Podcasting since 2005! Listen to Latest SolderSmoke

Showing posts with label SSB. Show all posts
Showing posts with label SSB. Show all posts

Tuesday, March 26, 2024

How to Feel Bad about Carrier Suppression (and How to Get Over It)


Version 2 of the 15-10 rig continues to give me trouble.  But I guess it is "good trouble" because I am learning from it. 

You see, after you build an SSB rig, one of the critical alignment steps is the placement of the carrier oscillator/BFO frequency in relation to the filter passband.  (The IMSAI Guy has a good video on this -- see above.)  You want to place this oscillator somewhere on the downward skirt of the passband curve.  This will add to the carrier suppression already done by your balanced modulator.  There will always be some carrier remaining from the balanced modulator -- putting the oscillator frequency on the downward skirt of the filter passband adds to the suppression the carrier remnant.  

But you can't overdo it.   If you place that carrier oscillator frequency too far down on the skirt, you will start to cutoff the low audio frequencies in your transmit and received signals.  You will notice that your once beautiful sounding receiver suddenly sounds tinny and high pitched.  Yuck. 

So you go back to the books and the websites.  You look at the passband promissed by the Dishal software you used to design the filter.  See below:  

Click on the image for a better view

Surely with a passband as nice as that one, you will be able to find the sweet spot where the carrier is suppressed and your audio remains pristine.  

But I couldn't do this with the 15-10 rig.  I was forced to compromise: I had to accept less than optimal carrier suppression for less than optimal low frequency passband coverage.  And here is why:
Click on the image for a better view

The curve above is a much more realistic picture of what my filter passband actually looks like (see NanoVNA picture below).  The curve above is from the AADE software.  I found out that the Dishal software DOES NOT factor in important things like Q or ESR.  Dishal treats all crystals as "loss-less radiators."  So when you get up to 25 MHz where Q is important, AADE and other programs will show you that your passband has become curved.  And you can see how this curvature makes it difficult to get the kind of carrier suppression and audio response we want.  

What my filter looked like in a Nano VNA
Click for a better view

Look, the rigs work OK.  The receivers sound good to me.  The carrier is so far down that no one can hear it.  I have to remind myself that we are using 'SSB-SC" -- suppressed carrier, not eliminated carrier.  I've worked a lot of DX with these rigs.  But still,  I would like to improve the situation.  It kind of bothers me.  Homebrewers will understand. 

I have been experimenting with different balanced modulators.  I started with the simple two diode, single transformer, singly balanced design from Farhan's BITX20.  It works fine.  But I think I get a bit better suppresson from a doubly balanced diode ring.  I may try an NE602 Gilbert Cell.   I may also try to build a higher Q 25 MHz filter using low-ESR surface mount crystals from Mouser.  Stay tuned.  

Thanks to W7ZOI, VU2ESE, WN2A, KA4KXX, KK4DAS, N6QW, W2AEW, and G3UUR for all the good advice and encouragement.  Please put any additional ideas in the comments below.  

Friday, March 15, 2024

Finishing up (?) Version 2 of my 15-10 Transceiver (Video) -- An Annoying Residual Carrier Problem


Front panel is on. RF PA is installed. Balanced Modulator problem fixed (?) Rig is on the air with about 3 watts, working lots of DX.

But there is an annoying amount of carrier that is still getting through. It is only about .5 watts with sidebands of 100 watts PEP, but it annoys me, and it makes the setting of the carrier frequency in relation to the filter passband very critical: If I set the carrier a bit too far from the passband I get improved carrier rejection (from the filter), but I also lose the lows in both received and transmitted signals -- the RX just doesn't sound as good. I see it in both of the 15-10 rigs (IF of 25 MHz). There is less of it in the 17-12 meter rig (IF of 21.4 MHZ), and none of it in the Mythbuster (75-20 meters) (IF of 5.2 MHz). I am now wondering if this might be a consequence of my using a very high (25 MHz) single conversion IF in the 15-10 rigs. What do you folks think?

