Category Archives: Homebrew

BD4LB’s Simple Homemade L-Match for Field Operating

Many thanks to HUAQIANG Gu (BD4LB) who shares the following information about his homemade L-Match. Note that BD4LB doesn’t speak English, and I don’t speak Chinese, so the following was machine-translated via Google Translate:


Homemade L-Match for Field Operating

by HUAQIANG Gu (BD4LB)

L-MATCH has a simple structure and is easy to make.
It is mainly composed of a coil and an adjustable capacitor.

  1. The coil is made of copper wire with a diameter of 1.8mm, and the outer diameter of the coil is 50mm.
  2. The capacitance of the thin film adjustable capacitor is 0pF–200pF.
  3. When using, a balanced ground wire needs to be installed.
    (Different bands, multiple quarter-wave length wires, and together. I use a row of wires. For example: two balanced ground wires 10 meters and 5 meters long, respectively 40 meters band and 20 meters band balanced ground wire.)

After many outdoor communications, I adjusted the end-fed antenna. The length of the radiator was 10 meters, which was appropriate.

One end of it is hung from the top of a 6-meter-long fiberglass fishing rod. On the other end, connect the red binding post of L-match.

Balance the ground wire and connect it to the black binding post. Spread it out on the ground.

The L-match is placed on the ground and connected to the HS1B or KVE60C antenna analyzer using a one meter long 50-3 coaxial cable. (This reduces the length and weight of the coaxial cable.)
When using an inverted V antenna, the length of the coaxial cable needs to be at least 8 meters.

My outdoor communication is mainly on the top of a hill in the park, or on the beach by the sea.

On the beach, there is plenty of space. In addition to setting up end-fed antennas, you can also set up inverted V antennas.

On the top of the mountain in the park, the space is limited, and it is difficult to deploy the 20-meter-long antenna oscillator. Only 10-meter end-fed antennas can be used.

After fixing the fishing rod, installing the antenna radiator and balanced ground wire, first connect the antenna analyzer KVE60C.
Use copper alligator clips to clip on the coil and adjust the adjustable capacitance to minimize the standing wave ratio of 7.023 MHz.
(Change different coil taps, adjust the adjustable capacitor, and try several times.)

I carry a compass to adjust the transmitting direction of the end-fed antenna. I won’t get lost.

The actual communication effect is quite good.

In the 40-meter band, it is suitable for short-distance communication within 800 kilometers.

In the 20-meter band, it is suitable for communication within 1000-2000 kilometers.

QRPer Notes: HA8SA’s Homebrew Transceiver, BuddiHex Review, and “Marine Mobile” in Iowa?

Because I receive so many tips from readers here on QRPer, I wanted way to share them in a concise newsletter format.  To that end, welcome to QRPer Notes, a collection of links to interesting stories and tips making waves in the world of radio!


HA8SA Stay At Home Transceiver

Many thanks to Pete (WB9FLW) who shares a link to HA8SA’s compact homebrew transceiver. As Pete notes, it’s a “very simple design but with a load of features!”

Click here to check out details on HA8SA’s website.


Buddihex review

Many thanks to John (VE3IPS) who writes:

I think the QRPers will be happy see the BuddiHex review:

https://ve3ips.wordpress.com/2022/11/10/buddipole-buddihex-deployment/

John VE3IPS


“Marine Mobile” in Iowa?

Many thanks to Rand (W7UDT) who shares this brilliant little video from K0KLB’s YouTube channel:

Had a lot of fun experimenting RMOOTA (Random Metal Objects On The Air) with the boat today.. The winds were so strong (sorry about the annoying wind/mic noise) and the noise of the engine kept us from actually driving while making QSO’s.. It was a challenge just the same being stationary in one location.

It was a big contest weekend and the QRM and Pileups were massive.. With my 5w and Random Metal Object as an antenna, it was difficult to get contacts.. I was able to catch them when they were short on business and looking for calls, lol..

We only achieved 4 QSO’s out of the 10 we wanted.. (40%) but, I’m happy with that.. I felt lucky to get one call, LOL..

Thanks for watching everyone.. We (the Skipper and Mate) hope you enjoyed watching it as much as we did making it. 73, Kevin ~ k0klb

The Lyrics written and sung by K0KLB


Many thanks to everyone for sharing their tips here on QRPer Notes!

