Saturday, January 14, 2017

A visit with an old friend ~ The KWM-4!

A Visit with an Old Friend!

1/17/2017 ~ Scratch built homebrew rigs!

Late in 2012, I decided to build a solid state version of the famous Collins KWM-2. This now must totally convince you that I am several corn flakes short of a full bowl. Well take a look at the masthead photo and you will see that I was successful. My KWM-4 even sports a keypad (like in the KWM-380) and two of the buttons let you up / down tune the rig. Try that with your Bitx40.
It has been some time since I last had it on the air so today was a good day to light up the old rig. The KWM-4 is QRP in that it will  produce 5 watts on SSB. About now I am expecting a correction on what constitutes QRP from some of the illuminati. Anyway I have temporarily put aside the FPM5 while I noodle a low drive condition on the higher bands which may entail a redesign of the famous EMRFD driver stage. Sometimes you will find EMRFD circuits are not pantyhose where one size fits all!
For those who may not know this, my KWM-4 is a dual conversion transceiver with the 1st IF at 10.7 MHz which puts it close to the 10 MHz ham band. For me it was an easy decision and I skipped 30 Meters but since I am not a CW fan it was no loss. The second IF is at 455 kHz and uses a tubular Collins mechanical filter. There is actually a crystal filter following the 1st conversion which use a 7.5 kHz wide  at 10.7 MHz for this application. This solves a problem when you up convert a 455 kHz SSB or CW signal for the subtractive mix that would put an undesired signal too close the band pass filters. Yes Virginia some real innovation in this rig. This is one of my few rigs that can actually do CW and features a separate CW oscillator that on transmit bypasses the mechanical filter. More innovation here. The KWM-4 works on 80, 40, 20 15, 17 and 10 Meters
More details of the KWM-4 are shown on my page under N6QW. As you will note there are many rigs on that page and so this is not just a one hit wonder!
Pete N6QW




Simpleceiver with an OLED
1/15/2017 ~ You Tube Video of Simpleceiver with the OLED and Si5351. This was made especially for those individuals with fancy smart phones and exotic tablets who could not open the movies below. C'mon guys I am doing all the hard work the least you could do is use a real computer to view this blog!
This video is also being provided for those who tried to put the OLED and Si5351 in a Bitx40 project and had noise problems with noise being generated by the OLED. You can decide about any noise issues after listening to this test with the Simpleceiver.
Pete N6QW

Late in 2015 I developed a project called the Simpleceiver which was fully documented on this blog. The evolution of the design relied heavily of the use of LT Spice to simulate circuits and to "make" Dual Gate MOSFETs by cascading J310 JFET's. I know of several duplications of this project both in Europe and in Asia. For a display I used a 16X2 LCD.
Fast forward to today where I am now using OLED's in various projects thus the foray into retrofitting the Simpleceiver with an OLED. There are several video that are presented below and you can listen closely to the audio as there have been reports of noise issues when using the OLED's. You be the judge.
The OLED, Si5351 and the Nano offer many possibilities especially for removing analog VFO's (you know the ones that drift) from your old homebrew gear and installing the new technology. A $20 Bill will put you on that road.
Pete N6QW

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