Why Did I Choose a Balanced L Tuner?

The Mod Bob antenna on 160 – 30M ends up looking like a single vertical on 160 and 80M and on 30M it models just like a Bobtail Curtain. It does look like a dipole on 40M, but my 2 element 40M phased array almost always beats it, so the Mod Bob is used on 160, where it is resonant, 80M, where it is a poor match of 20:1 and 30M where it is about 6:1. My guess (and I haven’t tried this) is that a 6:1 balun would work on 30M – but then mess up 160M, and that 80M will always be a tough match.

I read this article by antenna guru Richard Measures, AG6K:


And decided to try the Palstar BT1500A, which seems to be designed exactly with AG6K in mind. That link is an updated version of the February 1990 QST article.

You’ll see that Palstar did a very nice job staying faithful to that design, and since I had never tried such an antenna tuner, this time it just seemed to fit. You’ll see in an earlier blog post that the BT1500A worked out in a test exactly as I had hoped – that one switch combination would result in just having to tune the L and C constrols – because then it would make it much easier to build a stepper motor controlled remote tuner with less $100 in “maker” style parts. In fact, with just a rotator control line, I can supply the Arduino and stepper motors with 5V and the BT1500A with the 12V it needs. In fact, here’s a way to do that:

And here is are the specs of a few options – both are less than $20:

There’s enough power for all components in the remote box, and with the 8 wire heavy duty rotator control wire, it should be just fine. I could even put the power supply just a few feet away from the antenna feed in the basement, but that’s not really necessary.

VU2ESE also has the same idea that I do – but he is using low power:


With 100 watts or less you can get away with a lot and never know how efficient and antenna system is. K9YC likes to talk about “commiting unnatural acts” when trying to use a Hi Z ladder line fed doublet as a multi band antenna. He says that the ladder line – because it can’t be choked can pick up noise and also become part of the radiator. In my case – its hard to say if this is a good or bad thing.

More than anything, the Mod Bob – being resonant on 160M is esily what matters. In fact, if 80 and 30M don’t work out or cause 160M to be less efficient using this feed scheme – I’d drop the BT1500A at the antenna feed point. But I have to try this.

The next test though will have to be with high power on 160, 80 and 30M and see if there are any issues at 1500 watts. I will have to set the SPE Expert 1.3K FA to bypass its own internal tuner for these bands. I will still use the internal tuner on my 40 and 20M resonant antennas.

W8JI has an opinion and has looked into the balanced vs. unbalanced tuner and baluns at the input and output of tuners:


Tom argues that maybe my old Palstar AT2K in the shack with a 1:1 current choke at the antenna might not be any worse than putting the BT1500A at the antenna.

This weekend – with full power and the tuner mounted at the antenna I will find out. I expect that maybe Tom, W8JI is right – because when I had the Palstar AT2K in the shack with the ACOM 1500, it never arc’ed or caused any issues.

The coax feed from the shack to the Mod Bob does go through the Array Solutions Rat Pack remote switch, so maybe moving the tuner out to the antenna will be better in that regard – I’m really not sure. The length is only about 60′, so I doubt that losses are a big deal with the tuner in the shack or at the antenna. Not really sure though. Not sure exactly what happens along that feedline – as I sure hope the heavy duty 1:1 current choke does its thing – which I am confident that it does.

I look forward to my high power test this weekend – the big test will be to see if there are any issues on the three bands with high power. The only downside with the SPE amplifier is that it is much more “finicky” than the ACOM 1500 tube amp in respect to SWR. But this might be a really good thing – because it is forcing me to test and try this different approach.

I do know that coax fed dipoles on every band is a great way to go – but on the low bands this is simply not possible. I also know that my radial field for an all band (or all low band) vertical ends up being hatted and causes serious voltage issues on components at the base of that antenna – I have fried a switch that I used to switch in different L and C components in an unbalanced scheme.

