Podcasting since 2005! Listen to Latest SolderSmoke

Showing posts with label amplifier theory. Show all posts
Showing posts with label amplifier theory. Show all posts

Wednesday, March 13, 2024

Using the RF Power Amplifier of the BITX40 Module

 

PA shematic from the BITX 40 Module
Click on the diagram for a better view

C.F. Rockey W9SCH (who alerted us in SPRAT 22 to the chicken sacrifice option) spoke of transistors that exhibit "quantum mechanical necromancy."  Rockey explained that when this happens, "The transistor simply turns up its toes and dies. Not even an Atomic Physicist can tell you why!"  

This often (very often!) happens with homebrew power amplifiers.  So when we find a good one, many of us stick with it, using the same power amp circuit in rig after rig.  I have done this with the power amplifier from the BITX40 Module. 

Mythbuster (75 & 20 Meter) version (early)  
Click on image for a better view. 
https://soldersmoke.blogspot.com/2021/08/mythbuster-video-13-rf-power-amplifier.html

Same amplifier built into Version 2 of the 15-10 Transceiver 
Click on image for a better view. 

In the build for the 15-10 transceiver you can see some changes.  I used an RD06HHF1 instead of an IRF-510.  I used an 8.1 volt zener diode instead of the regulator chip. I set the bias at around 5.5 volts DC on the gate of the RD06.   I used a smaller, metal can driver transistor (it works fine). I changed the input/output physical configuration between the pre-driver and the driver stages (I think it was kind of goofy the way I had it in the Mythbuster).  Finally, you can see how I used a small piece of copper tape (with conductive adhesive) to shield the line going from the driver transformer to the gate of the RD06.  The wire was too small to use a bit of shielded coax, but I think the copper tape and the copper clad board beneath it work just as well. 

Farhan provided me with some fascinating background on this circuit: 

Bill,

I just saw your post on the bitx40 power amp. The credit must go to Wes for this, it is from the Lichen transceiver described in 6.9 of the EMRFD. I merely copied it with some modifications for it to work with junkbox components.

It bears mentioning that at that time I didn't have a way of generating two tone signal or measuring the IMDR. Those came later when I built my own spectrum analyzer based on Wes and Terry White's spectrum analyzer. It was sheer luck that I picked this power chain that already had careful gain distribution.

For the output, the original build used and LPF with inductors wound on a ballpen shell and TV baluns cores instead of toroids. Again, it was incredibly lucky that they worked at all. 

- f

Friday, September 29, 2023

"The Art of Electronics" #8 -- Why Not a Simple Emitter Follower as The AF Output Circuit?

Click on the image for an easier read

Back when Dean KK4DAS and I were trying to find a suitable AF amplifier circuit for our High School Direct Conversion receiver project, we were debating what to use as the final.  One option was the standard NPN-PNP push-push amplifier (like in Figure 2.53 above)  -- an advantage with this one was that it would not require an AF transformer.  But we decided that this circuit would add complexity to a project that we were hoping to keep very simple. 

Another option was a simple common emitter amplifier with a transformer in the collector circuit.  This worked, and was simpler.  We ordered the transformers.  

In the midst of all this, at the local radio club hams asked us why we just didn't put a single emitter follower at the output to handle the impedance transformation to an 8 ohm speaker (sort of as in Figure 2.52 above).  They were convinced this would work.  I was not so convinced and pointed out that we had never seen such a circuit in any of the ham radio literature.  If this could be done, why hadn't the likes of Doug DeMaw and others used this circuit in their many, many rigs?  

This discussion kind of ended there (we opted for the common emitter transformer circuit), but I have thought about it from time to time.  A couple of weeks ago, when I got the second edition of The Art of Electronics, I found the above discussion of the use of this kind of emitter follower circuit.  You can see why this circuit has not been used.  Just to be sure, I built one in LTSpice.  Sure enough, it takes way too much current.   

Thank you, Horowitz and Hill! 

