Hangin’ it up (the ET-2)

My ET-2 minimalist QRP CW adventure is (for now) officially over. I have taken the rig – festooned with the callsigns of all the stations I contacted — and have put it up on the wall. This may be a new form of art. I think I am the first radio amateur to do this. I think it is pretty cool.


Here are the stats: I made 20 contacts with the rig. I had it on the air from 12 October 2019 to 7 December 2019. Seventeen of the contacts were the result of my posting pleas for help on the SKCC Sked page and/or the Summit DX page. Three of the contacts were completely random. One station — W1PID — provided four of the contacts. Thanks Jim.

My power out was usually around 100 milliwatts. I used either a 40 meter coax fed dipole or a 135 foot doublet fed with window line.

My best distances were Wisconsin and Georgia.

Crystal control was the real limiting factor. 100 milliwatts didn’t seem to be much of an impediment. The most amazing thing about this rig is the N0WVA regen receiver. It took a lot of peaking and tweaking, and it took some skill to operate. but once I got it going it was an amazingly good receiver. Really Amazing for just ONE J-310 FET.

The last contact was really nice. I was calling CQ and AA8OZ came back. He was in a cabin on a trip with some scouts. He too was on a wire antenna. He was one of those guys who said WOW! when I told him about the rig. We had a nice long conversation on 40. It was a great way to wrap up the ET-2 adventure.

Thanks to all who helped me make contacts and for all those who tried to work me. Thanks to N0WVA for the regen inspiration. And thanks to Glen Yingling W2UW (SK) for the ET-1 idea.

The rig is standing by. On the wall. Perhaps it will return to service, maybe during solar max.




Farhan’s New uBITX Version 6!

I’m currently reviving my “version 3” uBITX and putting it on CW. It sounds and works great, but when I saw this I realized that I am falling behind.

Farhan wrote:

Here is what it looks like :
And of course, yoiu can buy it on hfsignals.com. The shipping will happen from Tuesday onwards. We have a limited supply of the first 200 boards. The rest is for after christmas.

The most important thing about this revision is that the Radio circuitry is almost unchanged. We have incorporated the connectors on the PCBs. So, this kit needs none of the confusing soldering. You snap in the TFT Raduino onto the main board, plug the power and antenna from the back, snap on headphones, plug in the mic (supplied with the kit) and off you go!

It is offered in two kits now : The basic kit (150 USD) is without the box (like old times) but with a microphone and two acrylic templates for the front and back panels.
The Full kit (199 USD) has the box with speaker, mounting hardware etc. Both are described on the website.

Now, about the TFT display:

For those who are using the 16×2 display and you would like to upgrade, you will have to do three things:
1. Add a heatsink to the 7805 of the raduino
3. Grab the new Arduino sketch from https://github.com/afarhan/ubitxv6

Background :
I have been hacking away at adding a TFT display for the Arduino for sometime. Finally, I managed to do this with a really inexpensive 2.8 inch TFT display that uses a controller called the ILI9341. The display update is slow but, clever guy that I am, the display very usable. it uses the same pins that earlier connected to the 16×2 LCD display. This display is available everywhere for a few dollars.

_._,_._,_

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.

VU3JVX’s Beautiful Homebrew Scratch-built uBITX

When Farhan announced that BITX40 Module boards would no longer be produced, my first thought was that it is, of course, still possible to homebrew a BITX. Anthony VU3JVX proves that in his wonderful description of his uBITX scratch-built homebrew project. Anthony obviously learned a lot — perhaps the most important lesson for new homebrewers is what Anthony did when he couldn’t get the receiver to work: HE TOOK A BREAK and went back after a few days. That is very important.


I also liked very much the fact that Anthony did what Farhan did when the receiver came to life — he stopped building the transmitter and just listened to the receiver that he had built. FB OM.

And three cheers for Anthony’s XYL — she was very wise to suggest that he take on a project like this when he found himself out of work.