I am avoiding the loss of my radial field with the Mod Bob, and sure hope that I have no issues on 160, 80 and 30M with this weekends test.

I hope it proves that this was a good way to go – we shall see.

The Mod Bob Feed Point Project

I’ve got a BUD weatherproof gasketed NEMA box that is perfect to house the Palstar BT1500A. This weekend I will put it out at the antenna and hook up the 12V supply line. I have an old switch box that I can use for now – and I might put a coax “tee” at the input so I can go out and plug in my AA-30 re tune it manually for whatever band I will be on with the Mod Bob antenna.

In the mean time I will be receiving 2 NEMA 23 stepper motors, drivers and possibly an Arduino DUE, which was recommended over the Arduino UNO that I have. I will also use the 8 conductor rotator line that is already set up to power the BT1500A and the Arduino – but will try to use wireless to control the actual steppers via the Arduino board. I am thinking I’d like to just use two optical encoders in the shack and I can just watch the SWR meter on the Expert 1.3K FA and K3 while tuning – just as if the tuner were in the shack.

I can’t get on 80 or 30M right now until I get at least the manual set up working. I know from writing code – that its always a good idea to run it manually as if you are in production while QA-ing – you always find operational quirks that you never ctch when in your development environment. Luckily there is absolutely nothing going on for me to chase – so I just play on 160, 40 and 20 with my resonant antennas. With the activity level and conditions as they are – I’m not missing a thing.

So – this weekend will be the time to do it – this past weekend was over 100 degrees out – so its was an indoor / air conditioned weekend for me. Luckily we then get our fog back in – and I saw it starting to build in San Francisco, so this means I should have a nice weekend ahead for the very start of this project.

I’m not in a big hurry – I want to play around with the Arduino stuff in the shack and also get my ideas well formed before I commit and “go live”. I have all summer to play with this stuff – which is tres coolio.

Bouvet Watch: Keeping Watch on 20 and 40M

It just so happens that after what seemed like a very weak 20M today, as we progressed to the later afternoon, the South American stations came to life. This would be a few hours past their sunset, and the one station of most interest was in Rosario, Argentina, which is exactly the same path as Bouvet will be. The station I worked was S9 +10 and stayed that way for an hour. At the bottom of a cycle – the N – S path is your best bet, especially non polar, which Bouvet will be for the West Coast. Now – from the West Coast, its also a water path. It won’t be open as long as to the East Coast US or EU and AF, but it will offer something decent.

The prediction was quite a bit below actual – and if you asked me about 20M conditions even 2 hours earlier – I would have said – forget it – we are at the bottom of the cycle . . . heh heh

If Bouvet were on right now – it would be pretty grim. The chart shows ZERO possibility at 2200z, but 0900z there would be an opening, but right now would be the middle of Bouvet’s Winter, so they wouldn’t go there now anyway.

BUT, the station I worked in LU is 2/3rds of the way to Bouvet, meaning I probably could work Bouvet today with full power and my 2 element home brewed yagi, but it would be like when I worked BS7H. Crummy summer conditions.

Now – look what happens just past the Autumnal Equinox – things really perk up. This is the point of this post – DON’T JUDGE CONDITIONS FOR BOUVET BY WHAT IS GOING ON RIGHT NOW. We are at a really crappy part of the year – even Field Day has crappy local conditions just about every year. Its funny – but conditions on all bands in the northern hemisphere seem to get better toward the end of July every year. (except the peak of a cycle maybe – like when I worked Turkmenistan on 20M – hi hi). But this coming October would be about the “last best” time for Bouvet – there could be openings from 160 – 10M, although I would bet mostly on 80 – 15M.

Now – look at what VOACAP Online says about next January – 20M will be fine, and I fully expect 30, 40 and 80M to be fine. 15 and 17M will be OK too – its not quite as good as October, but workable anyway. I fully expect this to be a lot like 3Y0X was in 2006 – maybe just a bit harder since 3Y0X was almost directly south of me and a full water path – 3Y0X was VERY easy to work, and conditions then:

Conditions for 3Y0X were a little better than they will be for 3Y0Z. Anyway back to the path to 3Y . .

