More Cuban Homebrew from the 80's and 90's -- A 160 Meter AM (Controlled Carrier) TX with Soviet 6P23s

 

160 Meter Transmitter

Jose CO6EC writes: 

I will be sending you some work of homebrew from the 80's and 90's when practically everything was manufactured by Cuban radio amateurs

The photos are of a Modulated Amplitude TX for the 160 Meter Band, about 25W of which several were made.  The final tube  was modulated in many cases by a 6DQ6, 2E26 or other similar ones that were very abundant at that time. 

This one in particular is  made with valves  6BH6 for the VFO, 6CL6 for the amplifier step and 6P23 Soviets in the final part, the modulator was made up of a 12Ax7 microphone preamplifier and a 6BM8 that came out through the cathode to the screen grid of the 6P23, in this way the carrier was controlled by modulation what we called  Carrier Control as there was no voltage on the grid at the ends there was practically no carrier  in the air which gave the impression of transmitting in SSB. hihihihihihi

For those who did not have a communications receiver, a conventional radio was adapted to receive that band, which in many cases was a VEF-206 of Soviet construction, to which an oscillator was adapted to beat the signal and get exactly on frequency. This was very popular here in the late 80's and early 90's. 

Thanks Jose.  We look forward to learning more about Cuban homebrew. The way in which radio amateurs got on the air with gear that they made themselves using the limited parts available to them is really interesting and admirable. 73  Bill 

SolderSmoke Re-Play: Shep tries to build a Heising Modulator -- Shep on Parasitics and Troubleshooting: "That way madness lies"

You guys really have to listen to this.  This is culturally important.   

In this 1965 radio broadcast, Jean Shepherd describes his teenage struggles with parasitics and other technical problems in his homebrew 160 meter transmitter.

He describes the sound of parasitics on a signal, saying that they sound as if the signal is being attacked by "debauched erotic locusts."

He really nails it in describing the scornful, dismissive tone that many hams use in telling their fellow radio amateur that there are problems with his signal. ( I have recently been on the receiving end of this kind of treatment.)

He observes that no one is more worried, "than a man who has built something and can't get it to work." Indeed.

During a date with a girl from his high school, he is so obviously preoccupied with his transmitter trouble that she tells him that something is wrong with him and that his mother "should take him to a doctor."

And he describes the joy that comes when you figure out the problem and get the thing to work.

The REALLY good stuff begins at about the 25 minute point.

http://ia310115.us.archive.org/2/items/JeanShepherd1965Pt1/1965_01_29_Ham_Radio.mp3

Shep was quoting from King Lear: "O, that way madness lies; let me shun that; No more of that."  In other words: "BASTA!"  

EXCELSIOR!

Narrow Band FM on 160 Meters? Using SSB phasing rigs?

On the G-QRP mailing list our British cousins are discussing the use of Narrow Band FM on Top Band.   160 meters has long been used for day-time local "chin wags" in the UK.   Noise, of course, is a factor to consider on 160.  FM would take care of the noise problem.

I was wondering if this would be legal in the USA. This is the kind of question that seems to provoke passionate, sometimes angry reactions.   I think the answer depends on the resulting bandwidth of the signal. 

There was an interesting discussion of this here:

http://www.eham.net/ehamforum/smf/index.php?action=printpage;topic=65481.0

Especially intriguing to me was Tom's comment about the link between Narrow Band FM and the early SSB phasing rigs.   I hadn't heard about that:

---

Title: RE: Narrow Band FM is it legal below 30 MHZ.
Post by: N5EG on January 22, 2010, 11:10:43 AM

---

Hi Tim,

Yes - NBFM is legal. This is actually a hold over from long ago equipment. Back in the olden days phasing SSB exciters could also be adjusted to produce NBFM.

It's a little different than modern FM, in that the signal looks just like an AM signal, except the phase of one of the sidebands is 180 degrees reversed compared to the AM equivalent (doesn't matter which sideband). This gives an angle-modulated signal with +/- 45 degrees phase variation, but also 3 dB of amplitude variation.

While we don't normally like amplitude variation on an FM signal, it has the effect of preventing the generation of the higher order sidebands that true FM produces. A receiver than has a limiter stage doesn't care that much.