From my log: March 7, 2024 PUT VERSION 2 of the 15-10 RIG ON THE AIR! 10S 1528 OK2RZ Jiri – said I was 57! 15S 1539 S52WW 58 Damian. 15S 1602 SP1NQH Stev said I am big signal! 10S S58N 1726Z 10S S58N 1726Z 10S S57S 1728Z 10S IK4GRO Lauro 1735Z 10S W0CJV 1825Z Ft. Collins Gary 10s 2000Zish KK7TV Gary in Randy. Asked what software/microcontroller I was using. 10S KJ5MFF 2015Zish a middle school in New Mexico. KI5MFF control op sent picture

 

Tuesday, January 30, 2024

Yet ANOTHER Homebrew 15-10 SSB Transceiver (Video #1)


A homebrew 15-10 SSB Rig for the Dominican Republic:

This is my second build of this rig.

I am using a 10 pole crystal filter that I built for the first build, but did not use. I am also using the tuning capacitor from a Galaxy V's oscillator -- I like the anti-backlash gears and the reduction drive. This rig is built on a pine board covered with adhesive copper tape. It has been built stage-by-stage on copper-clad boards using the Manhattan construction style.

The structure of the rig is basically that of a BITX rig -- the RF and IF amplifiers are Termination Insensitive Amplifiers.

Soon the receiver will be completed. I will then build the stages needed for the transmitter portion of the transceiver.

I will take this rig with me to the Dominican Republic.

Wednesday, January 3, 2024

Mostly DIY RF's Kit of Pete N6QW's P3ST

 
There it is.  Truly a thing of beauty. Order yours today!  


Monday, September 4, 2023

SolderSmoke Podcast #248 -- Back from the Summer -- Spurs and Filters, S-meters, 6BA6 mania, Shirtpocket rigs, MAILBAG

The PsssT Kit, coming soon from Mostly DIY RF

SolderSmoke Podcast #248 is available for download: 

Audio: http://soldersmoke.com/soldersmoke248.mp3

Video: (800) SolderSmoke Podcast #238 -- Spurs and Filters, S-meters, 6BA6 mania, Shirt-pocket rigs, Mailbag - YouTube


Travelogue:  Trip to the Dominican Republic 3-9 August.  Thinking about the M0NTV video on mixers...  

Solder Smoke Shack South is almost done.   I am thinking about workbenches, operating tables and antennas.  How high should an electronics workbench be?   Table height?  Or workbench (woodwork) height?  

My son and I went to see "Oppenheimer"  Trinity test scene very cool.  They wanted to see if the gadget would work! 

Is the SolderSmoke blog completely archived on the WayBack Machine?  Please check and let me know.  Thanks. 

Bill's Bench: 

-- I've been working a lot of DX with the homebrew rigs:  Indonesia, Australia, Japan, Hawaii.  Lots of fun.  15 meters has been especially good. But the rigs still need work: 

-- M0NTV's video got me to put TinySA to work.  I found that output from dual banders could be improved.  Spurs and harmonics. Yuck.  I need more TinySA -- ordered the TinySA Ultra. 

-- Allison KB1GMX helped a lot.  EB63A amp was unstable, especially on 10 meters.  Higher frequencies are harder!  Tightened up shielding, negative feedback, and bypassing.  This all helped, but I found that I needed to take the higher frequency LP filters out of the amplifier box.  W3NQN filters are better, with steeper skirts and better 2nd harmonic rejections. NanoVNA proving very useful. https://www.gqrp.com/Datasheet_W3NQN.pdf

-- Also worked on the Bandpass filters for these rigs.  Farhan's comments on skirts of different filter configurations.  Some are "LSB" filters (with steeper skirt at the highest freq) and some are "USB" filters (with the steeper skirt at the lower frequency)  See diagrams on the blog page. So I built USB new filters for 12 meters and for 10 meters. 





-- Danger that my unshielded wooden box rigs might be inviting feedback.  So I shielded the 1510 rig with copper guitar amp tape (conductive adhesive).  Good stuff.  

-- Phase Noise rears its ugly head again.  See blog posts. 