Friday, September 8, 2023

Why Building for 10 Meters is Harder than Building for Lower Frequencies


Recently my trusty CCI EB63A .1kW amplifier has been in rebellion.  On 10 meters, it now often insists on being an oscillator.   It calms down nicely on 20 meters.  But on 10, it has been a rebellious beast.  

Why is this?  Why would an amplifier that is well behaved and stable on 20 meters behave so badly on 10 meters?    

I used LTSpice to explore the problem.  

I looked at two ordinary wires.  I gave them each a value of .003 uH.  Very low.  Then I joined them together in a transformer.  I put a 1 volt signal into the primary and looked (in LTSpice) at how much of a signal appeared in the secondary.  First, the result on 14 MHz.  About 250 mV appears on the secondary. 


Now consider what happens at 28 MHz.  Nothing else in the circuit changes.   Just the frequency.


Here we get about 450 mV.  A lot more.   

Realize that my little EB63A amp has lots of wires in it, most of which are ready to serve as primary or secondaries in circuits like this.  Increasing the frequency makes it more likely that a ginal will jump to someplace that it is not supposed to be.  Output will couple to input and the Barkhausen criteria will be met. The amplifier will become an oscillator.   

Of course, something similar happens with capacitive coupling.  Same story:  the higher the frequency, the harder it is to keep the amplifier stable. 

Don't worry:  Improved shielding is saving the day.  The amplifier is now stable on 10.   More about this in the next podcast... 

Tuesday, June 7, 2022

SolderSmoke FDIM Interviews: A BRAVE HAM! Grayson Evans KJ7UM Presents a 50 Watt Amplifier to THE QRP GROUP!

Wow, talk about walking into the lions' den!  Grayson Evans, author of "Hollow State Design" and guru of all things thermatronic, went to FDIM and made a presentation TO THE QRP GROUP on how to build a 50 watt amplifier with a 6146 thermatron.  In New York that would have been called chutzpah.  The QRP ARCI guys seem to have tolerated this QRO-heresy; I'm not so sure the zealots over in G-QRP would have been quite so tolerant.

Grayson gave a nice shout out to SolderSmoke's Pete Juliano.  

And he offered some sage advice to those who live in fear of high voltage:  "Don't touch anything with high voltage on it."  Words to live by my friends.  He even managed to call those who shy away from high voltage "wimps."    This was all very reminiscent of the unforgettable safety advice he offered in his August 2021 interview on Ham Radio Workbench: "Try not to swallow anything, and don't sit on the thermatrons." I mean, who can argue with that? 

You can listen to Bob Crane's interview with Grayson here (about 6 minutes total): 

http://soldersmoke.com/2022 KJ7UM.mp3

Check out Grayson's  Hollow-State Design Book 3rd Edition: tinyurl.com/hollowstatedesign3

Check out Grayson's technical blog:kj7um.wordpress.com


Thanks Bob and thanks Grayson. 


Sunday, June 5, 2022

JFET (Junction Field Effect Transistor) Video -- Part 1


Good video.  I like how he related the real-world device to the Igs graph. Also, note the big variation in MPF-102 parameters.  Stay tuned for Part 2. 

Monday, April 25, 2022

75/20 - 17/12 Two Homebrew Rigs in Scrap-Wood Boxes

 



I moved the 17/12 Rig off the workbench and placed it (as planned) atop the Mythbuster rig.  Now I have four bands easily accessible.  In these pictures you can see all four bands being displayed on the San Jian Frequency Counters. 

I found a kitchen drain screen that is an ideal cover for the 3 inch speaker in the 17/12 rig. 


I reconfigured the Low Pass filters in the CCI .1 kilowatt amplifier.  I put a 12 meter LP filter in there in place of the 40 meter LP filter (that I haven't been using much). 

I have been working a lot of DX on both 17 and 12.   

