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Thursday, March 30, 2017

ND6T's Very Cool Power Meter (and drawing)

Don's drawing is so good, I just couldn't resist posting it here.  It is part of an article he did for the BITXHACKS blog describing how to add a Stockton bridge forward/reverse power meter circuit to your rig.  Check it out: 

Wednesday, March 29, 2017

N7SUR's Nice SSB Filter -- Nail Polish Stuff Adds Soul to the New Machine

That's a beautiful graph, don't you think?  In addition to the very pleasing results, I liked Bob's methods:  the "by hand" collection of the data points using an AD9850, a 'scope and a notepad (see below); the filing down of ceramic disc caps;  the use of nail polish hardener -- all this adds a definite artisanal element to this project and puts more soul in the new machine.

Like Bob, I too kind of bailed out on the Q calculation when I was doing this.  But as I recall there is a variation on the G3UUR method that yields this parameter too, right?


I'm reluctant to share this with you because the results appear too
good.  I've attached a graph showing my four crystal, 11Mhz
filter measurements.  The graphed points are read values using my
AD9850 DDS VFO feeding to a TEK scope.

A TIA amp was used for input and output of the filter.  My development  software was the Steder-Hardcastle software as presented in November 2009, QEX.

I am now practiced in the black art of filing off the tops of disc
ceramic caps to "adjust" their values.  This black art also involves
the mysterious qualities of Sally Hansen Nail Hardener.

Let me share my method for developing the filter.

I've built CW filters before but this was my first effort at SSB
bandwidth which is less forgiving.

The G3UUR oscillator method (see page 3.19 in EMRFD) is a simple and
effective filter design method. but it does not provide a measure for
crystal Q, a value which impacts filter insertion loss.

So I decided to choose crystals with proven pedigree. These were 11 Mhz crystals from Mouser, part number 20-HCA1100-S.  A lot of ten costs $5.  These were the crystals selected by Jim Kortge, K8IQY, for use in his 2N2/20 rig.

For software, I use the Dishal package that can be downloaded from the ARRL and other sources.  This package was the basis for the
Steder-Hardcastle article in November 2009, QEX. The "Xtal" pull down
menu provides entries for an individual G3UUR oscillator.

Simply put, all critical filter input values are generated by reading
the change in crystal frequency as an additional capacitor is added
into the oscillator circuit.

I suggest starting with a 4 crystal filter. Only two capacitor values
were required for my filter.  Five capacitors were required--two series
and three shunt.

Start by reading the "open switch" frequency for each crystal.  Sort
the crystals into increasing frequency order and choose the four with
the most narrow frequency span.

Using the pull down menu measure the individual crystal measures for
Lm, Cm, and series frequency.  Average these across the four crystals.

The Lm or Cm and series frequency are placed into the Dishal software
main menu.  Also enter the average Cp which is the measured capacitance across the crystal leads.

Finish up the main menu entries by entering the number of crystals (4), and the desired bandwidth--generally 2.4 to 2.9 Khz.  Finally enter the acceptable ripple, which is often 0.1db.

Let the software calculate the filter values.  Expect some odd
capacitance values.  By changing the filter bandwidth--say from 2.4 Khz to 2.35 Khz I can move one of the capacitance values to a standard value.

The software also displays the input and output impedance.  If the
filter is centered between two TIA amps, this filter impedance must be
transformed to 50 ohms in the amps.  This provides the transformer
winding ratios.

The Dishal software has always given me good results.  But I haven't
compared its results to Ladpac--especially GPLA.

Bob -N7SUR

Tuesday, March 28, 2017

Pete's 60 Meter DifX

Oh man, run -- don't walk -- to the N6QW blog and check out Pete's amazing 60 meter DIFX transceiver.  DifX is another N6QW contribution to the lexicon: it refers to a transceiver that has an architecture DifFERENT from that of our beloved BITXs.  Pete means no disrespect to the BITX -- he just sees the value in sometimes doing something different.  I understand this completely -- I myself am on my FIFTH BITX   (three scratch-built and two modules) and definitely felt the need to do something different. (That's why I built the OLED NE602 rig.)  

