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Showing posts sorted by relevance for query KA4KXX. Sort by date Show all posts
Showing posts sorted by relevance for query KA4KXX. Sort by date Show all posts

Thursday, February 23, 2017

Walter KA4KXX's "Al Fresco" Oz DSB rig with VFO Mod


A while back we ran a post about the MDT 40 DSB rig out of Australia. Walter KA4KXX liked the design so much that he built his own version and, with it, made his first homebrew phone contacts. I always say that DSB is a great way to break into the world of microphones.  Walter is obviously on the right path -- not only did he come up with a nice Al Fresco DSB rig, but he modified the VFO to get additional coverage and to incorporate a frequency counter.  FB Walter!

Walter KA4KXX writes:

Since I earned my Ham Radio license in about 1979, I have always operated only on CW since I like to build all my own equipment, but recently at the SolderSmoke website I discovered the MDT 40 Meter DSB Transceiver, and decided this was the design I had always been looking for to finally build and operate on phone.

After I made my first phone contact after only 5 minutes of trying, just a few weeks ago, I was so excited I sent an email thanking designer Leon of ozqrp.com.

Then I modified the VFO further to cover the entire 40 meter USA General Class License phone band, which is 7.175 – 7.300, in two overlapping steps.  I also added a 5K fine frequency adjustment, used a more friendly 1SV149 Varactor diode which I purchased on EBay at very low cost, and also added a high impedance buffer (found at the website listed below) to the VFO to drive a frequency counter.
 
http://www.arising.com.au/people/Holland/Ralph/buffer/highimpedanceprobe.htm


I was able to implement these modifications very easily since I always make my own un-crowded state-by-stage Manhattan style circuit boards and build first on a breadboard.
So far I am very pleased with the results.


Walter KA4KXX

Sunday, January 15, 2023

Working Walter KA4KXX from Hispaniola

 Walter KA4KXX in Orlando has been a prolific builder of rigs for many years, and has been a great friend of SolderSmoke:  Here are some of the SolderSmoke podcasts and blog posts in which Walter's solder melting was mentioned: https://soldersmoke.blogspot.com/search?q=KA4KXX

As we approach the end of our current stay in the Dominican Republic, I could not miss out on the chance to work Walter with his homebrew rigs.  Even though the space weather was stormy, and my dipole was droopy, we arranged to meet up on the high end of the 20 meter CW band this morning.   See the results in the video above.  A solid QSO with Walter.  He says it is HB2HB, but truth be told I was on a uBITX that was built more by Farhan than by me.  But this was a great contact.  Walter started with a 50W rig, then switched to his 3 watt rig with a DC receiver.  FB

Here is the e-mail I received from Walter after the QSO: 

Dear Bill:

Many thanks for the great video, and when
you return to Virginia look for your mailman
to bring a postcard from me!
Just after your phone call this morning I scanned
the band from 14.025 to 14.300 and heard only one
SSB QSO at 14.347, and even now I only hear
a half dozen SSB signals, so that makes what
we did even more amazing. 
The first photo below is my 3.5 watt NE602 direct conversion 
rig which is about 2 years old.  The transmit signal is created
by putting a 3 MHz VFO signal into an NE602 mixer with an 
11 MHz crystal, so the rig can receive CW and SSB from 
14.025 to 14.300 and can transmit CW anywhere in that range
with good frequency stability. 
The bottom photo is my new full break-in CW 50W rig which 
I just put on the air about a week ago and is still in the finalization stage.  
I am not yet happy with it, but then again I am more particular
now than I used to be.  It is really a trans-receiver with a single 
conversion superhet receiver at the bottom of the board using 
an NE602 pair with a 3-crystal 4 MHz 900 Hz bandwidth filter, 
and a single 10.080 crystal VFO which is tuned with a polyvaricon
for operating between 14.061 and 14.068 MHz.  
At the top is the VXO transmit section using a pair of 14.070 
crystals pulled down into the operating range.  This signal
is buffered and amplified to about 500 mW which is all that 
the MRF101 RF Power Amplifier needs.  Visible behind the
board is an AC-powered 24 VDC switching power supply which 
is connected in series with the 12 VDC battery to 
power the final stage with about 36 VDC.  The main 12 VDC is 
provided by a bench power supply which is not in the photo.
In both rigs the morse code key is the microswitch 
at the lower right corner.  (Way more handy and elegant 
than your key, I might say?)
This morning each of these rigs was connected to its own
end fed half wave antenna, one in my backyard 
and the other on the side of my house.  My antenna analyzer
shows them to be essentially equal, but my 50W rig does
not like one of them at all.
Making our international homebrew-to-homebrew contact 
today was a terrific ham radio experience, so thanks for all 
you do!
73,
Walter 
KA4KXX
Orlando, FL

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Tuesday, May 4, 2021

Ciprian's Romanian Ten Minute Transmitter with Roots in SPRAT, KA4KXX, and the Florida Sunrise Net


It sounds great Ciprian!  It was really cool to see your video and hear you reference not only the SolderSmoke blog, but also SPRAT, the Michigan Mighty Mite, and Walter KA4KXX. Your little rig has a very fine lineage!  