Wednesday, April 13, 2022

The 17 & 12 SSB Transceiver -- Circuit and Build Info -- Video #4


I REALLY LIKE THIS RIG. IT IS LIKE A MAGIC CARPET THAT CARRIES MY VOICE ACROSS THE SEAS.

Cutting Display Hole sets off smoke alarm. Reverse Polarity Protection. IF and Crystal Filter at 21.470 MHz 50 ohms! TRGHS! Amp for VXO Carrier Oscillator/BFO. Mic Amp from uBITX. Transmit/Receive switching from mic connector. VFO: NO DIE CAST BOXES! HT-37 Variable Cap, Frequency Shift. BP filters from QRP LABS designs (G0UPL). TIA amp boards from K7TFC. Needed RF amp to hear band noise. BITX40 PA design, but RD006HHF1 instead of IRF510. Should I run receiver input through LP filter? Frequency Readout Story: How to use one San Jian counter on two bands.

Saturday, December 4, 2021

Dean's Supercharged, 16-Watt, Furlough 2040, Simple SSB Rig

 

'Tis a thing of beauty. 

It is especially appropriate for us to use that Irish phrase because the design of the rig's new final amplifier is out of  Ireland. Our friend Dean KK4DAS added a 16 watt RF amplifier based on a design by EI9GQ to his homebrew N6QW Simple SSB rig.  Note the IBEW label on the top. 

Here is Dean's blog post on this wonderful project (with video and more pictures). 

Dean has it on the air and is getting good reports.  He has clearly come a LONG way from his Michigan Mighty Mite build of just two years ago.  FB OM. 

Here is Dean's build of the EI9GQ 16 Watt Final

Final final assembly! 


Tuesday, October 5, 2021

Dean KK4DAS Builds an EI9GQ 16 Watt RF Amplifier (and Noodles in the Process)

 

I really like Dean's description of the building process, especially where he describes the need to sit down with paper and pencil for some noodling.   We see that in the picture above.  Too often we hear from guys who seem to be looking for detailed, step-by-step instructions, and then get frustrated and stuck when this kind of detail isn't available. Dean shows what to do in this situation:  noodle! 

Check out Dean's blog post on this project: 


Dean's post made me think about the origin of the verb "to noodle."  We know it has its origins in music.  Google provided this interesting explanation: 

To noodle around on something, while it does make use of the noodle (head), may derive from the regional German nudeln, to improvise a song, or from the late-19th-century Scottish sense of noodling as humming a song to oneself. By 1937, to noodle was to fool around with notes to create music.

We noodle around with parts and schematics to create rigs. 

Tuesday, August 3, 2021

AFTIA! The Audio Frequency Termination Insensitive Amplifier from W7ZOI

 

It really pays to check Wes Hayward's web site.  I looked yesterday and found something that we really need:  A termination insensitive amplifier for audio frequencies -- an AFTIA.  Just last week I was looking at the AF amplifier of my Mythbuster rig, wishing that it had TIA properties.  Now, thanks to Wes, we have a circuit available: http://w7zoi.net/audio-fba.pdf

And let's not forget that it was Wes Hayward W7ZOI and Bob Kopski K3NHI whose 2009 article alerted us to the RF variety of termination insensitive feedback amplifiers. 

Saturday, March 6, 2021

ZL2CTM's Simple SSB Transceiver


Congratulations to Charlie Morris ZL2CTM for his first contact with his Simple SSB rig.  

There are so many cool things in Charlie's video, starting with his mention of having been woken up early (2 am)  by the very strong earthquake off New Zealand.   Exhibiting true homebrew spirit, Charlie apparently went straight for the shack and worked on his rig.  FB OM. 

Al fresco!  I love the spacious layout on the board and the obvious division into stages.  And I like the wooden board that holds it all together. 

I like the idea of two bandpass filters -- this is simpler than switching one from transmit to receiver.  

Hooray!  Homebrew diode ring mixers!   Yes! 

