1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
    Dismiss Notice
Dismiss Notice
This forum does not allow a single user to have more than one username. If anyone wants to change their username contact an admin and it will be done. Multiple accounts belonging to the same member will be deleted without warning.

The next generation of linear amplifiers has arrived.

Discussion in 'Amplifiers' started by Shockwave, Sep 5, 2019.

  1. linearone

    linearone King of NY

    Joined:
    Apr 2, 2005
    Messages:
    615
    Likes Received:
    8
    Sooooo, is this thing for sale anywhere yet?

     
    Shadetree Mechanic likes this.

  2. sp5it

    sp5it Master of puppets

    Joined:
    Jul 9, 2009
    Messages:
    1,914
    Likes Received:
    2,169
    I doubt it's even in prototype stage
     
  3. Shockwave

    Shockwave Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    3,744
    Likes Received:
    3,150
    Yeah, I get the point. It's time to show the next step. Locally, we have four of the one transistor and a pair of the two transistor models, working for over a year. The entire project has taken much longer than anticipated and this is a part time job for me. It just keeps expanding with the push to go bigger and better with the four transistor model.

    While we have had the four transistor PA board working for many months, it did undergo revisions to improve RF layout once the final splitter and combiner arrangement was decided upon. Since we announced a working four transistor PA, it shifted most interest away from the smaller versions and local people are holding out for the completion of the four transistor version.

    The goal post keeps getting pushed further down the field with well over a thousand dollars worth of transistors needing the type of protection required to offer the unheard of, lifetime warranty. The protection board used on the 4 transistor model is now up to 8 channels, where it monitors 8 different parameters in order to allow normal operation. All of these circuits are strictly analog and avoid the use of a microprocessor to insure the highest level of RF immunity.

    The last one has been the trickiest and most innovative. How to protect against a severe overdrive condition, WITHOUT applying that overdrive to the transistors first... In other words, not only will the amplifier shut down if the drive rises above a certain limit during operation, it won't even allow the TX relay to key unless the drive is first within the preset limits. That entire circuit is nearly done and ready to test. Meanwhile, things like the PEP op-amp board have already been built and perfectly calibrated against the Bird 43P.

    Now that we know the deck height , we still have to make a front and back panel and build the wiring harness to connect everything to the existing PA board. Being this close to a finished product that I can demonstrate like the two smaller ones, has me excited and eager to complete it soon. I've reached the point where I'm more than happy with the amplifier performance and now it's time to package it up into something presentable.
     
    #198 Shockwave, Dec 19, 2020
    Last edited: Dec 19, 2020
  4. Shockwave

    Shockwave Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    3,744
    Likes Received:
    3,150
    The following videos show completely functional prototypes of two different models. The third and much larger, is coming soon.




     
  5. AudioShockwav

    AudioShockwav Extraterrestrial Admin
    Staff Member

    Joined:
    Apr 6, 2005
    Messages:
    6,724
    Likes Received:
    3,755
    Excellent protection.
    That's about as simple to operate and error proof as you can get.


    Lifetime warranty.
    That is a bold step in today's market.
    Looking forward to the next model.

    73
    Jeff
     
    G GOLLY WAlly, wavrider and Shockwave like this.
  6. Shockwave

    Shockwave Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    3,744
    Likes Received:
    3,150
    The simple LDMOS protection boards they sell online, only monitor drain current with forward and reflected power, when you add your own line section. Thermal protection is easy with the right sensor and location. That keeps the output transistors safe most of the time. It's even able to detect overdrive conditions by excessive drain current or forward output power... to a point.

    The trouble is, this technology depends on the overdrive condition passing through every part of the amplifier, before it can even be detected, in order to trigger protection circuits. That's fine for perhaps a 50 to 100% overdrive condition, if the settings were adjusted with enough headroom to allow the circuit the time to save the transistors. What happens if some idiot decides to place a "driver" in front of it and hits it with 10db or more of excessive drive?

    By the time that overdrive condition makes it to the output where it is being detected, chances are slim that the protection will be able to do its job in time. The overdrive condition needs to be detected much earlier in the amplifier, preferably at the input connector. Now it can be triggering protection circuits before the drive has to even be applied to the transistor gates. This is likely to be another "first" and makes something like that lifetime warranty, at least a possibility.

    This protection board allows another easy to add feature. That is a user adjustable power limiter. For example, if a specific maximum power output is required for any reason, you could set a front panel control to trigger a shutdown, in the event exciter power ever moves beyond your preset limit.
     
    AudioShockwav likes this.
  7. nomadradio

    nomadradio Analog Retentive

    Joined:
    Apr 3, 2005
    Messages:
    4,776
    Likes Received:
    6,436
    I would simply insist that the thing be keyed like any other HF amateur amplifier. Through a patch cord. Ground the center pin, the amplifier is active.

    The trick is to shut down drive to the transistors before the safe limit is reached, not afterwards. A "too late" protection circuit isn't all that sexy.

    Using a typical RF sensor/built in keying circuit like a CB linear creates a problem. How do you detect the excess drive amplitude before it can cause harm?

    Afterwards is too late.

    The protection circuit will most reasonably be monitoring the RF level at the input all the time.

