Welcome to VK3HN’s amateur radio blog. My interests are radio craft, homebrew, QRP (low power communication), SOTA, repair, repurposing and ‘ad hoc-ism’ (making things from what’s available in piecemeal, bricolage fashion). I also like to write. For more ‘about me’ search up my QRZ.com page. If you like what you find here please leave a comment, no matter how brief.
Homebrewing
‘Homebrew’ is an American term for user-designed and hand-made radios and electronics equipment. I have always built radios, mostly from scratch with whatever parts are on hand or could be scrounged, re-purposed or bought cheaply. I consider radio-making to be a kind of a craft, comparable with traditional hands-on crafts like model-making, tool-making, ‘Bush carpentry’.
Using homebrew radios and minimizing spend does not compromise my enjoyment of amateur radio — it is the basis of it. I choose designs and construction techniques not because they are State-of-the-Art but because they bring me engagement, enjoyment, or fulfill a whim. I have only one commercial transceiver (Icom 746Pro) which is mostly used for oscillator and signal monitoring. It’s not that I don’t like it, I just prefer to use my own project creations.
My projects are a curious mix of hand drawn/etched and manufactured circuit boards, surface mount and leaded components, analogue oscillators and Arduino micro-controllers and their software. I particularly like re-purposing a salvaged or liberated component, chassis, ‘found object’ or long-held piece from my (or someone else’s) youth. Because I make most of my own boards, I frequently cut them to snugly fit a corner, or layer them to achieve a pleasing or compact configuration. No two projects or even PCBs are ever the same. That’s why I call it radio ‘craft’.
Project preferences
I mostly build QRP SSB and CW transceivers from the late twentieth century, with digital oscillators and controllers but analog signal paths. Returning to radio making in 2015, I have found that it is now possible to build a transceiver with coverage and performance for less than $100 that I could only have dreamed about when I started in the late 1970s.
In late 2018 I started my first Class D 100 watt AM transmitter for 160 meters, with Pulse Width Modulation. This was followed with four more similar solid state PWM AM transmitters for 160, 80 and 40 meters. I have added a page of AM Transmitter Modules (on the blog menu) documenting a set of modules required to build one of the QRO transmitters, including JLCPCBs — this page has proven very popular with a new cohort of visitors.
Blogging and Vlogging
This blog is an open project and SOTA diary. I use it like a classic logbook, recording stories and narratives, design decisions, layouts, sketches, measurements, and reference material. All my SOTA posts include enough navigation information to help me or anyone else get back there in the future. I find I look things up here more than any other reference. Since it started in 2015, there have been over 350,000 views.
I use YouTube to supplement this blog. Video conveys so much information so efficiently it’s hard not to use it.
https://www.youtube.com/channel/UCJS-RCJIkCgLLj3xAkEicWQ/videos
Summits On The Air
I do SOTA activations around VK3, using CW and SSB, mostly 40m, but also 160 to 20m. I use homebrew QRP rigs that I call ‘Summit Prowlers‘. SOTA is, for me, a form of leisure and recuperation that involves three healthy and enjoyable things — bush-walking, exercise, and portable low power radio operating. SOTA gives my homebrew projects a purpose. Here are some favourite quotes on the experience of climbing mountains:
It’s always further than it looks. It’s always taller than it looks. And it’s always harder than it looks. — The 3 rules of mountaineering.
On respect for the mountains and the environment:
Take only pictures; leave only footprints. — Anon.
There is no such thing as bad weather, only inappropriate clothing. — Sir Rannulph FiennesThe choices we make lead up to actual experiences. It is one thing to decide to climb a mountain. It is quite another to be on top of it. — Herbert A. Simon.
On why we climb:
Its not the Mountain we conquer, but ourselves. — Anon.
Chasing angels or fleeing demons, go to the mountains. — Jeffrey Rasley.
On mountain climbing as a metaphor for life:
Nobody trips over mountains. It is the small pebble that causes you to stumble. Pass all the pebbles in your path and you will find you have crossed the mountain. — Anonymous.
To live only for some future goal is shallow. It’s the sides of the mountain which sustain life, not the top — Robert Pirsig, Zen and the Art of Motorcycle Maintenance.
QSO Today interview
In April 2020 I was interviewed by Eric 4Z1UG for the 298th episode of QSO Today. https://www.qsotoday.com/podcasts/vk3hn
History of VK3HN
In 2003-4 I re-licensed as VK3HN, a callsign distinguished by at least one of its former holders — J . McCandlish is engraved onto the Remembrance Day Trophy (with only 25 others) as an Australian amateur who lost his life in World War II (see the trophy and the list of amateurs here). He is listed in the text of the 1936 callbook at Sea Lake, north west Victoria.
