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Showing posts from March, 2017

A New Line of Transceivers ~ DifX

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Transceiver Architecture 2.05 The Big Kahuna 3/31/2017 ~ All Back Together Only a hint of burnt wiring but working FB. Made several contacts and all back to normal. My ham friends this too is a DifX! 73's Pete N6QW

 3-30-2017 --- A Case of Smoked Parts! Just thought I'd share a moment of grief when I was working on one of my rigs (LBS-II). Today I decided to convert the LBS-II back to 20 Meters. The rig originally was on 20M and then I moved it to 40M and now decided back to 20M. The boards and wiring are really compact and while I was making an adjustment some wiring came into contact with ground. Wow a vapor cloud similar to a nuclear explosion was emitted from the rig and you could smell the burnt wiring. My heart sank! Well as it turned out just the wiring harness got melted --yes melted, more like welded wiring.  When I replaced the harness -- I actually found a better way to do the wiring. About 1/2 half hour and the rig was back working. I just plain got lucky. Below is a …

A New Line of Transceivers ~ DifX

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Transceiver Architecture 2.04 N6QW on 60 Meters!
Today we have a post about an exciting new 60 Meter transceiver from N6QW and of course it is a DifX. The 60 Meter band must be the world's best kept secret as operating on this band is like a breath of fresh air. With but five channels it would seem to be almost a non-starter. But that soon will change with the addition of more channels. The 2015 WARC approved the new channels and effective January 1, 2017 they are indeed a reality BUT and double BUT so far they have not been actually authorized by the FCC for use in the USA -- Essentially the new channels center around what is now Channel 3 [5.357 MHz] and includes specific allocations for data and CW as well as specialized applications. But the bulk is for USB operation. Essentially Channel 3 is expanded by about +/- 7 kHz with the reasoning that you end up with 4 additional USB channels. But that also comes with a price of a power limitation of 15 Watts ERP. While not a proble…

A New Line of Transceivers ~ DifX

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Transceiver Architecture 2.03 The Dual Conversion Scheme an evaluation of Frequencies. In the KWM-4 I was presented with a real engineering problem that being how to take advantage of the Collins Mechanical Filter capabilities yet deal with its low frequency of 455 kHz. The path quickly leads to a dual conversion scheme, where you can manage the gain at the higher IF and manage the selectivity at the lower IF. This is a clue in that at the higher IF the filter does not have to be 2.1 KHz wide but something on the order of 7.5 KHz will certainly keep down the crud ending up in your receiver band pass. The lower IF (Collins Filter) can do all the heavy lifting as now signals in the pass band coming into the filter are very narrow and the mechanical filter is essentially slicing that down to about 25% of the bandwidth -- 2.1 KHz. Below is the frequency scheme for the KWM-4. Five years ago this is how the frequency mixing was handled. This exemplifies the concept of gain at the higher IF…

A New Line of Transceivers ~ DifX

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Transceiver Architecture 2.02 In our last post we hit the highlights of the KWM-4 and in the closing paragraphs I mentioned the band switch decoder and how using the three digit code provided by the K5BCQ digital VFO that automatic band switching was possible. Today we have with the Arduino far more efficient means of doing this; but this was how it was done before the uBitx.

Basically the circuit detects the BCD code and translates it into decimal outputs from 1 to 6 (Six Bands). With each output is a PFET that is "switched on" to provide power to the appropriate Band Pass and Low Pass Filter banks. An Arduino Mega 2560 having lots of pins could provide the 3 digit code or if you wanted to waste 10 digital pins you could do it directly. Also shown is how you could switch the bands using 3 toggle switches.

Another innovation was how the "Push To Talk" was handled including how to key the transmitter for CW. This was a total "in house design" and I think …

A New Line of Transceivers --- DifX

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Transceiver Architecture 2.01Please note the DifX is not a singular transceiver (like the Big Kahuna) but instead is a concept to demonstrate that successful transceiver projects can be achieved with something other than the Bitx20 footprint. The Bitx is a long standing successful design; but is not the only approach to homebrewing a rig. We are now at a point where with the aid of low cost technology we can build in many new features from the outset. The DifX series of radios will provide some insight into the "how to do it."
As promised in the previous post, I will explore homebrew transceiver architectures that are different than a Bitx. I can think of no better place to start than with my KWM-4 design which began in late 2012 and resulted in a completed transceiver in early 2013. This project was published in an 2013 article in QRP Quarterly. What is significant about this project was that it is a dual conversion transceiver and covered six amateur bands and for my good…

A New Line of Transceivers

Transceiver Architecture 2.0
Several posts back I covered a few of the current crop of approaches to transceiver architecture. Judging by the number of visits to this post, it seems to have struck a chord with those who frequent this blog. Over the next few months I intend to cover in detail a line of N6QW designed and developed transceivers that I call DifX. The acronym DifX is a simple contraction of the words Different than a Bitx. While due respect must be given to VU2ESE and the solid Bitx design --there are other creditable designs and I think the DifX series satisfies that criteria. Hopefully you all will enjoy the journey. Stay tuned. The Big Kahuna (photo on the masthead) is a DifX. 73's Pete N6QW

A Solid State QRP Rig from 1955!

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A 1955 Solid State QRP Transmitter using the Philco SB-100.3/14/2017 ~ Late breaking -- I put a 4:1 transformer in the collector lead and as measured across 50 Ohms on the secondary side I am seeing 3.2 Volts Peak to Peak. If you perform the rigorous calculation that transforms into 25.6 Milli-watts or 14 dBm. Now we are cooking! That is better than the rig on Bill's blog.
See Photo addition at the end --just to posit where 60+ years have taken us --and I have personally seen the amazing change to our tools, techniques and toys!

Recently my friend Bill, N2CQR posted data on his blog ~ soldersmoke.blogspot.com about a vintage late 1950's early 1960's 10 milliwatt 10 Meter transmitter. That was quite a feat!

But given my Italian heritage I could not let that pass without building my own solid state transmitter using a transistor from 1955. My rig operates on 14.060 and produces 0.4 milliwatts with a 3 volt collector supply using a Germanium transistor from Philco. The SB-100…

New Rigs ?????

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Buying a New Car and that New car smell! Almost makes you forget that you just paid $55,000 for a 9 passenger Toyota SUV. It looks cool but scary to park. The ride is no better than a bucking bronco! I am a small framed guy and my visibility is like looking at a picture framed between the steering wheel and the top of the dashboard. No I didn't buy one --just looked at one while my Avalon was being serviced. But the new smell is much like the buzz of building a new transceiver! Pete, N6QW  

Mystery Transceiver

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Or is it? 3/5/2017 A special shout out to active duty  US Navy Seabees and former Seabees world wide. Today is the 75th Birthday of the founding of the Seabees. Happy Birthday fellow Seabees! Our motto "Can Do" resonates even today! The first Seabees were civilian construction workers who were formally organized as Naval construction forces shortly after the start of World War II. Seabee's were instrumental in building the advanced bases that made the Pacific island hopping strategy a reality. Today that legend lives on in places like Iraq and Afghanistan. We Build, We Fight is the Mission Statement!  If you followed the prior post on Transceiver Architecture look at item #3. The circuit below IS the hardware described in number 3.