I found Ciprian's video just after seeing the wonderful Herndon Mighty Mite of Jack NG2E.  TRGHS!  The Color Burst Liberation Army is on the march!   For more info on NG2E's Mighty Mite, check out his blog: https://jackhaefner.blogspot.com/2021/05/mounting-to-perfboard-and-scope-test.html 

Jack has in his possession one of the  7.123 MHz crystals that Walter KA4KXX sent me back in 2019 (during my ET-2 craze).   It seems obvious that Jack should build a Ten Minute Transmitter and use it to check into the Sunrise Net  https://qsl.net/srn/

Friday, April 17, 2020

Walter's VFO

Main VFO board under plastic -- buffer board off to the right
There is a lot of tribal knowledge in this short article by Walter KA4KXX.  (The most recent issue of SPRAT has a picture of a SPRAT cover from more than 30 years ago, announcing an article by Walter.  OM has been at this for quite a while.)  Walter's advice is similar to that of Doug DeMaw, especially on the air-core coil.   FB Walter,  thanks for sharing.  

Regarding the last line in Walter's article, please direct any complaints about drifting analog VFOs to Peter Juliano.  He will be delighted to receive these complaints, and will promptly provide all correspondents with very succinct advice on how to overcome the instability.  

My Way to a Low-Drift Analog VFO, by Walter KA4KXX

I recently built a digital VFO (from a QRP Labs Kit) to see what everybody is talking about, and it has been quite handy for my first two-band homebrew transceiver, but by the time one adds the low pass filter, a low-level RF amplifier to boost the weak output, a 5 VDC regulator, and a hefty +12VDC power line filter to the beast to keep the digital noise out of the rest of the radio, for a single band project I still prefer a low-drift analog VFO.  

My approach to minimizing drift is very simple and works well for a VFO range of 3 – 7.3 MHz, which is all that is needed for the 20 to 80 Meter bands, either direct conversion (adding a doubler for 20M) or single conversion with approximately a 10 MHz IF.  

First, see my schematic (adapted from Small Wonder Labs 40+ transceiver, original BITX40 Analog VFO, and other sources) and wind an air core inductor with stout magnet wire such as 24 or 22 AWG.  Use a thick, rigid plastic form of a diameter so that you need about 12 turns, and single coat with water-based sanding sealer, Q-dope, or similar.  Use hot glue to mount the coil firmly to the single-sided circuit board, and build a cover of some type, especially if the radio is to ever be used outdoors.
   
Second, all the VFO capacitors (except power supply bypass) should initially be the modern C0G type, which can be obtained from Mouser (such as TDK FG28C0G1H681JNT06 or the like), which I trust more than those labeled NP0.

Then, power up the VFO and tweak the coil, tuning arrangement, and range capacitor to get the frequency range you desire.

Next, monitor the drift from a cold start to see how fast it is moving as it warms up, and whether it stabilizes nicely (my goal for SSB Phone use is less than 20 Hz drift during any 10 minute period) after 10 – 15 minutes maximum.  If it does not stabilize to your satisfaction, then start substituting polystyrene caps for the C0G units one at a time until you are happy with the performance.

[Also remember that a stable BFO is important as well, and if you use the BITX 40 crystal oscillator design, I recommend installing a dedicated 78L09 power line regulator.]

If you build this VFO at the higher (7 MHz) frequency end, just change the inductor value to about 0.5 uH, with everything else about the same, but expect to do more tweaking to get stability, and the warm-up time may be closer to 15 minutes.  After years of experimenting, this is what has worked for me.  If it works for you, please send me an email (see my QRZ page) of thanks.  If not, file a complaint with Soldersmoke. 



Monday, July 29, 2019

Walter KA4KXX Operates his FB Al-Fresco HB Scratch-Built BITX 75 (Video)



Dear Bill N2CQR:

For your amusement, the attached video (from 2:20 - 3:40) shows
me operating portable at a tailgate event using my second
scratch-built  BITX, with this one running 45W on 75M. 
Features include analog VFO, a 16-pin LM380 with all ground
pins heat-sinked for powerful audio, and 3-transistor uBITX-type
low-level RF amps.  The 8-crystal filter is also like the uBITX design
but at an 11 MHz IF.  The microphone amp is a 741 Op Amp which I
believe has better gain, gain adjustability, and frequency response than 
any of the transistor designs. The transmit adjustable driver amp is adapted from the FET 
circuit used in the Wee Willy.  The Transmit LPF is hard-wired to the antenna connector 
for simplification and to minimize RF losses, so in receive mode the single relay in the rig 
connects the receive section in parallel, which causes some signal loss, but not much. 
Finally, and most notably, I believe that my RF Power Amp is the only one in the world to use 
model airplane engine mufflers as heat sink cores...

72,
Walter
KA4KXX
Orlando, FL     

Wednesday, August 17, 2022

Daylight Again on the Sunrise Net! Walter KA4KXX Builds a PTO


Dear Bill: 

I had never built a PTO, but after reading Farhan's Daylight Again Transceiver article I cobbled one together with parts and pieces I had on hand. My observations so far are as follows. 


1. The frequency-determining capacitors (shown on the schematic as three 470 pf) are very critical, so I feel the usual experimental cut-and-try technique is a must, even using all NP0 and C0G types. 

