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K7DYY

Discussion in 'Amplitude Modulation' started by N2DTS, Jun 2, 2020.

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  1. N2DTS

    N2DTS Ham Member QRZ Page

    I ordered a transmitter for 80 and 40 meters, and the version 2 audio processor for the D104 base.
    I received the processor a few days ago and put it in a D104 with the correct connector on the cable.
    I then made an adapter and put it into the 3X4D32 rig into the dummy load and checked it out in the mod monitor.
    Version 2 has a jumper for the noise gate, the gate is very annoying, its not subtle, so I removed the jumper
    to disable it.
    It seems to work like VOX, it does not just reduce the gain a bit, it seems more like it shuts the audio off.

    I need to test the compressor/limiter more, it seemed to limit the negative modulation well when I tested it into my Flex, but let the positive mod exceed 100%.

    On my 3X4d32 rig it looked like I COULD over modulate on sudden loud words into the mic.

    There is also no EQ, whatever the D104 gives you is what you get, including real low frequency stuff.
    That would be fine for the class D and SDR stuff, but might be rough on the mod transformer in tube rigs.

    Its a basic design, its not supposed to be a fancy do it all device, to be fair.
    Line level output, not mic level, with a very wide range of output level.

    I think it has a 6000 hz roll off, not brick wall. I am unsure what the typical D104 goes out to anyway.

    It seems fine for a minimalist setup with the DYY transmitter, but not a do it all processor.

    I have a MAX kit to build, that should do almost everything in one device, compression, limiting, phase rotation, preamp, level controls, mixer, selectable bandwidth limiting.

    Should be just the thing for the K7DYY rig.
     
  2. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    The K7DYY processor is tailored specifically for the K7DYY transmitters.

    http://www.wirelessgirl.net/Projects/AMTransmitters/K7DYYaudioboard.html


    We tested this processor with a D-104 on a friend's DX-100 and the resulting audio was terrible because of the impedance mismatch and its frequency tailoring.

    So I would caution using this 2167-based processor on any vintage or homebrew transmitters.

    Pheel
     
  3. N2DTS

    N2DTS Ham Member QRZ Page

    I put it into the screen modulated rig and it seems like it really brings up the background noise, but did not seem to
    over shoot the modulation.
    Most modern compressors have a threshold, the K7DYY does not.

    Also, its 600 ohm line level output so it might not work well into a transmitter expecting a D104 directly into it.
     
  4. WA3VJB

    WA3VJB Ham Member QRZ Page

    I have been curious as to what the K7 wants to see at its mic input. The one at W1AW includes an input transformer for balanced 600 ohms, but the level itself is not broadcast standard line or mic level. They had to substantially reduce the output of the audio processor feeding the rig so that it did not overdrive the input of the transmitter. The processor, an Orban 9300, delivers broadcast line level, so I presume the K7 wants to see a lot less than that, but more than what we would consider mic level.
     
    AC0OB likes this.
  5. WA3VJB

    WA3VJB Ham Member QRZ Page

    Bruce's page says the transmitter comes stock with an input wanting 600 Ohm unbalanced at 0DbM.
    Broadcast "Line Level " is +4DbM so that's why they had to cut back the output of the Optimod. You could also use an in-line attenuator. I think that's what Paul, N2JTD is configuring with his new K7 he has put on the air, but he too has the little pre-amp board initially.
     
    AC0OB likes this.
  6. N4RMT

    N4RMT Ham Member QRZ Page

    I've had a DYY 80/40 for a couple of weeks now. I love it so far! I'm running a D-104 with the new version of the DYY audio processor. I use an REA mod mon and do see 100% negative peaks, but have received stellar audio reports from both W0VMC and WA1HLR as well as many others. I bought the little board just to hurry and get on the air, with plans for a rack of limiters and EQs, but I may leave it as is. I do have my eye on the Inovonics 223 for some better limiting though.
     
    W1TRY likes this.
  7. KA4KOE

    KA4KOE Ham Member QRZ Page

    Finally got my 223 tweaked. Its my first good limiter. Get nothing but outstanding audio reports and run it around 250-275W carrier, with 120% peaks.
     
    W1TRY likes this.
  8. N2DTS

    N2DTS Ham Member QRZ Page

    Takes a while to get one of these transmitters, a month or more.
    I did get the compressor (the new style) but it seems to have no threshold and picks up a LOT of room noise.
    Its more of a compressor then something that reduces gain over a set point, it brings up the background noise.
    Have others found that?

    The gate is annoying, on or off kind of thing and I disabled that.

    It does seem to limit the maximum negative modulation level though.
     
  9. N2DTS

    N2DTS Ham Member QRZ Page

    Ok, I got my 80 and 40 meter version today and tried various setups.
    First off, let me say I am not a fan of this transmitter.
    I want to support homegrown radios and AM equipment and would overlook some things to run such....

    First off I notice that the interconnects on the back are on a 9 pin mic type connector and the one I received was broken and missing a screw.
    No big deal, but the use of a very small 9 pin connector does not really mix with boat anchors or older gear? Seems like an odd choice.
    Ok, no big deal, I solder up a PTT and key on TX wires and hook it up to my system.
    Trips every time. Ok, maybe my T/R relay is too slow or not sequenced, so I hook the antenna directly to the DYY rig.
    The 80 meter dipole has a 1.2 to 1 swr and can take 600 watts carrier without any issues. It has no baluns or traps or anything except wire.
    I key the transmitter and adjust the very small pot with a screwdriver to 250 watts carrier.
    Why can't we have a knob for this adjustment?

    Running a D104 with the dyy v2 processor which brings up the background noise a lot and I get 700 watts pep, about 80% positive modulation.
    80% positive, 80% negative on the REA mod monitor.
    If I increase the audio (pot inside the mic) it can go over 100% negative but will not go over 80% positive.
    Sometimes the protection trips as soon as I speak into the microphone, even at 200 watts carrier and the gain low.

    Switch to the normal audio chain, works better, but still trips out randomly, I suspect its tripping on over 100% negative modulation.
    It will not do over 80% positive but will do over 100% negative very easy.

    Switch to 40 meters, swr is 1.5 to 1 (higher then the 80 meter antenna and the transmitter works much better, it does not trip out
    at 250 watts, but still does not do over 80 or 85% positive.
    900 watts pep is the most I ever see on the watt meter which shows 1200 watts when I run the screen mod rig at 300 watts, so I know it works.
    I have never seen it go over 80% positive.

    When the radio trips out, it can go to the other band, it can change frequency 10 KHz, it can read 3885 on the display and actually transmit on 3875.
    It can have a blank screen or it can be filled with symbols.

    I kind of expected if I ran the thing at 250 watts (not 375 like its supposed to do) into an antenna with a 1.2 to 1 swr and 90% modulation
    it would work, but its not really usable on 80 meters the way it is.

    The flex 5000 does not complain, none of the tube rigs complain, they show good modulation levels and the pep power mostly tracks the
    4 times power.

    I then put a peak limiter in the audio chain with no difference in the end result.

    Ok, so maybe I have to buy a very expensive look ahead peak limiter, but I should not have to.

    This thing is way too fussy. I know people run them, I hear them on the air, and it seems amazing they get them to work
    long enough to make a qso.
     
    W1TRY likes this.
  10. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    I'm absolutely considering it and I know it's going to happen when I go SK
     

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