The next holder (HJ NEWLAND, PO BOX 1134, BENDIGO) is a mystery to me and I would appreciate hearing from anyone who knew or worked him.
In response to my QRZ.COM page I received an email from David GW0OGI:
I was checking through old VK contacts and saw on qrz.com you asked if anyone had worked late VK3HN. My log shows contacts on 17m 16/02/93..21/03/93 and 08/10/93 all 59 signals both ways. Henry was a lovely character,full of wit and good humor,loved a rag chew.
So it seems Henry, the second holder of the call, was active up until at least 1993. More reports of Henry are most welcome!
If you’ve gotten this far, thanks for reading, and please leave a comment or a ‘like’ !
VK3HN 
I have been looking to buy a couple of Motorola Varactors (MVAM109) and thus came to your site. There is some mention of the specs by you on this site. Perhaps you may have bought them and used it at sometime in the past. Do you by any chance know where I can find a couple of these MVAM109 locally in Oz? 73’s Raj VK2IPD
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Hi Raj, apologies for the delay. I think MVAM109s are now fairly old. Mine were bought on eBay some years ago. There are some on eBay and also from US specialty suppliers. I suggest you try to find an equivalent current varactor, if possible, they will be much cheaper and you will have learned something in the process. You can also ask on the internet groups, eg. G-QRP, vkzlqrp, etc. Good luck.
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Great website with lots of thought-provoking ideas, I have followed you on my blog, would you consider a reciprocal link, please. 73 de John G4YDM https://johnallsopp.blogspot.com/p/home-page.html
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Hi John, thanks for your nice comments. My goodness, you are a talented artist! What an amazing combination, art and amateur radio! You are a rare and highly skilled individual! Happy to follow your Blogger blog, just done that, you’re at the top of my blogroll. Regards Paul VK3HN.
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Thank you Paul, comments appreciated, stay safe and 73 de John G4YDM
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Hello Paul,
I was looking on your fine website and I like to build your ‘8 band Super AM Receiver”.
Unfortunately the drawing picture (in jpeg) is not visual clear (even magnifying makes it worse). Do you have this drawing in another format (PDF orBMP?)
Thanks
73 de ON4RDB
Roland
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Hi Roland, thanks for your comments, yes that particular schematic is a .jpg not a .pdf, I was having trouble uploading pdfs at the time but can do it now, I’ll fix it tonight.
73 Paul VK3HN.
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Roland, I have added PDF schematics to the AM Receiver blog page, please help yourself and let me know if you have any questions. –VK3HN.
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Hi Paul.
Help….
I’m in the (very beginning of the) process of building the 200Watt AM CLass D Transmitter as described on your (most interesting) site. I’m sort of stuck trying to generate the Arduino-code based on your Github-repository.
More specific, my Arduino IDE complains about the absence of “rotary.h” and “pcf8574.h”.
Can you please check whether you yourself are still able to build the code? And maybe even provide links to the exact sources of the forementioned two?
Any help appreciated!
73’s Christiaan PA3FUN
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Hi Christiaan, thanks for commenting and trying my script. Have you installed these libraries in your Arduino IDE? Please reads all the instructions including the Wiki. Also use one of the AM transmitter #defines to include only the code your project requires. Try #define SS_AM_TX_TEST_VFO and comment out the other project label, see line 38.
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Hi Paul. Is there a way to keyword “search” this site/blog?
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Thats a good question Neville. I’m not sure. I suggest you use Google , just search for “vk3hn topic”. The tags link posts in categories like a YouTube playlist but that may not help. Anything in particular you are looking for?
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Yeah, that’s sorta why I ask. I’ve googled various topics in the past and often there’s a link to you which makes you one of my “gold mines”. Many times I’ve wondered what other gems you may have that I’m yet to discover! Random thought … do you have a list of post topics? That might help with my googling 🙂 Nothing particular at the moment but I’ll keep your offer in mind. I have pinched your suggestion for SA630’s. Mine have just arrived and I’m planning to use them to switch between two homebrew crystal filters (ssb/cw) and also switch the filters between rx & tx. Your site also put me on to the most excellent book “Building A Transceiver” which I’m now delighted to own – many thanks to you!
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Thanks for your positive comment Neville, it’s nice to know other people find some of the content useful. There is no list of post topics, it might be possible to better organise the site using WordPress, I might have a look at the options during a quiet moment, WordPress is pretty good at that kind of thing.