2. After I built the 2 MHz version like the article (see first photo), the stability was terrific, but when I tried building the companion Daylight Again crystal filter, I was only able to get a bandwidth of 1.6 kHz, which is too narrow for my taste in an SSB radio, so I decided to build the same filter design but with 11 MHz crystals, where I could easily achieve a 2.8 KHz BW. 

3. Therefore, now I needed a higher frequency VFO, so I merely reduced the capacitance (from about 1200 to 370 pf) without changing the coil and I am very impressed with the performance of my 4 MHz PTO (see second photo). The bandspread easily covers the entire 40M band, CW and Phone. 

4. However, whenever I transmit on the 40M Phone band, I like to first set my VFO within 10 Hz of the operating frequency. That way, if I talk for five minutes or so and get up to 15 Hz of drift (which is quite common with many radios when I operate portable outdoors in the sun and wind), it will not be noticable and I avoid receiving any "you are off-frequency" chastising. But the shortcoming I have with this PTO inductor is that the 1/4-20 bolt has a coarse thread, so it is very difficult for an old fellow like me to get within even 20 Hz of a particular frequency just using this common bolt. Therefore I believe a better choice would be the fine thread 1/4-28 two-inch brass threaded bolt which is available from industrial supply houses like McMaster-Carr. However, for CW use or those with a very steady hand, the 1/4-20 works well enough. 

5. I solved my fine tuning problem by adding a varactor circuit using a common 1N914 diode in series with a 100 pf capacitor, operating from 0 to 6 volts. Another advantage to adding this feature is that since I have not so far enclosed my PTO, I can mount the varactor potentiometer several inches from the PTO so my hand capacitance does not affect the frequency like when tuning with the bolt. 

6. An easy way to "do the math" in my case with the common Sanjian counters is to simply create a small lookup table listing half a dozen common frequencies and stick it on the radio. For example, 90% of the time in the morning I am tuned to my favorite SouthCars Net frequency of 7251, so using a BFO setting of 10,999.900, I simply set the PTO to 3,748.90 on the 6-digit 10 Hz resolution counter I normally use (see third photo). 

7. I am currently using my Daylight Again PTO on a daily basis with an NE602 receiver, and I am thinking of adding a locknut to the bolt so it does not wiggle when I jostle or move the radio, essentially giving me a crystal replacement oscillator that I can use for any single 40M frequency. To date I have been able to listen for hours at a time indoors without even any touch-up of the varactor fine tuning. 

8. Also, if continuous frequency readout is desired without building a noise filter circuit board, a separate power supply for the counter is a solution. For portable operation I use Lithium Polymer radio control model airplane batteries which are light, small, and cheap, so one 12V 2000 mAH battery for the transceiver (allows a half hour of transmitting at 15 watts) and a much smaller 12V 350 mAH battery with a series resistor to reduce the current and brightness of the counter has worked well for me. 

73, Walter KA4KXX 
Orlando, FL

Saturday, March 20, 2021

SolderSmoke Podcast #229 -- G2NJ Trophy, SDR, HDR, CW! Mailbag


Soldersmoke Podcast #229 is available: 

http://soldersmoke.com/soldersmoke229.mp3


--  G2NJ Trophy is awarded to Pete Juliano, N6QW. 

 -- Get your vaccine shot as soon as you can!  

-- More from "Conquering the Electron" by Derek Cheung. 

-- Bad fire in the chip factory.  Such a shame.  Sad!  I had NOTHING to do with it.  I was home that day.  I can prove it.

 -- Bezos is not such a bad guy.  Turns out he is a space-geek.  

 -- Perseverance was the big space news.  Very cool.  

 

Pete's bench:

Raspberry Pi vs. Microcontrollers

Treedix display

Conversion of the Dentron Scout

CW rigs?

6L6 on a wooden chassis


SHAMELESS COMMERCE DIVISION-  

I NEED TO BUILD UP TIME VIEWERS VIEW MY VIDEOS: So please watch!

https://www.youtube.com/channel/UC20TcdWSSFliMhg3k2A1a5w

--  Our Patreon sponsors get an early look at our YouTube content.  So please, consider

becoming a Patreon sponsor.

--  Please continue to use the Amazon search engine on the blog page (upper right).   


Bill's bench: 

Hodgepodge:   

-- BITX40 Module.  

-- Ramseykit Amp. 

-- San Jian counter,  

-- CW using 750 Hz oscillator. 

-- RF-actuated piezo buzzer.  

-- SDR!  SDR using PC and tablet.  

-- Checking the output with SDR.  

-- Moving the carrier osc frequency.  

 Also, I put the Fish Soup 10 back on the air.  Nice contacts under 200 mw.

Up next:  A rig for 80/75 and 20 meters.  Single Conversion.  Using VFO from a Yaesu FT101 that runs 8.7 – 9.2 Mhz.   Quiz question:  What IF should I use?

MAILBAG

Mark Zelesky sent me wood tokens with power and Ohm's law formulae.  Thanks!

Scott WA9WFA Built a really nice Mate for Mighty Midget RX – getting it going!

Tryg EI7CLB found board of his George Dobbs Ladybird RX.  Rebuild it OM!

Tom WX2J – We talked about “No lids, no kids, no space cadets” nastiness.

