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.

RF Sampler

Discussion in 'Home Brew' started by Moleculo, Jan 21, 2009.

  1. GnG8d

    GnG8d Well-Known Member

    Joined:
    Jun 28, 2010
    Messages:
    2,037
    Likes Received:
    334
    I took the strap out and changed it to a wire for the toroid. There aint a whole lot of room in there, so I had to pull the resistor and mount. One thing I didn't take into account, is that the strap bent into an "L" actually held that end of the resistor up :whistle:


     
    Old_Crow likes this.

  2. Robb

    Robb Yup

    Joined:
    Dec 18, 2008
    Messages:
    11,404
    Likes Received:
    3,426
    OK - its a 100 ohm resistor.
    But is it a metal film 2 watt or 5 watt resistor?
     
  3. Captain Kilowatt

    Captain Kilowatt Professional Amateur
    Staff Member

    Joined:
    Apr 6, 2005
    Messages:
    16,513
    Likes Received:
    10,115
    Value doesn't matter as all it does is drop the voltage going into the scope and as long as the scope will handle it then fine. I can't believe the sample voltage will ever be high enough to damage the scope however unless unGodly power is used. As for power rating even 1/4 watt will do as there is no current being drawn by the scope.
     
    Old_Crow likes this.
  4. GnG8d

    GnG8d Well-Known Member

    Joined:
    Jun 28, 2010
    Messages:
    2,037
    Likes Received:
    334
    Here is how the dummy load sampler turned out BTW.


    [​IMG]
    [​IMG]
     
    rabbiporkchop likes this.
  5. MrSuburban

    MrSuburban Guest

    Joined:
    May 25, 2010
    Messages:
    393
    Likes Received:
    9
    I drilled a hole mounted the bnc made a 1 turn 1" ID coil inside connected to center of bnc and ground. works like a champ.
     
  6. Crusher

    Crusher Well-Known Member

    Joined:
    May 12, 2007
    Messages:
    837
    Likes Received:
    351
    I was wondering what mix toroid everyone used. wish i knew about this a week or so ago. just bought a sampler that fits slug for a bird and one that connects to side of meter. Going to build a couple of these as well.
     
  7. Kamikaze

    Kamikaze Active Member

    Joined:
    Dec 27, 2010
    Messages:
    318
    Likes Received:
    7
    A toroid is good for lower power. You really don't need it with anything over 10 watts at 30 mhz. A turn or two around the insulated center conductor will output a few volts at 1 kw into 50 ohm terminations.
     
  8. Crusher

    Crusher Well-Known Member

    Joined:
    May 12, 2007
    Messages:
    837
    Likes Received:
    351
    Ok, good to know. A friend told me the same thing. I was just double checking. Needed something to monitor a 6000.
     
  9. LeapFrog

    LeapFrog Wielding Hanlon's Razor

    Joined:
    Feb 15, 2016
    Messages:
    1,705
    Likes Received:
    846
    Im almost ready to view my carrier on the 'scope!
    I know this is an OLD thread but most posters involved are still active, my question is: is this an "inductive" sampler because of the toroid transformer? And what should I build?

    Compared to this resistor divider / capacitive coupled sampler designed by a Bob Heil (K9EID) I noticed in Ham Nation episode #110.
    Schematic and overview found here
    http://n9sja.com/2013/10/06/rf-oscilloscope-sampler/

    For around 27-28 Mhz would I be ok using the design wich uses resistors and a capacitor or should I build the one Moleculo posted?
    Advantages/Disadvantages to each design?
     
  10. BBB

    BBB Well-Known Member

    Joined:
    Jan 17, 2012
    Messages:
    744
    Likes Received:
    395
    If others don't want to construct a device, Rf Parts (and others) supply a Unidapt brand RF sampler that works great and can be had for less than $50. Just select and order what coax connectors connectors you want to use on the inline device.

    https://www.rfparts.com/rfa4059a1.html
     
  11. LeapFrog

    LeapFrog Wielding Hanlon's Razor

    Joined:
    Feb 15, 2016
    Messages:
    1,705
    Likes Received:
    846
    A very valid point by BBB one could be had for a fair price, any ideas on this:
    Thanks
     
  12. LeapFrog

    LeapFrog Wielding Hanlon's Razor

    Joined:
    Feb 15, 2016
    Messages:
    1,705
    Likes Received:
    846
    Well I learned the hard way that I cannot edit my post this long after I sent it.

    For Low Power 1-5 Watts, and 11 meter frequencies should I build wich style?
     
  13. Old_Crow

    Old_Crow Active Member

    Joined:
    May 11, 2016
    Messages:
    70
    Likes Received:
    63
    I used this for CB channels and it was less than $10 to make
    rfsamplediag1.jpg
    I made 1 change,put a 20K pot instead of the resistor to ground. Works great!
     
    LeapFrog and Steve_Buckeye like this.
  14. LeapFrog

    LeapFrog Wielding Hanlon's Razor

    Joined:
    Feb 15, 2016
    Messages:
    1,705
    Likes Received:
    846
    Old Crow Thank you, I will build the design published by K9EID.
    That potentiometer to ground allows for adjustments to be made, what does the variable compensate for/ allow for over the fixed value. Different power levels? It basically forms a voltage divider I can see that, just curious why the added ability to change the resistance?
     
  15. BBB

    BBB Well-Known Member

    Joined:
    Jan 17, 2012
    Messages:
    744
    Likes Received:
    395
    The Unidapt RF Samplers are adjustable as well by loosening the lock ring on the BNC connector shaft then slide the BNC connector in or out for more or less sensitivity.

    Good luck with your home brew unit (y)
     

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!