The SA630s are an excellent switch for small signal paths in homebrew projects. They will work fine to switch IF filters, RF preamps, and BPFs. Note that the open circuit connection sees 50 ohms, not infinite resistance as is the case for a mechanical switch. This is not normally a problem but worth remembering. The datasheet is simple to follow. They require a few parts around them but as a switch they exceed relays and will never wear out. If you leave the control pin un-terminated they may oscillate open/closed which will sound like noise. Ground it or take it to +5v. You still need relays where their is any power involved, so in the transmitter, LPFs, and of course the T/R relay. The other advantage is they can be driven directly by an Arduino digital output (0-5v), eliminating the need for a relay driver (2N7000) or the like.
The EI9GQ book is a superb resource, in the class of EMRFD, but more current. I particularly like they way Eamon experiments with each stage, trying different options, and always measuring and reporting on the performance.
I don’t know that you’ve missed to many other ‘gems’, if you have read the last years or so of posts you have probably caught most of the things I’ve been working through. I started collecting homebrew tips on a page on the menu, there are a few good ideas there, but that page could be used for tips on the components I’ve n=fond most useful.
The other thing to do is to look thru the Reference page, a grab bag and online workshop notebook of stuff I like to not forget, like calculators, components, tables, etc.
Good luck with your projects! 73 Paul VK3HN.
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Hello,
Do you sell the pll with dds and lcd all together?
Thank you very much from Greece.
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Hi there, I don’t sell anything, I build my own projects, but have a look at OzQrp for a tiny VFO kit. Or QRPLabs.
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Hello again and thanks for your answer. One more question. About the switching regulator that you have on circuit, This can manage any voltage and ampere? Thanks
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The switching regulator in the 200W AM transmitter delivers 0 to 100V DC at up to 5 amps. The absolute ratings depend upon the size of the DC power supply and the switching FET, as well as some of the key components.
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Paul, I have to tell you that YOU are an inspiration. I saw you on the QSO Today Expo last month and my brain is still spinning.
By my own admission, I do not know where to start. I’ve built some kits, etc, and those experiences certainly give a thrill when making a successful QSO on a summit. Wow. But after seeing your presentation, I realize that I know so very little about what is really occurring under the hood of the radio. Your resources on the site are amazing, but you and your fellow builders are intimidating!
Since it is really hard to find an Elmer on this subject, do you have any resources for building from a component level? I certainly cannot “design” a circuit, but I think I could understand components from a block diagram level. Are there such resources, parts lists, etc, for cobbling something together from, say, Adafruit components, breadboards, and jumpers?
Again, thanks.
Cheers,
Jack
NG2E
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Jack,
Thankyou indeed for your very encouraging comment! I have been building radio projects since quite young and have found in recent years, that if you adopt a focus (mine is obviously coming up with QRP radios for portable and summit activations) you can refine your methods and tools and get some really quite good results. Even when compared with some commercial gear.
Simplifying what you attempt to build is also key.
The latest Chinese SDR products that are just now emerging will challenge what we can do with homebrew performance for price. But that’s no reason to stop. If you love making things, and they bring you engagement and fun, keep making them, and make the next one just a little bit better than the last.
I see you are an accomplished QRP man, having won the distance per watt category in a recent QRP activity event. Congratulations! I built a 200mW CW rig a while back with this kind of thing in mind, but I didn’t have the patience to persist with QRPp from this little rig. QRP operating is a skill not to be underestimated.
I was slightly intimidated at certain stages of getting to where I could build complete QRP transceivers. Taking on Arduino coding and si5351 was one such step about 5 years back. But with some persistence I got it to work and in no time I found Arduino coding and driving breakout boards such as si5351, temp sensors, and relay drivers to be very engaging. It’s amazing what you can do when all control of your project is under your coding fingers. Proper SDR (with true digital signal processing) is intimidating to me. One day, if I ever get tired of building analogue superhets, I will do as Charlie Morris ZL2CTM has done, and dive in with a Teensy and sound shield. I am pretty sure it’s not hard once you get past those initial steps.
I am not sure how radio clubs support my kind of homebrewing in the USA. In my experience, clubs here cover the hobby very broadly. There are keen and skilled homebrewers but the club doesn’t necessarily ptomote scratch building. There is a homebrew group here in Melbourne which I would recommend you to join if you were local. Not because you would learn how to do this kind of work from the meetings (although you would to a degree), but because you would meet others and study their work and approaches. That forms Elmer and mutually supporting friendships. You can tackle projects together, and share results, parts, and ideas.