Nick M0NTV about sideband inversion.  I like the simple rule about subtraction.

Jonathan M0JGH – Always listen to Pete.  Got married, has mixing product. Leo?

Mike AE0IH.  Dad used a BC-348 in the service. Looking for one.  FB.

Adam N0ZIB – “Silent Shep” site --- with some ham radio shows I had not seen.

Walter KA4KXX in Orlando has a similar subtraction problem with San Jian counter.

Bill N5ALO sent me a really nice KLH speaker.   I’m using it now.

Jason N2NLY – interested in building SSB transceiver.  One step at a time OM…

Trevor in Annapolis sent xcsd cartoon that really hit home. 

Farhan is doing OK in India, diligently protecting his family from the virus.  

Peter VK2EMU also doing well.

Dave AA7EE Casually killed a DC receiver in Hollywood, and disposed of the remains. 

Charlie ZL2CTM doing great things with simple SSB.  Blogpost.

Phil VK8MC in Darwin sends article on "Mend not End" battle against planned obsolescence.

Bob KY3R re my SDR adventures, asked if I’ve had a recent medical/psychiatric evaluation. 


Saturday, August 1, 2020

SolderSmoke Podcast #224: Mars. Spurs. Bikes. SDR. NanoVNA. Antuino. MAILBAG



SolderSmoke Podcast #224 is available:


1 August 2020

--The launch of Perseverance Mars probe with Ingenuity helicopter.
--China’s Tian Wen 1 on its way – radio amateur Daniel Estevez EA4GPZ is listening to it! 
--Sci Fi Books:  Mars Trilogy by Kim Stanley Robinson.  No skip on Mars :-(
--We have some sunspots!  SFI now 72 and the Sunspot number is 23. 

Bill's bench: 
--Conquering Ceramic Spurs in Q-31   Roofing filter -- sort of 
--NE602 for a Q-75 converter – Gilbert Cell. 
--Measuring low power levels out of NE602.  Antuino better than 'scope . 
--NanoVNA   Really cool stuff.  SDR in there. 
--Building a 455 kc LC filter from QF-1 rubble. Using LTSPICE, Elsie... 
--Reviving my bicycle AM radio – The “All Japanese 6”
--Understanding L Network impedance matching. 
--Bill’s new resistor kit from Mouser. Thanks to Drew N7DA. 

SHAMELESS COMMERCE:  PATREON, AMAZON SEARCH.  THANKS

Pete's Bench: 
--Lockdown Special 
--BPF work on SDR Rig
--I U W I H 

Mailbag:
VK3HN Summit Prowler 7
VK2EMU “The Stranger”
SM0P  HB uBITX in Dubai
AE7KI  Worked him in VK from London
ON6UU  EA3GCY’s 4020 rig
KA4KXX A Simpler Mighty Mite
W9KKQ M19 DMR
KD4PBJ Radio Schenectady
W3BBO 12AU7 Regen
KE5HPY Another 12AU7 regen
N5VZH Ne602 Converter
KY3R Wall Art
G4WIF  Spectrum Analyzer in your pocket
W2AEW  Talks to UK Club
KK0S Sent 455 Kc IF cans
KL0S Making 9Mhz filters
VU2ESE  Diving into simple SDR schemes
Dean KK4DAS  Amateur Radio Astronomy

Saturday, September 7, 2019

SolderSmoke Podcast 213 WE'RE BACK!

N6QW's Analog CW QRP Transceiver
SolderSmoke Podcast #213 is available. 

http://soldersmoke.com/soldersmoke213.mp3

7 September 2019

The dire consequences of our summer absence. 

50th PODCAST WITH OUR FRIEND PETE! 
THREE CHEERS FOR PETE! 

Pete's Bench Report

-- Transceiver Count:  FORTY!  
-- SDR RADIGS 
-- Colorful OLED screens
-- Pilgrims and Paisanos -- "Left Coast Homebrew SSB"
-- Pete builds a CW transceiver (see picture above)


Bill's Bench Report: 

-- Going minimalist
-- Tuna Tin 2 + Herring Aid 5 = Fish Soup 7 (and later 10)
-- My QRPp QSO with K1PUB overheard in Canada
-- Glen Yingling's ET-1 
-- Bill attempting a single transistor transceiver

SPACE NEWS

-- Antuino's Cubesat Origins. Farhan's Antuino Mods
-- Apollo 11 Anniversary
-- Possibly the best space book ever:  "Carrying the Fire" by Michael Collins
-- Chinese microsat sending eclipse pictures from the moon
-- LightSail 2 success
-- India has spacecraft in lunar orbit. 

Eric Sears ZL2BMI and Dino Papas KL0S on "QSO Today" Podcast

MAILBAG: 

ZL2PD's Sugar Cube VFO
N8WQ gets free samples
N5RWF Getting started, wisely wearing beret
VK2EMU Australian Ad for Collins Filters
W1PJE on new LDMOS PA transistors
KA4KXX Al Fresco 75 meter SSB rig with model plane engine mufflers!  

Forgot to mention:  W9TH still has manuals for whover owns Drake 2-B #4215.  Check your serial number! 

