WA7MLH – SolderSmoke Daily News

So Many Great Pictures, So Much Radio History

I make it a point to go back to Wes W7ZOI’s web site every once in a while. That is always a good idea. This time I found myself looking at the page that described Farhan’s 2017 visit. Wow, just look at the guys at that table.

— Wes W7ZOI. The man who launched the solid state direct-conversion receiver revolution. Author of SSDRA and EMRFD. And so much more.

— Roger KA7EXM. Son of Wes. The guy who developed the receiver for the Ugly Weekender transmitter.

— Rick KK7B. The guru of phasing type direct-conversion single signal receivers.

— Roy W7EL. Father of EZNEC antenna modeling software. And the optimized QRP transceiver, with the diplexer that we are using (perhaps improperly) in our high school direct conversion receiver project.

— Jeff WA7MLH. Builder of so many of the great projects in SSDRA. Made me feel good about gear that looked a bit rough.

— Farhan VU2ESE. Creator of the BITX20, the BITX 40 Module, the uBITX, the sBITX and so much more.

Just scroll through the site. You will see Rick there with his Classic 40 phasing receiver. Roy with his Optimized transceiver. Roger with the Ugly Weekender transceiver.

Finally, the morse key that Farhan gave to each of the participants. Farhan gave me one of these too. I will try to use it from the Dominican Republic on Straight Key Night.

Check out the site:

https://w7zoi.net/Farhan-visit.html

Band Imaging Rigs (Receivers and Transceivers) — Video from WA7MLH

In the video above (from 16 years ago) we see Jeff Damm, WA7MLH’s band-imaging receiver for 75 and 40 using an IF of 1.750 MHz and a VFO of 5.2 – 5.7 MHz, For a signal at say 3.579 MHz (!) you subtract the signal from the VFO and you end up at the IF. For a signal at say 7.030 MHz you subtract the VFO frequency from incoming signal and get to the IF. (By the Hallas rule you get sideband inversion on 75/80 meters, but Jeff was on CW so this doesn’t really matter.)

Sixteen years ago this receiver was a work in progress and Jeff was having some trouble with the bandpass filters. I had similar trouble with bandpass filters. Like Jeff, I eventually got this sorted.

I was happy to see a comment from my friend Joanthan-san on Jeff’s old video.

Jeff has an awesome and rececntly updated QRZ site: https://www.qrz.com/db/wa7mlh

Band imaging like this is an old idea, and a very good one: I used a slightly different scheme: Start out planning on using a single conversion design. Pick two bands you are interested in. Select an IF midway between the two. Build a single VFO that –when added to the incoming (or the outgoing) signal will get you to one of the bands, and when subtracted from the signal will get you to the other one. Bob is then your uncle. Two bands, with minimal switching.

I got started with band switching with my Mythbuster rig: I would get 75 and 20 meters. The IF was midway between the two at 5.2 MHz. My VFO (from an old Yaesu FT-101) ran around 9 MHz. Boom, it worked, with the added benefit of receiving and transmitting LSB on 75 and USB on 20 with no switching of the BFO/Carrier Oscillator.

Then I did 17 and 12 meters. Kind of a WARC-band special. IF was at 21.4 Mhz. VFO ran around 3.5 MHz. So by adding the incoming modulated signal 18 MHz signal and the VFO, you get to 17 meters. By subtracting the VFO from the incoming 24.9 MHz signal you get to 12 meters. And both are on USB (apply the Hallas rule), so again, no switching of BFO/Carrier frequencies are required.

Finally, at solar max, I built rigs for 15 and 10. Here the IF was 25 MHz. Again the VFO was around 3.5 MHz. Adding the incoming 21 Mhz signal to the VFO gets you to 25 MHz, subtraction of the VFO frequency from the in coming 28 MHz signal takes you to 25 Mhz and thus 10 meters. Again, no sideband inversion (Hallas rule). Both signals are USB and stay on USB. (I built two versions of this rig — one stays in Virginia, the other is heading to the Dominican Republic.)

In the ARRL book QRP Classics, there is an article from the 1990 Handbook entitled “A Band-Imaging CW Receiver for 10 and 18 MHz.” The article may have been based on a receiver built by Dave Newkirk AK7M (Rod Newkirk’s son). Unfortunately in the write-up for the ARRL handbook, the drafters repeat the oft-repeated myth about how 9 MHz IF and a 5.2 MHz VFO would supposedly produce LSB on 75 and USB on 20. This just doesn’t work. But if you put the IF at 5.2 MHz and the VFO at 9 MHz, it does work, as demonstrated by my Mythbuster rig.

