Lab599 TX-500 at about 10,000ft ASL on Montana’s Hellroaring Plateau back in 2021.
The Lab599 TX-500 is a fascinating radio and a great first entry from the Russian startup company. Hopefully they will be able to continue development of future products and further refine the design. I was an early adopter and have travelled a lot of miles with the TX-500.
On the TX-500 groups.io reflector, the question frequently comes up of what audio settings to use with the rig. As a fully SDR rig, it has a fairly extensive set of options to get the most from your SSB audio. When properly set, performance is excellent and I’ve never failed to make contacts with this rig if using an efficient antenna, even limited to 10 watts.
The first step is to set the MIC gain according to the procedure in the manual. This radio is different from every other ham rig out there in that it has separate indicators for MIC gain and ALC. ALC only engages on the the TX-500 if there is an SWR foldback issue so ignore the ALC meter and use the MIC meter for input level adjustments.
Once the MIC level is properly set, I adjust my filter width, compression, and EQ settings as follows.
I generally run the RX filter to match TX FIL 1 above.
I’ve noticed that the TX-500 allows you to set values that are well above the level required to cause clipping or distortion in the DSP signal chain. The best practice with this rig is to never max out any of the settings.
My voice is fairly low pitched and ruddy sounding and the above settings give me good bright punchy audio. My advice is to start use these settings as a starting point with your own voice and make recordings of your transmitted audio using another rig or a Web SDR. Make small adjustments until you are pleased.
The narrow TX filter combined with compression really helps concentrate your talk power to get the most from your 10 watts. As you narrow the filters, however, I’ve found I need to back off the compression to compensate.
My preferred mode of operation is portable HF radio and, like many operators, I like trying new rigs. The radio intelligentsia often speak highly of the Elecraft KX2 but up until now I haven’t been able to bring myself to buy one on account of cost and perceived lack of ruggedness. A couple of things have caused me to change my mind and give the KX2 a second look.
My main reason for giving the KX2 a try is I’ve been working on building a lightweight HF radio kit and the KX2 is exceptionally lightweight. Besides being inherently lightweight with its stamped sheet metal exoskeleton, the KX2 is capable of accepting a 2.5 AH internal lithium ion battery and an internal tuner. This saves the extra weight and bulk of carrying these items separately. Earlier this year, Elecraft released an add on board that allows for internal charging so it is even more convenient. It sips power so the internal battery is reasonably useful. I haven’t weighed this rig yet but it is remarkably light and compact.
At this point it is worth pointing out the importance of a tuner. No portable military HF radio made in the last 60 years lacks a built in tuner. Even with a resonant antenna, the portable HF operator can’t always prevent ground conditions or some other confounder from making your antenna less resonant than it should be. A built in tuner is simply common sense and good insurance and the amateur radio manufacturers are remiss in not providing this feature on their radios.
Moving on, I do have a Lab599 TX-500 also and have been exploring a lightweight kit with that rig as well. The TX-500 is such an interesting rig but it its not flawless. That takes me to my secondary reason for wanting a KX2. Namely, my TX-500 been sent into service twice for repairs and I question its long term reliability. The TX-500 deserves its own review so I’ll save further elaboration for another time.
I’ve had the KX2 now for about two weeks. Initially, I had some frustration with making sense of the controls but the manual is quite well written and easy to follow. For instance, the first time I used it on SSB I found a strangely distorted sound played back from the speaker. I thought this was RFI and was immediately concerned my used rig had a problem but I realized that there might be a monitor function left on by the prior owner. Sure enough, I quickly found the setting to check and was able to fix it with just a few minutes skimming the manual.
The Digirig I purchased for the KX2 also had issues. Since it was a new rig, I wasn’t sure if I had a settings issue on the KX2 or a bad cable. It turns out the Digirig itself had its jumper settings misconfigured. A few minutes with a soldering iron had serial rig control working just as it does with any of my other radios. After a couple of days of troubleshooting software and rig settings I’m glad it was a simple fix.
It is said the KX2 has digital modes as an afterthought. While true for a couple of reasons, I have found it usable so far and not too much of a hinderance. One thing I realized early on is this rig doesn’t have a full set of memory settings for data mode operation. For instance, the mic gain setting is shared by the hand mic and your data mode interface. This could be a serious problem but, in practice, I was able to set the computer audio out settings such that the mic gain can stay where it is with both voice and data modes. No issues there.