I think Charlie follows the UK convention with his T/R switch -- they have up as off.  I may be wrong but I think most US homebrewers have up as on, and up as transmit.  Cultural differences. 

Notice Charlie touch-testing the heatsink during that first QSO.  We all do that. 

I like the 24 volts on the IRF-510 drain.  Allison always said that IRF-510s run better at 24V than they do at 12V. 

Of course I disagree a bit on the issue of analog VFOs. But this is just a matter of personal circuit preference. 

Charlie's calculations and notes are really wonderful.  His candid discussion of impedance matching is especially useful.    I think his use of loose-leaf  sheets of paper is wise and it paves the way for a useful folder for each HB rig. 

Here is the introductory video for Charlie's Simple SSB project: 

Here is Charlie's 10 part video series on his simple SSB rig: 

And here is Charlie's YouTube channel: 


Thanks Charlie! 

Friday, August 14, 2020

Tor LB4RG Builds an IRF-510 Amplifier


Click on the link to check out Tor's very FB and artistic video about his homebrew IRF-510 amplifier. 

Very Nice.   Also, check out Tor's FB SolderSmoke hat.  

https://gopro.com/v/bQ1JGOXRrRqrQ

And here is an update from Tor" 

https://gopro.com/v/gv19pDDqQnO1a

Monday, June 22, 2020

Feedback on Farhan's FB Feedback Amp Video


As I said a couple of days ago, Farhan has put out a very informative video on amplifier design. During the video we can see him determine bias, feedback and load levels, then select component values. We then see him actually build the amplifier "ugly style" and use his Antuino to test it.  Fantastic.   

Watch Farhan's video here:  https://www.vu2ese.com/index.php/2020/06/18/feedback-amplifier/


I sent Farhan some of my reactions to the video.  In the hope of stimulating some discussion, I repeat them here: 

___________________

Wow Farhan, I really enjoyed your video and learned a lot.  You definitely have the Knack for explaining this stuff. 

I have been struggling to understand feedback amps for a long time.  I took up this topic on pages 187-190 of the "SolderSmoke -- Global Adventures" book.  I was more focused on the benefits of FB amps, and on how and why feedback affected input impedance.  

 I took notes as I watched: 

-- I liked the fulcrum analogy. 

-- Really wonderful how you describe the selection of components to get desired bias. 

-- Even better when you explain tapping down of RF coil to get 50 ohms to look like 200 ohms. Great stuff. 

-- Standardized on BNC.  FB! 

-- .1uF caps.  Love them!  No argument here! 
 
-- I copied your resistor list.  Will use it with Mouser. 

-- Saving the pigtails.  Indeed!
 
-- I like your ugly "resistors first" technique.  I may have to move away from Manhattan. 

--  Wow.  Ugly circuits IN SPAAAAACE!  FB!
 
--  2N3904   I always think it is EBC when looking at the flat end of transistor with leads facing down. Only had reverse pinout with PN2N2222.  EBC is my usual assumption.
 
-- I still have the big box of trifilars you left me.  I use them.  Thanks!

-- I like that VTVM in your Antuino.   Very handy. Want one!  Also, We need to get the Antuino to go down to below 455 kHz. 

-- I also like your dual Return Loss and SWR display.  I think in terms of SWR.  Return Loss sometimes messes me up. 

-- Didn't know about the Hold and Zoom feature on Antuino. FB.
 
-- Your measurement of the Q of the crystal was awesome.
  
-- I checked my soldering iron temp:  I'm at 480 C   A bit too hot. Will back off. 
 
-- Good description of need for an attenuator at amp output to keep it in Antuino's range.
 
-- As I watched you tug on the components after the solder cooled, I remember an old and silly admonishment from the ARRL Handbook:  NEVER  use solder for mechanical connections.  Ha!  They were WRONG!
 
-- Demonstration of the flatness of feedback was great.
 
-- I found your measurement of impedance using the SWR feature of the Antuino to be very useful.  Is there a chart relating the SWR/Return Loss to actual impedance values? 