Anthony VU3JVX wrote:


I would like to share my journey of building ubitx from scratch, I would also like to dedicate this to Farhan (hope he will read this sometime) as he has always motivated to homebrew stuff.

I got my license ‘VU3JVX’ on March 2017. Passing the exam and getting on HF bands is still two different things. Yes, I started to transmit to local VHF repeater with cheap Chinese Bafong radio, I believe the most economical way to start the ham operator experience. However, I knew that I am missing something since I was not able to operate on HF bands.Coincidentally I saw that bitx40 became available as kit from HF Signals during the same time. I was happy to try it and that’s how I made my first HF rig. Then I came to know about the BITX20 forum and joined the same, one of the best thing I did after buying bitx40. I have learned a lot from all the great people caring and sharing information. I will try to contribute whatever way possible from my side in coming days.

I was already thinking of building bitx40 for other band (because the way Farhan Sir has drawn the schematic it becomes so tempting for DIY) and then ubitx happened and it changed everything. I started studying the ubitx circuit and collecting all the required components, even ordered the exact toroid from W8DIZ website (during my good days and travel to US) but I was not having enough time to put things together on the bench as I am by profession a computer network & security engineer. I was not sure what to do next, during this time my XYL suggested me that why don’t I focus on something which I always wanted to do. And that’s how my journey started to build the ubitx from scratch.


Honestly, I was not sure if this was the right time to start this project. So I started to work on building the receiver segment of ubitx only. I had my challenges during this time and at one point I thought I made a wrong choice of building ubitx, instead I should had tried the bitx40 circuit first. I was almost on the verge to pack up and shelf the project because I was not able to hear anything from the receiver itself forget about building the transmitter. Then took a break for few days and then started troubleshooting each segment one by one. Finally I found it after reading through the bitx20 forum that my Q70 to be defective then I also came to know that is it better to replace it with audio type transistor 2sc945.
I believe during this process I have read most of the content on bitx20 forum. Some name which repeatedly comes to my mind are Raj (vu2zap), Allison, Jerry and thanks to all other hams out there. I had all the version schematics but started my work based on V5 and wanted to get the best out of all the version so I kept the build approach modular and laying them almost like the schematic for easy troubleshooting (you can see those pic on my qrz page).

Next challenge was trying to be too good student and follow everything the master said (pun intended). I made a cocktail of 12 Mhz with 11.059 Mhz crystal filter (Farhan Sir I believe the schematic is still showing X7 as 12 Mhz) and after changing the X7 to 11.059 Mhz I was able to see the radio signal making it through the crystal filter, then came the next hurdle of fine tuning the USB and LSB and fiddling with the software for the right value. After the receiver started working I took a break from building the radio and started enjoying the receiver and checking all bands. One evening I narrowly missed Farhan ji on air but anyway I would not have been able to communicate with him since my ubitx transmitter was not ready.
After that day I thought of building the ubitx transmitter soon. I was quiet confident about the transmitter build by this time and thought it should be straight forward. Logically yes it should had been that way but I was so wrong. Following all the recommendation from the forum about harmonic issue and how to avoid them I started building the BPF. Then I started to work on the PA section then came tuning the IRF510 current (I call it “Bell the cat moment”) luckily I never blew any IRF510. However, the output watt on 40 M was hardly 2-3 Watts and other higher band less than 1 Watt. I knew something was wrong with those MOSFET but out of circuit the test look normal. I had some other stock from different source even those performed the same. Played around with different PA transformer settings and checking/tracing the RF signal. Everything looked normal till IRF510. Chances of fake IRF510 is less (as debated on the forum) as it is not an expensive RF part like RD16HHF1. Now I was confused, I had some spare new RD16HHF1 which I got online, which I was not very hopeful thinking that it might be fake. I thought of giving it a try (pin layout configuration was easy for me as I have taken the island cutting approach on single side copper board).