----------------------

SHAMELESS COMMERCE DIVISION:  

Mostly DIY RF getting ready to release PsssT kits.  Target date:  December 18, 2023 (E Howard Armstrong's birthday).  https://mostlydiyrf.com/

Amazon Search box seems to have died.  I can't get it back.  Can anyone tell me what happened?  (There seems to be "explanations" from Amazon about this, but they are written in a strange language that I cannot follow.)  Something similar happened with the Google Ads on this blog page.  Apparently you can't have ads both on YouTube and blogger.  

But hey, there is Patreon for those who want to support the podcast and blog. 

-------------------------

Pete's Bench

An S-meter for Bill? 

6BA6 Mania! 

QRP SSB with 6BA6

Shirtpocket rig re-build

Mailbag: 

Walter KA4KXX has a great article about homebrewing in the September 2023 QCWA Journal.  

 Steve KC1QAY -- Has joined the CBLA.  I sent him a 3579 crystal.  He built a MMM and experienced JOO.  And Allison KB1GMX is in his local radio club.  TRGHS. 

Ajay VU2TGG in Pune, India -- launching a high school receiver effort. 

Denny VU2DGR The Wizard of Kerala: https://soldersmoke.blogspot.com/2023/08/the-wizard-of-kerala-india-denny-vu2dgr.html

Joe VK4BYER working with kids a remote Australian community.  FB. 

Todd K7ZF -- Wants to get into homebrewing. Advised him to start small. 

Dean KK4DAS:  Fixing Hallicrafters Worldwide RX. Ciudad Trujillo!  Got question from Mark in the VWS Makers Group:  HOW DOES Michigan Mighty Mite REALLY Work.  See blog. 

Trevor Woods -- Info on Super Islander Mark IV made in Cuba from old CFL bulbs.  FB. 

Bob KD4EBM sent me some great stuff:  Sony SW receiver,  QCX Mini.  Made a CW contact with the QCX.  Felt virtuous -- it is going to the DR.  Thanks Bob. 

Peter KD2OMV:    One of the guys I worked with the ET-2 transceiver.  Great to hear from him. 

Armand WA1UQO   Richmond area radio museum? https://www.youtube.com/watch?v=BSCmljje1p8

Mike WN2A -- Sent me a great care package with lots of toroids.  A lifetime supply!  Thanks Mike!

Nate KA1MUQ got his Doug DeMaw receiver going after 38 years!  FB.  Been there, done that! 

Tony: G4WIF Liked Valveman video about Gerald Wells.  He visited him! https://soldersmoke.blogspot.com/2023/08/valveman-story-of-gerald-wells.html 

Dean KL7MA  Bill talked to him on 15 SSB.  He had worked Wes W7ZOI!  FB! 

Thursday, January 12, 2023

On Ten Meters with a uBITX from the Eastern Tip of Hispaniola


On ten from HI7.  Cluster spots, DX, CW, and the Reverse Beacon Network. 

 

Wednesday, December 14, 2022

Faust Gonsett and the SB-33 in 1963

 
Click on the images for better views

When this ad appeared in 73 Magazine in February 1963 I was 4 years old, living on Manhattan Island.  Pete N6QW was in the Navy, heading to Midway Island. 

Pete writes: 

-------------------
This ad has a tremendous impact on the foundations of our hobby. The SBE-33 was pure genius in its design and implementation.

  1. It is a hybrid rig using Germanium transistors –the transistor was only 15 years old
  2. The Mechanical band switching showed the strong use of mechanical assemblies
  3. The small size was simply amazing
  4. The Bi-lateral circuitry predates any Bitx circuits.
  5. The urban legend was that a team of illuminati were involved in its design (Don Stoner is one name that pops up)
  6. The Japanese were a quick study and the FTdx100 in 1967 is a result, only better.
  7. Many are still around in shacks. I have three

 

Gonset was well known for innovative designs – the Gooney Box is another example. Look at all of his compact mobile equipment.

 

The next point – the final owner of SBE was Raytheon thusly the next generation of SDR Radio Equipment for the US Air Force can trace its pedigree to the SBE-33.

 

This was the appliance box of 1963. I saw my 1st SBE-33 (August 1963) when likely you were in the 2nd Grade and I was headed off to Midway island.

