John (AE5X) had suggested a while back finding a larger tuning knob for the Penntek TR-35.
I was striking out in finding one that fit but had to put in a Mouser order and thought I’d give this knob a shot (Mouser # 706-11K5013-KFNB) and I really like it!
I accidentally bought the gray version and had to paint it black. It’s shiny because of the clear coat and rough because of sanding and because I’m apparently awful at painting, but I find that it fits with the plastic bezel of the radio.
I recently built a tabletop QRP HF antenna for 17 and 20 meters, in the spirit of the Elecraft AX-1, so I could operate at lunchtime on the campus where I teach. My wants were something small, that would fit in my work bag, that didn’t require a tuner, and could work on a couple of different bands. But on a lark I decided to attempt a POTA activation at Lake Thunderbird State Park (K-2792) pairing this antenna with my Penntek TR-35 QRP CW transceiver. I figured I’d maybe get one or two QSOs and then switch to a long wire in a tree. But what happened amazed me.
I talked to seemingly everyone. Beginning at 9:00 AM September 26th I worked both 17 and 20 meters for an hour and a half and made 37 contacts from across the country. I even had a Swiss guy call me back on 17 but he faded before we could finish. This antenna, at least as a CW POTA activator, works. Granted conditions were very good, but I’ve replicated this multiple times in the past few weeks, just recently at a picnic table in the parking lot of the Route 66 Museum (K-8644) in Clinton, OK (there is quite a thrill in urban activations).
It has also reasonably low profile and very quick to setup and take down. It is also quite a conversation piece when I set it up at school. I elevated the counterpoise by attaching it to a nearby oak and an interested undergrad sheepishly asked if I was listening to the tree!
The build is pretty simple. Physically the antenna consists of a small painters pole from Walmart and an old tabletop camera tripod. I found a nut that fit the screw portion of the tripod and hot glued it into the orange connecting section of the pole. That way the tripod can then be screwed onto the pole. The RF parts of the antenna consist of a 38” telescoping whip that I scavenged from the rabbit ears antenna that came with my RTL-SDR. It connects using the original connector which was hot-glued into a hole I drilled into the top of the painters pole. I found similar small 3 or 4-foot whips from AliExpress for cheap and these would probably work fine.
I then soldered a long length of speaker wire that was wound into two coils: the top for 17 meters (24 turns) and the bottom for 20 meters (25 turns plus the former 24-turn coil). The speaker wire was the soldered to the center of a BNC connector which I hot glued and taped to the pole. I soldered a short piece of wire from the shield of the BNC for the counterpoise and added an automotive spade connector to attach to a 17-foot length of wire. I also included a switch between the coils and the BNC connector to select either just the top coil (17 meters) or both coils (20 meters) using solder, hot glue, and tape. I then covered my shame in silicone tape.
The most time-consuming aspect of the project was tuning the antenna. It required trial and error to first tune the number of turns on the 17-meter coil and then the 20-meters coil. I extended the counterpoise (for me it’s best when slightly elevated) and the telescoping whip. I performed the tuning with the whip not fully extended to give room to tune in the field. Using a nanoVNA was useful here, as was soldering a pin to the wire to poke through the wire at various parts of the coil to find the best SWR.
In use, the antenna can be affected by both body capacitance and how the counterpoise is situated, so I found that an in-line SWR meter was helpful in making sure all was well. Once set up it is easy to fine tune by just adjusting the whip length. 1.5:1 SWR is about how well I can tune on average. Obviously if you have a tuner you would just have to get it close.
There are a million variation on a small base-loaded vertical antenna, and you can definitely improve upon this design. And, besides the super well-built and elegant AX-1, QRP Guys sells an interesting looking kit, and there are some good 3D printed designs I might want to try out. But regardless how you go about it, it might be worth giving a tiny antenna a shot.
Many thanks to Sam (WN5C) for sharing the following guest post:
A Compact CW Filter and Speaker Build for the TR-35
by Sam Duwe, WN5C
I recently built a Penntek TR-35 and, like seemingly everyone, I love it.
Once the rig passed the smoke test I was having too much fun and wasn’t quite ready to put away the soldering station. I had two non-essential wants for this project: a narrower CW filter for listening comfort, and an external speaker. Here’s a quick description of how I crammed both of those into an Altoids tin. Nothing is new or groundbreaking here, but it has been a fun and useful project for me and hopefully will give some inspiration for others.