Voila ! I got a whopping 10+ Watt 40M, 5W on 20, 10W on 17M, 10W on 15M, 5W on 12M and 10M. Yes there are lot of fake IRF510 out there. Now it was time to test the homebrew rig on air, checked in at evening into All India Net and got 59 report and the net controller thought I am using commercial rig. Finally during these difficult time in my personal life I was able to smile and sleep well that day. The icing on the cake was installing the Nextion 3.5 display (If I remember correctly this is single most expensive component in the radio and thankfully it is optional).

Does that mean everything is 100% with my home brew ubitx ? Nope, I am still trying to figure out the feedback issue from the speaker during transmit. I traced the issue and found the audio leaking from emitter of Q6. I would like to mention that I tried all the audio circuit and finally settle for TDA2822 circuit. However, the issue is still there during transmit so I have made the audio circuit offline during transmit, I know this will impact my CW listening while transmitting when I upgrade my license . I have exhausted all solutions from Bitx20 forum but still no luck. I would be happy is someone can point me to the right direction. I would be also happy to share any information related to my build or the software settings/tuning, yes I like programming especially ‘C’ so I am comfortable with Arduino programs. I am thinking of building another PA module with IRF510, I personally feel IRF510 (I got the original finally) has made the home brewing so interesting.

Anthony VU3JVX


Antuino Filter Analysis

Farhan had given me one of the early Dayton Hamvention models of the Antuino SWR/PWR/SNA RF test lab. He later identified the need for a few mods to improve performance on that early model. So I brushed up on my surface mount soldering, got the needed (tiny!) parts and made the mods. I also put the battery pack inside the box and put some feet on the Antuino cabinet (it just seemed like the right thing to do).

Antuino has already proven to be very useful as an SWR analyzer. I know have a much better understanding of the SWR bandwidth of my wire antennas.

And it is very useful in evaluating the passbands of filters. I had an old 11.273 MHz filter from an old CB radio in my junk box. I have no specs on this device — I didn’t know what impedances it was designed for. So it was time for some Antuino technical detective work.

First, take a look at the filter with nothing between it and the Antuino. Input and output on the Antuino are 50 ohms, so here is what the passband looked like with 50 ohms:

Next I put in two 47 ohm resistors, one in series with the input, the other in series with the output. Antuino connected at the other side of each resistor. Here is what it looked like. Note the improvement in skirt shape. But there is still a lot of ripple in the passband:
Then I went to 100 ohms. The passband ripple was reduced noticeably:
Then up to 330 ohms. Here the passband doesn’t seem quite as flat as it was with 100 ohms:
Finally, 1000 ohms. Definitely too much. Note the ripple.

Farhan prefers the passband with the 100 ohm resistors. I agree.

BTW the filter is from TEW of Tokyo, Japan. Model FEC-113-2 11.2735 MHz No. 2 A 2
It had three crystals on the board with it: 11.275 and 11.272 — these are obviously for LSB and USB. The third crystal is at 11.730 MHz, indicating to me that they had a second IF of 455 kHz in this rig. If I use it, I think I’d stay with single conversion. At 11.273 MHz the filter is of ideal passband width for SSB. I do feel the urge to build something around this filter.

Doing the mods on the Antuino was fun, and having worked on the device at least a little bit I feel more of a connection to it.

ZL2CTM’s Inspirational Tramping Transceivers (videos)

Charlie Morris ZL2CTM is working on portable (tramping) transceivers. Check out his amazing and innovative enclosures and circuit boards. Really nice. A great way to keep that beautiful circuitry visible.

More details on Charlie’s blog:

https://zl2ctm.blogspot.com/2019/12/40m-ssb-tramping-rig.html

 Thanks Charlie. Happy trails! 73

VK3HN’s Inspirational AM Receiver (video)

I’m always delighted when I check the SolderSmoke blog and YouTube list (right hand column of the blog) and find a new post from Paul VK3HN. And this morning’s post is especially good.

