Current Project
Progressive Receiver

This project is loosely based on the progressive receiver in the ARRL handbook,designed by Wes Hayward. It includes modifications for lower noise, switchable filters(including AM). It will be built in modular ugly bug format, thus allowing for easy circuit mods. Below is the completed vfo, which tunes 4900 to 5550 allowing easy coverange of the 80 75 meter band. The first goal, provide 20 and 80 meter coverage using band imaging.

Completed receiver on workbench. I was using the rx on 3885 am when this picture was taken. The crystal filter limits the bandwidth to about 3khz, but is very usable. I am in the process of making a crystal filter for am about 6 khz. It is harder to make a wide filter with the proper skirts, than it is to make a cw filter.





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Above the modules of the receiver, starting at the left, a lowpass(80 meters) highpass(20 meters) front end. To a SBL-1 mixer, here the signals for 20 or 80 are mixed with the vfo (5.0 to 5.5 mhz) which converts it to a 9 mhz if with one stage 2n5108 amp. The 9 mhz if is then fed to the 2.4 khz crystal filter. The output of the filter goes to the if ampstage in the shielded box. The if amp uses 2 mc1350p for about 60db gain. At the present time I feed this out put into a receiver tuned to 9Mhz. I have had several qso's on am in its present state. The bfo mixer stage is next for construction.





Closer look at the front end filters. This is a very simple front end (which works really well), that I am using for testing, while I am waiting on parts for a bandpass design. I will replace both the 20 meter and 80 meter.



Here is the replacement front end. The upper bandpass is for 80 meters. The lower bandpass is for 20 meters. The 20 meter utilizes a series tuned circuits. The circuit was described in Methods for Rf Design, available from ARRL. The relays are for band switching, as well as for the addition of an selectable rf amp for 20 meters. The bandpass for both filters were checked using a rf noise source and plotting signal strength for a given frequency. Another method, sugggested by Jack KE4ID, was to utilize a function in most modern transceivers/receivers the sweep spectrum function. Just place a noise source at the input to the band pass filter and run the output to the receiver. Tune the receiver to the middle of the designed pass and start the sweep . It provides a real time look and helps with adjusting the trimmers. I used a Ten Tec Pegasus.





Here is a closer look at the sbl-1 mixer. The toroids in the bottom left, combine to form a harmonic filter for 5 mhz on the vfo input to the mixer. The transistor is a uhf 2n2108 post mixer amp followed by broadband matching transformer and 6db pad for isolation. Then onto the 9mhz 2.4khz crystal filter. The pot on the end of the filter is temporary, it allows me to adjust the filter for the best performance. The output of the crystal filter goes directly to the if amp.





Close up view of inside the vfo.
This vfo is housed in a homebrew copper clad box. The vfo cap is a boadcast band 10 to 400 pf . I used 1 + 2 kv npo's, because that is what I had. The vfo was actually more stable than expected. I attribute this to the larger surface area of theses caps.




Close up view of inside the bfo/product detector.
The BFO/PD is housed in a altoids tin for sheilding. The bfo selects upper and lower side band with a single crystal. I use a relay to switch in different values of inductance and capacitance, to shift the freq. The oscillator has an output of about +10dmb going to the filter. The filter takes it down to about +8 dbm. I use solder in rca jacks for signal connections, and feedthru caps for power and usb/lsb select. The Altoids tin makes a perfect box, it solders well.




The if amp uses 2 mc1350 video amps. This was the typical if used in the early 80's. Somewhat noisey but has a lot of gain, and it should be easy to implement AGC. The noise can be corrected by adding a tail end crystal, or ceramic filter. The band width of the filter can be wide 10khz, that makes the ceramics attractive.




Nice and junky audio amp, using 1 stage npn amp to a lm380 dead bug style. This happens to be the part of the project that was the most difficult. I had thought I home free after the if amp, but I was mistaken. Not enough gain, too much, squeals from feeding back to the if amp thru the power. It is still not finished, I may just start over on this.







Things left are to add agc, add 40 meters, find a case, and vernier. .