Dave Richards AA7EE

September 17, 2016

A Single Lever Paddle From QRP Guys

When building the SST for 20M, my plan was to kit it out with a paddle, battery, and an easily deployable antenna, and head for the hills. That’s still the plan. I don’t operate portable very often, preferring the comfort of the operating position in my small apartment, where I can make as many drinks and snacks as I want, and do it all with the company of my 3 kitties. Bliss! However, having just made a small, lightweight CW rig, I have to take it out in the field at least once in order to prove it’s mettle.

Currently, the only paddle I have is a Bencher, which is a bit too heavy and cumbersome to carry in my backpack for a portable set-up. There are some really neat portable paddles on the market, but I didn’t want to spend much, so settled on the idea of making one from PCB material, inspired by Wayne NB6M’s paddle, and KI6SN’s version, which was based on Wayne’s design. Two things happened to stop that idea in it’s tracks though. The first was that, nearing the end of building my SST, I was beginning to feel a bit lazy. Occasionally, when wading my way through a scratch-built project, I ponder how nice it would be to build a kit and give my brain a rest. At around the same time, I came across the website for The QRP Guys and realized I’d hit paydirt. They have a selection of small and low-priced kits for the QRP’er, including some small paddles made from PC board for very affordable prices. Perfect! The QRP Guys are Chuck Adams K7QO, Doug Hendricks KI6DS, Ken LoCasale WA4MNT, John Steven K5JS, and Dan Tayloe N7VE. Holy moly – that is some serious QRP starpower. I think we’d all be well advised to keep an eye on what these guys are up to.

QRP Guys ship out once a week on Wednesdays. With any small ham business such as this, where the owner/operators have many other things going on, setting expectations is an excellent idea. I decided on a single-lever paddle, and ordered it over the weekend. Later in the week, a small bag of parts arrived in the mail –

QRP Guys provide a scale for you to gauge how easy or difficult each of their kits is to build. On a scale of 1 to 5, with 5 being the most difficult, this paddle kit is rated as a 4. They do mention that some kits may also be rated as requiring what they term “expanded skills” – meaning, I assume, more difficult than 5. The rating of 4 for this kit makes sense. The PCB paddle parts need to be positioned fairly accurately. The way to do it is with a light tack solder in one point, re-adjusting until the exact positioning is reached, at which point you can commit with fully soldered joints. There are quite a few small screws, washers, and other small parts, so care, and a container to put all the small parts in are good ideas.

Here’s the final paddle. What a neat-looking little assembly –

A view of the underside –

This paddle is intended to be fixed to a panel, such as the side of a portable transceiver. I wanted it to be on a base, so decided to fabricate one from single-sided PCB material –

The cable is a cord from an old set of earbuds that came to an early end in the washing machine. It has a small molded 3.5mm stereo jack on one end, which is perfect for the task. It is held to the paddle base with a loop of twisted wire that threads through 2 holes in the base. At the point where it is secured, the cable was covered with 2 layers of shrink tubing. Luckily, the flexible wires in the earbud cord were insulated with heat-strippable enamel, so all that was necessary to remove the insulation was a generous gob of solder on the tip of the iron, and a few seconds, for the enamel to burn off –

You can’t see them, but there are 4 stick-on vinyl bumpers on the underside, purchased from the local Ace hardware store – the same type I used on the SST –

The copper is not lacquered, so if I take the same photo in a few months, it won’t look quite as shiny –

For size comparison, here’s the paddle with the SST20 and a pack of playing cards –

Despite the little stick-on feet under the base, I’ve found that the most comfortable way to send with this paddle is to hold it in my hand. This will work well for portable ops, when a suitable surface on which to place it might not be available. The lever is made from springy stainless steel. Doug Hendricks reminded me of an old tip for finding suitable flexible metal strips for making your own paddle, if you wish to do so. Just visit your local auto parts store and purchase a feeler gauge – the tool that is used for measuring spark plug gaps. It contains multiple flexible metal strips, of varying thicknesses (and degrees of springiness), so you can pick the exact one to suit your preference.