-- Loved your description of how output impedance affects input impedance.  That is why you advised use of TIA amps in my DIGI-TIA.   But now I'm thinking that if I can accurately measure impedances of non-TIA amps, I can design L networks that will keep the crystal filter passbands ripple-free, right? 

-- Great explanation of the benefits of the 6 db pads at amp output.  Allison often recommends this. Now I know why. 

-- Wow!  Now I KNOW what that two-tone box you left with me is for!  Now I understand how it can be used to measure IMD on FB amps.  I pulled mine out just as you began to discuss yours.  Really cool. 

Thanks a lot Farhan for doing this.   These videos will be of long-lasting use to homebrewers around the world.  I hope we will see many more VU2ESE videos like this one. 

73  Bill 

Saturday, June 20, 2020

Excellent Video from Farhan on Amplifier Design


Farhan has produced a really excellent video explaining the theory behind the feedback amplifiers that we use in so many of our circuits.  He takes us through the design and construction of these amplifiers, then uses his Antuino network analyzer to test an amplifier  and to measure input and output impedances.  

There is a lot of tribal knowledge and wisdom in this video! 

Check it out here:  

https://www.vu2ese.com/index.php/2020/06/18/feedback-amplifier/

Thanks Farhan! 

Wednesday, March 4, 2020

N3FJZ's Al Fresco. BITX-inspired, TIA. 50 Watt, SSB Rig (Video)



The last blog postings on Rick N3FJZ were in 2015.  Rick sent me a very uplifting reception report, then we had a pretty amazing Homebrew-to-Homebrew contact.  

Paul Taylor VK3HN yesterday alerted me to a new YouTube video that shows the progress Rick has made with his homebrew SSB rig.   

This is a great example of true amateur SSB construction.  Rick is making use of a combination of digital and analog technology.  He is adapting circuitry developed by others and using it to meet his needs.  During the development stage he is keeping the circuit open (Al Fresco) so that he can easily work on it.  

FB Rick.  

Thursday, February 20, 2020

Tribal Knowledge: More on Tapping Metal


Back in 2014, when I was putting together my EB-63A solid state amplifier, I had to learn how to tap aluminum so that I could attach my transistors to the heat sink.  I did short YouTube video on how I did this (with tales of woe!).  This video turned out to be amazingly popular -- more than 27,000 views!  Apparently there is a great thirst for this kind of knowledge out there.  Recently someone in Alaska came across my video and shared with us some more useful information on how to tap metal.  Here is some tribal knowledge from Paul KL7FLR:  

Hi Bill and Pete,

Stumbled over Bill’s YouTube video about tapping in Aluminum and I would like to add my experience doing such. I have probably tapped over a 1000 holes in various metals, cast iron, steel, aluminum, bronze and brass from 0-80 to ¾-20. Each metal poses its own problems and solutions. There was nothing in error with your video or the method you presented.

My comments:

What causes broken taps is the tap is not being perpendicular to the work. A hole not perpendicular to the work, a worn/dull tap (this applies to the drill bit too) and lack of lube.
Every hole to be drilled and tapped must be perpendicular to the metal. A hand drill electric or battery will not be perpendicular unless two other people can spot the drill operator. Not possible when you are alone in the shop.

Any serious homebrewer should have a drill press. A small bench drill is very inexpensive. Even the $69 Harbor Freight model is adequate for the average ham’s workshop.  I see these items at flea markets and on Craigslist all the time cheap. Estate sales not so cheap but sometimes on last day you might get a bargain. Adjustable from 500 to 3600 rpm will cover all the normal sizes of drills. An x-y table could be added ($$) for added accuracy if desired. (search x-y table for examples and sources)

The size of hole you drill makes a difference too. Most drill charts assume you are tapping at 75% of thread contact. This is amount of the male thread of the bolt/machine screw threads contact the female thread in the piece. This is about the max you can expect without some precision tooling that won’t be in the average home shop.  75% provides maximum strength of the fasteners.  So unless you’re working on something that requires strength like a tower support bracket or the wings of an airplane you don’t need 75% as 50% thread contact is more than adequate. So when the drill chart shows that a #43 you can instead use a #42 or a 3/32 drill. A little bit larger hole will be a lot easier to tap threads.