The heart of the project is a Hi-Per-Mite 200 Hz CW filter, designed by David Cripe NM0S, and sold as a nice kit for $28 by Four State QRP Group. Hans Summers G0UPL uses the circuit in the QCX so many will be familiar with the filter’s sound. It’s nice and narrow with no ringing, and makes using my base station (a Kenwood TS-520 with the 500 Hz crystal filter) a joy.
To be clear, the existing narrow filter in the TR-35 is great, but I like the option of going narrow(er). It’s a Pixie-level build difficulty so it should come together in an easy couple of hours. I originally built mine in an Altoids tin using inspiration from Phillip Cala-Lazar K9PL’s review and it worked very well. It sips current and is powered by a 9-volt battery. With a DPDT throw switch connected to both the audio path and the power you can easily switch the filter on and off.
A neat aspect of the TR-35 is that there is a lot of audio gain so you can drive a non-amplified speaker. I have a little Bluetooth speaker that does this trick when I want to use CW to annoy people, but I figured if I’m already hauling an Altoids tin to the field maybe I could get it to talk, too. I looked around my junk box and found a broken Baofeng speaker mic and salvaged the speaker. It works really well: a robust but comfortable volume.
I’m sure any little speaker would do the trick… nothing fancy here, it gets hot glued it to the lid of a mint tin after all.
After I built the Hi-Per-Mite here’s what I did: first I ate a tin of Altoids and felt a little sick. Then I drilled some holes. The one on the left is for the audio input, the one on the bottom for the headphones (both of these are 1/8” stereo jacks), and two on the right for two mini DPDT switches. I also drilled holes in the lid for the speaker sound to come through. I gave the tin a good sanding and tried to remove sharp edges, and then sprayed the lot with black primer and spray paint.
I must thank my buddy John (AE5X) for this excellent tip.
I was watching one of his YouTube videos some time ago and noticed that he added fold-out feet to his Penntek TR-35.
Like John, I appreciate my radios sitting at a bit of an angle as I operate and these fold-out feet looked like the perfect addition to my TR-35.
These feet are designed for laptops which are much heavier than the TR-35 or pretty much any similar field radio.
They arrive in a small package with an alcohol wipe to clean the bottom of the radio. The adhesive pads on the feet are made by 3M and high quality. I doubt they’ll ever fail. Since they’re designed to allow airflow under a hot laptop, I believe the adhesive should withstand hot summer days in the field as well.
“Look at this, Tom! Only the stuff I need and nothing more,” cheerfully noted my good friend and Elmer, Mike (K8RAT). It was Field Day two decades ago, and Mike was gazing at his TEN-TEC Scout. I glanced over, and agreed. “So simple and so effective,” Mike added.
I’ve never forgotten Mike’s sage words. That Scout (Model 555) was about as simple as a then-modern HF transceiver could be: it had a total of three knobs––one for AF gain and IF bandwidth, one for RIT and Mic gain, and an encoder. It also had three mechanical switches on the front: one for power, one for TUNE and NB, and one for CW speed and RIT. It also had an analog SWR/power meter. The Scout used plug-in band modules for each HF band and featured a large segmented bright green LED frequency display that was characteristic of so many TEN-TEC rigs of the day.
And Mike was right. For those of us who appreciate radios with a simple, uncluttered, and an almost utilitarian interface, the Scout was, in vintage parlance, “the bee’s knees.” And that the Scout also performed beautifully was just icing on that cake.
When the Scout first appeared in 1994, embedded menu options and spectrum displays were not yet commonplace among amateur transceivers. Embedded menu items can open the door to near granular level control of your radio’s functionality and features. Then again, if those embedded menus aren’t well thought out, it can lead to awkward operation practices in the field, during a contest, or even during casual operation.
As a radio reviewer, I spend a great deal of time sorting out embedded menu functionality and design. Perhaps it’s for this reason that I so enjoyed reviewing a radio that bucks this trend and reminds me of a time that was simpler, not to mention, easier.
All of his transceiver kits are available at his website WA3RNC.com.
I was first drawn to the TR-35 after reading the opening paragraph of the product description:
“Compact but powerful 4-band, 5-watt CW transceiver kit that uses no tiny push buttons, and without those seemingly endless and hard-to-remember back menus. There is a knob or a switch for every function!”
