Yaesu has it wrong! FT-891 RX/TX Current Test

Discussion in 'Amateur Radio News' started by OH8STN, Mar 13, 2018.

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  1. KJ6ZD

    KJ6ZD Ham Member QRZ Page

    I take it, the test was done into a good 50 Ohm resistive load.
    If not, mileage may vary greatly. A 50 Ohm Z can be achieved with more capacitance or inductance, changing the whole game.
    RF current and voltage can be out of phase (should be IN phase) and mimic a certain power, but at less current draw (reactance).
    Also, the manufacturer does specify, as some said, to a worst case scenario.
    In some case, the output power can be more than 100W, most final amplifier stages, in modern HF rigs, can produce well beyond 100W.
    They can peak beyond 100 Watt and we wouldn't know about it. These peaks are for just a few milli seconds and could draw the 23 Amps for the same amount of time.
    Because of the very short time, it is probably not of interest to portable operators, unless there is a lot of keying and un-keying over a long period of time.
    This might add to the all over power consumption from a battery.
    The measured current, with standard HAM equipment, is merely a guide....

    I once did a test with a Kenwood TS50, modified the heck out of the final stage, bringing it up to roughly 300 Watt, however just for testing purpose.
    What keeps it from staying at this power is the "pseudo SWR circuit" manufacturer call it protection circuit, which will reduce power if the reflected power exceeds a preset value.
    Most final transistors, can handle a mismatch (SWR) of 30:1 or until they start to oscillate, which is their death wish.
    Also, the thermal dissipation, would have to be redesigned to keep it from burning up, hi, hi...
    Point is, they can produce for very short times more than the rated 100 Watt and this is what the manufacturer use in their specs.

    A precise test would always have to be done into a precision 50 Ohm load (return loss -25dB or greater / SWR 1.1:1 or better), with a peak read and hold current meter.

    Edit:
    The average current measurement is a good guide to estimate the approximate run time out of a battery in good condition. The actual output power will vary on the different bands, due to thermal load condition (higher frequency = higher temperature), whereas builtin circuitry tries to compensate at the given frequency.

    Cheers,
    KJ6ZD, 73
     
    Last edited: Mar 16, 2018
  2. OH8STN

    OH8STN Ham Member QRZ Page

    The filtering is incredible!
    I never had a rig with filtering, incorrectly believing I would be missing something, had filters been enabled. My ridiculous assumption could not have been more wrong. The filtering in the 891 is astonishing. weak gGateways, nodes and digi stations which were unreadable previously, can be isolated and brought to perfect readability using the passband, and/or by pushing down the noise floor with the DNR set on level 2, from what was previously an s5-7.
    The thing which gets me. Yaesu has proven it can build a portable rig, with an excellent receiver and filtering, but still chose to release the 818!? WTH?
    I'm sold on this rig!

    73
    Julian oh8stn
     
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  3. KK5R

    KK5R Ham Member QRZ Page

    RMS (Root Mean Square) readings are at play here. The same thing happens with the SWR readings and protection in a transmitter. If everything were done instantaneously, though, we'd probably hear a sloshing of hash similar to a high freq ripple (if it were not somehow suppressed).

    You are right; just reading the peak voltage and current and not correlating them into an average peak shows up as a much higher power. The readings have to be in phase to make that power reading meaningful if instantaneous readings alone are used. Because they cannot be perfectly in phase unless in an ideal world, the SWR protection circuitry does not average it all out and use the power reading for protection. It protects the devices for maximum voltage alone, usually, because over-voltage is an instant killer for solid state devices. However, both too-high voltage or current not only can but will destroy solid state devices. If either of these is allowed to wander into the forbidden zone, we can get smoke or power supply shutdown.

    Voltage can destroy because it causes a form of arcing across the internal elements and Current because the higher current causes thermal destruction which may take a few milliseconds longer but in either case, you end up replacing those expensive power transistors.

    If the last phenomenon is contemplated with the transmitter, it suddenly becomes a case of being sure the voltage-current peaks are well within spec lest you want to ignore the "Better safe than sorry" axiom and become a statistic.

    I sigh in relief when my FT-450 barks at me and shuts down the drive to the finals when the SWR is too high. I do not care very much as to why Yaesu put that protection circuit in there but I happily accept it as something good being done for me, saving me the expense of replacing finals. I then check out the reason for why the protection circuit burped before going further. Thank goodness it has not happened very often.
     