Once again Pete Juliano shows himself to be a man ahead of his time: Anticipating FCC approval of a VFO tune-able segment in the band, Pete has made Channel 3 on his rig tunable with a rotary encoder.  Hopefully, we will all soon need this.  Pete is already there. FB OM.

My reaction to 60 meters has been very similar to Pete's.  We will talk about this on the next podcast (this Saturday).  

Pete's blog has a great description of the new rig, complete with a really nice video.  Check it out:

Monday, March 27, 2017

A Slovakian Al-Fresco Digi-Tia Homebrewed In France (and an improved AD9850 VFO)

Hello Bill and Pete,

Thanks for the podcast! My normal occupation is more computers and
software but your podcast got me motivated to melt some solder. So I
want to share a bit of what has been cooking on my bench.

I used to have a Yaesu FT-450 but sold it - I am living in a tiny rental
apartment in France without any place where to put a proper antenna so
it was only collecting dust. And where is the fun in operating a
factory-made rig, right?

So I have been working on this instead:

This "al fresco" rig is "half-DigiTIA". Half because there is no
transmitter part (I don't have a French license and I am too lazy to do
the paperwork and convert my Slovak one).  The purple modules are TIAs,
as designed by Wes Hayward, using 3x 2n3904s, only built using SMD
components to keep them small and tidy.

VFO & BFO are Si5351 + ATMega328, with an OLED module and code adapted
from Pete N6QW. It uses 11.997450 MHz IF because that's where most of my

12MHz crystals actually matched.

The 40m bandpass filter is taken verbatim from the BitX 40 design - I
have only changed the coils to use toroids instead.

For audio I have used LM386 with a NE5532 opamp as a low noise preamp
because the audio was a bit low. The TIAs don't have a lot of gain and I
have only an indoor magnetic loop for antenna so had to compensate for it.

I have another, a bit older project that became quite popular - firmware
for the AD9850 DDS VFOs using an Arduino and a character LCD. It is a
much improved replacement for the one from Richard, AD7C.

Perhaps it could be useful to someone.

Keep up the good work and 73!

Jan OM2ATC (at the moment "in exile" in France)

Sunday, March 26, 2017

An Si5351 Ham Sandwich from China (with video)

Ernesto Marquez alerted me to the offerings of CRKITS -- Chinese Radio Kits:  Their Si5351-Arduino Pro Mini "sandwich" is quite interesting.  Here is a video on the device:

I must say, that nice little sandwich seems to be crying out for an organic slice of OLED.... How about it Adam?

While there is, of course, an enormous amount of electronics coming out of China,  I haven't seen much that comes from actual Chinese radio amateurs.  But CRKITS is the work of a real Chinese ham.   Adam Rong (Rong Xinhua) BD6CR seems like a very interesting fellow. From

About BD6CR/4

Adam Rong (Chinese name: Rong Xinhua), BD6CR/4 was first licensed in 1996 while in university in Hefei, Anhui province and now holds Class 2 Chinese amateur radio license (FCC Amateur General license equivalent). After graduation from university, he moved to Shanghai and call sign changed to BD6CR/4 in July 2003. Adam is now living in Pudong new district with his XYL and their son.
Adam holds a Master of Engineering degree in computer architecture and is an Engineering Program Manager in computer hardware industry. In spare time, Adam has written a lot about ham radio for magazines and papers, mainly about QRP, homebrew projects, APRS (Automatic Packet / Position Reporting System) and ham radio software applications. Adam has also translated two ARRL's books into Chinese for Post and Telecom Press in China, including part of the ARRL Handbook and ARRL's Low Power Communication: The Art and Science of QRP by Rich Arland, K7SZ.
You can contact Adam by email, or track Adam's real time position on Google map by clicking this link.

