Kenwood TM-241 – No TX

One of our club members recently requested me to take a look at a Kenwood TM-241 he bought a couple of years ago, but never used it. He plans to use it just for some monitoring of a couple of frequencies for local traffic.

In any case, RX is just fine, however, when clicking the PTT-button, nothing happens. No TX.

These transceivers are known to be – let’s say – “difficult” when it comes to the PA stage. They use a monolithic module which houses the complete PA. They tend to fail.

Upon inspection, someone had already been in there, and there was cooling paste between the heatsink and the module. The PA wasn’t dead either. It just wasn’t TX’ing. I remembered that the OM said that he tested the mic on another Kenwood transceiver, and it was working fine.

Could there be an issue in the front panel? I disassembled it a bit more, and yep, there’s the issue.

Kenwood used some kind of glue to tack down SMD components before soldering (I suppose they used wave soldering, hence tacking components down). Nothing wrong with that actually, however, the glue they used, absorbs moisture with time. This in turn, turns it acidic.

The trace damage can be seen in the middle – follow the trace of the center pin of the connector down, and you’ll see it. The part of the trace that goes up was also starting to go bad.

The ground trace for the mic was completely eaten away. After recreating the traces with some enameled wire, everything was fine again. Happy days.

73 de ON8AD

Yaesu FTM-100D – the best Fusion – no wait – .. DMR radio?

I recently bought a Yaesu FTM-100D (I’ve been wanting to buy a decent mobile set for some time, altough I primarily work via DMR Hotspot) and have been quite impressed by it’s feature set and work-flow.

The device includes GPS support, an APRS modem, Wires-X /Fusion digital mode and supports programming via a micro SD-card. 50W output power both on VHF and UHF. The head of the unit is removable. The mic has an abundance of buttons: 4 programmable, a numerical pad, 2 buttons on top for channel switching / scanning and is backlit (in red by the way – easy on the eyes)

It’s a dual-watch device by the way – not a true dual-receiver. Antenne is coupled via a SO-239 connector. At least in Europe. Maybe an N-connector would have been a better choice.

What I like about the fact that it comes with a removable head, is that it uses standard connector. Just your regular RJ-11 4p4c for the head; and a RJ-12 6p6c for the DTMF mic. None of this vendor-specific, overpriced cabling. Great! This allows for a nice concealed install in the trunk of my car.

I previously mentioned that I also run a hotspot when I’m mobile, and just recently, there have been made vast improvements on the MMDVMHost program, and also on the YSF2DMR client.

One the the nicest things, is that the developers have started to decipher the Wires-X commands (are you listening Yaesu? Proprietary signaling has no place in the ham radio world! Not even by law!). The cool thing about this, is that you get to use the e.g. Brandmeister DMR network, with a click of the “D-X”-button, accessed via your hotspot. The Wires-X menu allows you to select the talkgroup, and the hotspot does all the rest (like disconnecting from the current TG, linking to the new one, etc…).

Callsigns and Talkgroup names are all forwarded digitally to the FTM-100D. Awesome. You can even key up e.g. #02061# – this will bring up Belgium North. Try that with any DMR radio, and you’ll have to program TX contacts, zones, RX groups, upload the userDB,… With this YSF2DMR + Wires-X support; I just put in the frequency in the FTM-100D, and off we go.

Overall, I’m really digging this little radio, and I haven’t even figured it all out… 73 de ON8AD!


Kenwood TM-V71 low power

…Or not? Here’s a short post about often overlooked issues with supplying power to your mobile rigs (or any rig for what it’s worth..); Here’s the story I told to the owner of a Kenwood TM-V71…

First of all; let’s start with some basics:

  • Ohm’s law
  • Resistivity of a wire
  • Contact resistance

We all know, that the higher the resistance, the higher the voltage across the component. Ohm’s law right? Imagine your power supply wire is a component.

Every gauge of wire has a certain resistance for a certain length. The thicker the wire, the lower the resistance. Choice of material plays a great deal in this as well.

Contact resistance. Often overlooked. A picture is worth more than words:

This is what contact resistance does. The fuse itself survives; but due to lack of good contact between it’s blades and holder – be it due to oxidation, bad design, or lack of pressure – the resistance will cause heat to be formed in the holder. Eventually degrading it further and further.