If you haven’t already done this, one suggestion to get you scratch-building is to get just a few basic tools together and scratch-build a CW QRP transmitter. It can be anything from 2 transistors to a dozen. Just solder the leaded parts to the copper, don’t bother with a PCB. Test it with your Elecraft receiver and whatever test tools you have. Monitor it with remote KiwiSDRs. Peter VK3YE has lots of good examples. The experience of getting it going stage by stage will be valuable. More importantly it will test your interest in taking it further. As for Elmers, it does help to have one, or several. Maybe reach out to Bill N2CQR as you are both in Virginia.
Building a digital VFO is not difficult. Try to build out an Arduino Nano and si5351 on a breadboard, or soldered to Veroboard. You will spend most of your time in getting a script to work as you expect. I get lots of enquiries frompeople who need a bit of support to get my scripy running on VFO /Controller boards, just like this.
Whatever you do, keep having outdoor fun with QRP, it’s a healthy, honest and highly rewarding hobby.
73 Jack. Paul VK3HN.
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HI Paul,
Thank you!! Those are wonderful suggestions. Exactly what I needed! Your last three paragraphs are right on the money for me! By the way, I looked up Bill N2CQR… He lives not 30km from my home QTH….
Cheers,
Jack
NG2E
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Hallo Paul,
very fine to found your page, call and ideas. I do share same Ham view, I do practice homebrwing since I was a teen, in 1973 when I begun this wonderful journey into the Ham Radio and sill enjoy as a child todays. I do prefer old radios and develope further old techinuqes as regen, for example, using modern knowhow and also trying to improve them, but in these last times I came across the DIY idea of a modern PLL using the SI 5351 and so found your space. Very fine to share results and schematics, THANKS a lot and very finw your true Ham Spirit. Personally will try your arduino and SI5351 VFO sw and will do some use of it. I use Arduino since beginning, but just for high school students in Electornics as I did not like too much the idea to not see inside the equipment I design and do. But now times maybe are changes and so let’s try something new, HI. Dear Paul have my best wishes, and once more, mnay thanks for all detals and pics for your equipment. Hope to hear your call someday in future, who knows….HI 73/72 de Alex I5SKK always QRP
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Hi Alessandro,
Thankyou for commenting, it is always good to meet another keen home brewer. I have looked at your QRZ.com page and I can see that you are a ham who delights in the old amateur radio craft, doing things the traditional way and doing them properly! Although I have been a ham since the late 1970s I am still intrigued by a three transistor CW transmitter, and given a few hours, I am likely to build it up to try it out! I particularly like your solid state CW transmitter with a Mitsubishi RD16HHF FET, a very good choice as a 5 watt QRP PA.
I can see that stretching into Arduino and si5351 will be a shift, as it was for me back in 2016-7, but for me it introduced a wave of new possibilities, such as software generated CW, supporting multi-bands, and absolute frequency stability. There are a number of scripts you can try, so if you set up an Arduino Nano, mechanical encoder, LCD and an si5351 breakout board you will be able to try a few of them. My script is really a multiband transceiver controller, but it will work on the most basic configuration.
Besy wishes Paul VK3HN.
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I am having trouble compiling your WSPR sketch please contact me
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Hi Loren, I’m keen to understand why the script does not compile, can I ask you to post this comment on the WSPR beacon blog page, that way I keep the discussion on the blog post page where I and others can follow the resolution.
https://vk3hn.wordpress.com/2021/10/07/20-meters-200mw-12000-miles-wspr-magic/
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I do not know how to get to that blog
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Click on the link above, or pull up the WSPR beacon post, scroll down, post your commentt and we can take it forward from there…
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Hello Paul.
Commenting here as I cant see any option to coomentb on the specific entry. Anyway I wantted to thank you for your post describibg the Summit Prowler 6B. As someon73e who loves hiking and /P amateur radio opperation I’ve been playing with such lightweight rigs for some time. My latest project design was essentially going around in circles trying to figure out a low current but effective portable TXVR. Then I came across your summit prowler 6B. Immediately interest was tweaked!
I quickly became aware that the MC3362 had been superceded by another chip the MC13125 which has possibly slightly better specs (although I cant confirm this as I dont have adaquate hi spec test gear right now. However, haveing obtained a few of these chips I have a prototype laying on the work bench and its working rather well. A lot more to be done to get it up to a state where I can stick it in my backpack and head off into the mountains but its looking promising! thanks for the inspiration!!
73 de Kat MM0BST/M0BST
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Hi Kat,
Firstly many thanks for your kind comments. I immediately wondered why you could not comment directly under the SP6b post, when I looked I discovered I had omitted to check the Comments checkbox. My mistake! If you don’t mind I will copy your comment over there, please go to the bottom of the SP6b page to continue the discussion.
73 Paul VK3HN.
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edit: MC13135
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Thanks!
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