There is one other odd consequence to the way the KX2 handles data. Namely, the lack of receive audio monitoring when a data mode interface is connected. Since the Digirig connects through the headphone jack, plugging it in interrupts the speaker output. I’m accustomed to listening to ensure the channel is clear before transmitting but with the KX2 I’ve had to learn to monitor the waterfall display on whatever app I’m using. Time will tell if this is a real issue or not. What I will say is, like we did back in the 90s with telephone modems, I can tell if a VARA HF session is performing correctly just by listening to it. Without jury rigging an audio splitter, that won’t be possible with the KX2. The KX2 even uses pin diode switching for TX so there isn’t even a relay click during data operation. It is completely silent.
More work needs to be done to flesh out the TX/RX EQ and voice compression settings as these are critical to getting the most out of voice operations and 10W. It will be interesting to see if it is as good as the TX-500. Spoiler; the TX-500 has excellent voice performance when correctly configured.
In summary, here are the pros and cons of this rig as I see them after two weeks of use.
Pro: – Very lightweight and compact – Internal battery and tuner reduces the need for additional external devices – Great documentation – Aftermarket support mitigates some concern about lack of ruggedness – Rapidly deployable
Cons: – Data mode operation behavior is a significant departure from other rigs – MARS mod cannot be accomplished without factory coordination – Potentially more fragile than other comparable rigs such as the FT-817/818 or TX-500 – Internal speaker has lower sound quality than comparable radios
Time will tell how it shakes out and whether the new rig excitement will fade. For now, I’m happy to have the rig and will continue giving it a thorough shakedown.
81:1 UNUN with conductive metal eyebolt removed for testing.
TL;DR: The stainless eyebolt has such a small effect on the tuning of the transformer it can be safely ignored as a factor. For the full investigation into this question and why you should care, read on.
One of the things I’ve learned about EFHWs is they are rather sensitive to their surroundings, or at least the transformers are. The transformer is a tuned circuit performing a large impedance transformation. As a tuned circuit, it has resistive, capacitive, and inductive components. Ideally, the capacitive and inductive components cancel leaving a purely resistive load at the frequency of operation. Since this is a broadband transformer, we can’t adjust the capacitive and inductive reactances when in operation. Instead, we have to make a best effort to tune the transformer for optimal performance in our desired environment and then operate the transformer in such a way as to maintain that performance. Stray capacitance or inductance in our design may result in a less than optimal result.
So what does that mean? It means ensuring we do not introduce anything in the environment around the transformer that might affect the tuning.
My linked EFHW transformer design uses a stainless steel eyebolt to carry the tension between the support and the suspended wire elements. Mechanically, this is a great arrangement as it takes any lateral stresses off the polycarbonate enclosure and places them on a steel component that won’t bend, warp, or crack in extreme heat or cold.
The stainless eyebolt is very near the output of the transformer, however, so we can’t discount the possibility of it affecting the tuning and performance of the transformer. I’ve had it in mind to do some testing with and without the eyebolt to measure the effect it has and finally got around to doing so this past weekend.
20m as-built results with eyebolt in place.
20m results with eyebolt removed.
Removing the eyebolt shifted the SWR null on the 20m band down 26khz. At this frequency, the result is inconsequential. Using the classic formula for the length of a halfwave antenna in feet as 468/f, we find the difference here is the equivalent of a mere 0.7″ of wire.
On 30m, the SWR null shifts only 12khz. As you move down in frequency the effect will eventually disappear. For the purposes of this project, a linked EFHW covering 80-20m, it can be safely ignored. On higher frequencies, however, it might be a factor.
Given the direction of the observed shift, it is safe to assume the eyebolt is acting as a small stray inductance in the system. In practice, stray capacitance is much more likely to be a problem while fielding the antenna. While I had the antenna up and hooked up to the analyzer, I measured this effect by placing my hand near the transformer while running a sweep.
Holding my hand near the transformer output shifted the SWR null almost 250khz!
Holding my hand near the transformer output shifted the SWR null a whopping 248khz. In our operating environment, there are many things that can cause the same effect. Wet trees or leaves, the earth, or a nearby metal building or roof can all have drastic affects on the performance of an EFHW. This is why I recommend keeping your EFHW transformer at least six feet away from nearby objects, especially when first tuning the antenna so you have a reliable baseline.
I am working on learning OnShape so I can design a 3D printed enclosure for my linked EFHW. The results of this testing are encouraging and will give me more flexibility in my design.
There is nothing better than combining portable HF radio ops with an overnight trip to the backcountry.