In short, the ‘repair’ of this TM-V71 was one of refreshing some basics to the user.. Lengths of thin wire, with cheap fuse holders and a plug that shouldn’t be there is a big no no.

Ham radio operators: keep power runs short, with thick wires, and premium fuse holders. Always. No exceptions.

FTdx3000 – Omnirig Digital Mode

Hi All,

Just a little something I’ve run in to when setting up my new FTdx3000. I had an OmniRig setup with my previous FT-450; worked like a charm, including SDR-Console tracking, etc etc. I run everything trough OmniRig as I don’t need any virtual serial ports that way, and it works pretty fast and stable. Even WSJT-X works with it.

Here’s the deal though: the supplied FTdx3000 profile for OmniRig, puts “Digital-UP”-mode in RTTY-DATA mode instead of USB-DATA mode. To fix this, I’ve created a modified profile. Just put it in the Afreet OmniRig install folder and select the profile in OmniRig. Should save you all some head-aches. Click here to download it. It also works great when working Split in WSJTX (set split to “RIG”) – e.g. it doesn’t toggle VFO like the default data profile.

Here’s my menu settings list:

  • 067 – Data Mode: Others
  • 069 – Other Disp: 1000Hz – This is needed as the FTdx3000 adds a 1000Hz shift in data mode – utmost importance for FT8!
  • 071 – Data Lcut Freq: OFF
  • 075 – Data In Select: USB
  • 077 – Data Out Level: 1

This way – you don’t have to switch any mic settings – data modes have their own profile.

73 de ON8AD

ICOM IC-910h – Preamp bias troubles

Recently I was asked to take a look at a IC-910h VHF/UHF all-mode transceiver which had developed an issue where the bias kept being enabled. Even on transmit and when the preamp wasn’t enabled. It luckily didn’t cause any havoc as the operator’s antenna wasn’t DC shorted at the time..

If you look at one of my previous posts – you’ll know how a basic bias circuit works (check it out here – SEA remote ATU bias & mods).

The problem here, was that there was no way of turning it off and on. Nothing seemed to be burnt out or shorted on first sight. So what does this look like on the schematic?…

I’ve traced some lines to show you how things work. Q702 is a PNP transistor – a Rohm 2SB1132 T100R. This is the main switching transistor. Rated 500mA. Q703 is a DTC114EUA T106. A bit of a special beast. It’s a “digital transistor”. It has built-in bias resistors to enable the configuration of an inverter circuit without connecting external input resistors.

So to troubleshoot, I first checked if VPRI was being switched from the main processor with reference to ground. It was. Pfew – no main processor issue. Next step was to check if Q703 actually did any switching: it did as well. Hmm, odd.

Checked Q702; and it wasn’t shorted when checking in diode test from Base to Collector, or Base to Emitter. Maybe C703 or R702 failed? Nope, not that either. Any tin whiskers around due to lead-free solder? Nope.

I still suspect Q702, as for some reason, it conducts, without anything applied to the Base. (Otherwise known as a “Leaky” transistor). To confirm, I replaced it temporarily with a bog standard BC560. Works like a charm. Leaky transistor confirmed. Here’s the testing bodge in all it’s glory.

I quickly ordered a couple of Rohm 2SB1132 T100R from (I kind of like their fast service and clear website to be honest..). Delivery took a little longer than usual due to the fact that it was in stock in a HK warehouse and I’m in the EU.

Remember to really clean up the old pads when working with SMD components. It’s just much nicer. I used Chemtronics fluxed solder wick here. Pads clean up nicely with it.

Here’s the new part installed. Looking great.

And confirmation it works and can be switched on/off..

The UHF part is similar; so if you run into issues where bias is kept on with your IC-910h; make sure to take a look at these components. The UHF part is a bit trickier, as you need to disassemble the entire PA unit..

73 de ON3AD – Jeffrey

FT-2000 – Deaf as well?

I recently had a look under the hood of an FT-2000; and just as I’m done repairing two FT-897; I notice that the FT-2000 should be a suspect as well! Yaesu: what gives?!

You can see the same white oxide leaking out of the porous plactic of those filters.