I considered buying and building the TR-35 kit, but I wanted my eventual review––this one!––to focus on the radio’s functionality and performance. So a factory-assembled and tested unit was right for this purpose, just so that any performance issues wouldn’t be a result of any shortcomings in my kit building skills.
I pushed the last field report and activation video to the front of the line so that I could show how CW message memory keying worked in the TR-35’s updated firmware. It was, in my opinion, a major upgrade!
What follows is my field report from April 1, 2022: my first POTA activation with the Penntek TR-35. This video was made a week or so before I learned that WA3RNC was working on the new firmware.
Since I have a busy family life, I always look for opportunities to fit a little field radio time into my schedule.
My policy is to always keep a radio field kit in my car or truck so I can take advantage of any last minute opportunities.
On the morning of Wednesday, April 20, 2022, I was scheduled to take my car in for warranty/recall servicing at the dealership. I decided in advance that if the service could be completed in two hours or less, I’d relax in their waiting room with my MacBook, drink a cup or two coffee, and attempt to make a dent in my email backlog.
If the service was going to take longer than 2 hours, I decided that I’d use one of their loaner/courtesy cars and activate a nearby park.
The dealership is about 45 minutes from my QTH and I’ve activated most of the parks nearby it, save one: Holmes Educational State Forest. I’ve been wanting to activate this park for ages, but my travels these days simply don’t take me in the direction of the park very often; it’s a good 75 minute drive from my QTH.
Uncertain how long the dealership would need my car, I grabbed my SOTA backpack that had a full field kit inside based on the Penntek TR-35 transceiver.
Why the TR-35? Because I was testing new firmware that added a huge upgrade: two CW message memories!
Suffice it to say, I was itching to see how well the new message memories work during a proper activation.
Front of the line
Since this upgrade was just made public, I thought those of you who either own the TR-35 or are plotting to purchase the TR-35, might want to see it in action. For this reason, I pushed this video and field report ahead of all of the others in my pipeline.
The really weird part about publishing this video so quickly is that one of my next field reports and videos will actually feature the first time I took the TR-35 to the field about 3-4 weeks ago! Back then, CW message memory keying wasn’t even on the table.
I arrived at the dealership around 9:00 AM (local) and the first thing I asked was, “So how long do you think this will take?” The representative looked at the work to be performed and said, “Three or four hours, likely. If you’re in a rush, maybe two hours.”
I decided I wasn’t in a rush because I’d much rather be playing radio at a new-to-me park than sitting in a waiting room.
I asked if I could borrow one of their courtesy cars and he replied, “We assumed you might want one Mr. Witherspoon, so we already reserved one for you.”
John (WA3RNC) has just announced a new firmware (V.0.24) upgrade for the Penntek TR-35 that will start shipping in all TR-35 orders starting Sunday April 23, 2022.
The new processor adds two new features:
The ability to record and playback two CW message memories
A function to toggle the display from black with blue characters to solid blue with black characters
Of course, the big upgrade–in my world–is the addition of CW message memory keying and I can confirm that it works very well. More on that below…
Obtaining the upgrade
As John (WA3RNC) states in his announcement:
The good news is that any TR-35 can be upgraded with a simple replacement of a properly programmed plug-in microprocessor, or with the reprogramming of the original microprocessor. No other hardware changes are required.
But…there is bad news. The availability of the Atmega328P-PU microprocessor has gone from “buy it anywhere for $1.95″ in mid-2021″ to “virtually unavailable anywhere at any price” today. Delivery dates are quoted as May of 2023 for orders that I placed last year.
[…]Because of this critical chip shortage, I do not have a sufficient inventory of the Atmega part to be able to send out programmed microprocessors for upgrades. What parts I do have are destined for production of TR-35 and TR-45L transceivers.
Therefore, a TR-35 firmware upgrade will require that the transceiver be sent to me freight prepaid for reprogramming, along with funds for return shipping and insurance of $15.00.
Understand that there is no charge for the actual upgrade reprogramming, only for the cost of returning your unit to you.
I think is excellent customer service, actually, and a clever way to get around the chip shortage: use the chip you already have.
Again, if you’re buying a new TR-35, it’ll ship with the latest firmware.