Paul has built an AM receiver. Above you can see his video. Here is his blog post with details:
https://vk3hn.wordpress.com/2019/12/06/8-band-superhet-am-receiver/

 This is the kind of blog post that makes you want to heat up the soldering iron and start searching through the junk box. I’m thinking about putting Paul’s 6 kHz filter in my 40 meter HRO-ish receiver. And I may make use of his AM detector circuit. And maybe I can put that same receiver on 75 and 160… And then there are the SW broadcast bands… See what I mean?

Thanks Paul. 73

My QRPp Signal Arrived in Utah — 100 mW, 1950 miles, 26 db Above the Noise!

So yesterday morning I was calling CQ on 40 meters with my ET2 two-transistor 100 mW rig. Later, I took a look at the Reverse Beacon Network (RBN). Among the East Coast skimmer stations that regularly pick me up I saw an outlier: WA7LNW in Utah. He’s 1950 miles from me. And the RBN reported that his receiver had me at 26 db above the noise.

Here is a screen shot of the RBN report. Note the time: 1234 UTC. Around sunrise here — so gray line conditions.


But the really BIG factor explaining that 26db s/n ratio is WA7LNW’s location:

“Realtime spots are being received at this location and uploaded to the Reverse Beacon Network.”
“CW Skimmer antenna is located on cliff edge overlooking the Virgin River Valley, 1,200 ft. below.”

We reported on the WA7LNW RBN station back in 2013: https://soldersmoke.blogspot.com/2013/03/edgy-skimmer-antenna.html
Check out Jack’s QRZ.com page:
https://www.qrz.com/db/WA7LNW

RBN is an important resource for QRPers and homebrewers. Three cheers for Jack and all the skimmer stations. Thank you all.

Replicating N0WVA’s Regen Results

When I watched Doug N0WVA’s in action I was struck by how much more sensitive his was than mine.

I think this is do to the LC ratio in the main tank circuit. In my original version I used the variometer that I had in my junk box. It was about 4.5 uH. Doug used a hand-wound coil of about 35 uH.
For construction details on Doug’s receiver and variometer go here:
https://aa7ee.wordpress.com/2015/02/07/n0wvas-one-fet-regen-optimized-for-ssbcw-sounds-great/

So mine was heavy on the C, and light on the L. I think the larger coil makes it easier to couple the antenna to the receiver. I notice a lot of discussion in the online regen community about suitable LC ratios.

So I built a version more like Doug’s. I built my own variometer — that was a lot of fun. It is easier than it appears — Do not be deterred! And indeed the new receiver is much more sensitive.
On this second receiver I measured an Minimum Discernible Signal of -115 dbm. On my ET-2 receiver it was only -93 dbm. The improvement was very noticeable. I could even copy 40 meter AM signals at the top of the band. And on SSB I was actually having trouble with overload — the signals were too strong for the oscillations of the regen.

ET-2 Contact #18 W4FOA — RANDOM, UNSCHEDULED, AND NOT SPOTTED (Video)

On December 1, 2019, my 100 milliwatt signal flew more than 500 miles to reach Tony W4FOA in Chickamauga, Georgia. And — icing on the cake — this was a random contact. Tony just heard my CQ on 7038 kHz — he had not been alerted to my CQ by any spotting site or by the SKCC Sked page. I made a quick video of my side of the contact (above).