-----------------------

 


I have an SBE-33 that N6QW sent me. Thanks again Pete!

Also, I'd like to note that W6VR had a very cool name.  Faust Gonsett.  I just sounds like the name of a real radio guy.  Google says this of the given name Faust: 

"Faust as a boy's name is of Latin origin, and the meaning of Faust is 'fortunate, enjoying good luck.'   Indeed. 

Tuesday, August 23, 2022

SolderSmoke Podcast #156 -- November 4, 2013 -- Interview with Peter Parker VK3YE of Melbourne, Australia


November 4, 2013
Special hour-long interview with Peter Parker, VK3YE
-- Early experiences with radio
-- CW
-- DSB Gear
-- Simple gear, and gear that is TOO simple
-- VXOs, Super VXOs and Ceramic Resonators
-- Building receivers
-- Chips vs. Discrete
-- Making the leap to SSB
-- The Knob-less wonder and the BITX
-- No need for a sophisticated workshop
-- Advice for new phone QRPers


Peter's Blog: https://vk3ye.com/

Peter's YouTube Channel:  https://www.youtube.com/user/vk3ye/featured


Wednesday, May 25, 2022

HF Bandsweep with the Hammarlund HQ-100 (video)


It has been a while since we last did a bandsweep.  Too long.  Here is one using my recently fixed up Hammarlund HQ-100.  Repair details are in recent videos. 

For this bandsweep we cover most of the HF band and even briefly dip down into the AM broadcast band: 

Demonstration of the Hammarlund HQ-100: Radio Marti, 40 meter AM, 40 Meter SSB, 40 meter FT-8, 40 meter CW with and without the Q multiplier, classical music on WRMI, WFAX 1220 kHz AM, WWV 20 MHz, CB!, 17 meter SSB, the 20 meter BS position, the effect of AVC and the Noise Limiter, SSB with the internal BFO and with the Q multiplier as BFO. CW with the internal BFO AND the Q multiplier. 

Be sure to subscribe to the YouTube channel.  

Wednesday, April 6, 2022

The First Commercial SSB Trans-Atlantic Radiotelephone System


These guys didn't just complain about QSB -- they DID SOMETHING about it!  
Thanks to AWA and Hack-A-Day for disseminating this great video.  

Wednesday, March 23, 2022

First Ever Contact on 12 Meters: Homebrew, QRP, SSB, DX (Video)


I've recently finished most of the circuitry on the 17-12 meter dual band SSB transceiver. I have had contacts with it on 17 meters, but until yesterday morning (March 22, 2022) I had not had any contacts on 12 meters. This morning I talked to Paul EA5JZ in Valencia, Spain. I was running the 17-12 rig barefoot at about 5 watts with the final being one RD06HHT FET. The antenna was my 75 meter doublet fed with window line -- I had to modify the tuner to get it to work on 24.9 MHz. It was very cool to have my first 12 meter contact be QRP, HB and with Spain.

There is a LOT of soul in this new rig.  Here is a partial list of contributors: 

-- Overall BITX design:   Farhan VU2ESE

-- Termination Insensitive Amplifiers (TIA):  Wes Hayward W7ZOI and Bob Kopski K3NHI.  

-- TIA boards from Todd K7TFC

-- ASK-1 Mixer from Armand WA1UQO

-- VFO design parameters from Joe Carr K4IPV (SK) 

-- VFO stability ideas from Frank Harris K0IYE and Mike Murphy WU2D. 

-- HT-37 Tuning Capacitor bought from e-bay at suggestion of Pete Juliano N6QW. 

-- Pine board base of the rig:  Frank Jones (SK) W6AJF's preferred building technique. 

-- DTC Band-Pass filter circuits from Han Summers G0UPL. 

-- Low pass filter values from G-QRP web site. 

-- Idea of using RD06HHT instead of IRF-510 in the final:  Pete Juliano

-- Heat sink from Chris KD4PBJ

-- Trifilar Toroids used in many places from Farhan VU2ESE.

