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Monday, February 29, 2016

Antennas and National Monuments


We started SolderSmoke 185 with a brief description of my recent ascent to the top of the Washington Monument.  A few days later I was visiting George K9GDT's wonderful web site
http://www.qsl.net/k9gdt/radio/radio.htm  and in the humor section came across the above Gil cartoon from 1959.  That is the general idea. 

Pete then sent me this:


Pete originally had a three element Yagi coming out of Teddy Roosevelt's head, but that just wasn't right.  I asked that it be changed to a 17 meter Moxon.  Thanks Pete.

I would like to note for the record that I have no intention of using the Washington Monument, the Statue of Liberty, Mount Rushmore or any other national monuments as supports for any Yagis, Moxons, Cubical Quads, Ray Guns, Lazy H's, Inverted L's or any other type of electromagnetic wave launcher.


Sunday, February 28, 2016

75 and 40 Meter AM on my HQ-100 (Videos) + Digital Display






And here is how I sample the oscillator frequency for the digital counter.  I use an old trick:  I wrap some wire around the oscillator or mixer tube.  I made the coil out of an old coil form. I had to play around with the number of turns to get suitable pickup on both 160 and 40 meters.  The San Jian board allows for IF freq offset.  I use a similar arrangement on the transmit side with the DX-100.  By the way, the box that houses the two displays is the carcass of one of the Heath QF-1 Q multipliers from which I heartlessly pulled the nice reduction drive variable caps for use in my BITX rigs.  




Add caption

Saturday, February 27, 2016

Sputnik Replica Transmitter, an "Error" in the Sputnik Schematic, and Why 20.005 MHz?


Mark K6HX pointed me to very interesting Hackaday article on Frank PA3CNO's Sputnik transmitter replica.  As blog readers will recall, we went through a period of Sputnik-mania a few years ago:  http://soldersmoke.blogspot.com/search?q=sputnik  Chief Designer Comrade Mikhail Rainey AA1TJ sent me some of the Russian tubes (like those pictured above). 

The Hackaday article pointed to our post reporting that Oleg RV3GM had found the schematic:
http://soldersmoke.blogspot.com/2013/04/sputnik-schematic-found.html   Stefan reports that PA3CNO found "an error" in the original Soviet schematic:
http://www.radio.cc/post/Franks-power-supply-for-sputnik    A mistake you say?   HAH, I say!  Hah!  This must have been part of a sinister commie plot to prevent the capitalist imperialists from ever being able to reproduce the glorious transmitter of the Soviet people.  They almost succeeded. 

Just kidding.  

In the course of looking through our old Sputnik posts, I came across a question I posted:

I have a question: OK so the crafty Soviets picked 20.005 MHz for some good reasons: Being so close to the WWV freq, it would be easy for hams and SWLs to find it with precision. In the November/December 2007 issue of "Break In" (from NZ -- thanks Jonathan-san!) ZL3DW notes that this frequency selection would allow a receiver set to exactly 20 MHz to "produce an audio tone plus or minus the Doppler shift without ever going through zero beat." But zero beat with what? Most of the receivers out there would not have had BFOs, right? So the Soviets wouldn't have been using ordinary CW, right? Were they using AM, with the beeps produced by an audio oscillator modulating the carrier? 

Was their diabolical plan to use WWV as the BFO for those using ordinary AM SW receivers?   If so, a 5 kHz separation from WWV seems to be too much right?  Especially when the Doppler shift on approach would push the frequency up a bit. Maybe they just chose this freq to make it easy for listeners to find -- just a bit above WWV.  Comrade Rainey surmised that they were keying the PA stage -- the oscillator "backwave" was at times audible on the ground.

What do you think Comrades?
DSW and 73.

Thursday, February 25, 2016

"Hot Iron" New Issue, Great Articles


I was very pleased to find Tim Walford's "Hot Iron" journal in my e-mail this morning.  Lots of great articles in this edition, including one by a fellow we know:  Pete Juliano!  Pete writes about our esteemed dual gate MOSFETS.  All hail the 40673!  There is also a nice article about superhet receivers using a 6 MHz IF and a very convenient analog LC (yea!) oscillator arrangement.  Another discusses how to use Huff and Puff stabilizers to take care of VFO drift. N4HAY describes his initial foray into the world of homebrewing and how EMRFD helped him.