The result is that the old phasing exciters could produce this different kind of Narrow Band FM (probably the true meaning of NBFM long ago) that had the same channel width as AM, and a modulation index that's well below 1. Such a signal is compliant with current FCC regulations on HF bands.

-- Tom, N5EG

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.

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

Single Sideband + Carrier -- The Collins KWS-1

Back on 2 February I was on 160 AM with the DX-100, talking to WA4PGI.  At the end of our QSO we got a call from a station.  I was at first confused -- was this station calling on SSB?  Or was he calling on AM?   Turns out that he was -- in a way -- on BOTH.  K4DBK was -- I think -- running an old Collins KWS-1, the transmit side of the famous Gold Dust Twins.  Aptly named:  It was built in 1955. 1000 watts output.  $2095.00 in 1955.  Gold dust indeed.  

The really interesting thing about this rig was that it put out CW, SSB and SSB plus the carrier.  I think that was what we were hearing from K4DBK.  FB.   

Does anyone have an e-mail address for K4DBK?  I'd like to drop him a line.

http://www.collinsradio.org/cca-collins-historical-archives/the-equipment-of-collins-radio/the-black-boxes/kws-1/

Blizzard Prep Priorities: Protecting the 160 meter L network!

I'd been meaning to build a proper cover for my improvised 160 meter L network. The approach of Winter Storm Jonas pushed me into action yesterday afternoon. 

First I mounted the variable cap (from an old Johnson rig) and the roller inductor on a suitably sized piece of wood:

Then I put the tuner inside an old cooler.  I drilled holes in the bottom for the coax and the antenna wire and the ground.

Here it is at the feed point.  Pretty cool, don't you think?

And here it is 24 hours later:

The blizzard has been quite impressive.  Early this morning it featured lightning and thunder!

High-Pass Filter Knocks Down AM Broadcast Interference

WFAX 1220 AM was starting to bother me.  Each morning, I'd be drinking my coffee, listening to nice roundtables on 160 meters, when, right at 6 AM, WFAX would fire up its 5 kW AM transmitter, 1.5 miles from my location.  And they would crush the "front end" of my R2 phasing receiver.  It doesn't take much to do that, since the only thing between the SBL-1 mixers in the R2 and the antenna is a signal splitter.  Obviously I needed some filtering. 

I turned to the free program called Elsie (L-C, get it?) and quickly whipped up a design for a seven element, capacitive input high-pass filter that promised to take about 45 db out of WFAX's sails, without attenuating even the lowest end of Top Band. 

Last night I scrounged through the junk boxes and found suitable capacitors.  A visit to an on-line toroid calculator showed that around 35 turns on a T-50-2 (red) iron powder core would yield the needed 6 uH coils.   I built the filter  this morning -- picture below. 

It works very well.  You can see the results in the picture above.  The yellow trace on the 'scope shows the signal at the antenna terminal.  Yikes, it shows around 4 volts rms at 1.220 MHz (the scale is 5 volts/div).  The blue trace below is on the same scale -- this is the signal coming out of the filter.  Not enough to really measure on the 5 volts/division scale.  

This was a very satisfying "quick and easy" build.   I really like the sound of the R2, so much so that I'm not firing up the DX-100 as much as I had been.  Instead I find myself just listening to the R2.

Arduino Problems -- Back from the Ledge

As I was struggling through this, someone -- who will remain nameless -- told me that because of all the technical problems resulting from the many Arduino IDE "upgrades," suicide prevention hotlines now answer all calls with an automated question:  "If you are calling about an Arduino problem, press 1 for assistance."

It got pretty ugly but with the help of Tom up in NYC I managed to get through it. First he convinced me that it is indeed POSSIBLE to upload the latest version of the IDE -- the dreaded 1.6.7.   I just had to REALLY get rid of earlier versions.  This got me past the horrible Bundled Java Runtime Environment problem (who thinks up these names?).

We then worked with the libraries needed to upload the AD9850 code of Richard AD7C.  You see, I work on Arduino stuff.   Then I stop.  18 months pass.  I forget all I learned.  Then I start over.  The pain begins again.  In an effort to break this cycle, I am now taking notes (in the inside cover of Mario Banzi's book).