The type of tap will also influence the difficulty of tapping threads. The typical hardware store tap is a straight 3 or 4 flute taper tap. The chamfer of a taper tap is 9 threads making tapping much easier. This is the tap for hand tapping.  The plug tap has a chamfer of 5 threads and is best used in a tapping head or fixture. The bottom tap is for tapping threads in a blind hole, usually after started with a taper tap. That increases the pucker factor x10. The normal taper tap cuts as it is rotated in a clockwise direction or counter-clockwise for left hand threads. The cuttings will clog the tap and you must back the tap out frequently to clean the cuttings from the flutes preventing the tap from seizing and possibly breaking the tap. Breakage is easily done with the smaller taps but also will happen to a larger tap too.  There is a style of tap called a spiral point tap. It will push the cuttings up to the top of the hole and not clog the flutes as easily as the straight flute taps. I still back it out and clean it out of habit. These don’t cost any more than the hardware taps. A 4-40 is about $2.90 the last time I bought one.

Avoid “carbon steel” taps. These will break easier than “high speed tool steel” taps and they are usually a few cents cheaper too.

Lubrication is necessary. Bill’s use of 3-in-1 oil is a good lube but “Tap Magic 20016A Aluminum” fluid is better for tapping aluminum and regular “Tap Magic” for everything else. https://www.amazon.com/Tap-Magic-20016A-Aluminum-Yellow/dp/B00065VEUO

The metal you are tapping can be an exercise in patience. “Hardware” store aluminum comes in various grades from crappy to real crappy. They are of an alloy best suited for the extrusion process and are not wonderful for the tapping process. Aircraft grade aluminum is nice stuff to work with but not cheap. Comes in many grades from 1000 series to 8000 to match the application. Grade 2024 is communally found and is easy to work with while 7075 works like steel.  Since most of us won’t be buying a 21 foot stick of aluminum or a 5x8 foot sheet we must take the hardware store grade into account when tapping holes and lean towards the 50% thread engagement, plenty of lubrication and lots of patience. I frequent several aluminum boat building firms and they let me pick through their scrap piles and I’ve made frequent donations of a case of soft drinks or a can of coffee to the break room fund and have also paid the going scrap price for the scrounging privilege.

Worn taps:  These get dull with use and will break at the worst possible time and in an expensive  workpiece. Broken taps  can be removed but are time consuming and require some expertise in doing so. Best to retire them when worn. I used to keep a chart of how many holes a particular tap had been used and at 35 holes for the small taps they got retired. 50 holes for taps larger than ¼”.  I once spent over a week of evenings extracting a worn tap from a locomotive cylinder casting. Never again! As my mentor said many times, “dull tools cause accidents and ruined work”.

Clamp the work to be tapped stationary if possible. You don’t want it moving around thus inviting a broken tap. Use some method of a tap guide (as Bill did with a block of wood, not great but better than nothing). I use what is called a “Piloted tap wrench”, https://www.amazon.com/Set-Wrench-Piloted-Spindle-Capacity/dp/B077SVQD4S .

Picture is of my setup.
Step 1: Work clamped securely to table at desired hole location.
Step 2: Drill hole.
Step 3: Use piloted tap wrench to tape hole.
Step 4: Done.

Friday, January 31, 2020

WA2EUJ's NXP RF Power Amplifier Design Challenge Entry -- Won First Place Prize!



Congratulations to Jim WA2EUJ.   First Place the NXP Design Challenge. 

You can buy the board here: 

https://sites.google.com/site/rfpowertools/home/nxp-mrf-101

Thanks to Pete Eaton WB9FLW for alerting us to this. 

