Another SWR meter : the "Blinky SWR"

First some history ...

Long time ago (in 2003!) I built a circuit that showed SWR with  four multicolour LED's. It was designed in the NJQRP Club for their Rainbow Tuner, by Joe N2CX (SK).

Although the kit is no longer available, the info is stil found here.
And in case you're interested, I still have the Eagle files for the circuit and a PCB I designed for it, just send me an e-mail on my QRZ.com address. Note : my version does not include the tuner part.

The nice thing about it was that it is fully automatic : the comparator is fed with incident and reflected power from a resistive bridge, so it needs no adjustment for "full scale" forward power. Also the battery power is automatically switched on and off.

But it needs a battery ...

More recently I came across the TinySWR, another circuit that shows SWR with LED's, and this one needs NO BATTERY, nice !

It's a design by Martin, DK3IT, based on work by others. 

The circuit is completely passive, and energy to lit the LED's is taken from the RF you put into the SWR bridge. Info about the TinySWR is here , and you can buy a kit with all components here.

Here is how I built a TinySWR into an EFHW tuner.

Still a disadvantage : you have to wind a tiny toroid transfomer for the bridge, and this scares some people off.

The Blinky SWR

Recently, I saw a link on the SOTA reflector to another solution, the Blinky SWR.
Aha,  now we're getting somewhere ... no battery and no transformer !
The design is quite sophisticated, it uses an AtTiny13A microprocessor, which gets it power from rectified RF, and uses the same resistive bridge like the Rainbow Tuner above.

SWR is shown with 6 LED's, and by combining intensity of adjacent LED's, 21 levels can be shown.

Another clever trick is that the Blinky shows the transmit power (max. 10W) after you stop transmitting, with the remainder of the energy stored in the two big capacitors. 

Hmm ... there is still something that may scare some people off: you have to solder a tiny 8-pin SMD chip and 6 even tinier SMD LED's. Well, that didn't scare me off, and I ordered the kit here.

It arrived in a regular mailing envelope in less than a week, wrapped in several layers of paper and bubble plastic. It took me less than an hour to assemble. To make sure the PCB didn't move while soldering, I fixed it with some Scotch tape onto a plastic box. Here you can see I already soldered the CPU chip and three of the LED's.

And here a detail with all components soldered.

I didn't want to put the PCB into one of my QRP transceivers, instead I found a Pomona box with two female BNC connectors. This way, I can use the Blinky in any situation.

Now, to reduce the number of jumper cables, I replaced one of the connectors with a male BNC, so I can put the Blinky SWR directly on the output of a transceiver. Also there can't be any confusion of where is the input or output.

Using some stiff wire, I mounted the PCB inside the box, hanging between the two connectors.
I made a rectangular slot in the lid, and fixed a piece of plexiglass at the inside (cutout from a CD box), as a viewing "window". See top of this post for the final result.

To check if the Blinky really does what it claims, I made a few test resistors on two BNC connectors.

one was 150 Ohm, the other 470 Ohm, which should roughly give an SWR of 3 and 5 respectively.

The resistors I used may be a little inductive, but all they have to do is give a "bad" SWR for comparison. I also used a purely resistive 50 Ohm dummy load.

Checking and comparing with an "good old analog" SWR meter, I can confirm that the SWR shown is quite accurate (within the normal ham tolerances of course, hi), and so is the power indication.

Beware though, the power indication is only correct when transmitting into a 50 Ohm load (dummy load or well tuned antenna).

I did also a test with my Z-Match tuner (see this post), and must say that the Blinky SWR is even more sensitive to detect small differences in SWR than the single LED indicator in that tuner.

Now, if only I could remember where I left the little plastic bag with the four screws to fix the lid ... HI (see top picture). 

My version of a Z-match Tuner

 

Nothing new under the sun ... this type of antenna tuner has been built many times, and is all over the internet.

But since I learned that my new QDX Digital Transceiver from QRP-Labs  doesn't like transmitting in high SWR, I wanted to have something like a ZM-2 or ZM-4, to be able to use the QDX on a piece of random wire, when a perfectly tuned antenna is not available. Probably also useful for my 3 QCX transceivers.

Other inspiration came from a post on the SOTA Reflector, where some "lockdown projects" were shown. Armin, DL6GCA posted a few pictures of what he built: a Minimal Art transceiver, and a ZM-4 ATU.

The building manual for the ZM-4 with circuit diagram is here

As always, I tried to build this project as cheaply as I could, so I took a few pieces of PCB as a chassis, and started building on the fly ... .

First I mounted all the switches, connectors and the two tuning capacitors (polyvaricons).The BNC connectors were from old Ethernet cards, and were fixed with some drops of superglue to both pieces of the chassis, after which I soldered the PCB's toghether to form an L-shaped chassis.