Friday, April 1, 2022

SolderSmoke Podcast #236 -- Bill's 17-12 Rig, Pea Shooter, VFO Wisdom, Temp Compensation, Need Code for Max2870, Making Enclosures, MAILBAG

ARC-5 R-23 Nav Receiver Parts

SolderSmoke Podcast #236 is available!

http://soldersmoke.com/soldersmoke236.mp3

Winterfest!  Many Boatanchors.  Lots of old good analog test gear.  Talk with Dean KK4DAS.  Met up with Armand WA1UQO and Charles AI4OT. 

Pete's Bench: 

-- Looking for help in software development for MAX2870 board.  
-- Tapped Capacitance Impedance Matching
-- The Pea Shooter (See N2USD's version in videos
 below).
-- Tribal Knowledge on Making Enclosures

Bill's Bench: 

-- 17-12 Band Imaging SSB Transceiver.  It works on both bands. 
-- Plan for Glowing Numerals (N6QW has been there and done that!)
-- WU2D's videos on VFOs.  
-- Temperature Compensation:  HT-37 capacitor.  FT-101 VFO,  even in the ARC-5 receiver! 
-- Trying to get more rigorous about receiver design.  Gain distribution, IMD, Dynamic Range, etc. 
-- Do I need a true RMS audio voltmeter?  Or can I get the same info from freeware audio spectrum analyzer and soundcard?
-- 6EA8s replace 6U8s in MMRX 

SHAMELESS COMMERCE DIVISION:   We have a sponsor!  

PARTS CANDY out of Chicago produces quality test leads for your bench.  The guy who runs the company is Carlos, and he is one of us.  He is an electronic tinkerer. See the ad on the left hand column of the SolderSmoke blog.  Just click on the picture of the test leads and you will be taken to Carlos's ebay store.  Go for it. 

Mailbag

Walter KA4KXX in Orlando -- Diodes in BITX Bilats -- Why?  Farhan says To prevent reverse junction of off transistor from conducting and clipping waveform. 
Tony G4WIF -- Audio test gear and G3ROO paraset
Todd K7TFC Pine boards, TIAs and 12 meters
Dean KK4DAS  Ceramic Variable Oscillators on 40.   Juliano Criteria? 
Mike WU2D   VFOs and Temp compensation. ARC-5s
Chris KD4PBJ   A really nice parts care package -- Thanks Chris! 
Steve M0ECS.  Inspired by SS, moved something off the Shelf or Box of Shame. 
Jason KD2RKN Building a DC receiver.  It is all our fault. 
Chris Mannon in Indiana joining the CBLA
KC4GMH is listening! 
Ed N2XDD has been armed with a 3.579 MHz crystal.  
Harvey Wa3EIB working on his museum 
Tim AG4RZ is BACK IN THE SOLDERSMOKE! 
Fred KC5RT -- an old friend -- recommends Bangood RF sig gen for 88 bucks. 
Shlomo 4X4LF listening and homebrewing from a Kibbutz in Israel. 
Chuck KF8TI was a Peace Corps Volunteer in the Philippines. 



Saturday, November 2, 2019

SolderSmoke Podcast #214 is FINALLY out!



WE ARE WORKING TO IMPROVE THE AUDIO QUALITY.  IN THE FIRST RELEASE OF THIS PODCAST SOME OF THE AUDIO WAS KIND OF MUFFLED.  I TRIED TO FIX IT THIS MORNING AND I THINK I MADE SOME IMPROVEMENTS.  THE IMPROVED AUDIO IS NOW AT THE LINK BELOW.  


4 November 2019 (shockingly late!)

http://soldersmoke.com/soldersmoke214.mp3

The visit of Farhan to Northern Virginia
"I heard this guy from Southern California on 20..."
Fire Report from Pete

Pete's Bench Report
"When you know stuff, you can do stuff!" 
The CRAP rigs 
Old Boatanchors -- the Swan 120  with SUPER STABLE ANALOG VFO! 
Ten Tec rigs dial cord replaced with Chinese digi sig counter 
Pete's 500 mW encounter with a QRO curmudgeon
The ZL2BMI Challenge has Pete building crystal filters
The Left Coast Loafer CW rig 

Bill's Bench Report

ET-2 Refinements
N0WVA's Regen Receiver 
Going from ET-1 to ET-2
J-310s vice MPF-102
100 mW from a single J-310
Receiver kind of deaf -103 dbm MDS
10 contacts so far in 9 states 
THREE contacts yesterday.
Worked Wisconsin - 633 miles on 92 mW 
We are at sunspot minimum. 
"Rage, rage against the dying of the light." 
Simplicity is the real reason for CW 

IDEA:  Get those Michigan Might Mites on the air! 
Use Reverse Beacon Network to see if you are getting out 
Use SDR receivers to make contacts