Thanks to all.  73  Bill  

Sunday, March 13, 2022

Video #3 17/12 Transceiver -- Receiver is Working on 12 and 17 meters (Listen! Video!)


Here is an update on the 1712 transceiver project. The receiver circuitry is done and I can listen on 17 and 12 meters. In this video I was using my 75 meter doublet tuned to 17 meters (reception on 12 was pretty good using this antenna). As you can see, I found a temporary solution to the VFO dial problem -- I am using the cardboard tube from a coat hanger super glued to a knob. The tube fits snuggly over the shaft from the VFO assembly.

Hans Summers' QRP Labs Bandpass Filters:



Thanks Hans!


Wednesday, March 9, 2022

Video #2 17/12 SSB Transceiver -- Receive RF Amplifier Needed?


Lots of progress to report on the 1712 rig. 

With just two TIA amps (one on either side of the 10 pole filter) and the AF amplifiers, I now have it inhaling on 17 meters.  But nothing heard so-far on 12. On both bands I can hear the band noise, but just barely.  So I may try some RF amplification ahead of the mixer. What do you guys think about this? I think the two TIAs and the crystal filter are providing 30 db of gain.  

I want to get the receiver circuitry working well on both bands before I build the T/R and transmit amplifier circuitry.
  
It is nice to have a project on the bench!  

I am trying to find a shaft extender or adapter for that big beautiful HT-37 main tuning cap.  The shaft on the capacitor has a width of 1 cm or 0.393701 inches.  I need something that will grab onto that and allow for the connection of a tuning knob.  Please search your junk boxes!  

Tuesday, March 1, 2022

Dennis WC8C's FB Homebrew 6 Meter Rig -- Any Ideas or Suggestions?

 
Dennis WC8C is the event coordinator for the radio club in Michigan that I recently spoke with.  He mentioned to me that he was working on a homebrew 6 meter rig.  FB Dennis.  I see lots of tribal wisdom in your approach, especially in your decision to do this in a stage-by-stage modular form. 
Dennis's rig is obviously a work in progress, so if anyone out there has any helpful hints (especially on the carrier suppression and on the testing for spurs and splatter) please share them with him via e-mail or blog post.  

The files on Dennis's rig are on GITHUB: https://github.com/soligen2010/6_Meter_Transceiver

Thanks Dennis!  
----------------

This is my 6 Meter homebrew transceiver, currently work in progress.  It is a single conversion super –heterodyne design.  I constructed each stage independently with SMA connectors.  This is so I can re-make sections as needed, and will allow me in the future to swap sections to experiment with alternate designs.  The VFO and BFO are controlled using a SI5351 with an Arduino micro controller.  I currently have separate SI5351 modules for VFO and BFO because I suspected issues with cross-talk.  These issues may not actually be real, so once I am happy with the performance, I will test again with just one module to see if it is OK.  The Power Amp is still on the to-do list, so output is well under 0 DBm

The Blue boards were designed by me and ordered on-line.  The other boards I etched myself.  Construction is mostly surface mount because I find it easier than drilling all the holes.  SMD components are mostly 805 and 1206 size. Transistors are SOT23.

The Band Pass filter is a 5 coil design made with air-core inductors.

3 bi-directional termination insensitive (TIA) amps are used (blue boards).  Total RX gain is about 44db.  Total TX gain is about 16db.  Each board has its own independent RX/TX switching circuitry (mosfet based) and is fed with +12.5, GND, and RX/TX logic signal from the Arduino (3V logic and up will work)

The Mixer and modulator are both Diode Ring mixers.

The 12 MHz SSB filter is a crystal ladder filter similar to the one used in the uBitx.

The Mic and audio pre-amp (also a blue board) is made on a modified TIA amp board.  I had 10 of these boards made, and the needed circuitry was largely the same, so I modified the board with a rotary tool and jumpers.

The Audio amp is a PAM8403 module and drives a headset.  I did make some modifications to the module so it runs in-spec and to eliminate the power on audio pop.