Sam builds a tiny tabletop HF antenna

Many thanks to Sam Duwe (WN5C) who shares the following guest post:


A (surprisingly good) tabletop HF antenna

by Sam Duwe, WN5C

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.

72, Sam WN5C

Sam builds a compact external speaker and 200 Hz filter for the Penntek TR-35

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 Hi-Per-Mite

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.

The Speaker

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.

The Build

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.

Continue reading Sam builds a compact external speaker and 200 Hz filter for the Penntek TR-35

Scott Builds a clever Icom IC-705 Paddle Mount

Many thanks to Scott (KK4Z) who shares the following project from his blog KK4Z.com:

Paddle Mount for the IC-705

I kinda like the idea of being able to mount your paddle to your radio when operating portable. You can use the weight of the radio to help prevent the paddles from moving around and it frees your off hand for other tasks. We see examples of this with the Elecraft KX series of radios and there are some adapters for radios such as the Yaesu Ft-817/818.

I really like my IC-705. It is probably my best radio for POTA/potable operation. I think the only time I would leave it home is if weight became a problem or I needed to exercise one of my other radios. Recently, Begali came out with a mount to attach their Adventure paddle to the IC-705. It is a sweet set-up; however, the approx. $400 USD price tag got me looking for other alternatives. I have nothing against Begali, I own three of their paddles, and they are superb instruments. I think I wanted to tinker, and this gave me a good excuse.

For paddles, I have a set of Larry’s (N0SA) SOTA paddles. I love these paddles. When I go on an activation/Portable Operation, I bring these and my Begali Travelers. If I was going to do a SOTA activation, I would just bring Larry’s Paddles. Next was a trip to Tractor Supply Company (TSC) for a sheet of 16 ga. Steel. That set me back $16. I cut it to 3″ by 3 1/2″ using a cutoff wheel on my grinder.

I already have a stand I made out of 1″ x 1″ angle aluminum so I cut this to fit behind it.

The blue on the metal is Dykem Blue which is a layout fluid. In creating this project, I am only using hand tools. Power tools consisted of a grinder with a cut-off wheel. a hand drill, and my trusty Dremel tool. Here is a picture of me giving the mount a rough finish with a file. Continue reading Scott Builds a clever Icom IC-705 Paddle Mount

Xiegu X6100: Two effective ways of mitigating broadcast band interference and overloading

As I’ve previously mentioned, the Xiegu X6100–at least at time of posting (January 17, 2022)–has overloading issues. If you listened to the activation video I posted yesterday, you can hear a local AM broadcaster punching through the 40 meter band, especially noticeable before/after operating SSB.

Several subscribers asked if I tried using the attenuator and RF gain to mitigate the level of overloading.  Attenuators and RF gain can be an effective means of mitigating noise levels, but they essentially affect everything on the band–all signals somewhat equally.

A better approach is to use a BCI Filter.

BCI Filters

BCI filters reduce or notch out AM broadcast band signals so that they don’t overload your receiver.

BCI Filters are placed between the radio and the antenna. They can have a dramatically positive effect if you live near a broadcast station and/or if you have a radio that’s prone to overloading.

I see them as a more “surgical” approach to solving broadcast band interference.

BCI filters are simple, inexpensive, and effective. Here are two options shared by QRPer readers: Continue reading Xiegu X6100: Two effective ways of mitigating broadcast band interference and overloading

Portable Doublet-Building Party & my 2022 Activation Challenge!

This past weekend, my good friend Vlado (N3CZ) and his wife came over to the QTH for the afternoon. It’s been a while since our families got together, so it was fantastic to hang with them.

I’ve been trying to tempt Vlado to do more field activations–we’ve done a number together in the past and it has always been loads of fun. Thing is, both of us have pretty active family/work lives, so it’s challenging to make schedules work out.

Nonetheless, our 2022 goal is to do at least one activation per month as a team!

MK-911

If you recall, a couple months ago, I posted an activation report and video using my buddy Eric’s 40-10 meter doublet. I called it a “stolen” antenna because it had been on loan to me for so long, I think Eric forgot it even existed.