Jeff Damm WA7MLH on QSO Today

Happy New Year!

There was so much wisdom and tribal knowledge in Eric Guth’s interview with Jeff Damm WA7MLH. It was almost overwhelming.

You should all listen to it. Twice. At least twice:

https://www.qsotoday.com/podcasts/WA7MLH

My notes:

— I sympathize with Jeff’s decision to go solid state and give up on high voltage after an encounter with an undischarged 600 volt capacitor.
— I really like the 1700 kHz IF with a 5 MHz VFO for an 80 and 40 meter receiver.
— Interesting that EE degree didn’t help much in his efforts to understand ham gear. Better to read Wes’s books and Doug’s.
— Tek Spectrum Analyzers were specially made to fit down a submarine hatch.
— Building and measuring just as important as studying the theory. Inked-up text books.
— Learned ugly from Wes as a teenager.
–Searched for old commercial gear to gut and use as homes for homebrew solid state gear. The enclosures, panels and controls are very useful. Great way to avoid metal work. These rigs are no longer boatanchors! Again, I sympathize. I’ve sacrificed many Heath Lunchboxes and QF-1s.
— Jeff Builds the VFO first. My preference too. But he understands Pete’s AF-first approach.
— Finger on the input of the AF amp! Buzz! Yea! Step your way back to the front end.
— ALWAYS one stage at a time.
— Osh Park Boards for standard circuit modules. Like Legos.
— Cubic Feet of air variables. Jeff has a lifetime stash.
–Thinking about what was and should have been his section of EMRFD. Go for it Jeff. PLEASE!
— Hesistant about chips. Analog guy. Would have been a huge time sink. Analog guy.
— Buying parts on e-bay. Fewer and fewer RF parts at hamfests.
— People reading QST Tech Articles for entertainment. Editor apprach: “Nobody will build it anyway.” Handbooks giving priority to entertainment and less to information and education.

Homebrew History is Made: Farhan @ W7ZOI

Thanks to Wes W7ZOI for sending me the link to his page describing the visit of our friend Farhan. I think this visit was a historic gathering of homebrew heroes and their groundbreaking rigs. Read all about it here: http://w7zoi.net/Farhan-visit.html

Please help me convince Farhan to visit SolderSmoke HQ before returning to India! Send him (or me) e-mails, texts, tweets, or just post messages of support below this post.

HB2HB! Pete Talks to Famed SSDRA Project Builder Jeff Damm WA7MLH

Jeff “Roadkill” Damm

Wow, THE RADIO GODS HAVE SPOKEN (TRGHS). Pete gets on 40 with his new-old FPM5 homebrew rig and works homebrew legend Jeff Damm WA7MLH, who was also running a homebrew SSB rig. HB2HB! For those of you who don’t know, Jeff is the guy who built many of the inspirationally ugly rigs in Solid State Design for the Radio Amateur. Pete’s second QSO was with SolderSmoke podcast listener K7ADD. TRGHS!

Hi Bill,

Was on 40M yesterday with the FPM5 rig and after finishing a QSO was called by WA7MLH (Jeff Damm –the road kill guy and protégé of Wes Hayward). Jeff was operating portable 7 in NW Montana running a homebrew 40 Watt SSB transceiver off of batteries being charged by a solar panel. Now that is real radio. I thanked him once again for sending me a goodie box about 5 years ago and am still using those parts.

Later after another QSO was called by K7ADD, Ben, and he couldn’t wait to tell me he was a long time SS listener and stated listening to SS made him take a whole new interest in ham radio –especially building stuff.

So you never know.

Pete

Homebrew Heroes at Rickreal Hamfest: W7ZOI and WA7MLH

Bob N7SUR was getting discouraged. The hams at the Rickreal Hamfest didn’t seem really interested in his display about homebrewing. Then THE RADIO GODS INTERVENED! (thunder). Two TITANS of homebrew appeared at Bob’s table. Keep up the good work Bob, Thanks for the e-mail and the great picture of you with Wes and Jeff.

To N2CQR, N6QW

Feb 15 2015

The Salem, Oregon, Repeater Association puts on two hamfests each year
at Rickreal. This event was mentioned in SolderSmoke #78. During the
last two events I’ve taken a “science project” display and circuit
boards to encourage more hams to experiment. The boards encourage
experimenters to use software packages to design and build their own
receiver modules. It is uncommon to see this type of material at the
event.