L20F at 0330z on 40M – S9 +20

Well, that says it all – this path during the late afternoon on 20 and early evening on 40M is bone crushing. Since its 2/3rds of the way to Bouvet, me thinks at the right time it will be a done deal – even with these awful bottom of the cycle scraping conditions. I’m guessing if L20F was > S9 on 20 and 40M today that 3Y would be very workable – perhaps between S7 – 9. If the Bouvet team were on that little beach in the NW part of the island the US West Coast would get a leg up on EU especially, maybe even US East Coast. 3Y0Z, on Slakhallet would mean that the US will need higher angle DX, and that’s fine because the openings will be near our sunset with enhancement at higher angles. I talked to Ralph, K0IR, and he said he fully understands this situation, so I do expect that 3Y0Z will be looking for West Coast at what will be a critical time – and will work all of the West Coast by explicitly asking for West Coast. 3Y0X was so strong for so many hours on the West Coast that nothing special was needed – I do think a little more attention will be needed from 3Y0Z.

In fact, the entire reason I am doing my summer project is because I am so sure that 160 – 15M will be where its at. I will make sure I have antennas that cover these bands with gain or great pattern – will you?

I actually expect this 3Y0Z expedition to be similar to 3Y0X – which happened just before the bottom of the last cycle – with very similar conditions.

And for all my worry – I am feeling like we will do just fine and this will be an epic activation of Bouvet.



Palstar BT1500A (semi) Automation

WD4ED’s stepper tuning project

I have three antennas – two that are resonant – a home brewed 20M 2 element yagi and a 2 element 40M phased vertical array. They both work great with the new SPE Expert 1.3K FA full power solid state amplifier that I just received a few days ago. Here is another video on a great home brewed Arduino based auto tuner:


The non resonant antenna that I have (that requires a tuner for multi band use) is my “Mod – Bob” 3 element vertical array.

Its resonant on 160, but I also want to use it on 80 and 30M, an on those two bands, the SWR is way too high for my new amplifier. Here is a video of my test setup at the base of the center element of the Mod Bob:

The Rig Experts AA-30 shows the Mod Bob as resonant on 160M, and really no where else. Luckily, with the same switch settings on the Palstar BT1500A (> 50 ohms and Low C), the only thing that needs to be done is to power the tuner up (which activates a relay inside), and then tune the L and C front panel controls. This means a 12V DC control line with whatever USB command line wires would make for an easy project – perfect for 2 stepper motors to control the BT1500A. Here are the plots once I manually tuned the two controls for 160, 80 and 30M:

160M at the BT1500A

80M at the BT1500A

30M at the BT1500A

My goal will be to control the stepper motors using a program that has memories. One click of a mouse and the tuning controls move for 160, 80 and 30M.

I don’t see any need to also tie it into the K3’s RS-232 band data line – but maybe I will do that later. For now I have emailed Ed, WD4ED, who no doubt can give me a parts list for this project since he did the exact same thing.

One good thing I found in the SPE Expert 1.3K FA manual is that I will have to disable the ATU in the amplifier when I use this remote tuner. That is easy because its menu configurable – when I switch to 160, 80 or 30M, the amplifier will automatically bypass the ATU.

I think what I need is:

  • Two stepper motors, perhaps bipolar (?)
  • An Arduino board (I have one already)
  • Two stepper motor drivers
  • Anything else?

I’ll first just play with the Arduino and other boards and whatnot in the shack. I’m guessing the voltage for the stepper motors will be 12V, and not sure if the Arduino board and drivers will stay in the shack? Hopefully all I will need are voltage lines for the Palstar and control lines for the two stepper motors. I already have an 8 wire heavy duty rotor control cable run from the shack to the Mod Bob – so this could be a fun and easy project.