Exhibit A: The stolen antenna.

Eric’s doublet was build around a Hughes Aircraft MK-911 Dipole Fixture that was designed and manufactured for the US Military and appears to have been part of the PRC-74 manpack radio-set.

I had assumed Eric found this as a one-off at a military surplus sale. Turns out Eric (and a few readers) made me aware that it was available at Fair Radio Sales in Ohio for $10.

Image of the MK-911 from Fair Radio’s product catalog.

In fact, here’s a link to the MK-911.

I decided to buy two of them: one for me, and one for Vlado. The temptation was strong to purchase a few more just for the 30 feet of 72-ohm military-surplus twinlead, however I understand that there’s a limited inventory and wanted others to be able to purchase this gem.

I was also thinking this antenna fixture would pair beautifully with Vlado’s Yugoslavian RUP-15/PD-8 manpack or even his IC-703 Plus.

Doublet time!

While our wives were catching up, Vlado and I made our way to the storage shed and opened my antenna parts boxes.

I did a little digging and found what I was looking for: some wire I purchased at a thrift store many years ago.

This wire has a black jacket that’s quite slick. Guessing it might be 20 gauge and might even be teflon coated. It was ideal for antennas and eyeing it, I thought there might be enough for two doublets.

For a Norcal-inspired doublet–which covers 40-10–we would need two 22′ legs. I decided (prior to cutting) that I wanted our doublets to go as low as 60 meters (5,332 kHz) and cover everything above. 60 meters is such a useful band. Thing is, I hadn’t done research into suggested leg lengths in advance.

We decided to pick a longer non-resonant length and just give it a go. If it worked, great–if not, we’d cut them down to 22 feet and be happy with 40M and up.

We cut the legs to 31 feet, so there’d be a total of 62 feet of wire in each doublet. Many thanks to my daughter Geneva (K4TLI) for helping stretch, measure, and cut the antenna wire with us!

Assembling the antennas was incredibly simple as there are built-in binding posts attached to the twin lead on the winding fixture.

Vlado and I both decided to use the winder as the center-insulator of the antenna. This is actually how this military fixture was designed to be used. The negative, of course, is that the center insulator is relatively heavy. This isn’t a problem for me at all since I use super strong arborists throw lines to deploy my antennas.

From WD8RIF’s website.

Eric (WD8RIF), by the way,  actually detached the twin lead from the fixture and posts on his unit and built a new center-insulator from a discarded 35mm film canister (see photo above). He wanted to keep the weight down so he could support the center of the doublet on his fiberglass masts.

Testing QRV!

I had planned to hook up the doublets to my RigExpert antenna analyzer, then I realized it was essentially an unnecessary step.

The big question for me was, “Will my Elecraft KX2 find impedance matches on 60M and above?”

Vlado and I connected the doublet to the KX2 and tuned to 5,332 kHz. After confirming the frequency was clear, I pressed the ATU button. The KX2’s internal ATU churned for a couple of seconds and confirmed a 1.4:1 match.

Score!

We checked all of the bands above 60M and the matches were even better.

Standing in the middle of my driveway, I asked Vlado to load the POTA.app website and look for CW spots.

I couldn’t put the antenna away without chasing some parks!

We then proceeded to work about three stations on the air in CW with 5 watts. All of them gave us 599 reports!

Vlado chasing a POTA activator.

It was serious fun.

As I mentioned to Vlado, it might have been the first time I’ve ever used an HF “Handy Talky” with a doublet antenna!

In the end, we both walked away with two effective military-grade field doublets. A perfect antenna for our monthly “Team Baklava” activations.

2022 Activation Challenge

Last year, my personal challenge was to validate all of my park and summit activations with 5 watts or less.

Since I’m very much a QRPer and primarily a CW op these days, this turned out to be low-hanging fruit; lower than I would have guessed in this part of the solar cycle.

For 2022, I plan to continue the 2021 five watt challenge and add another layer…

This year, my challenge will be to build a new antenna each month and deploy it at least once during that month during a field activation. 

The MK-911 doublet will count as January’s antenna.

I’m going to allow myself to build these antennas from anything and everything. I might even cannibalize a few of my broken/worn-out antennas.