The challenges I have been having are mostly related to spurs, splatter, carrier suppression and TX audio quality.  I have been gradually tweaking these things to improve operation before I start on a power amp.  My IF is 12 MHZ, and I was using the LSB side of the crystal filter because it is sharper (VFO 62 – 66 MHz) but have recently changed over to the USB side of the filter (VFO 38 – 42 MHz).  This eliminated the spurs I was seeing near the pass band.  I still need to make some adjustments to the crystal filter as it is too broad.

I still have some splatter and audio quality seems low, but I am starting to doubt my test setup.  I see the splatter on the RTL SDR, but I don’t see it on the Tiny SA.  The spatter happens at ~160 KHz intervals.  I am hoping to find someone local with a better spectrum analyzer to help me verify if it is the rig or my SDR dongle/test setup.

The modules to the side of the picture are my rejects/experiments.  The one covered in copper shows how I eventually will shield all the modules.  I 3D printed a cover for the board, when wrapped it with copper tape, soldered to the bottom ground plane.  The one shown is a diode ring modulator.  For some unknown reason the carrier suppression is rather poor.  I had previously made a junk-box modulator that had much better carrier suppression.  I don’t know why it is better than the one I more carefully made for the radio, but until I figure it out, I am using the junk box version.  The junk box modulator uses unmatched schottkey diodes, whereas the “final” one uses a 4 diode SMD package because I wanted them matched – I thought this would be better, but maybe not.

Sunday, February 27, 2022

VK3HN's Amazing Summit Prowler 9 Homebrew Transceiver - A Masterpiece of Miniaturization (VIDEO)


I was wondering what Paul VK3HN was up to. Now we know: the Summit Prowler 9 transceiver. 

This is yet another amazing rig by Paul, with GREAT documentation.   

I was impressed by those bandpass filters.  I will try to do something similarly robust on my 17/12 rig. 

Paul's miniaturization of this rig is really astonishing.  I would go nuts trying to keep it this small. I just couldn't do it. 

Look closely at the boards he uses.  They look like printed circuit boards, but with all the components and all the soldering on one side.  This is very smart -- this makes it easier to troubleshoot and to change components.  

I was glad to see at least one NE-602 in there.  FB. 

The video is above.  Check out Paul's blog for more info: 


Thanks Paul!

Monday, February 7, 2022

SolderSmoke Podcast #235 NE-602, Azores Rig, Spur Problems, SSB Rigs, Peashooter, HB Filters, MAILBAG


SolderSmoke Podcast #235 is available for download: 

http://soldersmoke.com/soldersmoke235.mp3

Travelogue:

6 weeks in the DR for Bill
One contact on uBITX. More SW listening.
Repaired my Chrome Book in Santo Domingo!
Christmas Present for All: James Web Space Telescope launch

Bill's Bench
-- Understanding the NE-602 (see blog post)
-- Thinking about a 17/12 dual bander.  Looked at old G3YCC Tx for circuits... 
-- Using Spurtune08. WB9KZY found it.  In the LADPAC zip file here:
-- Then Put G3YCC Acores SSB TX back in operation
-- Now working many stations with this old "split" TX/RX

Pete's Bench
-- Dean's VWS build of your DC RX
-- Homebrew Crystal Filters
-- The shrinking of the PSSST

Bad Dead Soldering Stations
-- My X-Tonics 4000 dies.   But it left behind a great box with ample socketry. 

Mailbag: 
AA1TJ Mike Rainey --- Again in the Hobbit Hole! 486 kc RX
Thomas K4SWL -- Radio Astronomy and the Raspberry PI 
WC8C Dennis Invite to the L'Anse Creuse ARC   FB  Fun
Todd K7TFC got boosted at Tektronix Beaverton Ore.  
What happened to Chuck Adams K7QO?  His work taken off the net.
W1MJA ex WN2RTH 
N7DA worked W7ZOI in Sweepstakes.  FB
Kirk NT0Z formerly of ARRL HQ
Farhan VU2ESE was up in the Pench Forest, trying to spot a Tiger! 
We spoke to Farhan's Lamakaan ARC in Hyderabad.  QO-100 beam down! 
Dean KK4DAS's 16 watter.   On SS blog
Scott WA9WFA  Bad 6U8s?   Ordering 6EA8s
Bruce KC1FSZ Peppermint Bark gift box
Bob Scott KD4EBM So many good ideas and links 
Rogier PA1ZZ sending parts packages -- Thanks Rogier

