[600MRG] LF / MF Kit Transverter

[J Mcvey]

Here is a pic my modified version of the dongle SDR project that was in the January issue of QST. The author offered a PCB and most of the parts in a kit for $60,
so I figure it would be easier that way. In fact, some of the parts as specified are no longer available  and modern subs had to be found. For $60, it all came in a bag so I didn't have to chase the parts.

The original project called for an addition 12v supply to run the converter.
IMO that was extra wires for no good reason, so added some filtering and tapped off the USB power. I happen to have lots of junk PCBS where I can harvest USB female connectors. I found a USB A to USB A 3.0 cable on Amazon for a couple of bucks to connect from the box to the computer.

It works pretty well, but I'm going to look into improving the sensitivity
on the low end (630M, 475Khz) . It may be the mixer module isn't up to the task or the high amplitude output from it may be de-sensing the dongle a bit.

Worst case scenario is to add a IGfet preamp. The main reason I built this was to monitor MW and VLF.

None the less, it was educational and I can now find my way around SDR. 

    On Thursday, April 14, 2016 1:32 PM, Brian Pease <bpease2 at myfairpoint.net> wrote:
 

 Looks like ten cents to me!
I have been offering circuit boards and kits as a non-profit service for 
many years for audio-frequency Through-The-Earth radiolocation use by 
cavers for correcting maps, etc, a very small market.  I have always 
used thru-hole parts & DIP ICs with sockets.  I use large 1/4W CF 
resistors. The first receiver design was done 22 years ago and is still 
the state of the art.  All parts are still available because I used 
popular common parts and ICs that are multi-sourced.
It would be nice if the transverter was very freq accurate and stable.  
There are cheap ultra stable TCXOs out there now.  For those 
transceivers that can be altered to TX anywhere, using a 10MHz LO is 
nice to allow use of a surplus external frequency standard or GPS 
disciplined oscillator.
Personally, I broke down and bought an Elecraft K3S kit with external LO 
sync from GPS to drive my 630m amp.
On 4/14/2016 12:54 PM, Frank Lotito wrote:
> I'd like to throw my two-cents in regarding the possibility of a LF / MF commercially available kit to salvage good performing transceivers, many which are current models:
>
> (1) Lets remember who we are building the kit for - A limited audience of people who are not turned off on the prospect of building, and who are interested in participating on these proposed new bands.  To be successful, as well as snare  those sitting on the fence, the kit should be all inclusive, including an optional cost, preferably all metal case with all the necessary machine work done, and TR switching for at least the popular modes, such as QRSS, hand sent CW, and WSPR.
>
> (2) The audience will be heavily biased to the "older generation. " That population, me included, are all to frequently afflicted with tactile and visual acuity problems, and whose endurance and steadiness leaves a lot to be desired.  Thus SMT is not justified from an ergonomics point of view, as well as not justified from a  technical point of view.  This is a super-extra l-o-n-g wave device, not a millimeter wave device! For many died in the wool scratch-built home brewers, dead bug construction for this device in this frequency range is more than adequate; but for a commercial kit, not the best idea.
>
> (3) Along with (2) above, use of only "full sized" leaded components intended for at least one-tenth inch pitch PCBs, and this included ICs.
>
> (4) Be careful when choosing components - It definitely is a bad idea to choose components already obsoleted, or the manufacturer earmarked as "not recommended for new designs."
>
> (5) Be careful of the LO.  Choosing the wrong LO could open the user up to interference problems.  Fort example, as I vaguely recall the mid to late 1970's era 160 meter receiving up converter that appeared in QST that converted up to the 20 meter band.  A choice of LOs may be desirable to minimize the possibility of birdies just where you don't want them.  The LO probably does not have to be stable enough for QRSS 1200, but definitely stable enough for standard format WSPR.
>
> (6) I see no justification in being able to shoe-horn the transceiver kit into the already fully-packed innards of a modern transceiver.  That is asking for trouble.  It may be the cat's meow to accomplish this, but again not required for successful transverter performance.
>
> (7) An option to hire someone to assemble and test out the kit, or fix a kit that never worked since day the assembly person finished the kit.  The assembly instructions should also have in-process tests.
>
> I'm sure there are other concerns - GL
>
> 73 Frank Lotito  K3DZ / WH2XHA
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