If CW message memory keying or inverting the OLED screen colors aren’t important to you, it’s not necessarily worth upgrading because the new firmware only includes the new features.
Testing message memories
Recently, John sent me an upgraded chip with an early Beta version of the new firmware to thoroughly test in the field. I replaced the TR-35 chip myself.
I tested the new functionality in the shack and on a dummy load.
As with most built-in CW message recorders, you’ll need to set the CW speed to a comfortable setting before recording. During the recording process, you need to send accurately spaced characters, else, for example, the software might interpret the “AN” in your callsign as a “P.”
The first time I set memory 1 to “CQ POTA DE K4SWL” it took three tries to get it right. When I set the second memory to “BK TU 73 DE K4SWL” I recorded it in one go.
Recording message memories on the TR-35 is at least as easy as directly recording a message on my KX2 or KX3. I’m pleased.
In the field
Last week, I took the upgraded TR-35 to the field and used the message memory keying during my activation.
It worked beautifully.
John sorted out a clever way to initiate playback without having to make any hardware additions to the radio:
To play a message memory, simply tap the AUX switch down and then hit the left side of your paddle to send message #1 or the right side to send message #2.
Recording messages works the same way, but instead of a short press of the AUX switch, you initiate a long press.
Even this early version of the upgrade worked well.
Field report and video coming soon!
I’m going to push the field report from last week to the front of the line because I know many of you will be curious to see how it plays in the field. Hopefully, I can post this by Monday (April 25).
Today was crazy: when I woke up I thought it would be a good idea to attempt a first activation of DA-0171 in central Berlin after dropping off the kids at day care. So I grabbed my KX2 bag and jumped on my bike.
Shortly later I arrived at the park and pulled up my 40-10m EFHW and started calling CQ on SSB 40m.
It took me about 30 mins to realize that the KX2 was regulating the power down to 5W since both the internal and the external 4Ah battery I took with me were nearly dead.
I had one QSO with a German station and felt I wasn’t really heard anywhere. Then my KX2 started showing “low batt”.
It’s funny because attempting an activation isn’t really what one would call a very important thing, but I do develop quite an ambition if I have decided to get it done. So my only chance was using CW even though I am all but ready for that.
Fortunately I didn’t run into a classic pileup which would have been super overwhelming for me, but instead about every 2 minutes someone would reply to my call and in a very patient fashion – including one P2P QSO with an operator from Italy.
So all in all I completed 13 QSOs on a “low batt” warning of my KX2.
CW literally saved by butt and I am a very happy person. Without your work for the ham radio community this would not have been possible. So many thanks again.
On a different note: Last weekend (kit building seminar with the club) I had my first DX QSO. It was K3LU who picked up my call from my KX2 and a random wire 9:1 Unun antenna (L-Shape on a mast) with 28 and 17ft legs. I had to sit down and open a beer not able to do anything for about an hour but smile. Such a motivating event and I am happy he was such a great operator instantly QRSing with me and repeating his call. I am in touch with him and looking forward to receive his QSL card which will probably go in a frame.
I also finished the TR-35 and must say I am super impressed. It runs very quietly and the reduced concept is something I really appreciate. When will you take it into the field?
All the best & 73s de Leo (DL2COM)
Oh wow, Leo! I love this–thank you so much for taking the time to share your experience.
First of all, thank you for the kind comments–I’m honored to have even played a minor role in your CW activation. In truth, this is all chalked up to your determination and bravery! I’m guessing what you discovered is what I discovered during my first CW activation: not only is it not as bad as I had imagined, but it was actually fun and got the adrenaline pumping! 🙂
I’m now happy to know that when I hit the Low Battery warning on my KX2, I still have some time left! In truth, the KX2 is so efficient, I’ve made six individual CW 5 watt activations on one charge of the internal battery without even hitting the low battery warning.
Again, this story just makes my day. CW is such a fabulous, efficient, and magical mode! Good on you for diving in, OM!
I also think it’s brilliant that you worked Ulis (K3LU). You couldn’t have worked a better op for your first CW contact–he’s the real deal and a wonderful fellow. Not only that, but he has some amazing QSL cards!
And the TR-35? I couldn’t agree with you more. I did an activation with the TR-35 last Friday so a video and field report is forthcoming!
Thank you again, Leo! I hope others share their experience hitting CW for the first time (hint, hint!).