Saturday, March 25, 2017

N8NM's SR-16 Hallicrafters Tribute RIg

Bill,  Pete:

The rig is loosely based on the Hallicrafters SR-160 transceiver, since I'm using a RD16HHF1 in the final RF, I'm calling it the SR-16.   It's a tri-band rig covering 80, 40 and 20m.  Architectually, it's similar to Pete's JBOM, which is partially coincidental (thanks for sharing the article, Pete!)  The heart of the rig is the W7ZOI hybrid-cascode IF, a really slick circuit that really makes the rig a joy to use. 
Frequency generation is handled by the ubiquitous Arduino/Si5351 combo and a sketch based on Tom, AK2B's "Multi Function VFO", to which I added functions for selecting the appropriate bandpass and IF filters, generating CW, RIT, and dual VFOs (with split functionality), the state of which is saved in EEPROM when the rig is powered-down.
The rig's just about finished - I've got the remaining parts ordered and hope to have it on-the-air soon.
73! - Steve N8NM

Wednesday, March 22, 2017

DARK SIDE TO THE MAX: WA7HRG's Android Tablet SDR (with a question)

Jim's experience with the Android tablet SDR was very similar to mine.  But he used a "Ham It Up" up converter ahead of the RTL-SDR while I used an RTL-SDR modified for direct sampling of HF.  I built a pre-amp/pre-selector stage for mine.   On my Android Tablet (50 bucks via Amazon) I found the touch screen to be kind of clunky -- it was hard to get the receive passband lined up with the incoming signal. The touch screen was not nearly as smooth as the one on my IPhone.   A Bluetooth mouse solved that problem.  

Like Jim, I am using SDRtouch from the GooglePlay.  I'll have to follow his lead and try Droid RTTY and PSK.

My reaction to the completed project was also similar to Jim's: He writes that this is, "The first and last of my SDR adventures.  This is just not the same as scratch building!"  Indeed, it is not.  But still, for very little money you end up with a pretty impressive receive capability, and you get some valuable insight into an intriguing method of receiving radio signals.  And you don't have to mess with Linux!

I have a question for the SDR gurus:  With direct sampling, we are  just running an ADC at RF.  So we no longer need an I-Q front end to take care of the image problem we had when we were running soundcard-based SDRs, right?  But I sometimes I hear that even with direct sampling systems, there is a digital generation of I and Q signals.  Why would you need I and Q if you are just digitizing the incoming passband, multiplexing it,  and sending it to the software?

Hi Guys

OK, so I am a little (A LOT) behind you guys in my bench work.  Several unfinished projects are waiting in the wings.  But I thought I would also dabble in Software Defines Radios.  Thought I would go the Raspberry Pi route as Pete did.  Then I woke up and sided with Bill.  I don’t want to learn Linux!!

For about the same price as a Pi-3 and a 7” screen I bought one of Bills Android tablets and I found on eBay an estate sale that had a bag of NuElec parts.  The RTL dongle, a Ham it Up vs. 3, and several cables, all unused.   Last but not least I bought an Android ‘On the Go’ USB cable adapter.
I removed the LED and UV diode for the remote to drop the current some. Then tapped some power off the USB connector and ran it out to the Ham it Up.  A few holes and some double sided carpet tape and ‘Bobs Your Uncle”.   I added an enable switch to the up converter for the noise source but still waiting for the SMA connector to come in.  Then I’ll see what that can do as a poor man’s spectrum analyzer for filter design.

I found several interesting apps on GooglePlay.  Besides the SDRTouch program I downloaded Droid PSK and RTTY.  Also the RFCorb client that allows you to connect to hundreds of remote stations around the world.  That I may have to spend some time exploring but not really part of this build.
The Up Converter fired right up and after tuning around some I jumped to 14.070, the PSK hot spot. The tablet truly does multitask.  I left SDRTouch running and opened Droid PSK.  A waterfall full of signals jumped up and I was easily copying stations on the East coast and Canada.

All this running on the USB power from the tablet!  How cool is that.  After about 45 minutes or so the battery was about half.  The only problem that I may have to address is that the tablet and/or the Ham it Up gets pretty warm and my carpet tape lets go and things fall apart.  HA.  Haven’t ran it long enough yet to see what else the heat might effect.

So that was fun and I will be playing with it some more.  I have coffee on Mondays with some ham buddy’s.  When I showed them the PopCorn radio they jibbed about it not being battery powered. 

Well Monday is coming!!  HA

Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column