I am using the AD9850 with a Kanga Arduino shield designed by Paul M0XPD.   It takes the AD9850 output, divides by 4 and puts it out as 2 square waves in quadrature.  I use this with my R2 phasing receiver.   The problem was that the display on the Arduino showed a freq 4 times the actual tuning freq.  Believe me, this gets old fast.  I considered just getting a San Jian freq counter and supergluing it on the top of the DDS box.  I was going to connect this to the square wave output.  That would have given me one readout with the actual receive freq, and another (on the Arduino) showing the (4X) freq coming out of the AD9850.  But that would have been too much of a Kludge. Tom talked me out of it and modified the code so that the Arduino display shows the actual receive freq.   Thanks Tom.  

Armed with the new IDE and with my knowledge of Arduino basics refreshed, I was able to reload the LA3PNA Si5351 code into my 40 meter DIGI-TIA.  But not before having to swap out the Arduino that drives the Si5351.   One Arduino happily accepted the code, another did not.  Why?  Who knows?  It is a digital mystery.  Those little 1s and 0s are fickle you know.

The Radio Gods rewarded me for all this.  At about 5:45 AM today I was listening to a very friendly SSB roundtable on 160.  The guys were getting ready to sign off.  The last one ended the conversation by asking the others to "Be kind.  Smile at your neighbors."  Nice.
Then WFAX AM started the broadcast day at 6 am, wiping out my 160 meter reception.  Next project:  High-Pass filter at 1.7 MHz.

SolderSmoke Podcast #184 160 AM and CW, R2 Phasing Receiver, Mailbag

SolderSmoke Podcast #184 is available

http://soldersmoke.com/soldersmoke184.mp3

16 January 2016
-- The Radio Amateur is BALANCED
-- Pete exhibits CLEAR symptoms of Dilbert's disease!
-- Santa brought me a 160 meter antenna
-- Ground Radial systems large and small
-- Clip lead L network
-- ON THE AIR ON 160!
-- AM contacts
-- SKN 160 CW with sidetone from the DX-100 transformer
-- Stations with character and personality on 160 AM
-- Pending projects for the AM station
-- R2 phasing receiver Trials and Tribulations 
-- Bill's Astatic D-104 goes into rebellion
-- Ramsey Kits closing down
-- SPRAT 165,  Sidetone,   M0XPD's VXO
-- "The Martian"  movie 
-- Little Gustavo is doing well.  Thanks to all.
-- MAILBAG (an especially good one)

Happy New Year! Straight Key Night on 160 Meters

A while back, when I first mentioned getting on 160 meters by year's end, Pete suggested I shoot for Straight Key Night.  As many of you know, suggestions from Pete somehow seem to have a way of becoming ham radio MORAL IMPERATIVES.  He seems to be a prophet of sorts, a prophet of THE RADIO GODS.  So following the guidance of the oracle of Newbury Park, I found myself in front of my DX-100/HQ-100 on New Year's Eve, on 160 meter CW for the first time in my 42 years as a radio amateur.

It was great.  A couple hours prior to the official 0000Z start of Straight Key Night I had my first 160CW QSO.   It was with John WA2MUA up in Summit, NY.  John's QRZ page includes this: “Years ago--as a teenager-- in an attempt to get enough wire for 160 I wrapped a quarter wave of wire around a pvc pipe, strapped it to a wooden gutter----burned a large notch in the gutter and could have burned my parents' house down!”   That, my friends, is 160 meter KNACK!  

Then, just minutes after SKN kick-off, I worked John W3LR in Eastern Pennsylvania.  It was also John's first SKN contact.

Next up was Eric NO3M.  Wow, this one was amazing.  Eric was running the homebrew rig pictured above.  On his blog Eric describes the rig:   "The transmitter is running a 89 Clapp oscillator, 802 buffer, 811 final...  Output power is approximately 75W. "

Eric's antenna is even more amazing:  it is a 160 meter four square featuring FOUR aluminum tubing vertical elements with capacity hats and --GET THIS -- a radial field consisting of 22,000 feet of bare copper wire. TWENTY TWO THOUSAND FEET OF BARE COPPER WIRE.  Wow, you just don't run into stations like that on 20 meter sideband.   Eric's blog: http://no3m.net/  But Eric -- a Vibroplex Champion?  On SKN? 

I then worked KC2LSD and K1EEE.  FB!

