The VHF/UHF DX Book

The VHF/UHF DX Book is now out of print. There are no plans for any new or revised edition.

We hope it made a difference for the development of VHF/UHF DXing.

This page lists the corrections in the 2nd printing, and later corrections that are not in any printed version.

  1. Formulae: the font problems in the 1st printing were fixed.

  2. Chapter 3: Some of the specialist newsletters mentioned in the book no longer exist - largely replaced by the Internet!
    For details about DUBUS magazine, click here.

  3. Attenuators: on page 12-14, column 2, the formula for PR2 in a T attenuator should be:
    PR2 = PIN x (R2
    /50) x (1-1/n)²

  4. Directional couplers: In Fig. 12.9, the COUPLED and ISOLATED ports were drawn reversed. The COUPLED port should be next to the INPUT port, and the ISOLATED port should be next to the OUTPUT port.

    In Fig. 12.12, the junction of the 1p0 capacitor and the 22p variable should connect only to the junction of the two 33R resistors (not to D1-R1 and also not to ground). Thanks to GI0GDP, the first person ever to have reported this error in 21 years!

  5. Suffolk transverter:
    The second printing now describes the Mk2 design, re-packaged to fit into Teko tinplate boxes.
    The only electrical change is to the transmit converter, to eliminate risk of inverter noise sidebands due to marginal decoupling of the +12V line: add a 47uF 16V electrolytic capacitor (C41) from pin 8 of IC8 directly to ground.

    All of the PC board layouts are in the book, and you are very welcome to scan them for your own personal use. Here are the files for G4DDK's Suffolk Mk2 28-144MHz transverter:

    These scanned images are not commercial quality, but they are quite OK for amateur PC boards. 
    Note: These images are copyright, and are not licensed for commercial reproduction.

    Many of the components are becoming obsolete and hard to find. Some of the TOKO components are still available from Bonex, now called BEC Distribution Ltd. For semiconductors, try a distributor who specialises in amateur RF components like Barend Hendriksen.

    In the TX converter, note that TR2 (BFR96S) must be mounted upside-down to match the e-b-c markings on Fig 8.15.
     

  6. 432MHz transverter:
    There were several corrections, mostly concerned with inappropriate values of RF bypass capacitors.
    The transformer core for the 28MHz IF amplifier should be the larger B62152-A7X17 - same supplier, same numbers of turns.

    The connections to the LM317T regulator in Figures 10.11 and 10.13 are incorrect. R2 should be connected from the ADJ pin to the OUT (centre) pin. Also R3 should be about 1360 ohms for the correct 9.0V bias - try 1.2k + 150 ohms in series.

    Having worked on a copy of this design, I can now only recommend it as a source of ideas for the expert constructor - I would NOT recommend a beginner to copy it exactly.


  7. K2RIW amplifier:  
    The height of the anode line above the chassis should be 1.5", (not 1.0"). The rest positions of the flappers C3 and C4 should still be 0.5" below the line.

    All the feedthrough (FT) capacitors are 1000pF or similar. C7 is a high-voltage feedthrough capacitor. C6 should not be necessary.

    RFC1 and RFC2 are each about 6 turns of bare wire on a 12mm drill, spaced and located as shown in Fig 10.19. RFC3 is about 6 turns of wire on a 6mm drill. 

    C1 and C2 are miniature "0-5pF" Johnson-type variables with a low minimum capacitance... if these are hard to find these, try the flapper alternative as mentioned in the book. Until you can achieve full output with less than 10W of drive and a low input SWR, the input circuit is not working correctly!

    The width of the output loading flapper C4 should be 9/16". The original width (5/8") may be OK - it depends on your anode voltage.

  8. Antennas: For newer and even better Long Yagi designs, see my VHF/UHF Long Yagi Workshop.

  9. Power Combiners - even better impedance formula. Ole, OZ2OE, has made a thorough investigation of the impedance formula for a round line in a square tube. The formula in the DX Book is quite accurate, but if you want the full story, click here.

 

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