (7.0 to 7.18 MHz respectively).  The LO signal level is 3.3 dbm at 7 MHz and drops only to 2.5 dBm at 7.18 MHz.

I found out that the oscillator will also put out a signal from 3.47 MHz to 3.627 MHz…and the LO signal level is 4.5 to 3.7 dBm.  Considering the capacitance swing needed, I can use a simple polyvaricon  (Nine Volt Transistor Radio variable capacitor type) for the tuning capacitor.

We are getting our RV ready for our annual trek to Dayton for FDIM/Hamvention in a couple of weeks, so not sure how much of this project will get done till we get back… but it has been fun  so far.  I want to play with the oscillator a bit before I move on with the rest of the receiver.  I used molded inductors to make the 3.3 uh tuning inductor and want to try a roid and then try the whole circuit with the small variable capacitor.

Enjoying the bench time and snuffing solder fumes. It was so cold this winter and the shack/workbench are in the unheated basement…so needless to say, I spent less time this winter down here than I had hoped too.  Either I have to move the shack/workbench upstairs or come up with some sort of heating that is affordable when the outside temps tend to stay below 32 degrees (if not below zero) for days and weeks at a time!