According to the league, the stated objective of Field Day is:
To contact as many stations as possible on the 160-, 80-, 40-, 20-,15- and 10-Meter HF bands, as well as all bands 50 MHz and above, and to learn to operate in abnormal situations in less than optimal conditions.
ARRL Field Day is one of my favorite activities on annual calendar of ham radio events. So it is for many other amateur operators. So popular, in fact, the included bands are wall to wall signals. This can be a frustrating experience for those who are serious about operating low power “in abnormal situations in less than optimal conditions.” Optimizing for ARRL Field Day doesn’t necessarily mean you have a practical station for the types of contingencies the league hopes you are preparing for.
Winter Field Day seems to attract more practical minded participants. Cold weather seems to weed out the faint of heart. Still, it operates on the same rules as summer Field Day so still encourages a contest mentality.
As an alternative for 2023, Gaston, KT7RUN, came up with the idea of Anti-Field Day (AFD). The concept was to operate during the same operational period as ARRL Field Day but do so on the WARC bands where, by gentleman’s agreement, contest activity does not occur. Instead of the make as many contacts as possible contest mentality of Field Day, the objective of AFD was to make targeted contacts with a pre-determined list of participants. This required actual communications planning to determine the bands and times most likely to permit contact with the target stations. JS8CALL was chosen as the operating mode for its excellent weak signal characteristics, automation capabilities, and ability to store and relay messages for stations that are outside of your coverage area.
Planning
I was on vacation to Michigan during AFD so planned to operate from there. The challenge of operating from an off-grid field location was irresistible so I started looking for options near where I was staying. A friend turned me on to the Tin Cup Springs Off-Road Vehicle (ORV) trail in the Pere Marquette State Forest. After doing a map recon and confirming that dispersed camping was allowed there I committed to this location for AFD.
I’ve had a subscription to Gaia GPS for a couple of years now and it proved an excellent tool for conducting a map recon of the operating location. In addition to accessing countless maps from topos to satellite imagery over the internet, Gaia GPS allows you to select map layers to and locations to save off-line so these maps were available to me even off-grid.
In the image above, I’ve circled the area I identified in advance as my preferred site to setup camp. This area was off the main trail and slightly elevated. Since distance contacts where going to be required I didn’t want to setup in a valley that might block lower RF take-off angles. Once I arrived here, I parked and surveyed the area. This entire area is heavily wooded so there was enough clear ground to setup camp but not much more.
Luckily, I knew AFD was in the planning before I departed and so was able to pack the gear I thought I would need. For this outing I took my FT-857D and End-Fed Halfwave (EFHW) antenna kit. For power, I took a supplemental 23AH LiFePO4 battery to augment the 10AH battery packed with the radio. Additionally, I brought a 100W Powerfilm solar panel. Past experience with this combo gave me confidence that I would be able to operate off-grid all weekend if needed. Lastly, I had 2x CF-20 Toughbooks with me as I was in the process of setting up a new one when I left home and wanted to keep working on it on the road. This would prove fortuitous as we shall see later.
It is worth pointing out that this is a fairly heavy load to carry. I would hike with it for a day it would be too much for a multi-day man portable hike for a single person. On the other hand, one needs to be realistic about power needs when operating a 20W radio and laptop for 24 hours in the field. A less power hungry QRP rig would draw less power but would have reduced the chance of successful contacts coast to coast. Everything is a compromise but for this deployment I chose to pack for a vehicle borne mission and kitted out accordingly.
Early in the planning for AFD it looked like 12m, 17m, and 30m would all be included in the comm plan. Since my EFHW kit only covers 30m I built a linked dipole using a combination of hardware store materials and gear I had with me.
Execution
On arrival to the site, my most important task to was to deploy my antenna. I was flexible on where the rest of my equipment would go but I knew most of my contacts were going to be south and west of me so wanted to deploy my EFHW accordingly. A sloper configuration is mildly directional so luckily I had a tall tree at the site with enough adjacent space to allow me to orient it to the southwest.
30m EFHW deployed for Anti-Field Day 2023. The apex of the sloper was about 45′ up in the curved tree in the background. It sloped down towards the southwest leaving the transformer about 8′ above ground.
I used the tonneau cover on my Ranger as space to unfold the solar panel. The radio and computer were hooked up next to the truck and I was on the air in time to send my first JS8call heartbeat 20 minutes before startex.