Thursday, February 3, 2022

Exorcism Lite -- Spur Suppressed on 17 meter Transmitter -- Split TX/RX Station On The Air


I spent most of January in the tropics, away from my workbench.  This seems to have had a good effect on my 17 meter split TX/RX project.  As I was leaving, heading south,  I was thinking about several difficult options to deal with my spur problem (see previous blog posts). I thought about turning the transmitter into a transceiver by building a receiver board.   I thought about putting San Jian frequency counters on both the transmitter and the receiver, then doing a visual numerical "netting" by just putting the two devices on the same frequency (I actually ordered 3 San Jian counters).   The counter option was even more complicated than it at first seemed -- I would have to build a converter to shift the RX VFO frequency up.  VK2EMU suggested a tube type "Magic Eye" (interesting idea, but also complicated).   This was getting out of hand. 

When I got back home, I took a new look at the problem.   I decided to take one more shot at suppressing the 8th harmonic of the carrier oscillator.  I had already built a new oscillator and buffer using the circuit from Farhan's BITX20.  And I had put it in a metal box.  Now I decided to do three things: 

1) Tighten up the low pass filter at the output of the buffer by moving the cutoff frequency lower (to around 7 MHz) thereby getting a bit more suppression at 41 MHz

2) Try putting a series LC shunt circuit tuned to 41 MHz  at the output of the carrier oscillator (between the oscillator and the buffer). 

3)  Reduce the voltage to the oscillator/buffer.  I have this on a pot, so I can adjust it down to the point where the remnant of the harmonic is no longer audible, while keeping the main carrier osc signal sufficiently strong. 

It seemed to work.  I could now hear the desired frequency for spotting, without the confusing tone from the spur.  

Why had I been able to do this back in 2002 in the Azores using a simple trimmer cap to ground?  My guess is that I was using my Drake 2-B as the receiver.  The trimmer cap to ground may have reduced harmonic output.  And I was probably cranking back the RF gain on the 2-B to the point where I could hear the desired signal but not the remnants of the spur.  I have no RF gain control on the Barebones Barbados receiver that I am using in this project. 

So, what's the lesson from all this?  Well, if you are faced with a serious technical problem, and you find yourself considering complicated and difficult solutions,  go to the Dominican Republic for about a month (especially if it is January or February), and then take another look at the problem when you return.  If you are unable to travel this far or for this long,  taking a walk or taking a weekend break from a troublesome problem will likely have a similar mind-clearing effect. 

The video above shows part of a February 1, 2022 QSO with Gar WA5FWC using the split TX/RX 17 meter rig.  Gar is an amazing long-time SSB homebrewer who got his start with phasing rigs back in the day. 

Friday, January 21, 2022

"From Crystal Sets to Sideband" -- A Great Book about Homebrew Radio by Frank Harris K0IYE (FREE!)

I first came across the above picture of K0IYE's inspirational, completely homebrew station many years ago in the pages of "World Radio" magazine. I have already linked to Frank's book many times over the years, but it is so good that I regularly feel compelled to write about it again. Frank updates the book. Just check out the introduction to his website. Frank even has a Spanish language version of his book. All for free. Thank you Frank.


The introduction to Frank's web site:


Over the last century amateur radio has evolved into numerous different
hobbies. Some hams enjoy weekend contests in which they try to
contact as many stations as possible. Others talk to as many of the
world's 341 call areas as possible and collect QSL cards to prove it. Other
hams just like to ragchew with friends. Still others communicate over
long distances at UHF frequencies using satellites, meteorites, aurora and
other substitutes for a sunspot-charged ionosphere. Some hams provide
communications for their communities during emergencies.

Many of us have returned to the early days of radio by building our own
equipment from scratch. Most home builders start by building QRP (low
power) transmitters. If this doesn't satisfy your urge to build something,
you can move on to build the entire station. That is what this website is about.


https://www.qsl.net/k0iye/

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