ICOM 7300 not exciting my amp enough for full output

Discussion in 'General Technical Questions and Answers' started by KE0EYJ, Aug 3, 2017.

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  1. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    I'm pretty frustrated...

    I have two radios: Icom 7300 and Yaesu FT-891.

    The Icom 7300 is not exciting my Tokyo Hy-Power 1.2KFX enough to get more than 400w out on SSB in speech. I can get the full approximate 600-630w out in RTTY or CW (max for those modes is less than SSB), or if I whistle I get about 600w on my THP's meter. But if I speak, the peaks on the amp's meter rarely peak above 400w. I am running the 7300 at 95w, which is the max I should be using. I have read that the THP amp can accept a max of 100w drive (but 95w max suggested), which I have tried, but that has little effect on peaks.

    The FT-891 is easily reaching near 700w+ on SSB speech peaks, even at just 85w-90w drive output (the max suggested input for the Hy Power is 95w). It is reaching the full 700+ watts if I whistle. I am driving the ALC to the halfway point, so I'm not overdoing anything with the FT-891.

    I have seen videos of how these THP amps run, and I should be getting 700w+ on SSB peaks, on this meter.

    Is there a way to adjust the Send output of the 7300? I read the extended manual, and all I see is this about some initial setting and a MOSFET setting? I cannot find such a setting in my 7300? Or possibly, I may need external help?

    Please note: I do not have a proper watt meter, but I'm seeing the same issue on my MFJ-962's tuner. There is a substantially reduced total output from the 7300/Amp combo, compared to the 891/Amp combo, but in SSB only. CW and RTTW outputs are fine with the 7300. I have the THP amp's ALC limiter wide-open.


    From the amp's manual:

    Last edited: Aug 3, 2017
  2. K6LPM

    K6LPM Ham Member QRZ Page

    hmmmm ??? Interesting problem... Just a guess on my part. I have run the 7300 on three separate amps without any problems that I am aware. My best guess is that maybe its the ALC circuit cutting back the power on the radio. Try removing the ALC jumper and see what type of output you get without ALC Might be the ALC signal from the amp is too high for the 7300 and is throttling it back more than it needs to or maybe with the other radio it isnt throttling it back far enough?
    Just a thought. See what happens without the ALC and let us know what happens. Just to be on the safe side start at lower output power on the 7300 and gradually increase it until it reaches the proper output.
  3. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    You mean try removing the ALC RCA plug from the amp, but leaving SEND attached? Just tried that, and no effect. I am nowhere near tripping amp protection with the ALC cable removed.

    I'm running my amp using RCA outputs, as specified for non-Icom amps. Were you running non-Icom amps, and using this connection, or the other ACC connection, for Icom amps?

    I don't have another 2xRCA cable to try, so I flipped the red/white so that the proper connections were just working off of the opposite color (kept them same on both ends, of course) and again, no difference. Still peaking about 400w in SSB.
  4. K6LPM

    K6LPM Ham Member QRZ Page

    Well so much for that Idea... i have run both the RCA ALC line and also the ACC plug interface. The three Amps I have used are the Dentron GLA 1000, Ameritron ALS 600 and The SPE Expert 1K-FA
    I have used the RCA ALC and the RCA SEND.
    I am now using the Ameritron interface that utilizes the ACC jack. However the ACC jack is the same as the send and alc with different pins. The Ameritron Interface just acts as a buffer for the send signal to key the amp relay.
    Strange incompatibility with that Tokyo Power Amp and 7300. Wonder if any others are running that same combination. Maybe someone will chime in.
  5. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    It could be watt drive output?

    There is a lot of chatter on the Facebook 7300 forums about various people feeling as if the ALC is too limiting. At first, people thought it had to do with wattage output, but some engineer who offers info on a mod says it's a problem with ALC talk power output, limiting of voice peaks, or some such. Too much limiting?

