Category Archives: Homebrew

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

Dan’s clever chalk line homebrew EFHW antenna

Many thanks to Dan (KQ8Q) who writes:

Hi Tom,

I discovered something you might have an interest in for your wire antenna deployment. Years ago when I was a building contractor, we used chalk line for floor layout. It has a very high tensile strength and is very light weight. After reflecting on this, I recently bought a 100’ spool of braided 1 millimeter chalk line and used it for a field deployment. I attached my “throw weight” to it and easily launched it about 60’ into a tree. You can see it in the attached photo holding my homebrew EFHW to my Jeep.

This link is what I used: Tajima PL-ITOL 100 ft .04″ Bold Braided Replacement Chalk Line New | eBay

Click here for full parts list (PDF)

The magnet wire was scavenged from a HUGE transformer from a neighbor’s discarded light fixture.

Lug Nut Throw Weight: left hand threaded from a 1966 Plymouth Fury

I did the new installation for him and he gave me the old one. I promptly disassembled it and collected miles of 14 and 20 gauge magnet wire 😊!

I haven’t added the capacitor to this antenna yet because it is sufficiently resonant and broadbanded on 40, 20, 15, and 10 Meters. I did some testing with the capacitors though on my previous build which was the PVC tube EFHW transformer. I believe I may have sent you a photo of that in a previous message. It too was resonant in the same places, but adding the capacitor smoothed and widened the acceptable SWR range.

The attached photos are my complete antenna assembly: matching transformer (49:1), 65.5’ speaker wire, 100’ braided 1MM chalk line, and throw weight (epoxy filled lug nut with short paracord pigtail).

Compact and lightweight.

Dan/ KQ8Q

I love this, Dan! I also like how self-contained and compact it is. What a professional job, too, with heat shrink, proper connection points and tie-offs.

Brilliant work!

Do you have an antenna or radio project you’d like to share on QRPer.com? Contact me!

Joe’s DIY stand for the Icom IC-705

Many thanks to Joe (KD2QBK) who writes:

Hi Thomas:

Like many I’ve taken the plunge on an Icom IC-705. Even though I sold off an old Yaesu 817 to finance part of it, it still cost a very pretty penny and I didn’t want to shell out more for a tilt stand or bail.

Especially at the rather extravagant prices they’re going for now. $30, $40? No thank you. (Really, the radio, at $1300, should have come with one in the box, but why beat that dead horse – it is what it is.)

In any case, I looked around the house for something to DIY one with. I found a couple of metal angle brackets, screws that fit the mounting holes, and some tiny rubber bumpers to shield from nicking up the radio’s plastic case. Voila! Instant tilt stand. See pics:

And just the right angle too. My plan is to plastic-dip the brackets so I can get rid of the bumpers as well as not nick up any softer surface the radio sits on.

IC-705 Bluetooth Question

Meanwhile, a question for you and other owners of this radio.

What’s up with the Bluetooth function? I have three bluetooth speakers and a small audio amp with built in BT, and I can’t get audio to play through them. The unit sees the accessories and connects. But no sound. I’d updated the firmware to 1.24, just in case they might have addressed any issue. Still no joy.

That being said, I can control the radio via BT with android apps, etc, but no audio. A very disappointing development for such an expensive radio.

Oh well. The good with the bad and all that…

Joe Patti (KD2QBK)

Thank you for sharing this, Joe!  That’s a very clever and simple solution for the IC-705 stand. 

As for the Bluetooth functionality, I’ve yet to use it. Hopefully, someone here can chime in and comment with advice!

Guest Post: Creating pick and pluck inserts for radio cases

Many thanks to Mark Hirst, who shares the following guest post:


Pick and Pluck Foam

The old adage of ‘measure twice and cut once’ is very apt when using pick and pluck foam. The inserts are not cheap and mistakes are hard to rectify.

Whether you are preparing a large case with several items in a shared insert, or focussing around a single item, planning the layout is key.

Item weight is also a factor to consider, as this will affect decisions on wall thickness between items and the case.

Finally, how hostile is the environment likely to be? Is the case going in your backpack or car where you’re in careful control, or is going to be subject to careless handling by others?

Planning the layout

Once you’ve settled on a case size and how much padding you need, a non-destructive way of planning the layout is to use cocktail sticks.

These can be inserted into the corners of the foam segments to trace the outline of the radio and any items such as controls and ports that may extend from the body.