A warning to FT-2000 users: you should check them periodically.

Yaesu FT-897 – Deaf on receive

In our local ham radio club ( UBA-ARA ) – two of our club members had a Yaesu FT-897 who seemed deaf in certain modes. I took both transceivers home with me and took a closer look.

Upon opening the transceivers, I quickly saw what looked like water damage on the IF crystal filters:

You can see some white deposit on those filters. My guess is that after re-flow/wave soldering these boards, Yaesu probably washes these PCB’s. However, the plastic used in these filter either is brittle, porous, or the bottom isn’t hermetically sealed.

Removing these filters is a pain in the ass. And I’m not overreacting here. The ground plane in this PCB is quite good and you can really struggle to get the solder out. (lead-free as well!). Here’s the PCB with the filters removed:

Looking at the flux in other places on this board, I suppose this transceivers has had work done before…

I opened up one of these filters to get an idea of the damage done. A sharp blade does the trick:

You can clearly see the copper oxide. No wonder this thing was deaf!

Anyway, it’s worth opening up your transceiver if you have an FT-897 to check and see if there’s any of that white “powder” on those filters. Big red flag if you see it.
Here’s a picture with already one new filter in place. Make sure to put the right filter in the right place…

Yaesu FT-450 – deaf on higher bands

I’ve always wondered why my FT-450 I bought second hand had a lower RX level on the higher bands, starting around the 20m band. I took a look at the schematic, and the input on the RX side is very classic: a DC blocking cap and protection diodes.

Protection diodes, wait – those aren’t RF protection diodes; they are bog standard SMD red LED’s! What was Yaesu thinking here? (“Let’s save 2 cents?”). Only reason they might have used these (and the only reason I can think of) – is that they maybe have a low capacitance. But seriously, Yaesu.. ?

Anyway, I set my multimeter to the diode setting and quickly realized that one of them was shorted. Really, who tries to use LED’s as protection diodes? Really not up to the task. Here’s one that was still working. The picture gives a good indication where you can find them on the PCB (underside of the transceiver).

The diodes are placed anti-parallel to clamp any over-voltage/ESD. But there are better parts to be found. I came across the Infineon ESD0P4RFL. It’s quite a bit smaller, but we can move the part a bit. It’s actually made for these purposes:

  • Very low line capacitance: 0.4 pF @ 1 GHz ( 0.2 pF per diode)
  • Very low clamping voltage
  • ESD protection of RF antenna / interfaces or ultra high speed data lines acc. to:
    • IEC61000-4-2 (ESD): ± 15 KV (air / contact)
    • IEC61000-4-4 (EPT): 40 A (5/50 ns)
    • IEC61000-4-5 (surge): 5 A (8/20 μs)
  • Ultra small leadless package:1.2 x 0.8 x 0.39 mm³

Read that last line, yes – THAT small

I cleaned up the original location of the LED’s with some solder wick; also cleaning any flux residue on the board with IPA as flux does have a capacitive effect. I removed a bit of solder mask up the trace a bit as to fit the component correctly and applied some solder paste before re-flowing the part. Measures like a standard diode with a voltage drop of about 0.6 V – so easy to verify. It’s really small compared to the original LED’s – check it out at the bottom right of the trace.

Overall if you have a FT-450 – check that these aren’t already blown. I see *some* complaints about bad RX on these transceivers, but that’s really not the case *if* these diodes aren’t blown. So check up front, and replace “just in case” would be my advice.

Sea 1612c Remote ATU – bias & mods

So I acquired a SEA 1612C remote ATU for cheap, but without an enclosure. I figured I’d buy my own enclosure anyway, so no big deal.

As I didn’t want to use any remote cable at all, I had a little challenge:

  • I need to give it power. Okay, that can be done via a bias-tee. The tuner isn’t made for it, but can be modified.
  • I need some way to be able to “tune-on-demand”. I settled on a small Arduino Nano, but will eventually do this via a ESP8266 (I can remote control it via WiFi then)

So what is a bias tee? It’s actually no more than a handful of components: a couple capacitors, some ferrite to make a choke, and some nuts, bolts, sockets.. and a fuse. You double up these components to make one for the other side as well.