I experienced a small learning curve with this paddle. Firstly, I had never used a single lever paddle and secondly, I wasn’t used to the springiness of the lever, as most keys and paddles use stiff metal for the pivoting part. It doesn’t take long to get used to though. If you’re looking for a cheap and rugged paddle, this is a good value for the money. QRP Guys have both single lever and iambic paddles, with and without a base.

February 9, 2010

The Fort Tuthill 80 – A Direct Conversion Transceiver For 80M

A week ago, the Arizona ScQRPions released their Fort Tuthill 80M TX/RX kit. I’d been keen to build it ever since I became aware of it (thank you AE5X) due to a long standing interest in DC receivers, and the fact that the first transceiver I ever built was also for 80M and also utilized a DC receiver. That was back in the early 1980’s.  I brought that rig with me to the US when I moved here from the UK in 1987 and then fried several of the active devices in it by accidentally connecting the power the wrong way round.  Yes I know – for some reason I didn’t want to use a diode to polarity-protect it (probably didn’t want to lose the 0.6V forward-bias voltage drop).  At the time I was going through a phase of my life in which I was distinctly uninterested in amateur radio, so rather than replace the fried devices, I threw the whole thing out and somewhat regret that decision to this day.  I don’t remember it suffering from any of the problems normally associated with DC receivers – microphony and hum pickup. However, this could very well be a case of my looking through the past at rose-tinted glasses.  As it was the first transceiver I had ever built, it was the apple of my eye, and well, proud parents can be quite good at ignoring flaws in their offspring.

OK, here’s what you get for your $53.  The silvery bag contains the active devices, and you also get 2 sets of decals:

Considering the amount of work that goes into designing something like this, designing the PCB, sourcing and ordering all the parts, as well as bagging them all up ready for delivery to you, the end consumer, $53 is a steal. Dan N7VE, the designer of this transceiver, knows a great deal about active filtering in receivers and has applied his expertise and knowledge to the design. Look here for a presentation he gave on the subject of active filtering in receivers.

A closer look at the board that Dan designed for this radio:

One of the many great things about the internet is that manuals for kits can be more detailed, with more pictures than ever before.  Dan’s manual makes building this little radio a lot of fun, and with the help of the Yahoo Group, expert advice from the designer, or other builders, is not far away.

The build went smoothly.  As tends to be the case with these things, I stayed up all night to finish it off and ended up finally hitting the hay at 9am.  I find that it’s easy to get so engrossed in a project that I’ve barely noticed that it’s something like 3am.  By that time I’m within spitting distance of finishing – or so it seems.  I’m not fast at doing things, tending to get distracted easily by things like the need for coffee breaks, the urge to look at something on the internet etc, so what some might call an 8 hour kit build, is closer to 3 times that for me. Next thing I knew it was 9am, but the board was finished, and all the external connectors temporarily connected:

The board with external connectors temporarily attached. On the far right just above the middle you can see the 2 PA transistors epoxied to the heatsink. Just above that is the trimpot for controlling output power. The VFO toroid is on the far left about 2/3 of the way up the board.

Initial impressions are favorable. Although some of the capacitors are microphonic (to be expected in a DC receiver), I can tell that this is not going to be a problem in use, especially when the board is mounted on standoffs in a case.  The other main problem with DC receivers is the issue of hum pickup.  I’m a little concerned, because I am getting quite a lot of hum pickup through the antenna connection. I’m hoping that enclosing the board in a metal case will help.  An enclosure will be arriving later this week, so we’ll see how that helps.

The receiver is sensitive and VFO stability seems to be good enough for regular usage.  Using my FT-817 as a reference,  I measured about 60Hz of drift in an hour from the VFO after it had already been on for several hours, operating in a room of reasonably constant temperature. I then measured the frequency drift every hour for 6 hours. After 6 hours, the VFO had drifted 90Hz higher than the original frequency; the maximum drift from the original frequency within the 6 hour period was 150Hz. Not bad! I intend to fix the VFO toroid more firmly to the board with a nylon nut, bolt and washer to help improve the resistance of the VFO to physical impact.

At this point, my main concern is that of hum pickup in the receiver.  We’ll see what happens when I’m able to install it in a metal case. To be continued………..

