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Penetrater HB-200

Discussion in 'Amplifiers' started by Shadetree Mechanic, Aug 9, 2018.

  1. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    Checking out an amp that one of our locals is letting me use. I am interested in using it for side band and it does have the SSB switch. He said he wants $200 and I hooked it up and it works, but I have a few questions if anyone has used this amp before. I am currently using a TS350HD and am looking for more power, the guy told me it is a 4 pill but I don't want to kill it if it is a low drive.
    #1 how much drive will it take? I am dead keying 3 watts and getting 75 watts swinging to about 200. Does this sound right?
    #2 The SWR is low except above channel 23. Then it is 3:1. Is this from the 23 channel days?
    I don't want to pull the cover off just yet as I am using it on a trial basis.

    IMG_20180808_193319542.jpg


     

  2. nomadradio

    nomadradio Analog Retentive

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    I remember this one having an unregulated 24-Volt power supply inside. It's a hot rod, and won't tolerate an antenna with high SWR for very long.

    Be nice to it. Driving it with excess power "just once" will kill it forever.

    73
     
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  3. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    I let the guy know about the SWR issue. It only happens with this amp. Not barefoot and not with my other amps. Just this one, maybe the input needs tuning? I let the guy know that I will be giving it back to him and thanked him for letting me try it out. He said he never had that problem with it so I don't know. Might be able to use it as a driver for an 8 pill but I think I will pass.
     
  4. nomadradio

    nomadradio Analog Retentive

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    So, uh, wait a minute.

    Where is the SWR reading in question?

    Measured at the amplifier's input side, with a separate meter and jumper between the radio and the amplifier?

    Or at the amplifier's output?

    Or both? (better)

    If you're driving an antenna, that's one thing. Unwanted extra frequencies tend to drive up the SWR reading.

    A dummy load won't typically do this, since it as a low SWR for all frequencies.

    An old amplifier like that may also be putting out unwanted frequencies, called "spurious" or spur outputs. Amplifiers built to max out the wattage will sacrifice stability to get it. Making an amplifier more stable frequently reduces the power gain. Almost never

    And if the amplifier is unstable and putting out wacky frequencies, there are ways to deal with that.

    73
     
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  5. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    The SWR I was talking about (3:1) was between the amp and the antenna. The dummy load has no problem. When I first hooked it up, I put my Autek meter between the Madison and the amp. Then after the amp is the MFJ Dummy load / Watt meter. Everything looked normal on ch20. So then I put the Autek after the amp to get a good reading on the power and I went up to ch28 and the SWR was way high. So I started taking the station apart to find a coax connection that must have come loose or something. I took the Autek out and the SWR came down on the MFJ so I thought I found something but I didn't it was just that I also switched back to ch20. Ch 24 was ok and ch25 had the SWR needle kind of bouncing around and ch 23, 26 and up had the same high swr all the way to ch40. I just seems strange that 27.235 and lower is ok and above is bad. Its all or nothing and I would think that it would be more gradual as the frequency increased but no.
    Chris
     
  6. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    I pulled the cover off for a quick look. Two Motorola 454s and a 12v output to run a radio maybe. I might try my stock Cobra 29 on it to see if it does the same thing.

    IMG_20180810_212531571.jpg IMG_20180810_212546627.jpg IMG_20180810_213322014.jpg
     
    #6 Shadetree Mechanic, Aug 11, 2018
    Last edited: Aug 11, 2018
  7. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    Ok so I hooked it up to my stock Cobra 29 LTD Classic. All channels out on the Autek are at SWR 2.5:1 dead keying at about 100w. When modulating, the SWR comes down below 1.5:1 and peaks around 200w. The SWR needle barely moves on the Cobra. Maybe 4w dead key drive is too much? The Madison has about 3w dead key.

    IMG_20180810_220025906.jpg
     
  8. nomadradio

    nomadradio Analog Retentive

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    It's a class C amplifier.

    No fixed bias.

    Turning down the carrier increases the harmonic-frequency output. A necessary evil to keep it from sounding terrible and overheating from too much carrier. Your antenna is not tuned for those harmonic frequencies, so you see a lot of reflected power at 54, 81, 108 MHz and so on. The wattmeter can't tell one frequency from another. It just lumps together the energy from all of them in one reading.

    An inline "TVI" low-pass filter usually fixes this. Probably shouldn't use one rated for much less than 1000 Watts.

    The SWR meter when placed between the TVI filter and the antenna should not show the SWR increase you saw without it.

    73
     
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  9. nomadradio

    nomadradio Analog Retentive

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    You will have an unpleasant surprise if you blow out the two MRF454s and try to replace them.

    First time I replaced blown transistors in one of these, I installed the exact, same 12-Volt rated transistor type you see in this one. Just looked at the type number and bought two of those.

    Lasted three days. The customer was not happy.

    I had failed to put a DC voltmeter onto the power supply. Showed about 24 Volts on standby. The voltage regulator inside is for the radio-power jacks on the front panel alone, not to run the amplifier.

    I bought a pair of the more-expensive 28-Volt transistors, put them in and gave it back to the customer.

    I puzzled over this for years. Just how did they get away with "volting" these transistors to twice their rating?

    Of course, they didn't get away with it for long. It did blow out for my customer in 1978.

    Later, it was explained to me that the folks who made these were doing incoming tests on every RF transistor they bought.

    They discovered that the breakdown voltage would vary from part to part. Enough of them would "pass" at 24 Volts to get put aside to build the base-station models.

    The parts that would not tolerate 24 Volts in the tester got used to build mobile amplifiers.

    Just goes to show that "volting" RF-power transistors is not a new thing.
    Replacements for this model should be rated for 28 Volts. Can't remember what we used in 1978. Probably MRF422. But whatever it was Motorola no longer makes it.

    73
     
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