While the bands are in the dumper – I at least have a very fun and worthwhile “summer project” – just like last year!






Announcing the World’s First DX-Podition


Mike, KJ4Z, here.  This is the first of a series of guest blog entries I’ll be doing about the future of technology in ham radio in general, and DXing in particular.  I’d like to thank Rich for all the interesting conversations we’ve had over the years and for this opportunity to share my thoughts with his readers.

As long-time readers of Rich’s blog may know, over two years ago he jokingly predicted a future DX operation consisting of a box that could be dropped off on some deserted rock and controlled entirely by satellite.  I believe the time is now right to bring that vision to life.  The technology is all here and readily available, and all it needs is someone to put it together and bring the project to fruition.

What would this contraption be called?  I thought about “DXpedition in a Box,” “Suitcase Remote,” and others.  But in the end, I think I’m going to call it a “DX Pod.”  I think the “pod” concept underscores the idea that the device must be a self-contained, self-sufficient unit.  And having named it the “DX Pod,” it seems only logical to refer to its deployment as a “DX-Podition.”  Because, whatever this will be, it isn’t a DXpedition; it’s something new.  I recognize that some people will not like the concept, but part of our remit is to “advance the radio art.”  There’s a lot of tradition, nostalgia and swashbuckling romance tied up in DXpeditions.  But the reality is that we now live in a world where technology is cheap and physical access is expensive — ludicrously so, in some cases.  And sometimes, physical access isn’t possible at all.  I think a DX Pod could serve as a pragmatic intermediate solution where the alternative is a quarter century between activations.

So, what are the characteristics of a DX Pod?  Here are at least a few to start with:

  1. Ruggedized.  Completely self-contained, and able to run for an extended (indefinite) period without human intervention.  May be much harder to achieve in some climates than others
  2. Self-powered.  Almost certainly this will mean solar panels, but I suppose wind power could be a possibility in some cases — but the moving parts are a source of concern.  Or RTGs if you can find a de-orbited Soviet satellite!
  3. Mono-band.  For simplicity, cost, antenna efficiency, only one band will be supported, probably 30 meters, or maybe 20
  4. QRP.  The problems with running QRO, or even 100 watts, are probably insurmountable in a practical and economical installation.  100 watts would require large solar panels, especially if the pod will be deployed in polar regions.  QRP has the added advantage of reducing the number of stations that can hear the pod at any one time, which is important because operations will be…
  5. Digital.  Operations will almost certainly have to be a weak-signal digital mode such as JT-9, JT-65, or possibly PSK-31.  I lean towards JT-65, because the exchanges are so robotic, and that is also important because operations will be…
  6. Totally automated.  This is the point I think some people will find most objectionable, but there will be no human on the other end of the line.  Why not?  Because satellite airtime is expensive, latency is high, and keeping the transmit link up is just one more thing to power.  The pod will have an onboard computer, probably a Raspberry Pi or similar, that is capable of making and logging QSOs.  And let’s be frank, the JT-65 QSOs made by the computer and those made by a human operator will be indistinguishable from the other end.
  7. Satellite connected, but not in real time.  Because of difficulties aiming antennas and maintaining links with geostationary satellites at high latitudes, and the fact that some skill is required in pointing the satellite antennas in any case, the satellite link will almost certainly be an LEO-based service, which realistically means Iridium.  Iridium has reasonably priced services for small amounts of data, but it would not be cost appropriate for a full-time link.  The pod will poll periodically for control signals, to make sure the control operator can maintain positive control over the station as required.  A few times a day, the compressed log file (a very small amount of data) can be inexpensively transmitted over the satellite link.  Automatic LoTW would naturally follow.
  8. Easy to deploy.  Even a non-ham should be able to deploy the pod with little difficulty.  Clear instructions, simplicity of form, and a few “idiot lights” should help.  The idea is that friendly non-hams can bring the pod along for the ride and deploy it as part of a separate trip.