Hot Iron is free.  Tim writes:  

"Hot Iron is published by Tim Walford G3PCJ of Walford Electronics Ltd. for members of the Construction Club. It is a quarterly newsletter, distributed by e mail, and is free to those who have asked for it. Just let me know you would like it by e mailing me at electronics@walfords.net"

Thanks Tim!

Monday, February 22, 2016

SolderSmoke Podcast 185 -- SPECIAL FEBRUARY ANTENNA SHOW


SolderSmoke Podcast #185 is available

22 Feb 2016

http://soldersmoke.com/soldersmoke185.mp3

Travelogue:  550 feet above Washington DC

Bench reports
Pete:  Simpleceiver update.  Adventures in Raspberry Pi SDR.
Bill:  A daring but failed attempt at divide by 2 I&Q.
Audio Mods on the Hammarlund HQ-100.
Dual Digital Readout for the AM station.

SPECIAL FEBRUARY ANTENNA DISCUSSION
Why we build antennas in February.
Why hams should concentrate on antennas.
The importance of noodling.
Pete's beam project.
Pete's Lazy H.
The pernicious influence of automatic antenna tuners.
Bill's Ray Gun Antenna.
Bill's Moxon and his 160 inverted L.

MAILBAG
Tom Gallagher NY2RF (new ARRL Exec VP).
Mike Rainey AA1TJ on the air with a unijunction transistor.
Dale W9DKB sends me 160 meter book.
Alan Wolke W2AEW builds a Mighty Mite.
Daniel HK4DEI builds a DSB rig in Medellin.
Chris KD4PBJ modulates an AD9850.
Charlie ZL2CTM Builds a Teensy Superhet.
Jim W8NSA -- a Tek 465 goes toes up.
Thomas KK6AHT has roof, needs antenna!
Grayson TA2ZGE homebrewing crystal filters in Ankara.
Ian G3ROO and I had QRP QSO in 2001!
Steven G7VFy sent me a box of VALVES.
Frank KM4AXA repairs a rig and thus adds SOUL to the machine.

Design Wisdom from Allison, KB1GMX


Allison KB1GMX has helped me out of numerous battles with recalcitrant amplifiers.  She provided an interesting contribution on the r2pro mailing list thread that I referenced yesterday:  

Interesting thread...

 I see Rick as having provided the basis and tools and it up to the collective 'US" to use them to 
create that next generation radio.  All you have to do is decide the performance and 
then go about looking at the means to do so.  All the blocks are there.

Dynamic range, how much is enough?  When I'm portable or mobile raw sensitivity is 
more useful as the antenna is usually a compromise.  Overload is easy to handle with
switchable attenuator.  The exception to this was a radio designed for contesting in a 
hostile environment (a KW user 800ft away) if you burn power you get overload 
performance.  Its not a battery friendly radio (RX power is over 1A for headphone output).
Look at what you need and not what you want.

TX power is just adding stages.  I've worked MOSFETs, LDMOS, GaN FETS and there 
are some pretty cool devices out there and some not designated for RF are cheap.
If all else fails the IRF510 gets both raves and derision.  At 12V its a tepid device
but at over 20V and at 24V it starts to wake up and really perform. I've run The WA2EBY
design for a few years at 45W level using two of those push pull at 28V and its clean and 
solid and the original pair are now over 6 years old!  I also run 8 of them  (4x4push pull) 
at 32V at 6M for a cool 210W  with good IMD.  I'd add all the good (high gain, low IMD) 
power fets perform better at 28  or 50V.   For those into CW consider class E as I've 
worked with this and using GaN fets have generated 15W with 82% efficiency at 
13.56mhz (includes driver and osc) and using the lowly IRF510 at 12V a full 10W 
with 85% efficiency. Class E can be amplitude modulated.

As to the thermionic FETs, a 6AU6 crystal osc driving a 5763 for 10W  gets a lot of raves
on 40M from a buddy that runs CW.  The same deal plate modulated can sound good 
at 5-6W AM on 75M.  For those that want more a 6C4, 6aq5, 6146 will get you over 
50W on CW and 25W AM.  Change the bias a little and inject IQ SSB into the driver grid
and be running 50-80W PEP.  A 12BY7 or 6CL6 driving a pair of 6146 will get you into 
the 180-200W DC input range for about 100W.   Remember the hybrid radios solid state 
low level and rugged tubes for the heavy lifting.  The Pi network (or Pi-L) will load anything 
from about 28 to 100ohms more if you use enough taps and variable caps.  That and DC-DC
converter for the HV are not terrible at 80% or better (even the 1960s transistor designs 
were better than 75%).