    Anyway here is a page someone made about the mod (which I won't be doing):

    Could it be that, since my amp requires as high as 95 watts drive, that this issue is more of a problem than the amps you listed? If my memory is correct, those amps all require quite a bit less drive?
    Last edited: Aug 3, 2017
  6. K6LPM

    K6LPM Ham Member QRZ Page

    Try turning the mic gain on 7300 up higher and turn the ALC Adjust on amp fully clockwise or just remove the ALC cable between radio and amp. See if you are getting more power now. I think that maybe your Yaesu just has a hotter output or is punchier due to audio compression or processing. Try cranking more audio or compression on 7300 . Are you using a stock microphone? difference between 400 and 600 isnt that great a difference on the recieving end but it might be a big difference from overprocessed Yaesu audio or superb natural clean Icom 7300 audio?! I dunno, but I know with my Expert 1K FA is rated at 1 kilowatt and I can get 1.2+ some change pretty easily with my 7300 on the peak reading watt meter. My 7300 power setting is max hundred watts . The audio is set at 64% and the compressor is at 3 or 4 using the stock hand mic. I often get unsolicited comments on how good my audio sounds.... My amp ALC is in fact throttling back the output quite a bit as can be noted watching the 7300 ALC meter. The Expert Amp only requires about 25 watts for full output.
  7. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    I turned the gain up on the 7300 higher, and I begin hitting the red of the Icom's meter. I don't want to splatter. Have also removed the ALC cable from the amp, etc. The signal stays about the same. Maybe a smidge more if I'm overdriving the ALC, but not much.

    I have been using the HM-219 hand mic. That seems to peak me at about 400ish, most of the time. I switched to a Behringer XM8500 mic, with adapter, and I can peak about 500w, which is a bit more. I'm still not hitting the 500-600w average that the Yaesu is giving me with the hand mic, or achieving the full 750w peaks of the Yaesu.

    Neither radio is causing the peak protection to shut the THP amp down.

    I'm just getting about 100 to 200w lower average output on the Icom. Still not sure why? Do I need some sort of device to raise the ALC output of the 7300 that the THP amp is getting?
  8. K6LPM

    K6LPM Ham Member QRZ Page

    ok just read your reply and the link to the published mod.
    Yes I believe your reasoning might be correct. My amps dont require as much drive power and appearently according to the article the Icom indeed has a very conservative ALC "time constant" and the mod is an improvement that is supposed to slow how agressively it reacts to the peaks. I would think that would similiarly be like added compression. I always thought of Icom HF radios as not being very hot or real talking radios with lots of punch. I think of punchy radios and I think of classics like the Kenwood 830 with its audio processing or some of the Yaesu 101 line like the EE. While I always thought my Icom 735's were always quite anemic when compared to my friends Yaesu 757 but I always validated the radio by its finer more sophisticated reciever. The Kenwood 430's were somewhere inbetween. I remember that some guys actually would trick the 735 by adding a positive signal to the ALC jack to pull ALC back for use on AM. The 7300 impressed me for being more of a talker for Icom but then again I have been in a major time warp and just walked into the future from being last seen active late 80 or early 90's Think like TS 940 being the top dog radio of the time with lets say a Henry 3k and a TH6DXX being the cats meow...
    KE0EYJ likes this.
  9. K6LPM

    K6LPM Ham Member QRZ Page

    It seems to me it is as what the article you linked to describes. I think its probably just what the radio will actually do... if you didnt have a different radio to compare, perhaps it would go by unnoticed and you would not realize the difference? The mod seems simple enough if you are experienced with a soldering iron and have good average skill with modern circuit boards. I would not be too afraid of doing the mod if I wasnt satisfied. It appears very easily reversible. I however am happy with mine and if it aint broke I have no need to fix it. So I suppose that point is moot. I will step aside and let the more technically knowledgeable or adept add comment. I am just shooting from the hip but it seems you are doing a top notch job of researching this matter. Please continue to post your experiences and whatever else you find out. I think that link was informative and thank you for sharing that tid bid.
    73 Brian
    KE0EYJ likes this.
  10. WA4SIX

    WA4SIX Ham Member QRZ Page

    Is the tuner/wattmeter capable of PEP reading? This usually needs a 12V power source. You may be reading average?
    Otherwise, as stated, run the compression or mic gain up.
    I did not read the mod for the 7300.

    WB5YUZ likes this.

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