In a follow-up e-mail Tony explained how my CQ sounded to him:

“I was just listening on the 40 meter band and having been a QRP’er for 50+ years, I tend to notice the weaker stations, thus explains my calling you. Also, your signal had that little “sound” of “yesteryear” when signals were not all pure, hi. Had it not been for the QSB and QRN we could have had a long chat despite the weak signal from your QRPp. Over the years I have QRP DXCC, 2 way QRPARCI WAS, and my best DX was two QSO’s with 2 different VK7 stations on 40 when I was running 1 watt. I’ve had a lot of different QRP rigs and still have some home brew stuff plus a couple of HW8s, HW9, Elecraft K2, etc…”


From Tony’s QRZ.com page, we learn more about his ham radio activities (note his homebrew rigs and his obvious affection for the Drake 2B and 2BQ)

First licensed as WN4FOA in April 1954. Other calls held include EL2AD, 7Q7AA, PY1ZBA. Prefer to work CW but I do work some SSB, primarily DX-related. Enjoy chasing DX on all HF bands. Have 9BDXCC and I now have worked and confirmed all of the current DXCC countries . I enjoy QRP operation and currently use an Elecraft K2 (#2213),Ameco AC-1, Kenwood TS-130V SW-40, DC-40, HW-8 (2), Heathkit HW-9 Deluxe (WARC) PSA-9 HFT-9B SP-99 HM-9 HD-420 VLF, MFJ 40T and MFJ 40V VFO, and a homebrew 6AG7/6L6 or a 6C4/5763 etc. I also enjoy operating boatanchor gear which includes a Johnson Viking Adventurer, Viking Challenger, an Eico 720 and an Eico 723 with a HG-10B VFO and a Heath AT-1 and a Drake 2NT. Recently added a neat Lysco 600 transmitter and a Knight Kit T-60, Johnson Viking II, and a Ten Tec 544. Boatanchor receivers include a Hallicrafters SX-100, SX-110, SX-71, Drake R4C and the incredible Drake 2B/2BQ combo. Recently added a Kenwood TS-830S, VFO-240, AT-230 and SP-230.

Tony W4FOA

Thanks a lot Tony. 73

ET-2 Contact #16 — Pete, KD2OMV, Builder of a 6T9er (with video)

Yesterday I had my first contact using the ET-2’s improved receiver. I had watched the video of N0WVA’s receiver and I realized that more sensitivity was possible. So I tried to replicate his LC ratio. I think that helped a lot. Today I posted a plea for help on the SKCC Sked page and then called CQ on 40. I was answered by Pete, KD2OMV who was so loud that I had to take the headphones off my ears! He was booming in, all the way from upstate New York. The receiver was running off a somewhat depleted 9 volt battery. I made a quick video (above). I’m just holding the I-phone up to the headphone, while also trying to copy the incoming CW.

This was a really great contact. Pete has a wonderful knack story. He was licensed as a kid but never made a contact. As an adult he found his old box of parts for a 6T9er in his parents house. So he builds it and uses the homebrew rig to make his first ham radio contact. FB Pete. Thanks for the contact OM. I wrote your call on the ET-2.

Pete KD2OMV

Mr. Carlson’s Analog Panadaptor — “Like a digital waterfall, but fun!”

We’ve been talking about Panadaptors — especially about NON-DIGITAL Panadaptors. Kind of like waterfalls without the digital water. A while back I rigged up a very crude non-SDR panadaptor using my Feeltech sign generator, my Rigol ‘scope and a DITX40. Here it is:
https://soldersmoke.blogspot.com/2019/05/diy-waterfall-quick-and-easy-panadaptor.html

 In the above video Mr. Carlson looks at the old PCA-2T-200 Panadaptor. The first five minutes give a really good overview of how the device operates. At around the 5 minute mark Mr. Carlson notes that modern digital receivers have SDR based waterfall displays, but noted (correctly!) that “that’s no fun!” Thank you Mr. Carlson.

Follow-Up on Scratch-built BITX17 — Board Map and Video

In my last post I put up a time lapse GIF of my BITX 17 build from about six years ago. Above you can see my drawing explaining what each of the stages that you see popping up on the board were. More diagrams here:
https://soldersmoke.blogspot.com/2013/11/bitx-build-update-19-layout-vxo-bal-mod.html
And a lot more info on this build are available on this blog. Just use the search box for build updates (but be aware that this search will also bring up updates on later projects).

Above is a slightly out-of-focus video tour of the board.