Audience interest has been underwhelming. Perhaps a dozen participants
have shown interest in my displays. In fact, I almost left the displays
home last Saturday.

In the course of the morning, two guys approached. The older guy had a look of
familiarity. He looked like a guy in the SolderSmoke blog. Bill,
N2CQR, was pictured sitting with him in California over coffee.

I blurted out, “are you ZOI?” He replied “yes” and I told Wes Hayward,
W7ZOI, it was nice to meet him. (That was a bit of understatement).
With Wes was Jeff Damm, WA7MLH, who built many of the circuits included
in the book “Solid State Design.” I suggested to Jeff he no longer
looked like a hippie, which is the style conveyed by his webpage. Jeff
said he had recently cut his hair.

We spent more than an hour sharing ideas and discussing various topics.
My focus was on encouraging experimentation. Kit building may be a nice
first step. I want to see builders pursuing more advanced
investigations. Wes noted the software and simulation tools available
for free it’s never been a better time to try out ideas. Wes commented
on the contribution of amateurs and how we often have fewer restrictions
to pursuing our interests. He emphasized measurement tools. I should
look more at noise figure in my receiver experiments. He was very
supportive, which contrasts with my recent experiences on various
internet groups.

Wes and Jeff were looking for Rick Campbell, KK7B, and Bob Larkin,
W7PUA. Imagine, the three authors of Experimental Methods in RF Design
(EMRFD) frequenting a little hamfest in rural Oregon. Yet, few people
knew they were there.

The experience reinforced my interest in continued experimentation.
I’ll take my updated displays back next time. Perhaps our efforts reach
a larger audience than we first realize.

Bob-N7SUR

Our book: “SolderSmoke — Global Adventures in Wireless Electronics” http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

SolderSmoke Podcast #163 Pete Juliano! Tribal Knowledge Part 3 “Sideband Sidecars”

Crystal Filters built by WA7MLH

SolderSmoke Podcast #163 is available:

http://soldersmoke.com/soldersmoke163.mp3

Saturday July 26, 2014

Part III with Pete Juliano: Tribal Knowledge — Sideband Sidecars

— Moxon Update “A Thing of Beauty”
— Pete is Building Peter Parker’s Knobless Wonder
— Ladder Filters
–Construction Practices for SSB rigs
— Essential Test Gear
— Junk Box development and parts storage

Next time: Tubes, Valves, Termatrons, Firebottles.

Thanks to Bob Crane and the FDIM musicians for this episode’s musical opening.

WA7MLH’s RD16HHF Amplifier

OK, so now that I have the MOXON in the air, my thoughts are turning to amplifiers and a possible winter project. Hey, even QRP guru Doug DeMaw conceded that every once in a while a fellow needs a few more db. And the sunspot count will be dropping.

On the BITX group there has been an interesting discussion of using RD16HHF MOSFETs in place of our familiar IRF-510s. I thought these devices were new, but some Googling this morning led me back to the wonderful website of QRP giant (hey, he is IN SSDRA!) Jeff Damm, WA7MLH. Jeff has been using these devices for quite some time. As with all of Jeff’s projects, I find his EXTREME UGLY building methods to be inspirational and reassuring. Even if you have been there before, you should visit his site:

http://www.neoanderthal.com/wa7mlh1.html

Even his QRZ.com page makes you want to build something:

http://www.qrz.com/db/wa7mlh

Thanks Jeff!

The Look of a True Radio Homebrewer

Jeff Damm, WA7MLH, is one of our gurus, a high priest of The Knack. I visit his excellent site from time to time, just on the off chance that he will have posted something new. This morning I was rewarded with this picture from 1988 — I think it somehow captures the spirit of the true radio homebrewer. Check out all the homebrew gear. Note the copy of SSDRA on the operating table. Jeff assisted with the construction of many of the projects in that book. He helped free us from the tyranny of excessive neatness and right angles, and let us know that ugly circuit construction works just as well.
Here’s Jeff’s FB site: http://www.neoanderthal.com/wa7mlh1.html

Homebrew Rigs from WA7MLH

Jeff Damm, WA7MLH, was the builder of some of the rigs that appear in “Solid State Design for the Radio Amateur” His DSB/CW Direct Conversion receiver for 75 meters is in that book. Last January, Jeff put together a video that describes some of the rigs and pieces of test gear currently in his shack. Beautiful stuff.