As it turned out, this was too close to the antenna and I started having RFI issues with the CF-20 about 30 minutes into the exercise. I’ve experienced this issue a couple of times before. With the CF-20, too much RF causes the touchpad and USB ports on the docking station to lock up. Recovering from this requires powering off the Toughbook and removing the batteries long enough to reset the hardware. This is the first time I’ve had this issue with my EFHW. While end-fed antennas have a reputation for causing RFI issues, I have measured this with an RF current meter and found my EFHW to be comparable to a dipole with no BALUN.
The RFI issue wasn’t an immediate show stopper. The CF-20 features a touch screen as well so I was able to continue operating for a time while I troubleshot the issue. Moving my operating position further from the antenna was all I needed to do. I had a second CF-20 with me so, being impatient to get back on the air, I used the backup for several hours and had no further RFI problems.
I moved a couple more times throughout the day chasing the sun. I wanted to optimize my use of solar to keep the battery charged for overnight ops so had to keep the panel exposed as the sun moved lower in the sky. Being in a small clearing meant having limited areas of sun exposure throughout the day. While it wasn’t a big deal, finding a larger clearing will be a consideration next time I do an event like this.
My car camping box made for a great expedient field desk during this exercise.
My laptop power supply also gave me RFI issues. Recently, I found a good deal on a case of Lind Toughbook power supplies. The advantage of these units is their dual voltage capability. Namely, they can run of 120VAC or 12VDC thus saving you from having to carry two power supplies. Lind builds these for the emergency services market and they have a good reputation. Unfortunately, I found that this power supply creates a measurable amount of noise on HF frequencies. Testing at home after the exercise confirmed these are generating a large amount of RFI due to a ground loop of some kind. The issue couldn’t be resolved with ferrite but did go away when the laptop and radio were powered by separate batteries. This isn’t practical for me so I may be ditching my Lind power supplies and reverting back to the PWR+ units I’ve used for the last two years in the field with no issues. The Lind units I have are model CF-LNDACD90. Lind makes many models and it could be that others do not suffer from this issue.
The remainder of exercise execution occurred in accordance with the comm plan without any issues. I operated from 1800 UTC Saturday to 1500 UTC Sunday. Others may have continued operating on Sunday beyond 1500 UTC but thunderstorms were coming in. That said, activity had largely tapered off by that point. During the operational period, I was able to make contact with almost everyone participating, either by direct contact or by relay.
Conclusion
Here is a summary of what I learned this weekend.
SUSTAIN: 1. The FT-857D and EFHW antenna kit both performed well and were easily adapted to the requirements of this exercise. 2. JS8CALL is an excellent weak signal mode with features that enable effective asynchronous communication. 3. The comm plan was well developed and allowed almost everyone to participate fully. 4. Continuous training with the same equipment builds familiarity and accelerates problem solving when issues do occur.
NEEDS IMPROVEMENT: 1. There was no pre-execution brief for participants. Having one would have clarified the requirements for all participants. 2. The COMMPLAN did not directly address relays or MSG deposits, at least in the example log provided. I suspect I contacted more folks than I logged because of this. 3. The first few comm windows had issues with simultaneous TX and the channel capacity with all the participants. A net control operator should be assigned or a staggered TX plan established to reduce the need for re-transmits. 4. Not all participants switched to slow mode on the schedule prescribed by the comm plan.
All in all, this was a great event and I look forward to participating again in the future. Next time I may try to challenge myself by operating entirely out of a rucksack instead of a vehicle. This would challenge me to use a lighter kit all around.
I’m travelling at the moment but need a WARC band antenna for TTP’s Anti-Field Day event coming up this weekend. I have individual antennas that cover 30m and could cover the other bands with a tuner but I decided to go to the hardware store and see what I could come up with. With some speaker wire, zip ties, and WAGO connectors I was able to put together a nice linked dipole to cover 12, 17, and 30m.
WAGO connectors and zip ties work remarkably well for a quick linked dipole.
This project was my first use of WAGO connectors. It was just happenstance that the local hardware store, Menard’s, had them. While familiar with them, I’ve never seem them in a store before. They probably aren’t the most durable solution but but they are small enough and convenient enough that I’m adding them to my radio possibles pouch for future improv solutions.
The cobra head and N9SAB nano BALUN are part of my normal portable radio kit so were already on hand to provide a feedpoint for this project. With the arborist throw weight and cordage from my EFHW kit I have a complete system ready for this weekend.
The whole project took about two hours to complete. It would have gone much quicker but I got cocky and decided to cut my elements right at 234/f after 12m ended up right on. It turns out 17 and 30m needed to be longer so those elements got cut twice….
My final dimensions for the WARC band linked dipole.
Hopefully this provides inspiration for your own projects.
The Orderwire 