Harv's DDS Function Generator

Nice looking DDS function generator Harv!  Glad to see the HT-37 in the background. (And it appears well protected -- is that some sort of digital shielding to protect it from the bits and bytes?) The eraser buttons are a nice touch. Good luck with the Minima!

Hi Bill,

 

Well I have nearly completed my DDS Function Generator as I prepare to construct the Minima.

 

The Function Generator was a necessity for the bench so I can tackle Tweaking and Troubleshooting my work.

It is housed an aluminum box and completely self-contained.

My objective was to have the choice, to either lay the unit flat on the work surface or stand it on a shelf for easy reading while seated.

The Generator has both a  DDS and HF-ECG output.

The buttons are fashioned from White Pencil Erasers since finding proper buttons for the membrane keypad beneath was difficult.

 

I have obtained a set of Farhan’s Boards for the Minima but will begin my effort with a Manhattan Style Construction so I can perfect my choice of parts.

The soldering iron is heating and I’m ready for a new and exciting challenge.

 

Happy Solder Melting Everyone!

 

Harv -=WA3EIB=-

Albq., NM.

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Remotely Controlled Stations on the Internet

Now for something completely different!  

I  find myself talking fairly often to hams who are using remote transceivers.  The operator will be in say, Michigan, with the rig in Florida.  Some of them are using the online system:

http://www.remotehams.com/

I signed up and downloaded the software.   It works very well.  Many of the stations are closed to outsiders, and some of them don't let you transmit, but it is fun to listen from remote locations.

This morning I hooked up the Tuna Tin 2 and was able to hear my 200 mW signal through AI4W's receiver in Kentucky. 

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Hackaday Goes to Shanghai

http://hackaday.com/2014/03/24/the-gathering-shanghais-hackaday-community/


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VU2JN's "Transistor Transmitter from India"

VU2JN

VU2INJ's very interesting blog led me to a wonderful 1967 QST article by VU2JN.  Check it out.  Necessity truly is the mother of invention and -- as is the case with our beloved BITX -- we see that in the design of this transmitter.  I love how the speaker was left in the cabinet and used as the microphone.  Check it out:

http://vu3inj.blogspot.in/2014/01/tribute-to-vu2jn.html

More on VU2JN (who very clearly merits "Homebrew Hero" status):

http://shipwreck1.hopto.org:8080/projects/hamprojects/VU2JNArchive/

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The Really BIG Discovery (Cosmology, Gravity Waves, Inflation)

The signals that were announced this week are a bit outside our normal frequency range, but this is a REALLY BIG discovery so of course, it needs to be covered by SolderSmoke Daily News. I liked this info-graphic from space.com. It is worth looking at. Note the line "The universe continues infinitely outside Earth's Hubble volume."

http://www.space.com/25075-cosmic-inflation-universe-expansion-big-bang-infographic.html

Source SPACE.com: All about our solar system, outer space and exploration.
Source SPACE.com: All about our solar system, outer space and exploration.

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A Short Video on my Herring Aid 5

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The Ladybird TRF (Regen!) Receiver

http://www.mds975.co.uk/Content/trfradios02.html

My feelings about regenerative receivers and their possible connections to the nether-world are well known.  But the receiver described on this beautiful British web site is almost enough to make me change my mind.  Thanks to Stephen, G7VFY, for alerting me to this (and to so many other great sites!)   I also find myself forced to give regens another chance because George Dobbs, G3RJV, was the original source of this design.  It comes from a book he wrote in 1972.    I love the wooden bread-board construction.  Thanks Stephen!  Thanks George!



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The Wizard of Sao Paulo

It has been about 4 years since Miguel, PY2OHH, has been mentioned in this blog.  That's too long!  Miguel has churned out an impressive series of homebrew rigs, the latest of which he calls the Baita Tche.  Does that name look familiar?  It is a play on words using slang from Southern Brazil.  "Baita"  means big or enormous.  "Tche" means "you."  Together they sound sort of like BITX!  Miguel has been building BITX rigs and rigs (like Baita Tche)  similar to Farhan's rig.  Here is his page on Baita Tche:
http://py2ohh.w2c.com.br/trx/baitatche/baitatche.html

Here is his home page with a LONG (almost JF1OZL-ish!) list of projects:
http://py2ohh.w2c.com.br/

Here's his YouTube channel:
http://www.youtube.com/user/py2ohh

Here's a Photostream of some excellent Brazilian homebrew:
 http://www.flickr.com/photos/py2jcm/2066764415/in/photostream/

Muito obrigado Miguel!

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Farhan's RM386 RF Amplifier

An RF amplifier inspired by a quest for an AF replacement for the LM386.  I like it!  Check it out:

http://www.hfsignals.org/index.php/RF386


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Herring Aid Motorboating STOPPED!

FIXED!   Following up on suggestions from Tony Fishpool and from Roy Morgan, I put a 10 ohm resistor between the two supply lines and put 100 uF caps to ground at either end of the resistor.   I can now operate the receiver at high AF gain (no problem running a speaker) without the KLUDGE of two power supplies.  The RX sounds great.    I will soon match it up with the equally awesome Tuna Tin 2 for 1976 QRP EXTRAVAGANZA. 

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Stopping the AF oscillations in the Herring Aid 5

Thanks to all who responded.   This morning I got a significant clue:  Following up on Tony Fishpool's suggestion, I separated the power supplies:  I ran the RF amp, oscillator and mixer base bias off a small 12 V battery, with the mixer collector circuit and the AF amps running of the bench 12V supply.   The AF oscillations completely stop under these conditions.  So the feedback is probably taking place via the 12 V supply lines.  73


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Direct Conversion Receivers, AF Transformers, and Motorboating

The Herring Aid 5 is a direct conversion receiver (scroll down for details).  It is a minimalist design from 1976 using parts available at Radio Shack stores.    One of the parts no longer carried by Radio Shack is a 10K-2K ohm audio transformer.  Following NORCAL's 1998 design update I ordered an equivalent Mouser part (Xicon 42TU002-RC).   I had been running the receiver with simple RC coupling instead of the transformer.

Yesterday the Mouser part arrived and I put it into the circuit.  An increase in AF gain was immediately apparent, but the thing went into AF oscillation as soon as I turned up the AF gain. 

I tried beefing up the AF decoupling.   But I think the real problem is just the presence in the middle of the board of a rather large (1 inch x 1 inch) audio transformer.    I moved it around a bit to get it away from the toroid of the preceding stage.  This helped a bit, but it still breaks into oscillation if I turn up the AF gain.

Any suggestions?  Or is this just part of  the minimalist 1976 lifestyle?  


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