Monday, November 6, 2017

Jan's FB Slovakian SMD TIA Boards


Hello,

I have put up my SMD version of the TIA amplifier boards online, in case
someone wants it. The files are here:


and direct OSHPark order link:

73!, Jan

Saturday, September 16, 2017

The Road to QRO Perdition


I want to start out by saying that this is NOT my fault.  I have been TRYING to do QRP things. Remember my recent Tuna Tin 2, Herring Aid 5 rig?    I am aware of the ever-present threat of expulsion from the QRP HoF.   We all remember what happened to poor Pete back on April 1, 2017. 

But sometimes people just deliberately put temptation in your path.   That is what happened this week.  Our old friend Rogier KJ6ETL (formerly known as PA1ZZ) sent me the very LARGE chunk of aluminum that you see in the picture above.  Look at that thing.  It is practically begging to be turned into a very QRO push-pull amplifier.  

At first I told myself that it would be impossible to tap the big heat sinks on the sides.  How would I get the drill in there?  But then I realized that I can just put the threads in from the outside.  I can almost smell the machine oil. And the heat sink compound... 

Thanks lot Rogier. This is all your fault. 



  



Saturday, December 3, 2016

TRGHS! HB2HB! Homebrew Extravaganza on 40 Meters!

AC7M HB Amp and HB Power Supply
I was flying solo last night.  Everyone else in the house was out.  So I turned to ham radio for some company.  And I was rewarded.    

I called CQ with my BITX DIGI-TIA rig and was immediately answered by Doc AC7M in far-off Twin Peaks, Idaho.   Doc was running a K3 to a homebrew solid state full gallon amp.  And get this -- Doc had also homebrewed the 3 kw switching power supply.  I looked at my store-bought supply and felt like an appliance operator.  I hang my head in shame.

As we discussed solid state amplifiers, we were joined by another builder of silicon after-burners: Don K9AQ, who called in from a beautiful cabin in rural Wisconsin. Don's amp is based on the venerable EB-104 design.   

Both Don and Doc talked about the work of W6PQL.   He has a really amazing site devoted to homebrew solid stat amps, and he is selling lots of great boards and parts for this kind of project:
http://www.w6pql.com/  

As I finishing up with Don and Doc, I got a very welcome call from an old friend from the SolderSmoke community: Dino KL0S.  He as booming in from Williamsburg, Va.  Dino has an amazing workshop.  He is building a serious vertical antenna for 160 meters.  Dino is going for the DX.

Dino's Bench

At this point Mike WA3O in Pittsburgh called in.  And get this:  Mike heard me on his new BITX 40 Module.  The Radio Gods Have Spoken! (TRGHS!).  We switched up to 7.285 MHz where I fired up my BITX 40 Module for a BITX40-BITX40 QSO (albeit not at QRP levels).
We should definitely make more use of 7.285 for BITX40 and other HB QRP SSB QSOs.  1930 EST (0030 Z) seems like a good time.

Finally, just when I was thinking that things couldn't get any better, they did:  Armand WA1UQO called in from Richmond.  Armand and I collaborate on parts acquisition at Virginia hamfests.  We specialize in the contents of the musty cardboard boxes found under the tables.  We discussed the DISRUPTIVE influence of Farhan's BITX 40: All around the world, other homebrew projects are being literally pushed aside on workbenches to make room for that fantastic little module from Hyderabad. 

I was very pleased to hear that Armand is building an analog VFO for his module, using a coil in the 4 uH range, wound on a piece of cardboard tube from a coathanger.  The inspiration for this kind of coil (which I now have in THREE rigs) came from Farhan, who used sipping straws from fast-food restaurants as coil forms in a sig generator that he built years ago.  This week, seeing a Facebook picture of my daughter and me in a restaurant with drinking glasses in front of us, Farhan asked if I had brought home the straws. 


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