In the end it all starts with the receiver.  For that you can always start with a 1T4 RF and 
a 1R4 converter and a 1T4 as regen driving a 3V4 audio.  Power it with 45V (five 9V battery)
and a C cell and go portable.  It should run for a very long while.  Hollow fets run well at low 
drain currents.  :)

Allison

Sunday, February 21, 2016

Words of Wisdom from Rick Campbell, KK7B

Rick Campbell KK7B recently responded to a question on the r2pro mailing list.  His answer was so good, and so full of design wisdom that I asked Rick for his permission to post his message here.  Here it is:

I have designed and built several new single band HF rigs for my own use since the R2pro, but have not done any complete transceiver designs intended for others to duplicate.  The R2pro was specifically designed as a set of modules so that a designer can combine an assortment of those modules with others and come up with a transceiver optimized for a particular, personal application.  Much of my recent most design work has been for instrumentation at VHF and UHF, so it doesn't really lend itself to the "high performance at HF" realm.  The R2pro design still holds up well in 2016.

Regarding being inspired to design a new high performance transceiver, I find complete transceiver designs uninspiring, hi.  I personally enjoy coming up with a particular application that isn't well served by anything currently available, and working on some unique design for that particular niche.  Occasionally it has been a large enough niche that I've worked with someone like Bill Kelsey to come up with a commercially available kit of parts, but more often I just design and build a few to fill the immediate need in my lab.  Sometimes that "need" is just a whim, and some of my most enjoyable and technically rewarding work has been to satisfy some personal curiosity or other.

Regarding your wish list:

"Best Sounding Audio Possible" is still the same as it has been since my first receiver with diode ring mixers to do the frequency conversion before any gain, followed by a serious audio amplifier string drawn from the audio recording industry.  In most of my recent work, starting with the R2pro, the limitation on dynamic range inside the audio channel is set by the op-amps.  About 80 dB from the noise floor to non-harmonic artifacts is relatively easy, but you have to be careful.  If the noise floor at your receiver volume control is 80 dB below a volt, that's about 100uV, and well below what you can see on an oscilloscope.  These are very old principles.  Though they haven't been common in the communications receiver field, no breakthroughs are needed, just careful design.  The R2pro is better than it needs to be.

"Good Dynamic Range" is an interesting concept.  I like to design receivers that have good enough dynamic range, which is different for every application, on every band.  Unlike during the 1970s, today most of our receivers have enough dynamic range, in the same sense that cars have had enough wheels since designers figured out that 3 was not enough.  Once you have enough, adding more is not an improvement.

Some of my recent receivers have had a crystal filter between the antenna and first active stage.  Those are stellar, but that's not usually needed.  They do illustrate the point that if you find yourself operating in a hostile EM environment with many very strong nearby signals, there are other ways to address the problem besides in the receiver circuitry.  Ever since I achieved "good enough" for all my personal applications a while back, I've focused on other receiver performance measures.  In particular I try to avoid sacrificing something important to make an improvement in a specification that is already good enough.  I have never been on a hilltop with Wes Hayward when anyone missed a contact because of inadequate dynamic range, but I have been when we missed contacts because the batteries died.

"SCAF type filtering."  I've played with switched capacitor audio filters and other commutating signal processing since the mid 1970s.  Each time I've built one into a  receiver I've run into problems with that danged clock.  I tend to listen at and below the noise floor, and one of my pet peeves is when I can hear anything at all other than pure thermal noise when the receiver is terminated with a room temperature 50 ohm resistor.  Since I routinely record signals for post processing in a DSP system, it is disheartening to discover that some harmonic of the SCAF clock beat against the LO at a particular frequency, ten dB below the noise so you didn't hear it when you made the recording, but 10 dB above the noise floor in your FFT waterfall plot.  So I have avoided such things for my last few decades of instrumentation-grade receiver designs.  When I have a digital dial, I include a switch so it can be turned off when I'm recording weak signals.  None of this applies to you--please continue to experiment with SCAF filters, embedded processors and other generators of digital noise that may well be far beneath the threshold of signals and antenna noise for your particular application.