Then I added the SWR bridge, and finished with the rather complex coil with different taps and extra windings, and connected the tuning capacitors. I basically followed the circuit diagram of the ZM-4 , except that I did not include the 160m band.

Here the SWR bridge coil (25 turns on an FT37-43, tapped at 5 turns)

And the rather complex main tuning coil (primary 34 turns on a T130-6, with taps at 8 and 16 turns, and secundary windings with 4 and 16 turns, for low and high impedance output)

This is the final construction, before adding another "wall", and making a U-shaped cover.

Labels were made with my "quick & (not so) dirty" method, just printing them on a laser printer, and fixing them with some Scotch tape. Also two discs were printed for the tuning capacitor knobs.

It may not look really profesional, but it does the job.

And best of all .. I tested the tuner on my "random wire endfed" (9.15m wire with 4m counterpoise + 9;1 UNUN), and I was able to tune it on all bands 80m - 20m. Higher bands were not tested because of lack of time, but probably will work as well.

Good reports on RBN confirmed that this tuner works and is a keeper !

73,

Luc ON7DQ

ON7DQ Friedrichshafen 2022 - Day 12

One more summit and then home !

As the title says ... we left Trier, filled up on fuel in Luxemburg and drove to the new LX summit I hadn't activated yet.

LX/LX-005, Preventbüsch - 436m, 4 points

Strange enough, the road to the summit that comes from the north, starting at 49.726124, 6.167494 along Route 101 (Rue de Fishbach), had no forbidding sign when I looked it up in Google Streetview, but now there was a sign. [EDIT : Google Streetview has since been updated and now also shows this sign]

On the other hand, it seems that the sign on the south side of the summit was removed, so now one can approach from here : 49.707111, 6.170286 . 

The parking spot is next to the radio tower, pos 49.711169, 6.166424

A short walk takes you to a wooded area where you can set up in the shade.

Now, as you can see in the above pictures, I had bad luck ... technicians were placing new cellphone antennas on the tower. They were very friendly and let us pass without problems. But they probably had cut off all cellphone transmitters, which meant I had no connection at all !

So this was an activation "old style", no self-spotting possible.
I used only CW, and hoped that RBN would pick me up.

And it worked, I was spotted on 40m 20m and 17m. 17 QSO's in the log, and thanks to Fabio IK2LEY/P, also one S2S.  

Nothing more to tell than that we had a long drive home, heavy traffic, and also heavy rainfall on the last 60 km. But we made it !

This was the last page of this story ... 

See you for another SOTA story soon ... 73,

Luc ON7DQ

Go back to overview HERE

ON7DQ Friedrichshafen 2022 - Day 11

From Heidelberg to Trier

Another day with a lot of driving, but still time to do one summit along the road.

I had found two summits that I needed for complete, Melibocus and Felsberg, both near Zwingenberg, north of Heidelberg. According to my info , DM/HE-314, Melibocus would be a drive-up summit. But at some point there was a sign that said it was forbidden for cars. Since we were in a bit of a hurry, we returned and took the other sumit that I hoped would be a drive-up, and it was! There is a restaurant and a large parking area on the summit.

DM/HE-102, Felsberg - 514m, 4 points 

The parking position is here 49.730188, 8.685477. The stone tower can not be climbed.

Being on a weekday, the whole place was deserted, so I quickly set up and started my activation. I had two good pile-ups on 40m and on 20m, resulting in 37 QSO's in the log, and three S2S.

After that it was time to drive to Trier, our last stop before going home. We had a BnB near the Moselle river that was very nice.

Continue reading ... go to the final day of the trip : DAY 12

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Go back to overview HERE

ON7DQ Friedrichshafen 2022 - Day 10

The city of Heidelberg and a SOTA summit

The morning was spent visiting the city and the castle in Heidelberg. We parked in the parking at the Karlsplatz (7.50€ for around 5 hours), and first took the cablecar to the castle (9€ per person, including entrance to the castle).

From the castle, one has a nice overview of the historic town and the old bridge over the Neckar river.

One building in the city caught my special attention because of a sign on the wall.

I always thought that Bunsen was the man of the Bunsen burner (what else?), and Kirchoff had done nothing but make the laws of current nodes etc. ... and spectral analysis had the name Fourier written on it ... but back home I looked it up, and yes, the sign is correct, but this seemed to be about something else than Fourier analysis ... read more about it here.

After a quick lunch we drove to the free parking on the summit of the day.

DM/BW-114, Königstuhl - 568m, 4 points

Parking spot is here : 49.402465, 8.727815

Parallel to the parking is a road (part of the Königstuhlweg) where cars are not allowed, so I set up in a quiet spot along that road. I had 21 QSO's on 60-40-20m , a mix of SSB and CW. Strange enough, I could not catch a single S2S here.