    The closure of a circuit in the radio that grounds the center pin of the amplifier's "relay" socket will only activate the changeover to feed drive to the transistors if it's already under the limit. This protects you from an overdrive signal already present on the input when the input relay activates.

    But if the drive peaks exceed the limit only a bit later, what then?

    Makes me wonder about how long a delay line would need to be. A thousand feet of coax between the input relay and the transistors' gate circuit would allow you some time for the peak detector and shutdown to respond quickly enough, maybe?

    Sure wouldn't need to worry about coax loss. An attenuator by any other name?

    73
     
  8. Shockwave

    Shockwave Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    3,744
    Likes Received:
    3,150
    The protection that inhibits the TX relay functions the same way regardless of if the amp is keyed through an RCA plug or a transistor. This part of the protection shuts down positive DC to the relay so that it doesn't matter what the ground side of the relay is doing through the RCA or a keying circuit.


    Before adding a delay to the drive, we should look at removing delay from the protection. The two biggest killers slowing the reaction time of overdrive protection are relying on a relay to be fast enough and triggering by monitoring the output side of the amp. If we continuously monitor drive power as it's being applied and use an electronic crowbar to shunt the transistor gates to ground, long before a mechanical relay could remove excess drive power, the bulk of that delay is gone.
     
  9. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

    Joined:
    Oct 23, 2017
    Messages:
    4,428
    Likes Received:
    6,842
    Sounds like the last amplifier I would ever need to buy. I am definitely interested when they become available.
     
    CherokeeSoccer likes this.
  10. Mr Fix it

    Mr Fix it Well-Known Member

    Joined:
    Dec 7, 2012
    Messages:
    119
    Likes Received:
    107
    I learned a long time ago, you cannot rush perfection

    If anyone would want it to be done , that would be me who has a exponential amount invested

    This latest model will be worth the wait I can promise you all that.

    We will make a much more comprehensive video on this one

    As shockwave stated , this is a part time project for him. With that being said , this is full time for me. Day in and day out. 7:30 am to 5:30 pm non-fri. With no distractions, no kids , no habits . I am setup for this type of work with near unlimited resources.

    I am well known for lightning fast builds . Never has a tube type rf amp taken me over 1 month, in reality usually 2 weeks to complete and ship . I can guarantee that the same will apply for these.


    I stock parts even the expensive ones unlike most. And do not procrastinate.

    I have since retired from building tube , just no money in it when using the proper, new, used and surplus parts. Just not enough net profit. Repairs of tube type rf amplifiers far exceed the net profit of a fresh ground up build or re build .

    looking forward to the fcc type acceptance


    Happy holidays all
     
    #205 Mr Fix it, Dec 20, 2020
    Last edited: Dec 20, 2020
    Shadetree Mechanic likes this.
  11. nomadradio

    nomadradio Analog Retentive

    Joined:
    Apr 3, 2005
    Messages:
    4,776
    Likes Received:
    6,436
    It is said that no work of art is ever really complete. The artist simply chooses an arbitrary point at which to walk away.

    Aiming for perfection means you'll take forever trying to achieve it.

    Engineering is the art of "how close is close enough".

    A well-engineered product can never be perfect. But it can be good enough to actually get produced.

    73
     
    Crawdad, Robb and freecell like this.
  12. Shockwave

    Shockwave Sr. Member

    Joined:
    Sep 19, 2009
    Messages:
    3,744
    Likes Received:
    3,150
    The flip side of that, is a lot of poorly engineered products actually get produced too.
     
  13. Mr Fix it

    Mr Fix it Well-Known Member

    Joined:
    Dec 7, 2012
    Messages:
    119
    Likes Received:
    107

    My perception of perfection in this instance is, a piece of equipment that you can turn on and use and then turn off. Turn on and use without being scared of blowing it up.

    That is well protected from mistakes it may encounter due to operator error or other unforeseen issues with the station setup.

    As no operator is perfect , Protection is a must.

    As solid state devises especially these , are not as forgiving as tube type based equipment.

    Tube rf amplifiers should also utilize a protection circuit.

    Transistors should not be looked at as a consumable like a tube in a well built properly run amplifier .

    Although a consumable, an electron tube should still last many years , I have seen 20 plus when used in a ham icas environment.
     
    #208 Mr Fix it, Dec 21, 2020
    Last edited: Dec 21, 2020
  14. Mr Fix it

    Mr Fix it Well-Known Member

    Joined:
    Dec 7, 2012
    Messages:
    119
    Likes Received:
    107
    Official site for the new amplifiers

    vdmosamps.com
     
  15. Alexis Mercado

    Alexis Mercado Well-Known Member

    Joined:
    May 17, 2016
    Messages:
    199
    Likes Received:
    122
    It says coming soon ! Stay tuned . How is it ?
     

Share This Page

  • About Us

    The WorldwideDX Radio Forum was originally established in 2001. We pride ourselves on welcoming Radio Hobby enthusiasts of all types, while offering unbiased, informative, and friendly discussion among the members. We are working every day to make sure our community is the best Radio Hobbyist's site.
  • Like us on Facebook

  • Premium VIP Member

    The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. Care to buy us a beer? We'd really appreciate it!

    Donate to us!