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Wednesday, January 26, 2022

Image of James Webb Space Telescope In Position at L2

A very nice shot of the James Webb Space Telescope, nearly 1 million miles away, taken from Rome. 

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.


Thursday, January 20, 2022

Mike WU2D on VFOs (with additional Tribal Knowledge from Frank Harris K0IYE)

Great stuff from Mike and from Frank Harris K0IYE.   But when I put the VFO in a box, I usually try to put the frequency determining components (the coil and most of the caps) in the box, with the powered components (transistor, Zener,  voltage dropping resistors) outside the box.  If I put these powered components in the box, I find there is some drift as these components slowly heat up the interior of the box. 

Dean KK4DAS and he VWS Builders have just stated building analog VFOs, so Mike's video is very timely for them. 

Wednesday, January 12, 2022

Looking at the Galaxy's Spiral Arms with a Dongle, a Raspberry Pi,and a Homebrew Antenna

I told Farhan that the world NEEDS a homebrew Raspberry Pi observatory at Lamakaan in Hyderabad. They are on it.  

This looks very do-able.  And fun.  And UHF.  And SDR. And Raspberry Pi. 

I'd like to build one too.  I was encouraged by the video demo -- it was done in Alexandria, Virginia, very close to where I live. 

A while back I was lamenting to Dean that I reluctantly threw away a DISH or DIRECT TV  satellite TV antenna.  I worried that I had discarded something that would have been useful for radio astronomy.  Turns out I didn't need it.   This video and the associated .pdf shows how to look at the galaxy with a simple homebrew (Home Depot!) horn.  

Thanks to Thomas K4SWL of the SWLing Post for alerting us to this. 

Monday, January 10, 2022

Exorcism Not Quite Complete -- Thinking of Other Options

As often happens, I may have jumped the gun in declaring the exorcism of my 17 meter transmitter to be a success. As readers of this blog will recall, my problem was that when trying to "net" my separate 17 MHz receiver and transmitter, at around 18.116 MHz I could hear more than one tone as I tried to get to zero beat.  The 8th harmonic of my 5.176 MHz carrier oscillator was mixing with the 23 MHz VXO signal and producing a spur.  I could probably knock the level of this spur down below FCC limits, but -- and here is the problem -- I probably could never knock it down to the point that it would not be audible in the sensitive receiver that sits right next to the transmitter.  So this is really a netting problem, not really a spur problem. 

I don't want to try another filter frequency -- I have VXO crystals that really work only with a filter at 5.176 MHz.

So here is my current idea:  Build a receiver board and turn this thing into a transceiver.  Switch with relays the input and output of the 5.176 MHz filter, and use relays to switch to the receiver board the VXO and carrier oscillator signals. 

Making this thing a transceiver would eliminate the need for netting.  This should solve my problem. 

What do you folks think? 

73  Bill 

Thursday, January 6, 2022

Roy Lewallen W7EL Gives Us All EZNEC for FREE! Thanks Roy! (Video)

Free download here: https://www.eznec.com/

Thanks to Roy Lewallen W7EL for this great gift to the amateur radio community.  

And thanks to G-QRP for the excellent video (above) of Roy talking about antenna modeling.  

Tuesday, January 4, 2022

Exorcism Completed! Getting Rid of the Spur in my 17 meter SSB Transmitter using a TinySA (video)

To re-cap:  The problem became evident when trying to "net" or "spot" my transmitter onto my receive frequency.  Around 18.116 MHz, I could hear at least two tones in the receiver as I moved the transmitter frequency.  I needed to get rid of the extra tone. 

First, thanks to all who sent in suggestions.  They came in literally from around the world, and this is a demonstration of the IBEW in action.  I used or at least tried all of them.  They were all good ideas. 

Following Vasily Ivananeko's pseudonymous suggestion I rebuilt the carrier oscillator (apologies to G3YCC).  I used the carrier oscillator/buffer circuit from Farhan's BITX20.   

Henk PA0EME said I should look at the signal level at the input ports of the NE602 mixer.  Henk was right --- the VXO input was far too high.  I lowered it, but the problem persisted. 

At first, I thought that the spur in question was so small that it would not show up on the air.  I could not see it in the TX output using my TinySA spectrum analyzer.  That was good news and bad news:  Good that it was not showing up on the air, bad that I could not see it in the TinySA and use that image in the exorcism. 

