There's an SP-980 on the auction site at the moment.

Note there are two versions of the speaker, as with the SP-101, 102 and 901. One has a phone patch built in; the other, a switchable passive audio filter. I have two of each, and several SP-102s for my FT-102/FT-726R side of the shack.

When you run an FT-980 in conjunction with an SP-980, you have yourself an AMBCB or SWBC DXing setup that has very pleasant, non-fatiguing audio.

73 - Fred, N8YX

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If you do, broadcast/ping to the group. The "paper" speaker that Yaesu used appears to be high quality: see the article I put in the files section. The impedance is certainly matched.

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-Mat Breton, N8TW

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One of the greatest analog receivers ... I don't think Yaesu had anything like it until the FT-1000 came out a decade later. And the PA is so overdesigned you can operate continuous at 100W.

The SP-980/SP-980P speakers are rare (just like the FT-980), but like other series products that Yaesu sold this one was rebranded for later rigs: also look for SP-767/sp767P, and SP-102/SP102P. Just changed the number on the front.

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-Mat Breton, N8TW

I was given a ft 980 in pieces and after cleaning and replacing a 20 pin IC in PLL I have it working great! What a rig. Bought a MD1 for it, and now need the matching speaker. I think I want to keep this one a while . Randy K5SL

I'll be running my FT-980 on RTTY for the NAQP contest this weekend. I use AFSK w/ fldigi via a SignalinkUSB interface.?

The setup works well (also use it for FT4/8), and I have no fear running the RTTY signal to 80W+ ... the FT-980 finals aren't going to burn out :) It is rare that both fans kick in even in digital contesting.

The only thing I don't like is that I can't kick-in the 300Hz filter when in a SSB mode. That would help somewhat with strong adjacent signals ... more than the notch and PB filters allow.

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-Mat Breton, N8TW

Hi Fred, thank you very much for your comment. I'll consider that when I'll start the tx review! I'll follow the steps present in Service Manual but I also want to check the dynamic behaviour of ALC.
I'll let you know the news.
Ps: my congratulations for your Four '980! Sure you ARE an enthusiastic for this great rig!!

Enrico IK2XEI

Getting back to this one (after spending time on other projects, radio and real-world alike):

If I let the rig in question thoroughly warm up, it won't tune at all in either direction with the VFO - though other tuning methods are fine. Commonality in theory looks to be the voltage fed to the optocouplers or a questionable solder joint on that board itself. Time to dig into the Technical Supplement and see what's what.

73 - Fred, N8YX

On Thu, Jul 1, 2021 at 05:20 AM, <e.tallone@...> wrote:

I plan to check in depth the TX modulation paths because I suspect that some AGC behaviour will need attention.

Enrico,

I have four '980s. All of them exhibit a condition wherein a carrier of, say, more than 30w will cause ALC saturation - and as a result, output power will creep up to the maximum set point (~110w) if the rigs are kept in transmit for more than a few seconds.

All of these rigs have had their ALC systems set per the Technical Supplement. This leads me to believe there's an inherent (unintentional) feedback loop with a long time constant; I don't really see the issue when running the radios on SSB. So yes...I'd have a look at that portion of the transmitter circuit while you're analyzing the radio.

73 - Fred, N8YX

Dear Mat, sorry I was very busy and weren't able to reply to you soon.

I wasn't able to find the data sheet of the TDK Caps, but your proposal seems better than mine (tantalum caps)! Please note that, according to simulations, the ultimate out of band attenuation is achievable when ESR is less than 20 mohms or so.? Also, using a single 22 uF will preserve the response time during band switching that, in case of 2*47 uF, will become four times larger.

About other "time bombs": I had no time to think about it, I'll try do do so... It is possible, you know aged electrolytic caps may change their characteristics, I found one of them in tx audio path responsibe of tx spurs...

I also tried the new bandpass 28-30 MHz alternative filter but results were not good. Even though the filter was simulated and pre-tested with very good results (my previous picture on stand alone 28-30 MHz filter), once fitted into the equipment the overall response were bad (also modifications of polarization paths were performed and checked before). So I paid better attention to the schematic and I understood that the output impedance termination of the filter (the input impedance of the RF Jfet preamplifier) is NOT 50 ohm!
So, in order to synthetize the correct filter,?I got a Nanovna to measure the real terminating impedance, but I wasn't not able to get good results from it. After calibration the Nanovna reports an impedance of 120 ohm with open circuits, denying any reasonable measure different from 50 ohm. I subscribed to a Nanovna group to understand wether a solution is possible. I'll keep you informed.?

Also, once the full RX performances will be verified, I plan to check in depth the TX modulation paths because I suspect that some AGC behaviour will need attention.

And what about your new IF buffer??

Enrico IK2XEI

Wow: there have been a few "douzies" submitted recently. This is another one that doesn't trigger anything in particular:

I haven't seen anything like this with my one 1983 rig. BTW, it performed very well in the ARRL Field Day contest last weekened, where I operated a 1D station from my basement. Next weekend I'll do the Marconi CW contest, but I'm going to fire up the Henry (vs going barefoot).

