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Recent content by CCC GGG

  1. CCC GGG

    Texas star 667 trouble

    Yep when you realize going from 1500 Watts to 3000 Watts only adds 1/2 of an S unit (3 dB) it sure is pricey when you might not even illuminate the next segment of the far end receiver’s S meter. Even the gain of going from the typical 100 Watts PEP ham transceiver output to the legal max of...
  2. CCC GGG

    In theory low level modulation

    First a little theory; you can represent an AM signal (which is composed of a carrier and upper and lower sideband) using phasors (not Star Trek type) or vectors as follows: Draw the carrier vector as a reference voltage arrow pointing straight up. Then add a single tone upper sideband vector...
  3. CCC GGG

    Palomar TX-5300 using four MRF421's

    I picked up a TX-5300 on EBay for $81 and just for grins put in a set of four MRF421 transistors. Had to bring the bias down to about 0.4 Volts to keep the thermal runaway in check. Also added 150 ohms in series with 0.1 uFd between each collector and base to help stabilize it. I'm mainly...
  4. CCC GGG

    Palomar 350Z

    When you calculate 20xlog(250/400) and see that 250 W is only 2 dB down from 400 W (less than half an S unit) the motivation gets a bit 'squelched'. In fact the 250'ish level is a good practical level for yakking with the group at night that's spread out over a 25 mile radius. Why run a pair of...
  5. CCC GGG

    Palomar 350Z

    Just a quick follow up. I eliminated the 2 ohm cathode resistor by jumpering around it and no help on the output. The resistor is only in there to give the plate current meter a voltage to work off of. Dang it the 350Z low power output on 10 meters lives on. Maybe I should put an old Datsun...
  6. CCC GGG

    HW-8 on steroids

    I picked up a clean HW-8 a while back and finally did a mod I've wanted to try for a while. I designed a super simple amp using a single MRF-454. It uses a 9:1 broadband balun on the input and output in order to sort of match the 'few ohms, mostly resistive' input and output impedance of the...
  7. CCC GGG

    Dead Key vs Big Swing

    I have a neat vintage Hallicrafters HT-37 that can run true AM or SSB and even DSB-SC (double sideband suppressed carrier). That last mode helps explain the notion of "more than 100%" AM modulation. When running AM with the HT-37 you can adjust the carrier injection anywhere from the equivalent...
  8. CCC GGG

    Why do HF transceivers have such low level AM modulation?

    I have a neat vintage Hallicrafters HT-37 that can run true AM or SSB and even DSB-SC (double sideband suppressed carrier). That last mode helps explain the notion of "more than 100%" AM modulation. When running AM with the HT-37 you can adjust the carrier injection anywhere from the...
  9. CCC GGG

    Why do HF transceivers have such low level AM modulation?

    Seems like a lot of HF radios have ALC that kicks in pretty early when operating AM. In other words when operating SSB the ALC allows the PA output to get to the rig's PEP rated output, typically 100 Watts. But in AM it seems like the carrier's presence "pre loads" the ALC loop so when the the...
  10. CCC GGG

    Palomar 350Z

    I have tried many things to try to bring the 350Z up to what the 300a can do on 10 meters with no luck. The strange thing is I can get about 400 PEP out with the 350Z on 40 meters but max on 10 meters is about 250 or 275 PEP out. But the 300A hits over 400 PEP out both on 40 meters and 10...
  11. CCC GGG

    Palomar 350z bias

    Speaking of sweep tubes for these 70's renegade amps; I get about the same output on the 350Z (250 PEP 10 meters and 400+ on 40 meters) whether I run 6LF6's or 6KD6's or the relatively cheap 6KN6's. The 6KN6's really surprised me since they often go for $10 a tube on EBay. One more comment- I...
  12. CCC GGG

    Palomar 350z bias

    The 350Z I picked up on EBay already had a plate voltage relay installed so the high voltage is only on the tubes when it's in transmit mode. But it sounds like you got the bias dialed back enough. I think a good rule of thumb might be a total idling plate current of perhaps 100 mA with no RF...
  13. CCC GGG

    Low or variable power for 2 pill amp help!!

    If you want to drop the output a bit you can squirrel in a 50 ohm Pi Pad attenuator using three resistors on the input side of the input matching network. Make sure you add it after the input relay so it only comes into play when transmitting. The basic idea here is to simply reduce the gain...