At first I thought that the spur was being caused by the 10th harmonic of the carrier oscillator and the third harmonic of the VXO.  This seemed to fit.  So, following VK3YE's sage advice, I built a little 69 MHz series LC trap (using a coil sent by AA1TJ, on a board CNC'd by Pete N6QW).  That trap succeeded spectacularly in crushing the 10 harmonic.  Look at these before and after shots on the TinySA: 

Before Trap

After Trap

Spectacular right? But guess what?  The problem was still there.  

I scrutinized the situation once more. I realized that the spur would be more visible if I put the TinySA on the input of the transmitter's PA (a JBOT amp designed by Farhan) as opposed to putting it on the output.  Watching the spur and the needed signal move in the TinySA as I tuned the VXO, I realized that they were moving in opposite directions.  This indicated that the spur was the result of a carrier oscillator harmonic MINUS a VXO-generated frequency (as the VXO frequency increased, the spur frequency decreased).  Looking at my EXCEL spread sheet, I could see it:  8th harmonic of the carrier oscillator MINUS the main output of the VXO. 

To confirm this, I plugged the values into W7ZOI's Spurtune program.  Yes, the spur popped up and  moved as predicted.  

For further confirmation I shut down the carrier oscillator by pulling the crystal from the socket, and then just clipped in a 5.176 MHz signal from my HP-8640B signal generator (thanks KB3SII and W2DAB). Boom!  On the TinySA, the spur disappeared.  Now I at least knew what the problem was:  a harmonic from the carrier oscillator.  

Following good troubleshooting practice, I turned off the gear and went to bed.  When I woke up, an idea came to me:  Before launching into a lot of filtering and shielding, just try running the carrier oscillator at a lower voltage, seeing if doing so might reduce the harmonic output.   I disconnected the carrier oscillator board from the main supply and clipped in a variable voltage bench supply.   Watching the signal on my TinySA, I watched as the spur completely disappeared as I reduced the voltage from around 13V to 10V  (see video above).  The main signal frequency level did not change much.  I tested this by listening for the hated extra tones.  They were gone.  Exorcised.  

Key lessons: 

-- Spur problems are difficult to troubleshoot.  Armstrong's superhet architecture is, of course, great, but this is definitely one of the pitfalls.  Single conversion makes life easier.  IF selection is very important. Choose wisely! 

-- When looking at the TinySA as you tune the rig, pay attention to which way the spur is moving.  This provides an important clue regarding the combination of harmonic you are dealing with. 

-- The TinySA is a very useful tool.  It seems like it is easier to use than the NanoVNA (which is also a fantastic tool). 

-- It can be fun and rewarding to re-visit old projects.  In the years between original construction and the re-look, new test gear has become available, and the skill and experience of the builder has improved.  So problems that once seemed insurmountable become fix-able. 

-- Thinking through a problem and thinking about possible solutions is very important.  It pays to step away from the bench to think and rest.  Rome wasn't built in a day. Here's a rough block diagram that I drew up (noodled!) while trying to figure out this problem: 

Monday, January 3, 2022

1BCG -- The 100th Anniversary of the Trans-Atlantic Test

Thanks to the Antique Wireless Association for this really wonderful video, and for their involvement in the 100th anniversary event.  Special thanks to Ed K2MP. 

On December 11, 2021, the 1BCG team in Connecticut had some technical difficulties.  As we all know, that is part of being a radio amateur. Details of the problems are presented here: 


Phil W1PJE managed to hear and record some of the 2021 transmission (Thanks Phil).  Listen here: 


Phil also sent this spectrogram of the signal. 

Good thing Paul Godley ran into Harold Beverage on the ship going over. 

And imagine me complaining about having to step out into the carport to adjust my antenna -- Godley had to trek one mile THROUGH SEA-WEED to adjust his.  Respect.   

Sunday, January 2, 2022

SolderSpace! N2CQR from Geostationary Orbit


Farhan VU2ESE kindly invited us to talk to his Lamakaan Amateur Radio Club.  They did a simulcast through the QO-100 Geostationary Satellite.  This picture shows N2CQR being beamed into India from 22,500 miles.   Note the ET-2 and the Mythbuster on the bench.  This was a lot of fun.  Thanks Farhan! 

Saturday, January 1, 2022

Straight Key Night 2021/2022 (Videos) -- Happy New Year!

I made a few contacts on 40 meter CW using my old Hallicrafters HT-37 and Drake 2-B. 

Happy New Year to all!  73   Bill 

An Interview with Paul Lutus (Audio)

Thanks to Bob Scott KD4EBM for alerting us to this wonderful interview. 

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