My last contact of the evening (and the year) was K1WHS, Dave in Maine.  On his QRZ.com page, Dave reports:

“On 160 meters, I have a small setup right at my house. I use a K3 with a homebrew 3-1000 amplifier that runs at 1300 watts. The antenna is an 80 ft Rohn 25 in my backyard with some top loading and shunt feeding.  I laid out a bunch of radials in an effort to get the efficiency up. At last count I had about 107 1/4 wave radials strung out. 160 is the only band where my feedline is not big fat hardline. I use a run of RG-213.  For receive, I have several beverages running in the woods. I use this setup often in the winter as many times, the hilltop shack is not accessible due to heavy snow.   I have nothing up for any of the bands between 160 and 10 meters”.

 Thanks to all of my SKN contacts!  And Happy New Year to all  SolderSmoke readers and listeners! 

The K7DYY Solid State Class D Legal Limit AM Transmitter

I was on 160 Meter AM this morning, talking to Chet WB2AHK in New York City.  Chet had a very strong signal here.  He was running a rig that I hadn't heard about before, a K7DYY transmitter.   See above. Very interesting.   Here are the details:

http://k7dyy.com/index.html

Chet's receiver was at the opposite end of the technology spectrum -- like me he was listening on a Hammarlund HQ-100.  He told me that he had replaced the old mechanical clock with a digital "glowing numerals" device.  This got me thinking that that space on the front panel might be suitable for a small frequency counter...

First Contact on 160 Meters

Hooray!  After 42 years on the ham bands I have finally made a contact on 160 meters.  And it was on AM, using John Zaruba's DX-100.  My antenna is the 185 foot wire that I mentioned in yesterday's post.  I built an L network using a roller inductor and a bread-slicer cap -- the network is at the base of the antenna.  Before dawn this morning I threw my call into a round-table on 1885 kc.  Pete WA1SOV up in Connecticut heard me and we had a short contact. Hooray! 

I hope this puts some pressure on Steve Silverman and Pete Juliano -- they have sworn A SOLEMN OATH to get on top band.  I'm especially worried about Pete's adherence to this pledge -- he seems to be going a bit wobbly on us, playing with Raspberry Pi's and things like that.  C'mon guys!  Top Band awaits!

My antenna needs improvement.  More radials might help. 

"Receiver Here is My SWR meter OM..."

Santa managed to include in his delivery some of the materials that I needed to build my 160 meter inverted L antenna.   You see, Steve Silverman, Pete Juliano and I have collectively more than 150 years in ham radio, but none of us have ever operated on Top Band.  The three of us have taken A SOLEMN OATH to correct this horrendous deficiency.   I am in the vanguard, partly due to a weather pattern that is perfect for antenna building. 

Armed with a new elastic band for my Wrist-Rocket sling shot and some perfectly shaped lead sinkers,  yesterday -- with the obvious cooperation of The Radio Gods -- I managed to get two ropes over some 70 foot trees.  Soon -- with minimal gnashing of teeth -- I had 185 feet of wire in the air. 

This morning I was messing around with L networks at the base of the antenna.  I took a coffee break, leaving the 185 foot wire and the ground system connected to the coax.   I had the transmitter off, so I was surprised to see the SWR meter jumping around a bit, up significantly from zero.   What could that be?  It wasn't coming from my station, so it had to be coming from some other transmitter. And the slight bit of jumping that I saw on the SWR meter had the familiar pattern of the human voice.  Some radio sleuthing ensued.

I flipped the station antenna switch to the  "bench" position, and connected my scope to the coax.  Wow!  I immediately saw a big strong AM signal with modulation, at about  5 or 6 volts peak to peak.  The Rigol 'scope gave the frequency:  1220 kHz.  

I tuned the HQ-100 to that frequency.  As I listened to Gospel broadcast, I could follow the voice peaks on the 'scope. 

Some Googling ID's the station:  WFAX 1220 AM.   5 kilowatts in the daytime.  1.5 miles from my house.  The vertical portion of the inverted L is obviously picking up a LOT of energy from the WFAX tower.  And the horizontal portion of my antenna is broadside to the WFAX tower.

Of course this all made me think about throwing together a crystal radio, but then I realized I'd already listened to WFAX with simple diode -- the one in my SWR meter.  That little SWR meter was acting like a crystal radio with a visual output!