I could continue, but that’s enough to be going on with.  I plan to try to assemble such a pod and send it away with someone else (TBD) for deployment.  I expect it will take me a little while, so who knows, maybe another enterprising DX-poditioner will beat me to it!  I’ll be blogging about my progress here.  Hope the pod will see you down the log.

KY6R Summer Project: Arduino Stepper Motor Driven Palstar BT-1500A!

K8AC’s wonderful balanced antenna tuner with stepper motors and controller

K8AC Control unit


One of the coolest projects you can do in ham radio is automate an “analog” or manual antenna tuner. I just bought the Palstar BT-1500A, which is a balanced tuner, and I fully expect that it will be great on 160 – 30M with the “Mod Bob” antenna that I wrote about in an earlier blog post. In fact, for 160, I can bypass the BT-1500A completely if I want, but that would require as much work to come up with a safe switching scheme than just using the tuner in line and probably having the L and C set to pretty much zero in both places.

WD4ED  also has a set of videos on his project that looks really close to what I would need. If all I could do is set memories for the stepper motor locations, then I’d be set. I’m not too concerned about making the control part fully automatic – just to make sure the remote stepper motors go to their right positions. The reason I don’t need it to be “perfectly” automated is because my SPE Expert 1.3K-FA just needs < 3:1 SWR, which would be easy to do with some memories that I could manually click on ion the shack on the PC. Maybe I’ll tie into the K3 band control line later.


Anyway, there are so many variations on this project with videos and circuits and other hams to contact and get some pointers from.

Last summer I started a project that ended up almost lasting a year – I feel like I took a real “trip around the universe” trying to find the best / lowest noise / highest RDF 160M receive antenna system, and that was a huge success.

This time I expect that this will be a bit more straight forward. What’s cool – I can mount the BT-1500A at the base of the antenna and use my AA-30 to first check to see if just manually I can get the antenna to be < 3:1 SWR on as many bands as I can from 160 – 30M, and maybe I will really luck out – but I expect that something will need to be tuned. Maybe it will be really easy and I can set the roller inductor in one position and then have one stepper motor on the capacitor.

Ed, WD4ED went this route and explains in his video that he went this route because he smoked one of the high power LC based remote tuners (like the MFJ), and his concern has been my concern because I have smoked a remote switch before. This is mainly because the voltage can be in the several KV range when tuning and when off the mark – and also you just don’t know exactly what a remote auto tuner is doing. When I used to use the Palstar AT2K in the shack with my ACOM 1500, I never had any doubt what was going on and that my rig and amp were being operated correctly. I avoided amp faults by being really careful.

The Mod Bob is a balanced fed antenna, so it requires this different kind of tuner – the BT-1500A.

I’m excited that I have such a cool project because on the air – conditions have just been poor, although I did hear W1AW on 160M last night better than its been for a while, and for the first time in several weeks heard a ZS on the long path on 40M this morning.

The “summer project” is a great way to compensate for crummy conditions. I used to assume summer is no good for the low bands, but last summer I proved that is not exactly true. However, having less daylight means it gets harder to DX on the lowbands and still get sleep!

Caveat: I have no lightning. That makes a huge difference.

I have a theory that we really are going to experience better low band conditions “just around the corner” because 160M is so long over due for an improvement. But as always, DX-ing takes a lot of patience – especially on 160M.

Guest Blogger – Mike Coffey, KJ4Z

The absolute BEST thing about working on VK0EK was making new friends and sharing in the success of the project. Mike is a forward thinker and the master mind behind the VK0LD Remote operation, and he also worked very hard behind the scenes – on the OQRS system, networking and the satellite gear, and many other critically important behind the scenes tasks and programs behind the VK0EK scene.

I’ve kept in touch with most of the team, and all of the “Diablo DX-ers” – the “back office” team, and Mike and I have a running dialog about DX-ing and Ham Radio.

Mike has graciously agreed to Author some blog posts on this blog, and I am very excited about this – thanks again Mike!