So what’s it look like? Well, see below. C1 in my case is 2x 10nF – 3kV capacitors (in parallel – so 20nF in total). F1 is a Ferroxcube 4C65 ferrite, wound with about 30 turn of magnet wire. It makes a nice 3-30MHz choke when testing it with a Vector Network Analyzer. F2 is a 3A fuse.

So how does it work? Well – RF in to the left – the capacitor blocks any DC; the choke blocks any RF going back into the DC supply. Build the same thing twice, and you can run DC over the same coax. Easy, nice, elegant. Great!

Alright, that’s one solution. Now we need to be able to “tune on demand”. There’s a pin called “DTN” on the connector block of the SEA 1612c – “Demand Tune”. The thing is:

  • This only works when it already has a stored tuning
  • Keeping this permanently low (instead of the usual “high” impulse when triggering something) locks the microcontroller up, as it’s on an interrupt pin. So no easy fixes.

Simple solution: slap on an Arduino which pulls DTN down, only once, after being powered on 3 seconds. Just an NPN and an Arduino, collector to DTN; gate to the Arduino output pin and emitter to ground.

I piggybacked the Arduino on the 5V regulator on the board (7805 regulator) so in terms of power: no issue.

To force a re-tune, I press a normal-close momentary switch which breaks power to the tuner. Upon release power is fed back to the tuner. I press PTT which recalls the previous setting. After 3 seconds, the Arduino pulls the DTN line low, causing the tuner to clear the memory setting. I can then put some RF on the tuner and it’ll force re-tune for that frequency.

I found a nice enclosure for the tuner at, a German web store. The enclosure is IP65 rated, well priced, has a window, and comes with all locks and mounting hardware.

I used two aluminium “L”-profiles to securely place the enclosure in the ground. Here’s the end result feeding my 40m long multiband half-wave end-fed antenna.

Yaesu FT-450 – SDR Panadapter & SDR-Console

I was recently gifted a SDRPlay RSP1 (thanks again ON3HVP!) and have wanted to install an RF-tap for a long time in my FT-450.

Now, there’s a couple of ways you can do this:

  • Get an extra RX antenna (duh..)
  • Tap at the antenna port (but you’ll need to disconnect on TX)
  • Tap at the RX circuitry
  • Tap at the IF (in case you’re using an RTL-SDR which doesn’t handle HF too well..)

In our case, we’ll tap at the RX circuitry. It doesn’t see any TX power, so it’s all safe. There’s one caveat: you can’t just solder an extra wire and be done with it. If you connect an extra cable and receiver; you’ll load this stage down, causing your receiver to be less sensitive. Not something we want on HF!

Enter a great little board by G4HUP (who is sadly an SK at the time of writing…). The board Dave designed is essentially a high-impedance buffer. So it avoids loading down the RX section, while making sure it has adequate power to drive the input of the RSP1.

Seeing we want the full spectrum delivered to the RSP1 – I chose the “PAT V”-board: no filtering, straight from RX on the transceiver; to the RSP1.

Here’s how it’s all connected (click the image for a large version):

FT-450 Panadapter

FT-450 Panadapter

Basically, we’re tapping at the little BalUn next to the white relay; and we’re powering the buffer from a regulator providing 12V – but only at RX (it mutes the adapter on TX by not providing any voltage).

You might ask: “Why aren’t you using a thin coax?” – It’s a recommendation from G4HUP himself: it adds less capacitance which would in turn load down the RX and thus decreasing the signal.

OK – so we got the adapter installed, we have the RSP1 connected and OmniRig is working like it should. (See other post..)

Enter SDR-Console V3 with… External radio support (you can see where this is heading… HI). If you have OmniRig set up; you can enable external radio support in the SDR-Console options. You’ll have to restart the program once you do that.

You’ll notice an extra window in the DSP setting. Enable the “play” button and the “tracking” button. That’s it. Your PC (and thus RSP1) is tracking your radio, but also the other way around: If you see a signal in the waterfall: click it and you’re QRV on the other station’s frequency.

Even better, my logging program (Log4OM) uses OmniRig as well. So I could even click an entry on the cluster, Log4OM sends a CAT command; the transceiver tunes to the frequency; and so does SDR-Console V3.


sdr-console V3

SDR-Console V3