Since the size of the segments is in fixed increments, matching the exact dimensions of the radio is down to pure luck. I would go for a slight squeeze on the radio body if feasible to make sure it’s always in contact with the foam, but give some breathing room around the controls and ports.

The example below is a case I use for backpack transport. It has rather thin but adequate side walls for that purpose. I prioritised wall thickness facing the front and back of the radio, and also on the side opposite the carry handle. Note how the foam comes right up against the body of the radio, but leaves the front controls with some clearance.

Outlining using cocktail sticks

This has the benefit of keeping any sudden shocks away from the controls, and also reduces the number of places where foam is subject to tearing and compression when the radio is inserted and removed.

The completed insert

Separating the foam

The best place to start is along the planned route of a long side wall. Use your thumbs to separate the surface of two segments on one side from two segments on the other.

Once the surface tear has got going, you should be able push a finger down between the four segments, extending the tear till it reaches the bottom of the foam. At this point, you have a cut all the way through.

Separating the foam

Now you can peel the foam apart at the upper surface in each direction, using your forefinger to again push down between the segments to complete the separation down to the lower surface.

Work carefully around the cutouts and protrusions accommodating the controls. The protrusions are potential weak points at this stage, so be sure to proceed slowly.

If you need to practice, you can always start by separating segments deep within the section that will be removed till you get the hang of it.

Reinforcement

While pick and pluck means you don’t need special tools or templates to cut the foam, the remaining material in your insert is inherently weaker than a solid structure.

The solution I’ve used is to fill the residual cuts with a solvent free adhesive. Solvent free adhesives are often aimed at children for safety reasons, and while there are solvent based adhesives for foam, the one I used dries clear with a resilient flexible bond that is stronger than the foam itself.

I run a finger gently along the exposed walls, edges, and around the protrusions. This makes the potential weak points and stress areas immediately apparent as segments naturally separate along the pick and pluck cuts.

Armed with a tube of adhesive and a finger (usually a thumb), you can gently open the weak point and then run the nozzle of the tube down the cut, dispensing generous amounts of adhesive as you go. The two sections of foam close up as the nozzle passes by, with the adhesive soaking into both sides. As long as you don’t go overboard, the adhesive will stay within the join and you won’t have to wipe away any excess.

Reinforcing corners

Side walls are not subject to the same stress as protrusions, but you will probably still spot sections with deeper cuts that need attention, and you will definitely want to reinforce the corners.

Reinforcing sidewalls

I’ve allowed at least a day to be sure the adhesive has set. It’s worth going over the insert again to see if you missed anything the first time round.

The Adhesive

The Bostik solvent free adhesive resembles runny white toothpaste when dispensed from the tube, but dries clear when set.

Inevitably, when I tried to find more of it recently, I discovered that the easily recognisable colour and branding had made way to a confusingly generic scheme shared across a variety of different adhesive types from the manufacturer.

I found this old listing for Bostik 80518 on Amazon UK, and another here on Amazon US. Based on the product number, a modern equivalent seems to be here.

I’m sure there’s nothing unique about this particular product, other than I’ve found it to be foam friendly over the years. Aside from being solvent free, its ability to seep into the foam is a key asset.

Since the first step of creating an insert leaves you with a potentially discardable piece of foam anyway, you have plenty of raw material to experiment with if in doubt.

Additional Reinforcement

Even if you have been generous with the side walls of your foam insert, a heavy radio might demand some additional work to ensure the longevity of the foam.

While the example case shown above worked OK to start with, I noticed that the floor of the case and the side wall facing the back of the radio were taking a beating.

The problem was caused by the feet of the radio, cooling fins, power and antenna connectors. During transport, these were pushing into the foam with the full weight of the radio behind them. Subject to such concentrated point forces, I could see that the foam wasn’t going to last.

Using very thin and very cheap flexible plastic cutting boards from my local food market, I cut out panels which spread the point compression across a much wider area.

Additional Reinforcement

Now when I put the case into a backpack, I ensure that the radio is sitting on its tail with the cooling fins against the rear panel.

Conclusion

While it’s possible to create ad-hoc transport solutions for radios, there’s nothing quite as satisfying as a sturdy padded case that is made to measure. The cases are forever, but the foam needs care and attention, so I hope these tips help you build a lasting solution for safely transporting your pride and joy.


Oh wow! Thank you so much for this timely post and for helping me as I kit-out a Pelican case for my Icom IC-705.

Readers, click here to check out Mark’s previous post about the case he uses for his Yaesu FT-891.

Thanks again for sharing your best practices, Mark!