Continue reading ... go to DAY 11

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Go back to overview HERE

ON7DQ Friedrichshafen 2022 - Day 9

From Friedrichshafen to Heidelberg

A lot of driving today, but still time to activate one summit along the road.

DM/BW-484, Bussen - 767m, 8 points

This is a very nice summit. There is a large free parking here : 48.160800, 9.556214, in the village of Uttenweiler. From the parking it's a short walk, about 150m, but it is rather steep (yellow line). 

You can also go to the church (blue line), then you have some stairs, and walk to the summit from there. There are free toilets in the building near the church, the toilets at the parking were closed that day.

First we climbed the tower (the Burgruine Bussen), where you have a nice view of the area.

From the tower I made already two S2S contacts on VHF with Sylvia DL/OE5YYN/P on DL/AL-271 (distance 85 km) and Reinhard OE7RGF/P, who was on OE/TI-112. 

WOW! What a great DX of about 200 km, using only 5W, and a Chinese telescopic 5/8 λ whip.

In front of the tower is a large area with picknick benches, where I set up my station for HF.

From this position, I had three more VHF S2S contacts (DO4TE/P, OE/HB9EVF/P and OE/IW3AGO/P, another DX with 140 km!). 

Total number of contacts was 30 and this included 12 S2S QSO's, a great catch !

The rest of the day was spent on the motorways and in traffic jams ... only to arrive a bit late in our BnB near Heidelberg.

Continue reading ... go to DAY 10

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Go back to overview HERE

ON7DQ Friedrichshafen 2022 - Day 8

Two summits and a museum ...

On the sunday after the fair, I wanted to activate the two nearby and easy summits, Höchsten and Gehrenberg. The weather promised to be very hot again, so we started early morning at the first summit.

DM/BW-854, Höchsten - 838m, 8 Points

This is a drive up summit, since the main road passes over it. Parking position is 47.819749, 9.402346. It's a very short walk to the bandstand on the summit, from where you have a nice view over the area. 

I went around the bandstand to find a place in the shade, and already saw another ham setting up his antenna. It was well known SOTA activator Marcel DM3FAM. 

We agreed on what bands to use, to reduce the chance of interference.

I used the long endfed and operated CW on 60m and 30m, while Marcel operated on 40m.
I had a nice run of 25 QSO's, including 6 S2S contacts, NICE!
Of course, one of those S2S was with the nearby summit of Gehrenberg, which is only 5 km away, line of sight. During the days of the fair, there are activators on these summits almost all day, and often several at the same time.

A while later, Marcel had finished his activation and came by for a short talk.

The summit of Höchsten is quite an interesting place, all around the walkways are displays of texts in German and Schwäbisch (Swabian), one of the local dialects.

See Wikipedia for some info here.
I don't think that Google Translate will be of any use to read the "Schwäbisch" ... but if you know some German, the texts are rather funny. 

Now my YL found nothing better to do than take my QR-code pancarte and hang it from one of the statues , hi.

Another property of this summit : it seems to attract the most unusual misunderstandings!

If you have followed my blog for some time, you may remember I had a funny encounter with Matt, OE6FEG on this very summit in 2019. Read that story here.

At some point, my YL was walking somewhere around the summit, and suddenly she saw the back of a man with a backpack and a fishing pole walking along the track. 

She thought I had already packed up and was leaving, so she shouted "Hey what are you doing? Where are you going ?"

She probably thought I was going  to leave her behind on the summit.
The mystery person turned around and said something like "Excuse me, did you say something ?"

Hahaha, of course I hadn't packed up yet, it was Martin, HB9GVW, who was looking for a shaded spot to set up his station. Sorry for the mix-up Martin !

Shortly after, Martin came to visit me, and we had a nice chat.

Now judge for yourself the similarities or the differences between me and Martin ;-)

I let Martin do his thing, and now I packed up for real, hi, and we moved to the next summit

DM/BW-348, Gehrenberg - 754m, 8 Points

Normally, it is forbidden to drive the forest track to the summit, but I couldn't find any forbidden sign (maybe it was overgrown ?), so I continued driving to this parking spot 47.742086, 9.423339. From there it is only 50m to the summit.

I kept the activation short, made 17 QSO's which still included 5 S2S contacts. One of those S2S was now Höchsten, which I had activated just a while before.

Then it was time to go to the city of Tettnang, to visit the old town and the Elektronik Museum.

I had been in the museum before, see some other pictures from my previous visit here.

And this is the website of the museum (in German only): Elektronik Museum

The nice City Hall

After that visit, we called it a day ...

Continue reading ... go to DAY 9

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Go back to overview HERE