MAILBAG
DL1AJG
KC6SAX
W9VNE
KA4KXX
N0WVA
Zl2BMI
AJ6BD  











Saturday, March 4, 2017

SolderSmoke Podcast 194 - Approaching the Digital-Analog Singularity


SolderSmoke 194 is available (scroll down for link)
March 4, 2017
BIG NEWS:   uBITX from Farhan
BENCH REPORTS
Pete: Recycling Old Boards
Working on Arduinos and advanced displays
Bill: SDR Adventures and Misadventures.
RTL-SDR is fun.  Built HB front end.  
HDSDR under Windows is fun and easy.
Thought about Raspi3, 7 inch touch screen, Linux, software YUCK.  
Followed advice of Ken G4IIB and got a 50 buck tablet with Google Play. 
Who needs tiny OLEDs?  Use a 7 inch tablet as your display!
Building a Ceramic Resonator for the HRO  455 kc filter
The value of doing something different. 
Boxed up my NE602 OLED rig. 
OLED noise and ACTIVE decoupling.
NE602 and MOSFET tips
LEXICON:  
OTD   Obsessive Tinkering Disorder  G6LBQ
"A Thing of Beauty"  
Source of Tombstoning term:  Don ND6T.
Ken G4IIB’s extremely smooth audio.
ON THE AIR:
On AM on 75 and 40.  Fun.  Old Military Radio Net and "The Lonely Guy Net" on 75 Saturday morning.
Good old 17 meters. Open at mid-day
HB2HB on 40 with W0PWE.
Listening on 60
Hambrew magazines disappeared, but are back now.
EMRFD Classic Edition available
New Posts to BITX HACKS
MAILBAG:
Gloves follow-up. Not a good idea.
VK3YE’s QRP by the Bay event  and a new book!
Colin M1BUU achieves Mountaingoat status
Martin A65DC JoO MMM in the UAE
Tom NY2RF Editorial with mention of JoO!
Lots of Al Fresco rigs: W8LM BITX on a board, Brad WA8WDQ DC RX, KA4KXX Al Fresco OZ DSB
ON6UU DSB from Spain via Belguim
Hugh ZL1UEM SMALL Si5351 OLED
Cookie Tin rigs VK2EMU’s Biscuit Tin DC RX,  WA7HRG’s Popcorn rig
VK4FFAB FB LTSPICE intro
Ken G4IIB’s BITX adventure (with VERY smooth audio.  How smooth? We can’t say.)
VU2XE’s BITX with a CAD box
G0ETP’s shockingly beautiful SDR receiver
Alan W2AEW on the mend with broken ankle.  His videos are a treasure trove of tribal knowledge.

Friday, December 13, 2019

Crystals -- Old and New and World War Two


I was watching Greg Charvat's great video about the WWII ARC-5 receiver yesterday. Greg admonished all of us to preserve any WWII gear we might have in our shacks.  Just one day earlier I had found the crystal pictured above in my junk box.   There is some old stuff floating around in here! I will preserve this one. 

Speaking of crystals,  Walter KA4KXX recently sent me some 40 meter crystals for use with my ET-2 transceiver.  Walter suggested that I use them to check into the daily (1300Z) Sunrise Net on 7123 kHz.  These were modern "short" computer crystals.  So I put them into FT-243 and FT-241 holders.  (Don't worry Greg, no WWII gear was destroyed in the process).  It was kind of fun to put the new rocks in old boxes. They work just fine in the ET-2.  Thanks again Walter! 



Finally, Chris KD4PBJ has been helping a buddy of his buy a Drake 2B.   This morning Chris asked about the E Crystal adjustment coil on the back of the Drake.  I told him that was to allow the use of "overtone" crystals.  But, sadly, I advised him not to worry about it too much because the days of ordering bespoke crystals (overtone or otherwise) are behind us. 

Saturday, January 21, 2023

A Call for Builders! Please help us Test this Receiver! Please Build this Receiver!

 

This is the Direct Conversion receiver that Dean and I have built.  We plan to have students at a local high school build it, starting in early February.   We would like to have some others build it, to make sure that the design is re-producible without problems.  

Please build this receiver!  But we ask that you build it exactly as per the schematic above and below. Innovation can come later -- for now we just want to make sure this thing works, that there are no errors in the schematic, and that it can be built by the students with minimum woe.  Thanks in advance! 

Dean or others with 3D printers may be able to supply the plastic form for the PTO inductor.  

We know of one other builder, but he is having some trouble.  We would like to confirm that this design is sound.  

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

Above is the screenshot of the LTSpice model of the 40 meter Direct Conversion receiver that Dean KK4DAS and I have been working on.  I will post a larger scale version of the picture below.  Click on the images for a better view.  Comments welcome.  Please let us know if you find any errors or mistakes.  Realize that we wanted to keep this all simple, discrete, and entirely analog. 

Here (I hope!) is the net list for the LTSpice model: 


First, one of the surprising things about the LTSpice model: IT IS ALIVE!  I never had a VFO or PTO actually turn on for me in LTSpice.  This one did!  So I just connected the PTO to the Mixer and the receiver works in LTSpice.   I just put an RF signal at the receiver input, and you can see the resulting AF across the 8 ohm resistor at the audio amp output.  I was even able to calculate the precise frequency of the PTO:  7078 kHz.  As in the real world, in an effort to stabilize the frequency, I changed the capacitors to NP0 in LTSpice.  Very cool.  Dean joked that all we need is a way to get RF in and audio out and we will have made an SDR receiver.  

About the receiver:  

--  Four stages that will be built by students Manhattan-style on four copper clad boards: Bandpass filter, diode ring mixer, Permeability Tuned Oscillator (PTO),  AF Amplifier.  