I do want to keep these projects quite simple and easy for anyone to build in one sitting. I’ve gotten so much positive feedback from the super-simple speaker wire antenna I built in the field last year no doubt because it was so easy to build and super cheap.

I already have enough ideas to take me through the summer months, but I plan on dusting off some of my antenna books for more ideas!

With that in mind, I welcome your input! If you have a suggestion, feel free to comment!

Dan’s homebrew Icom IC-705 protective case

Many thanks to Dan (KQ8Q) who writes:

Hi Tom,

I saw your recent video post of an activation using the IC-705 and I thought you might appreciate one of my recent related projects. Earlier this year I purchased an Icom IC-705 and because I planned to carry it backpacking for Parks and Summits on the Air, I knew I needed some type of physical protection for it since it would be knocked around a bit on rocks and rough surfaces and during transport. The only cases I could find did not fit my vision; they were either too expensive or too flimsy. So I decided to fabricate my own.

I purchased a 9″ x 18″ sheet of 1/8”, 5052 aluminum. I bent it (with LOTS of effort) in two places which created a “U” channel. The lengths were 4.5″ x 3.5″ x 4.5″. I then cut off the excess and used it to make the side pieces. I then did some research on aluminum brazing which led me to purchase some “AlumiWeld Rods” from Harbor Freight and a canister of MAP gas. I then cut the pieces for the front and sides and brazed them in. You may notice the amateur looking joints on the sides of the armor.

I also wanted to have a mic and key port on the front of the enclosure so as not to be continuously connecting and disconnecting those items directly from the radio and for convenience.

The entire assembly was planned to fit perfectly in the plastic orange ammo box also shown. It is made by a company called Sheffield which is in the U.S.

The radio mounts in the armor via the AMPS pattern screw holes on the bottom. I believe they are 4mm screws… not supplied by Icom. The radio is also electrically connected to the armor via the four screws as well as the shields of the mic and keyer ports.

I recently added the vent holes on the top panel for a less than obvious reason. Although they do serve a dual purpose, my primary reason for adding them was to avoid blocking its GPS reception, but factors of cooling and weight reduction do apply.

73 de Dan (KQ8Q)

This is an absolutely brilliant project, Dan, and to my eye, there’s nothing amateur about it. The coating looks fantastic and I like all of the effort you put into stand-off space to protect the rig and connections. Mounted in that orange box, I think you’ve got an all-weather solution. 

Thank you for sharing this project, Dan!

Definitely not SMD: A 1944 era soldering iron training film

I just discovered this film in the excellent Periscope Film archive.

I used to think I was something special when I wielded a soldering gun, but it would look like a toy compared to the soldering irons in this film:

Upgrading the ICOM IC-705 with BHI’s Amazing Noise Reduction Module

IC-705 switch/LED control for the BHI NEDSP1901-KBD module
An easily accessible, multi-function button on the IC-705’s “back rim” gives a great improvement over the stock noise reduction. (ICOM, with all your resources, why can’t you design a DSP NR circuit that works as well as BHI’s? )

I admit it! I’m in love with BHI Ltd.’s DSP noise reduction accessories. I’ve owned most of their popular models like the DSP Desktop Speaker, and have installed BHI low-level audio modules in six different receivers and transceivers.

How is it that an audio-based DSP noise reduction accessory can be so effective? Only BHI knows, but they clearly have top-notch algorithms that rival the best of noise reduction circuits in contemporary Yaesu transceivers. (Personal bias alert: I find Yaesu’s approach to noise reduction (“DNR” in Yaesu-speak) to be quite superior to ICOM’s, and this is what got me thinking about improving the transceiver with an internal BHI NEDSP1901-KBD module in the first place.)

The noise reduction feature in the IC-705 and its IC-7300 base station counterpart is merely “OK” in my opinion, but the addition of BHI’s NR makes a significant difference in S/N and intelligibility of signals. It’s simple enough to use an external BHI product and connect it to your rig’s speaker or headphone’s audio path, but it adds wiring and complexity. The ICOM IC-705 modification described in this article is a neat, clean, internal solution needing no external wiring or power supply.

Continue reading Upgrading the ICOM IC-705 with BHI’s Amazing Noise Reduction Module