I’m posting this stuff partly in reaction to the news that the BITX 40 module is no longer for sale. I hope these posts will serve as a reminder that it is quite possible to homebrew from scratch your own BITX transceiver. This is a fun and rewarding project. Three cheers for Farhan!

SolderSmoke Podcast #215 Regen Madness, KWM-4, Paesano, Mailbag

Latest N2CQR version of N0WVA’s Regen

SolderSmoke Podcast #215 is available.

25 November 2019

 http://soldersmoke.com/soldersmoke215.mp3

 Happy Thanksgiving!
Transit of Mercury
Book Reviews

Bill’s Minimalist Adventures:
— 15 Contacts with the ET-2
— Ethical issues: Is spotting yourself OK? OK to use TWO FETs?
— Using Reverse Beacon Network
— How to keep receiver on the right frequency
— N0WVA’s receiver sounded better, so I built a second N0WVA receiver
— Regens reach back to Edwin Howard Armstrong’s 1912-1923 breakthrough
— Regens are fun, but they are not good projects for new builders.

— Pull out those Michigan Mighty Mites and listen for yourself via on-line SDR receivers.

 Pete’s Projects:
“WHEN YOU KNOW STUFF YOU CAN DO STUFF!”
— Left Coast SSB — “The Paesano” — To be featured in December 2019 SPRAT.
— Pete’s KWM-4 on The Collins Collectors Net
— Pete builds an N0WVA regen — just in time for Sweepstakes CW Saturday!
— Arduino IDE Library trouble
— uBITX 6.0? Fake News?

No more BITX40 Modules. Long Live BITX40 HOMEBREW!

BITX-101. Intriguing but on second thought, no.

MAILBAG

 Steve Silverman: Lexicon: “Audible Modes.”
Felipe CU2BD Old buddy from the Azores
Michael Rainey AA1TJ: Come back Mike! The ionosphere needs you!
Jack Welch AI4SV is in 5G land (Cyprus, not the cell phone thing).
Walter AC4IM is at the San Vito Solar Observatory in Italy. DO SOMETHING WALTER!
Kostas SV3ORA has an amazing homebrew web site. Thanks Kostas!
Mike KC6SAX — How to deal with the frustration of HB projects that don’t work.
Paul KL7FLR — Pete is 7 Hz high.
Keith W3ISZ sent his photo of the Transit of Mercury.

PLEASE USE THE AMAZON SEARCH BOX ON THE SOLDERSMOKE BLOG PAGE WHEN DOING YOUR CHRISTMAS SHOPPING.

PLEASE SUBSCRIBE TO THE SOLDERSMOKE CHANNEL ON YOUTUBE.

N2CQR’s ET-2 with callsign Tattoos

SolderSmoke Podcast #215 Regen Madness, KWM-4, Paesano, Mailbag

Latest N2CQR version of N0WVA’s Regen

SolderSmoke Podcast #215 is available.

25 November 2019

 http://soldersmoke.com/soldersmoke215.mp3

 Happy Thanksgiving!
Transit of Mercury
Book Reviews

Bill’s Minimalist Adventures:
— 15 Contacts with the ET-2
— Ethical issues: Is spotting yourself OK? OK to use TWO FETs?
— Using Reverse Beacon Network
— How to keep receiver on the right frequency
— N0WVA’s receiver sounded better, so I built a second N0WVA receiver
— Regens reach back to Edwin Howard Armstrong’s 1912-1923 breakthrough
— Regens are fun, but they are not good projects for new builders.

— Pull out those Michigan Mighty Mites and listen for yourself via on-line SDR receivers.

 Pete’s Projects:
“WHEN YOU KNOW STUFF YOU CAN DO STUFF!”
— Left Coast SSB — “The Paesano” — To be featured in December 2019 SPRAT.
— Pete’s KWM-4 on The Collins Collectors Net
— Pete builds an N0WVA regen — just in time for Sweepstakes CW Saturday!
— Arduino IDE Library trouble
— uBITX 6.0? Fake News?