Based on the symptoms, I might suggest the following obvious ones:
1. Clean the opto-interrupter on the VFO knob. I don't "think" that is the case ... but you never know.
2. Measure the power rails that feed the uC/memory and interrupter. It sounds like it could be a bad/leaky cap ... I've seen them where they are getting "borderline", and when they heat up they shift enough to cause issues.

Anyhow, just my two cents, and not even worth that much ...?

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-Mat Breton, N8TW

Got one with an interesting problem that I thought I'd throw out to the group before digging into it:

The particular '980 in question was my main 20-40-75M rig for a number of years, where it's always worked flawlessly. I moved it into the digi-modes operating position (where tuning is predominately done via CAT control). I fired the rig up today after an extended "off" period of a few weeks and wanted to do a little tuning around the bands with the VFO.

The problem is that the VFO doesn't want to tune reliably after the rig has been on for a few minutes. Going up in frequency results in almost no change, while going down shifts the frequency somewhat...though not as smoothly as a properly working rig. Spinning the VFO knob rapidly allows for tuning - albeit jumpy - in either direction.

The Band Up/Down and 5KHz Up/Down buttons work properly.

I'd seen the condition once before with this particular rig. Changing the memory backup batteries fixed it then, but now is a different story. It's also misbehaving with no batteries installed.

Anyone seen similar weirdness with theirs?

73 - Fred, N8YX

I wonder if I could drop in an MLCC ceramic in place the electrolytic: TDK?FG14X5R1E226MRT00 for example would have negligible ESR and parasitics well past 100MHz. Definitely added to the list to check out ... I also have a new IF buffer circuit to put in (panadapter), and a new backup battery case.

I wonder if there other pin-diode switched circuits (shared xmit/rcv circuits like the filters maybe) that are also ticking "time bombs"?

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-Mat Breton, N8TW

First off, congrats on having TWO FT-980's!

Wow: I watched this video twice. I haven't seen this one before.? I'm going to have to mull this on over.

First off, I'm not sure why the FM VFD segment doesn't come on when the switch is in FM. Then we have the whole boots up OK in FM, but not in other modes. And if you switch to any other mode from FM it switches. Very likely all related ... but it isn't triggering anything yet. I'm going to have to look at the signal paths to see if I can see something. I wonder if we lost a uC I/O multiplexer or something ... they have been known to die.

Q: Can you check to see if it is actually transmitting (is it in transmit mode), either by checking the TX-GND pin on ACC2, or check the actual power output when using? a mic or something?




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-Mat Breton, N8TW

Hi Mat,
Here is a quick video clip of the actual issue.?

?

I did notice that while making this video clip, the receiver seems to switch on when the mode switch is in the FM mode even though FM doesn’t appear while in this state.?

Hi Mat, thanks for your kind reply. Sorry for pictures not being uploaded, I'll try again right now.?

I do not have VNA, I'm thinking to buy NanoVNA because I read very positive reviews, but now I use a Siglent SA that is enough for my present needs. Also, a HF RF Bridge prototype is waiting for me for many months?in order to be finalized, let us see next future...

About the modification: the cold side of each bandpass is RF grounded via capacitors, so the bandswitching PIN diodes can act being diven by direct or reverse polarization. But so doing the filter cold side is not really a solid RF ground because the capacitors are not ideal, an a low value resistance is inherently present inside. So the ultimate attenuation values far from the bandpass region is dependant on this residual resistance. You can also imagine the filter as a frequenct selective attenuator, where the ideal ground path has a low value resistor in series to the real ground, so that the desired attenuation out of band can't be achieved. Probably 40 years ago the electrolytic caps within the equipment were good enough for the purpose, but after this long aging the ESR tend to raise. I simulated the original circuit inserting a low value resistor in series to ideal bypass caps obtaining responses thhat are very similar to the real behaviour.?

Yesterday I built a prototype of a 28-30 MHz filter that could replace the original one. Measuring it as a stand alone unit results are very good, next days I''ll try to put it into the rig. With a very little arrangement the new filter can be referred to the real solid gnd and in theory no adverse spur variables will worse the ultimate out of band signals rejection.

Kind regards

Enrico IK2XEI

Hi Enrico,

I'm very interested in your work. Unfortunately your pictures did not make it through. Can you link through dropbox, or maybe try again?

Do you have access to a VNA (like a nanoVNA)? It would be interesting to see a S21 (or S11 into a 50 Ohm load) through the BPF segment. A entire HF sweep would be ideal, one or each of the band selections. I might do it myself next time I have the rig open.?

What is your theory? Without the electrolytic cap bypassing RF when the Filter line is not pulled low, that the BPFs were "self activating" through RF, and therefore multiple BPFs were "open"? Seems plausible, if that is your thinking ...

Kind regards and thanks,

Mat, N8TW




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-Mat Breton, N8TW