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Showing posts with label 20 meters. Show all posts
Showing posts with label 20 meters. Show all posts

Wednesday, February 14, 2024

We Get Mail! Red Poster? Really a Tapestry from Ecuador


Listener Tobias was laid up yesterday, following the extraction of wisdom teeth. (This seems like an appropriate follow-up to our talk in SolderSmoke Podcast #250 of sBITX "wisdom files" to correct FFT "hallucinations.") Tobias does not appear to have been hallucinating, but he was having trouble seeing what he thought to be a "red poster" in my shack.  

In fact, what he was seeing was a red tapestry from Ecuador that was sent to me by Galo Constante HC1GC way back in 1993.  I was in the Dominican Republic, running my first ever real homebrew transmitter.  Here is an article about this project: https://www.gadgeteer.us/TXHB.HTM  I think Galo was also QRP homebrew.  My log shows that I worked  him eight times from the DR. 

Mitad del Mundo =  Middle of the World (a reference to the equator). 

Here is the QSL I got from Galo: 


Here's a 2022 blog post about a resurrection of this old rig: 

Thanks Tobias for spotting the HC1GC tapestry and reminding me of some great QRP contacts. I hope you feel better OM.  73  Bill 

Wednesday, February 7, 2024

Videos from Mike AG5VG -- His Homebrew BITX Rigs


Here are two great videos from Mike AG5VG showing his two homebrew receivers in action.  (The transmitter portions of Farhan's circuit will come later.) See yesterday's post for more details. 

On the video above (40 meters) 
-- I love that speaker.  
--  The enclosure and the reduction drive for the VFO is really great.  FB OM. 
-- Very cool that Mike captures a 40 meter QSO with "Wild Bill" ZS6CCY in South Africa, someone who we've spoken to many times, often on the long path, sometimes from Mozambique. 
-- I like how Mike demonstrates the effect of removing the antenna.  You can definitely see what we mean when we say you should be able to "hear the band noise."   
  

Above you see the 20 meter receiver in action.  You can see one of the physical benefits of using a wooden base:  You can easily mount connectors, switches and tuning controls using just pieces of copper-clad board screwed into the wood.   This is what I am doing with my latest BITX 15-10 rig. 

For the tuning of the VFO, it looks to me as if Mike has a large "main tuning" control in the center, with a smaller "fine tuning" or "bandspread" control off to the left.  Does that smaller control work with a varactor diode or with a smaller variable cap?  Also, to the right of the main tuning control we see a 3 pole switch.  Is that switch putting additional L or C into the VFO circuit to move the frequency around?  These techniques would all be quite valid;  Mike demonstrates that there are many ways to skin a cat (or tune a VFO!) 

Mike:  Please send more info. 

Sunday, January 15, 2023

Working Vienna Wireless Society member (KA4CDN) from Hispaniola


We'll be heading back to the States soon and I was feeling guilty about 
not having worked anyone from my home club (the Vienna Wireless Society). 
On Wednesday night I Zoomed in to the club's Maker group -- this made me want 
to make at least one contact with the club.  Plus Walter KA4KXX  in Orlando has 
been trying to set up a sked on 20... This morning I saw that the SFI was up above 200. 
I lengthened the dipole so it would resonate on 20 meters (on this trip it started on 20, went to 17, back to 20, down to 10 and now, back to 20!). I worked one station on SSB, then sent a text to the club's DX spotter group, saying that I would be calling CQ on 14.060 MHz.   Soon I got a call from club member (and Maker) Mike KA4CDN.  We had a nice QSO.  Thanks Mike (video of our QSO above). I will try with Walter tomorrow.  

 

Tuesday, September 6, 2022

Michael AG5VG Builds a Sub-Harmonic Receiver and Moves it to Higher Bands


Michael AG5VG built a Sub-Harmonic Direct Conversion receiver.   But then he took it a step further and moved it up from the 80/40 meter version that I had built, and used the same concept to run it on 20 meters using an oscillator on 40 meters (after some re-winding of the front-end coils).   Using a station from Puerto Rico transmitting on 20 meters as an example, he starts out showing how well the receiver works in sub-harmonic mode (with the oscillator on 40), then quickly switches to normal Direct Conversion mode with the oscillator also on 20 (but using only one diode as the detector) -- he can still hear the Puerto Rican station in that mode.  Very cool.  

Good Evening Bill,

I built the Polykov and I attached a picture of it. I also used Pete's pre audio driver circuit from his jessystems.com site. Then I used an lm386 as the main audio driver. I could hear ft8 on the 40m band. Then I hooked the output of my lm386 circuit to a conventional set of computer speakers to really hear it. I am currently using an indoor wire antenna along the ground so it's certainly not optimal. Very fun build and I'll be learning more about it. When I have a better antenna system I'll hook it all up and send a video of it.