  4. AI6MC

    AI6MC Premium Subscriber QRZ Page

    I've had the 891 for just over a year. No measurements taken. I use it mobile with a 12V 20Ah 240 Watt Hours solar powered Lithium Iron Phosphate battery.
    During the August Solar Eclipse, I was camped out for 4 days in Idaho and used the radio regularly. Probably more listening than transmitting but I did my share.
    I kept the radio on for 3-4 hours at a time.
    At home, I use the radio as a second rig in my shack attached to a 7 band dipole. I use it for FT-8, JT65 and phone on 40 and 80 mostly. I use the same battery pack in the shack.
    I have not noticed any problem with it draining the battery pack in any undue manner.
    I am perfectly satisfied with the radio. Filtering on this radio is more than acceptable right out of the box. This is my first Yaesu.
    Seeing it in action, a couple of friends have purchased the radio and say they are happy with the performance.
    The photo is of Gordon West showing my 891 setup to a group of HAMS at Quartzfest.
     

    Attached Files:

  5. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    The 891 is a weird beast.

    The continuing problem with the rig turning off DSP and losing some settings between band changes is annoying. Mine hisses, unless I use a coms speaker, or headphones made for ham coms. I have heard that newer models don't do this.

    There are days when kicking-in the NR will allow me to hear a signal that the more sensitive Icom 7300 can't clean up at my noisy QTH. Overall, I much prefer using my 7300, about 90% of the time.

    Still, it's a lot of radio for the cheap price.

    I plan on selling mine before I leave Korea for the USA. I wrote a full review on it, but need to add that this is just not a good radio for digital modes, due to the documented clicking noise issues that take place over cat control. It can be made to work, but my honest opinion is that it is best avoided, if you are involved in digital work. I feel very much like Yaesu used early adopters as their R&D bug-finding team, then acted oblivious to the problems while they quietly fixed issues in newer releases. One guy with serious documented CAT clicking problems sent his in, and Yaesu refused to admit the issue. I believe he was out shipping, and they did nothing for him. He was pretty upset, and has a few videos on Youtube both showing the issue, and discussing the Yaesu response. No doubt you'll find out about it, via Youtube search.

    Here is my exhaustive review, including updates after 8+ months of use:

    http://thestingyham.blogspot.kr/2017/08/yaesu-ft-891-review.html

    I have also experienced the ARRL's warnings about it being dirty with IMD on transmit. It will probably get into other nearby rigs close-by on a field day, if you run it above about 20w to maybe 50w. My neighbors have lots of cheap, unfiltered Chinese crap speakers on their computers. My daughter's boom box is the same. This radio gets into those moreso than my Icom 7300 does, on one mag loop antenna I was using. I dumped the loop. Don't seem to have a problem with horizontal dipoles and my wire yagi. Purists may want to avoid this radio, based on IMD, alone.

    This radio will be attractive for portable SSB and likely CW ops. It will be good in a car. I no longer suggest it for use as a home rig. I'd probably pick a Yaesu 450D over it, if I had to do it over again -- but the 891 does certainly have better DSP. Guess I'm just tired of pushing lots of buttons to do stuff. These tiny rigs all have that issue.
     
    Last edited: Mar 17, 2018
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  6. KK5R

    KK5R Ham Member QRZ Page

    Also liked your QRZ bio page... I'm guessing that's not you on the ladder?
     
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  7. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    Yeah, not me.

    That guy went to way too much trouble making sure he was balanced, before climbing up. ;)

    My HL1ZIX page has far more photos and info about what I'm doing, antennas I have built, etc.
     
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  8. KK5R

    KK5R Ham Member QRZ Page

    Thanks for the information.

    I enjoyed even more the HL1ZTX bio. You have a lot to envy and I'm sure you are proud of it. I'm also an antenna experimenter but don't have much time for it — not as much as I would like. You have a precious family, too. :)
     
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  9. N8DAH

    N8DAH XML Subscriber QRZ Page

    Nice review, I tested the 891 at field day last year running PSK31/CW/SSB with a station in the same tent as well as all antennas within 200Ft or less. They got pretty much zero interference from me, I on the other hand had issues every time someone keyed SSB. It was easy to time my cq's, no one seemed to notice when I was TXing digi modes. We even had the other ops listen for it to make sure, while some reported a slight movement in the noise floor it didn't have any effect on their ability to make qso's in the slightest. Only issue I had at the QTH with digi modes was TXing to close to my PC but that was not the radios fault.

    The digi modes did have a click or chirp but, if you turn off "port interrogation" it will go away. The only negative is if you make changes using the radio the software won't see it, you can still control the radio via software and the rig will update. This does not remove Yaesu from having an issue but did make the rig run digi w/o the click.

    For the buck it was a good starter rig for sure, I wouldn't say digi is out of the question just comes with a click that you can either ignore or make changes.

    I too have a 7300 that I had a chance to use side by side before I sold the 891 and feel that my 7300 was much better in pretty much all aspects. I also feel its not a fair comparison though.

    Julian,
    Keep up the good work always enjoy your vids!

    73
    David
     
  10. K4JTP

    K4JTP Ham Member QRZ Page

    I wonder if you tried it with the back light at minimum? It might not make a lot of difference but it might be a little. K4JTP
     

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