MFJ Cub Drift issues?

Discussion in 'QRP Corner' started by KD5JBK, Aug 5, 2017.

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  1. KD5JBK

    KD5JBK Ham Member QRZ Page

    I was looking around the web for a decent and inexpensive 1st 40cw qrp kit and stumbled across the MFJ cub. A little bouncing around the webs brought up some old posts and info about the rig drifting horribly for the first 20-30 minuets or so then it settles down. I was wondering if the current versions have had that issue addressed and fixed or not. I am just starting out with my tech license and am learning code. I know QRP is a challenging way to enter the CW arena but I do love a good challenge. If the above kit is not worth the trouble what would be a good alternative? My ultimate goal is to be able to afford and build a K1 but that kind of $$$ isn't in the cards right now as I am having to setup my station from scratch right now.
     
  2. VK3YE

    VK3YE Ham Member QRZ Page

    This is a new product so hasn't had much of a track record.

    http://qrp-labs.com/qcx.html

    However other products from them have been highly rated.

    It's a far more modern design (I think the MFJ Cub was 1990s) so should be much more stable due to its' DDS VFO.
     
  3. G4COE

    G4COE Ham Member QRZ Page

    There U kits a cw only four bander but it's $270 see https://youkits.com/
    it's already assembled and ready to go with 4 Watts RF out and DDS controlled, it can resolve SSB no problem. Certainly no drift at all with DDS vfo's

    Plenty of circuits around to knock a qrp rig up, many of which are vfo controlled.

    Dave
     
  4. KL7KN

    KL7KN Ham Member QRZ Page

    You actually have a lot of very good choices for a nice station:

    On the low dollar end of things-


    NG9D has several vids - this one shows a station made of a Sony SW7600 and a cheap - and I mean cheap Ramsey kit TX. Like under $10 dollars cheap (http://www.ebay.com/itm/RAMSEY-40M-TRANSMITTER-1-WATT-CW-QRP-TRANSMITTER-AND-MANUAL/152628275733) -These show up flea bay from time to time. This really is to show just how basic astation can get and still communicate....

    The chirp is a free bonus that could be fixed with a better regulator.

    Fun stuff - eh?

    For a bit more $, but with a bit more TX power out:

    http://www.ebay.com/itm/QRP-40-Mete...s-extended-range-7-023-7-058-MHz/182681826263 $45 and includes shipping. SMT parts already mounted

    http://www.ebay.com/itm/NS-40-40M-5...e-Simpler-Class-E-IRF510-Classic/253048630167 $30 + shipping. NO coils to wind - from the very well done group at 4 States QRP
     
    KD2RON likes this.
  5. VK3YE

    VK3YE Ham Member QRZ Page

    Whatever you go with I strongly suggest something that's frequency agile over a good section of the band.

    Because in most cases you need to search for contacts with low power, crystal control is too much of a handicap (unless you've got other rigs and are just building it as a novelty).

    Some ideas on things to look for in QRP kits are on my website at http://home.alphalink.com.au/~parkerp/qrp/equipment.htm
     
    KK5R likes this.
  6. N8AFT

    N8AFT Ham Member QRZ Page

    I have not heard much any drift with ops using the Cub model.
    I have routinely heard drift (esp when cold) with the larger MFJ single bander.
     
  7. WA9UAA

    WA9UAA Ham Member QRZ Page

    There are easily found and done mods for the Cub, especially if you've built it your self.
     
  8. K8JD

    K8JD Ham Member QRZ Page

    I built MFJ cubs for 40 and 80M, this was quite a few years back and there were articles in the ham pages about replacing some of the capacitors in the VFO circuit, my 40M was not bad but the 80M version did have some drift but settled down after a while.
     
  9. N8AFT

    N8AFT Ham Member QRZ Page

    Ordered a new 40m Cub today. R&L had one assembled in stock. I hope to give it a shakedown QSO with you this week John.
     
  10. N8AFT

    N8AFT Ham Member QRZ Page

    Got the new Cub yesterday and tried it out. Answered a CQ with another QRP op in GA and carried out a good QSO for about 20 minutes. !.5 watts output feeding my full wave doublet.
    The Cub was drifting the entire time both on RX and TX. The tune pot is extremely sensitive also.
    I've left it powered up while I'm off to work so maybe after 15 hours of being turned on the little caps will reform and the drift will not be as apparent. If not I plan to ask for a credit against something else later today.
    Nice little rig but no good the way it is es just outta the box.
     

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