73s
MIchael
AG5VG


Bill,

I am just using a standard signal generator at 1 vpp output. The volume gets louder with every 100 millivolt I go up, but so does the noise. 0.8vpp was a little low for me so I bumped it up a bit.

The indoor antenna actually did surprising well but I'm looking forward to putting a wire up into a tree I have here. I just recently moved so I have to setup my outside antenna. I live in the San Antonio, TX area. 

I am currently using three stages of audio amplification to be able to really hear it. 1st stage is Pete's pre audio driver, then an lm386, then a standard set of computer speakers. 

I did plenty of playing around with it last night and the doubling function is so cool how it works. When I was around 3.538 MHz, with the variable cap tuned for the 7Mhz area, I was actually listening to 7.76Mhz, the FT8 frequency for 40 meters. I agree with You and Pete in a podcast you did a bit ago, that FT8 is great for seeing if the band is open and checking receivers with! 

The next project is the art of the 3.5 - 4Mhz analog VFO and use it with the Polykov. I am very dependent on the Arduino/Si5351 pair as the code is available and easy to hook up.

Will keep you both updated. 

73s
Michael
AG5VG

Two more videos from Michael: 

Testing

Operation
    
I think this is a great example of good experimenting.  Michael took the concept, made some mods,  and put the device on another band.  FB.  

Saturday, July 16, 2022

Hex DX! First Long-Haul Contact with the New Hex Beam - VK4KA on 20 SSB


This morning at around 1345 UTC I had the chance to try out my new Hex beam on some "down under" DX.  9,548 miles, 15,222 km    The DX Spot page told me that VK4KA was on 14.255 MHz.  QRZ.com said the beam heading for me was 270 degrees.   He was quite strong.  He was working a fairly huge pileup, going through callsign numbers.  He was on the 6s when I tuned in, so I had some time to test the Hex beam.  Above you can see a rough front-to-back test.  Below you can see a comparison with my old 75 meter doublet.  

A few minutes after the second video, in spite of the pileup I called VK4KA and made the contact.  I congratulated him on his homebrew Moxon.  https://www.qrz.com/db/VK4KA

It was fun to reach Australia with the new antenna. 

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.  

Saturday, August 7, 2021

Mythbuster Video #13 -- RF Power Amplifier, and Relay Switching Plan


In this episode we enter into the most fraught part of the construction project: the production of RF power. This is where amplifiers stubbornly turn into oscillators, and where components release magic smoke, or at least burn the fingers of hopeful builders.

I kind of ran out of room when I built the low-pass filters. But, thinking ahead, I wanted to have them on a separate board. And it is good that they ended up in the far corner of the rig.

Just going from one band to two bands adds to the complexity of the rig. I had to add two relays, one to switch the low pass filters, the other to switch the bandpass filters. I ended up with 5 DPDT relays in this transceiver. It was very helpful to have a plan and a diagram for the relays and all the switching.

It looks like each of the three RF amplifier stages provides about 15 db of gain -- about what I need to get to the 5 watt level.

Friday, July 16, 2021

Mythbuster Video #6 -- On to 20 Meters (But With Bandpass Filter Woes). Please help solve the mystery!

Here's how I started with the Elsie program. Note that to get a 50 ohm match on both ends it needs an impractically low value for the coils (.064 uH). 

But Elsie lets you specify the coil value.  So I then I went with 1 uH.  But with this value you don't get 50 ohms at either end.  You need a matching network.  Elsie provides this too!  

I asked Elsie to match my BP filter to 50 ohms.  It provided several options to do this --  I went with a simple capacitive impedance divider.  But alas, I was now bumping up against the 7 limit of the free version of Elsie so I had to reduce the number of LC elements from 4 to 3.  Bummer. 

With 3 LC tuned circuits and matched to 50 ohms the plot looks OK.  But I would have preferred 4 LC circuits. 
 

The rftools website created a BP filter for me with 4 LC elements, and matched to 50 ohms.  Very useful. https://rf-tools.com/lc-filter/

But here's my problem:  With both the filter designed by Elsie and the one designed by rftools, I found that the filter passband was too low.  It was in the 12 - 13 MHz range.   I found that by removing 3 turns from the 1 uH coils I could move the passband up to the desired range.  But why the discrepancy?  I was measuring the coils and the caps with an AADE meter.  I was testing the passband both with a NanoVNA and with a combination of an HP8640B sig gen and a Rigol oscilloscope (with the filter terminated into a 50 ohm resistor).  Any suggestions on why these filters should have passbands lower than predicted would be appreciated. 

