A Message from Walter KA4KXX -- On Bias Setting, the Joys of Al Fresco Rigs, Lawn--Sign Radio Base

 

Dear Dean KK4DAS:

...

3) Note that a rule of thumb I have used successfully in adjusting RF Power MOSFET

bias is to increase the voltage in 100mV steps, measuring the RF Output Power 

each time, and stop as soon as you start to see significantly diminishing returns.

4)  Although I did mention a plexiglass cover (the idea was from the Electroluminescent 

Receiver in photo below) in a 2017 entry I made on my QRZ page, I never built one, because I  have found a cover of any kind to be unnecessary and even detrimental based on operating portable outdoors in a public park with my rigs once every month for 10 years.  

From these experiences I have enjoyed the wonderment and respect I have received 

from fellow hams as well as passersby who have universally admired my creations. 

If the truth were known, my homebrew Alfresco transceivers might be the most 

photographed radios in all of ham history!  

Therefore, the only box I bring to my ham radio outings is for my lunch, because nobody

really gets excited about photographing just another box.

However, I do use plastic carrying cases per the photo for any rigs I carry 

in the trunk of my car.  If it rains, the top of the carrying case can be used as a 

temporary cover, so I know contacts can be made in a light rain because I have done it.

[Of course, credit card hams are not capable of operating portable even on a cloudy day

or their $$$$ radios would suffer from high humidity disease and need to be sent 

back to the offshore factory for $$$ refurbishment!]

5)  Lastly I will mention that I have never used any type of wood for a radio base because

wood is too heavy (and 1/8 inch aircraft plywood is too expensive), and the strength of

wood is not necessary to support a measly 5 pounds of electronic parts. 

Instead, per the photo, I have used Coroplast yard sign material (usually two sheets

with the channels crosswise then taped or glued together with the top covered using copper tape) common school science fair poster board, or good heavy duty cardboard such as from a TV set box.

Either light or heavy-duty double-sided tape and 4-40 or 6-32 nuts, bolts, and washers (sometimes oversized) are used to hold everything on board.  Occasionally L brackets, standoffs, hot glue, and foam or balsa wood support pieces are also utilized. 

In summary, keep up your good work as the new star on the Soldersmoke Podcast and 

please be certain Bill pays you as much as Pete.

72,

Walter

KA4KXX

The Awesome Homebrew of Will KI4POV

 

Will's homebrew station is really something.  The rig (it truly qualifies for this term of praise) is amazing all by itself  (see below), but a look at Will's QRZ page reveals other ingenious inventions and techniques:  There is the clock made from panel meters.  And the method he uses for making aluminum project boxes.  He even made an N0WVA regen receiver.  That's the one I used in my ET-2.   Fantastic.  

Will really needs to share his homebrew skills with others.   I hope he is soon in a local high school teaching students how to build things.  Thanks Will!  

Bill and Pete,

Just wanted to send a note to update you on the latest projects here. The last time I emailed, I mentioned wanting to build a superhet, which you (rightfully) discouraged, pushing for a DC receiver.

Well, I finished the superhet at the end of last year. I had most of the receiver working long before then, but got bogged down in an AGC system. The final receiver is a 5 band si5351a controlled single conversion superhet loosely based on Todd, VE7BPO's design with several modifications. I used a 9 Mhz IF instead of 4, I used a digitally controlled LO and BFO, and as mentioned, I added an AGC system, which ended up being the most challenging (and most interesting) part. The final AGC system I ended up with used the detector and amplifier side of Wes Hayward's "full hang" AGC from SSDRA, but I didn't have the IC IF amplifiers with variable gain, so instead, it fed a PIN diode attenuator circuit to control the IF gain. The final result worked great, but I nearly pulled my hair out getting it to work. I originally intended to build the receiver for 40 and 20 meters, but it ended up covering 80, 40, 30, 20, and 15 since I used the filter relay board from QRP Labs which had 5 slots.

After I got the receiver running, I decided I needed a matching transmitter, so I  built up a simple CW transmitter to match. It uses an si5351a VFO driving a 74HC04 hex inverter as the buffer amplifier. The trick here is that by driving all the inverter gates in parallel, the output impedance is ~14 ohms broadband, suitable for driving a BJT PA without any need for matching transformers. The PA is 3 2N2222s in parallel with heat syncs putting out about 2 watts from 80 - 15.

The part I'm most proud of is that I have the arduino for the receiver connected to the arduino for the transmitter through a serial line. The receiver sends it's current frequency to the transmitter so that the transmitter can track the receiver's frequency as you tune (like a transceiver). I'll attach a few pictures of my homebrew station below. The transmitter is on the left, receiver is on the right. The box on top of the transmitter is my homebrew keyer. Next up on my build list is a solid state T/R switch.

Bill, I've enjoyed following the updates on the school DC receiver build. My local club is wanting to do some youth outreach, and I'd love to get them involved in building. I'm the only builder in the club though, so I don't know if I personally have the manpower to make it happen. Also, thanks for the recent info and pictures of Cuban homebrew rigs. I grew up listening to Arnie Corro, so I love seeing their resourcefulness and ingenuity. Makes me want to take apart some old electronics.

Pete, I'm enjoying following the 10M SSB project. With the uptick in propagation, I've been bitten by the 10M bug, and I'm thinking a 10M rig may have to be on my project list for this year.

73,

Will - KI4POV

KI4POV's Clock

KI4POV's N0WVA Regen

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. 

Boxing it Up: Tribal Knowledge from Pete N6QW on How to Make Enclosures for Homebrew Rigs

 

http://n6qw.blogspot.com/2022/02/2022-return-to-peashooter-build.html

Thanks Pete!