Postscript – nothing better to do with my time this morning than stare lovingly at the PC board and ponder on what a thing of beauty it is:

The board after disconnecting the temporary knobs, switches, power etc and before mounting in a case.

Hum Problem Solved – I haven’t begun to put the FT80 in a case yet, but the hum issue has already been resolved.  The radio was connected to an antenna via an LDG Z11 tuner, which was powered by an unsmoothed wall wart transformer.  On unplugging the wall wart from the wall, the hum all but disappeared.  There is still a very low level of background mains hum, but only at the level you’d hear in a mains powered receiver with a well smoothed power supply. At this point, the radio is very usable in just the current bare board situation; things can only get better when it is installed in a metal case. Dan N7VE made the point that if you mount the board close to the bottom of the case, as the traces are on the bottom of the board, and the top of the board is mainly ground plane, then the traces will be sandwiched between two ground planes. The FT80 looks like it is going to be a very usable little transceiver. I’m really looking forward to when QRP Kits start stocking versions for other bands.

January 26, 2010

The Perfect CW QSO

I’ve started the packing process for my sojourn to Southern California (see previous post) and it looks like this particular move will be the most enjoyable so far.  I’m putting much of my stuff into storage in the Bay Area and moving down to So Cal with a small truckload of belongings.  Because I’m a QRP’er,  there will be no big heavy radio gear, and due to the tall trees at the property I’m moving to,  a roll of dacron antenna rope, a couple of hundred feet of stranded insulated wire and a pulley or two will pack into a small space and should make for a great antenna (with the help of a slingshot to get it up there.)

The ham radio gear at this end may well be some of the last stuff to be packed.  It gives me a good diversion from packing every now and then. Trust me – you don’t want to own 10,000 CD’s – it’s more music than anyone can properly take in during a lifetime, and all those boxes weigh a lot.

So while plonking CD’s into the umpteenth box this afternoon, I heard a very weak but fully copyable CQ on 7030 from KG6SNV. I called him back and we had a brief but very enjoyable QSO.  I gave him a 519 (he gave me a 529), but it was armchair copy.  I don’t have an S-meter on the Norcal 2N2/40 but band noise was probably at about an S4.  His sigs were almost imperceptible at an S1 (and below the band noise) but due to no QSB, no QRM and his excellent sending (his speed and rhythm were perfect for the conditions) copying him was a breeze.

I’m not sure how to put this into words, but any CW operator reading this will be able to identify with these sentiments. There was something very satisfying about receiving a signal so weak that I was able to copy with ease. There was nothing groundbreaking about our QSO; we were only 61 miles apart, in adjoining counties.  Mario was running 10 watts into an indoor vertical at 20 feet (apartment antenna maybe?), and I was running 4 watts to an outdoor vertical also at 20 feet. The thing that made this QSO so much fun was that I was able to take such a weak signal and decode it in my head. For anyone who is either thinking of learning morse code, or who has started and is having trouble becoming fluent, take it from me that your effort will be rewarded many times over if you keep on plugging away. Your brain has an amazing number of built-in algorithms and a lot of  “filtering”, and using it to decode CW signals is fun.  Just think – free DSP!

I’ve had one or two e-mails in the past from folk reading this blog who are learning the code and have taken inspiration from some of the blog posts here. I hope that if you’re on the fence about either beginning to learn, or continuing, that you’ll take heart from reading this.

Incidentally,  I’m no veteran CW op.  My speed lies somewhere in the 10 – 20 wpm range and I have a long way to go with the code, but I’m on course.  I guess a good analogy would be with learning the guitar.  Let’s just say that I’ve taught myself to play 3 chords and can bang out a lot of rock n’ roll songs at this point. I haven’t learned to play like Mark Knopfler or The Edge yet though.

On a side note, it looks like the Fort Tuthill 80M Direct Conversion CW Transceiver Kit is days away from going on sale and I hope to bag one of the kits in this first run of 100. Dan N7VE has just uploaded the assembly manual to the Yahoo Group and this looks like it’s going to be one fun rig to build.

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