Thursday, June 17, 2021

The Stubborn Myth about USB and LSB

It  has been repeated so often and for so long that many of us have come to believe it.  I myself believed it for a while.   Like many myths, it has a ring of truth to it.  And it is a simple, convenient explanation for a complex question: 

Why do ham single sideband operators use LSB below 10 MHz, but USB above 10 MHz? 

Here is the standard (but WRONG) answer: 

In the early days of SSB, hams discovered that with a 9 MHz SSB generator and a VFO running around 5.2 MHz, they could easily reach both 75 meters and 20 meters (True). And because of sideband inversion, a 9 MHz LSB signal would emerge from the mixer as an LSB signal (True), while the 20 meter signal would emerge -- because of sideband inversion -- as a USB signal (FALSE!)  That sideband inversion for the 20 meter signal explains, they claim,  the LSB/USB convention we use to this day. 

Why this explanation is wrong: 

There is a very simple rule to determine if sideband inversion is taking place:  If you are subtracting the signal with the modulation FROM the signal without the modulation (the LO or VFO) you will have sideband inversion.  If not, you will NOT have sideband inversion.

So, you just have to ask yourself:   For either 20 or 75 are we SUBTRACTNG the Modulated signal (9 MHz) from the unmodulated signal (5.2 MHz)? 

For 75 meters we have:   9 MHz - 5.2 MHz =  3.8 MHz    NO.  We are not subtracting the modulated signal from the unmodulated signal.  There will NOT be sideband inversion. 

For 20 meters we have 9 MHz + 5.2 MHz = 14.2 MHz.     NO.  No subtraction here.  No sideband inversion.   

So it is just arithmetically impossible for there to be the kind of happy, easy, and convenient  USB/LSB situation described so persistently by the myth. 

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

We discussed this several times on the podcast and in the blog: 

https://soldersmoke.blogspot.com/2015/05/sideband-inversion.html

https://soldersmoke.blogspot.com/2012/05/usblsb-urban-legend-debunked.html 

This myth shows up all over the place: 

We see the myth here: 

http://n4trb.com/AmateurRadio/Why%20The%20Sideband%20Convention%20-%20formatted.pdf

Here the web site owner warns that this is "highly controversial."  Really?  Arithmetic? 

http://9m2ar.com/lsb7.htm

The myth is very old.   Here is a clip from a 1966 issue of "73" magazine: 

https://worldradiohistory.com/Archive-DX/73-magazine/73-magazine-1966/73-magazine-01-january-1966.pdf

Finally, to my disappointment, I found the myth being circulated by the ARRL, in the 2002 ARRL Handbook page 12.3: 


The fact that the Handbook attributed this to a desire to "reduce circuit complexity" by not including a sideband switch should have set off alarms.  We are talking about hams who built their own SSB rigs, usually phasing rigs.  A sideband switch would not have added significant circuit complexity. I think they could have handled it. 

It is interesting that earlier ARRL Handbooks do not repeat this myth.  I found no sign of it in Handbooks from 1947, 1959, 1963, 1973, and 1980.  And I found no sign of it in several editions of that great ARRL book "Single Sideband for the Radio Amateur." 

For my next homebrew rig, I will build a rig that DOES do what the myth promises.  I will have the SSB generator running on 5.2 MHz USB.  The VFO (out of an old FT-101) will be running around 9 MHz.  So for 75 meters we WILL be subtracting the signal with the modulation from the signal without the modulation:   9 MHz - 5.2 MHz = 3.8 MHz.   There will be inversion.  This 75 meter signal will be LSB.   For 20 we will just add the 5.2 MHz USB signal to the 9 MHz  VFO.  There will be no inversion.  We will have a USB signal on 20.   I'm thinking of calling this new rig "The Legend." Or perhaps, "The Mythbuster." 

Sunday, May 30, 2021

QRP - QRP Contact from Dominican Republic



It took some brass pounding on my homebrew key, but on May 28, 2021 I made a real QSO from the eastern tip of the island of Hispaniola.  KJ4R came back to my CQ near 14.060 MHz. I was running just 1-2 watts from my SST transceiver to an end-fed half wave antenna. Ed KJ4R was in South Carolina running 5 watts, also to an EFHW antenna.  TRGHS.  Thanks Ed.  And thanks to Bob Scott KD4EBM and Wayne Burdick N6KR.

Friday, May 21, 2021

AA7EE's Amazing Homebrew SST QRP Transceiver

 

Look at that rig.  It is truly a thing of beauty.    

I was very pleased to see Dave AA7EE's comment on my SST rig.  This caused me to search his site for his SST article.  And wow, it is an SST treasure trove.  Lots of discussion of the circuit and mods. And Dave's usual wonderful photography and videography. 

Check it out.  

https://aa7ee.wordpress.com/2016/09/09/a-scratch-build-of-n6kr-and-wilderness-radios-sst-for-20m/

Thanks Dave! 



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