-- The bandpass filter is a simple dual-tuned circuit device based on the info on the QRP Labs site.  (Thanks Hans!)  We out a 10k pot as an RF gain control between the antenna and the filter. 

-- The mixer is a standard diode ring.  We included a diplexer at the output using a circuit from the famous W7EL  Optimized transceiver. (Thanks Roy!) 

-- The Permeability Tuned Oscillator is a very simple and very stable Colpitts design developed by Farhan VU2ESE.  We added a simple FET buffer using the circuit in Farhan's Daylight Again rig.  (Thanks Farhan!) 

-- The AF amp is a very simple three transistor amplifier based loosely on designs from Forrest Mims and from the Herring Aid 5 receiver. Both these designs use just two stages -- we added a third and put an AF gain pot between the first and the second stages. There is an impedance mismatch between the diode ring and the AF amp, but we found that most of the proposed solutions were more trouble than they were worth, so we left it as is.  

--Thanks to Wes W7ZOI for his November 1968 QST article on the solid-state DC receiver. Wes's article inspired our efforts.  

Dean and I have both built these receivers.  They work very well.  Dean has even decoded FT-8 with his. We used Radio Marti at 7355 kHz to test for AM breakthrough -- with the diode ring, the diplexer, and the RF gain control we were able to bring the AM breakthrough down to acceptable levels. You can see many videos of my receiver in action over on my YouTube channel:  (355) SolderSmoke - YouTube

Here is a larger image of the schematic (click for a full view): 


And here is a nicer schematic done by our friend Walter KA4KXX: 



Saturday, July 18, 2020

Overcoming the Complexity of the Michigan Mighty Mite: Walter's Sunrise Net Special


From Walter KA4KXX
June 21, 2020

Michigan Mighty-Mite:  Why So Complicated?

The April 2020 issue of QRP Quarterly magazine featured an article by Bob Rosier K4OCE which included a schematic for a “Ten Minute Transmitter” by G4RAW (SK), which apparently first appeared in SPRAT 82 in 1996. 
It is even simpler than the Michigan Mighty Mite, so this transmitter can truly be built on a solderless breadboard in about 15 minutes, because a complex coil is not required.  
The only tuning needed was for me to establish the correct value of the output series capacitor. 
This rig allowed me to check-in to the Sunrise Net (see details in blue text on my QRZ page) today on my very first attempt, and landed me a 549 signal report from 250 miles away.
The first photo shows the transmitter connected to a Transmit/Receive Switch mounted in an Altoids box. In the Transmit position the antenna is disconnected from my 1979 Heathkit HR-1680 receiver, which then coincidentally supplies a sidetone at an ideal volume level.  That little black pushbutton which can be seen in the second photo serves as my key, and works just fine for a five-minute daily QNI on the Sunrise Net.
Of course, part of the secret is having a crystal exactly on the Net frequency, and I have a few left, free to whomever in the Eastern U.S. is interested in building one of these simple Sunrise Net Special Transmitters and participating in our Net. 


Thursday, December 1, 2022

The 40 Meter Direct Conversion Receiver We Have Been Working On -- Comments Welcome


Above is the screenshot of the LTSpice model of the 40 meter Direct Conversion receiver that Dean KK4DAS and I have been working on.  I will post a larger scale version of the picture below.  Click on the images for a better view.  Comments welcome.  Please let us know if you find any errors or mistakes.  Realize that we wanted to keep this all simple, discrete, and entirely analog. 

Here (I hope!) is the net list for the LTSpice model: 


First, one of the surprising things about the LTSpice model: IT IS ALIVE!  I never had a VFO or PTO actually turn on for me in LTSpice.  This one did!  So I just connected the PTO to the Mixer and the receiver works in LTSpice.   I just put an RF signal at the receiver input, and you can see the resulting AF across the 8 ohm resistor at the audio amp output.  I was even able to calculate the precise frequency of the PTO:  7078 kHz.  As in the real world, in an effort to stabilize the frequency, I changed the capacitors to NP0 in LTSpice.  Very cool.  Dean joked that all we need is a way to get RF in and audio out and we will have made an SDR receiver.  

About the receiver:  

--  Four stages that will be built by students Manhattan-style on four copper clad boards: Bandpass filter, diode ring mixer, Permeability Tuned Oscillator (PTO),  AF Amplifier.  

-- The bandpass filter is a simple dual-tuned circuit device based on the info on the QRP Labs site.  (Thanks Hans!)  We out a 10k pot as an RF gain control between the antenna and the filter. 

-- The mixer is a standard diode ring.  We included a diplexer at the output using a circuit from the famous W7EL  Optimized transceiver. (Thanks Roy!) 

-- The Permeability Tuned Oscillator is a very simple and very stable Colpitts design developed by Farhan VU2ESE.  We added a simple FET buffer using the circuit in Farhan's Daylight Again rig.  (Thanks Farhan!) 

-- The AF amp is a very simple three transistor amplifier based loosely on designs from Forrest Mims and from the Herring Aid 5 receiver. Both these designs use just two stages -- we added a third and put an AF gain pot between the first and the second stages. There is an impedance mismatch between the diode ring and the AF amp, but we found that most of the proposed solutions were more trouble than they were worth, so we left it as is.  