No more BITX40 Modules. Long Live BITX40 HOMEBREW!

BITX-101. Intriguing but on second thought, no.

MAILBAG

 Steve Silverman: Lexicon: “Audible Modes.”
Felipe CU2BD Old buddy from the Azores
Michael Rainey AA1TJ: Come back Mike! The ionosphere needs you!
Jack Welch AI4SV is in 5G land (Cyprus, not the cell phone thing).
Walter AC4IM is at the San Vito Solar Observatory in Italy. DO SOMETHING WALTER!
Kostas SV3ORA has an amazing homebrew web site. Thanks Kostas!
Mike KC6SAX — How to deal with the frustration of HB projects that don’t work.
Paul KL7FLR — Pete is 7 Hz high.
Keith W3ISZ sent his photo of the Transit of Mercury.

PLEASE USE THE AMAZON SEARCH BOX ON THE SOLDERSMOKE BLOG PAGE WHEN DOING YOUR CHRISTMAS SHOPPING.

PLEASE SUBSCRIBE TO THE SOLDERSMOKE CHANNEL ON YOUTUBE.

N2CQR’s ET-2 with callsign Tattoos

Notes and Video on Doug N0WVA’s Amazing Single Transistor Regenerative Receiver

When I had trouble getting the regen receiver in W2UW’s ET-1 circuit to work, I turned to the internet and — through AA7EE’s site — found the circuit of Doug N0WVA. This circuit has completely changed my attitude toward regen receivers. I have been exchanging e-mails with Doug — below is a compilation of the info and regen-wisdom that he has shared. More to follow… Thanks Doug.

From Doug N0WVA:


I came up with the diode after exploring ways to ditch the source r/c combo. The thinking was the closer I could get the source to ground the less voltage/capacitance fluctuations the gate would see. Also I hated seeing everyone using .01 bypass to avoid audio oscillations and also losing audio gain.

The green LED works good but even better is directly grounding the source. Then feed a small negative bias through the gate leak resistor , adjustable via a potentiometer.

On video, the audio is taken straight from the radio shack headphones that are connected to the audio transformer. The headphones are held directly to the phones case ( no hole for the microphone seen on the phone)

The variometer is made with I think a 1.25 inch pill bottle and the tickler inside is around an inch in diameter pill bottle. I used a pharmaceutical syringe’s outside tube for a shaft. The tickler form has a couple holes cut for the shaft to pass through, it is a friction fit, more like slits cut and the rod pushed through. I used the soldering iron to melt round holes on the actual outside coil form for the shaft to turn on. On the back of the shaft is a small screw that goes through the outside coil form and screws into the syringe center hole that holds it in place. The tickler is one turn, I think, and routed through the inside of the shaft via small holes melted with the soldering iron.

A couple tweeks to mention is instead of a resistor in the gate, use a choke for less noise, makes a big difference, especially if you listen to AM. Also I have been using a gimmick for the gate cap. Just maybe a #36 enamel wire wrapped around the hot tank lead 5 or 6 times and then I remove turns till the thing stops oscillating, then add a turn. This helps cut down even more on strong signal pulling.


I have always been on a quest for more performance out of the least parts. This design was about as far as it could go, I think….

I have never done any real sensitivity tests on the regen, so you have gone farther than me already. One thing was noticed though is the gate resistor does add a lot of noise, especially noticeable just under oscillation in AM detection mode. So I took a one meg 1/4 watt resistor and wound as many turns of #38 wire on as I could, probably around 80 turns, then subbed it out for the gate leak. This dramatically improved the noise level just under oscillation. This was with a simple antenna band noise test. I think it also improved the noise under oscillating conditions.

Adding extra antenna coupling will probably help a lot, but, there is a point where we start getting too much strong signal pulling. The strong external bias battery trick will also improve this, although at the cost of extra parts.