"Audio output power."  In my lab I generally find about a half watt is more than enough for a radio tuned to a ham band.  In other applications I go as high as 40 watts of audio at the threshold of detectable two-tone IM products.  All of that is nicely covered in the audio literature, and there are a number of good designs available on the web.  The R2pro audio amplifier in EMRFD works well driving a compact, efficient speaker in a quiet room.  For more power output, use bigger transistors and raise the supply voltage up to about 24.  Above that, you need to add Darlington drivers, as in the original R1 and R2 circuit, and you can then raise the voltage up to around 40v with NE5532 op-amps and get more than 20 watts of superb clean audio.  That R2pro audio output stage in EMRFD has been borrowed and modified for more than one very high end professional audio application.

"RF Power" For either audio or RF power, I encourage experimenters to use higher voltages than 12.  Within a few years we should have available some nice GaN transistors that will allow us to use supply voltages up around 80, which really makes it easy to generate many watts of power into either 50 ohm or 8 ohm loads.  If you don't want to wait for GaN, there are some huge N channel depletion mode FETs that run the electrons in vacuum and will easily handle many hundreds of volts on the drain.  They need a separate low voltage supply at an amp or so to generate the electron stream, but are capable of astounding performance, particularly in narrow band applications.  If they hadn't been invented 100 years ago, we'd be all excited about the possibilities now.  A 6146 would just idle along at 5-10w out and last forever.

For my most recent contacts on 40m CW, I used an R2pro and ran a very stable premixed JFET Hartley VFO driving a 6C4 and 6AQ5 output stage.

Enjoy the experiments.

Best Regards,

Rick KK7B
__._,_.___

Saturday, February 20, 2016

Dr. Rufus Turner, W3LF. Homebrew Hero and Radio Pioneer


Thanks to Farhan for alerting me to this great Hackaday article about a homebrew hero who was -- sadly -- unknown to most of us.  He lived in Washington D.C.,  right down the road from where I live now.  The Hackaday article leaves no doubt about it -- Rufus Turner was one of us. He had THE KNACK.  He was a true radio pioneer and homebrew hero.  It is really a shame that we've known so little about him.  


Friday, February 19, 2016

Inside the Hammarlund HQ-100


I continue to work on this old beast.  I picked it up in the Dominican Republic around 1994.  One of the IF transformers had gone open.  I fixed that.  Had to replace the AF output transformer too. And the variable cap that tunes the antenna.  Check out the flywheels!  And the rope and pulley thing.  You don't find those kinds of things in any of those fancy modern rigs. 

Earlier I had removed "the exclusive Auto-Response audio output circuit."  See:
http://soldersmoke.blogspot.com/2016/02/snowed-in-audio-mods-on-hammarlund-hq.html

Today I installed a simple feedback network in the AF amplifiers (as prescribed here:  
http://www.amwindow.org/tech/htm/hqaudiomods.htm

It sounds nice now.   The rest of the bands have been ravaged by some sort of solar event, but 160 seems to be benefiting -- signals last night and this morning were quite strong.  I was being heard by WA1HLR way up in Maine.

UPDATE 20 Feb 2016: After installing the feedback network mentioned above, I noticed a big increase in AC hum.   It was not the electrolytics.  I reversed the feedback mod and the hum went away.  But the receiver continues to sound a lot better with the removal of the Auto-Response output circuit.

Wednesday, February 17, 2016

Just Below 160 Meters -- "Travelers' Information Service"

In the course of working on my 160 meter AM station I came across a strong AM signal a bit below Top Band.  Turns out it is part of something called the "Travelers" Information Service."

The signal from this system on 1.670 MHz is very strong here.  A Shortwave (Midwave!) Listener in Austria heard it too.  Check out the confirmation letter from the Virginia Department of Transportation.  Nice of them to do this.
Here is the QSL letter sent to Austria:
https://remotedx.wordpress.com/2014/06/01/very-rare-reception-vdot-highway-advisory-radio-1680-khz/

They are running 10 watts into a 49 foot tall vertical with 40 radials. They have a text-to-speech system that is constantly describing weather conditions.  Quite useful actually.

I found a web site that lists all the stations of this kind in the US:

https://www.fcc.gov/media/radio/travelers-information-stations-search

I can see that the station I am hearing is just 2 miles from my location.


More information on this system:

https://en.wikipedia.org/wiki/Travelers%27_information_station

Tuesday, February 16, 2016

A Phasing Receiver from Montenegro (Video)



Thanks to Peter Parker VK3YE for alerting us to this beautiful receiver from Bore 4O6Z in Montenegro.  This may be our first ever report on a Montenegrin rig.  And it is a thing of beauty. Bore says it is based on a phasing circuit by homebrew legend V. Polyakov, RA3AAA.

Here is 4O6Z up on the tower:

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