--Thanks to Wes W7ZOI for his November 1968 QST article on the solid-state DC receiver. Wes's article inspired our efforts.  

Dean and I have both built these receivers.  They work very well.  Dean has even decoded FT-8 with his. We used Radio Marti at 7355 kHz to test for AM breakthrough -- with the diode ring, the diplexer, and the RF gain control we were able to bring the AM breakthrough down to acceptable levels. You can see many videos of my receiver in action over on my YouTube channel:  (355) SolderSmoke - YouTube

Here is a larger image of the schematic (click for a full view): 


And here is a nicer schematic done by our friend Walter KA4KXX: 




Friday, August 5, 2022

SolderSmoke Podcast #239: Hex DX, VFO Temp Comp, DC RX, Polyakov!, DX-100, Wireless Set, Farhan's "Daylight Again" HDR rig, MAILBAG

N2CQR Hex Beam Aimed at Europe

SolderSmoke #239 is available for download: 

http://soldersmoke.com/soldersmoke239.mp3

TRAVELOGUE: 

James Webb Space Telescope.  Mars returning to opposition in early December.   

BILL'S BENCH

Hex Beam K4KIO - on roof – TV Rotor – 20-17-12  Lots of fun.  Working Japan regularly, Australia, South Africa on long path 17,000 miles.  52 countries SSB since July 11.

VFOs and Temp stabilization.  Dean KK4DAS found my ceramic resonator VFO for DC receiver drifty. He was right.  So I built a real LC Colpitts VFO.  Got me into temp stabilization.  A new hobby!  An obsession.  HT-37 and Ht-32 parts. Ovens?  WU2D’s second VFO video.  Understanding thermal drift and how to address it. Split stator caps.  Cut and try.  

Built a Polyakov DC Receiver. https://soldersmoke.blogspot.com/2010/03/polyakov-plus-dual-band-receiver-with.html  Lauser Plus.  Lauser = Imp or Young Rascal!  DK2RS.  He used a ceramic Resonator VXO at 3.58 MHz.   Mine works great on 40 with VFO running 3.5 -- 3.65 MHz. See schematic below. 

On 40 AM with DX-100 and MMMRX.  DX-100 died.  12BY7 VFO buffer went bad.  How common is failure in this tube type?  Nice QSO with Tim WA1HLR about the DX-100.

Got my Dominican license:  HI7/N2CQR!  SSSS on the way.   Thanks to Radio Club Dominicano and INDOTEL.

Getting more active in the Vienna Wireless Society.  

BOOK REVIEW:  

"The History of the Universe in 21 Stars” by Giles Sparrow.  Written during the pandemic.  Published by Welbeck, in London. https://www.amazon.com/History-Universe-21-Stars-imposters/dp/1787394654  Also:  From “Atoms to Amperes” by F.A. Wilson available for download.  See blog.

SHAMELESS COMMERCE DIVISION:   

Todd K7TFC getting ready to launch “Mostly DIY RF.”   I used his TIA boards in my 1712 rig.  He will have boards like this and much more.  Stay tuned.

I need more viewers on YouTube.  They want 4,000 hours IN A CALENDAR YEAR!  Please watch!

FARHAN’S NEW “DAYLIGHT AGAIN” RIG.  Analog.  VFO.   Comments, observations. We need to get him on the podcast.  Maybe two shows: SDR and HDR. 

PETE'S BENCH

Time very limited. But still sharing lots of tribal wisdom.

Wireless set with tubes!

Tool recommendation – Air compressor

 MAILBAG:

Farhan VU2ESE – Speaking of big antennas “Whenever I look at the huge construction cranes in Hyderabad, I always think how one could make 160m, 4 element yagi using it as a boom..

Todd K7TFC in Spain, spotting Log Periodics in Madrid.

Andreas DL1AJG:  Can Biologists fix Radios?

Janis AB2RA Wireless Girl.  Expert on Hammarlunds.  And was my first contact with the Tuna Tin 2. She too was HB!

Peter Parker VK3YE on Owen Duffy VK1OD

Lex PH2LB on homebrew radio

Would this really be homebrew?  Mail from H-A-D article on FM receiver

F4IET a DSB rig from France

Ciprian got his ticket YO6DXE    

Josh G3MOT sent us a good video about the Vanguard satellite and IGY.

Dave Wilcox K8WPE bought Chuck Penson’s Heathkit book.

Rogier -- So many great articles and links from PA1ZZ

Bill AH6FC  Aloha. Retiring.  Wants to build.  Mahalo!

Grayson KJ7UM  Working on an Si5351.  Gasp.

Mike KE0TPE viewing YouTube while monitoring 6 meters.   He will have a lot of time to watch!

Chris KD4PBJ spotted Don KM4UDX from VWS FB

Mark WB8YMV building a superhet.  Having trouble with 455 kc IF can filter.

Walter KA4KXX Great comment on the Daylight Again rig. 

Ramakrishnan Now VU2JXN was VU3RDD.  Found lost Kindle with SolderSmoke book on it. Building SDR rig from junk box.  Trouble with the LM386. 

Pete, Farhan and Tony:  Shelves of Shame

Daylight Again by Farhan

The Polyakov receiver I built yesterday (from SPRAT 110, 2002!)

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