Question about Heathkit DX-35

Discussion in '"Boat Anchor" & Classic Equipment' started by KE5YUM, Mar 12, 2010.

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  1. KE5YUM

    KE5YUM Ham Member QRZ Page

    Good morning, all

    My 78 year old dad is a soon to be ham who is relearning CW. He has bought a DX-35 transmitter and plans to use it on the air when he passes his technician test. I have looked at the manual for it online, but I cannot determine how to the rig tunes to the various frequencies on the 40 meter band without the VFO. Is it set on one frequency, and if so, what would that be? I think the old novice band was around 7.120.

    Any help would be appreciated.

    Terry Hall
    KE5YUM
    SKCC 5173C
    NAQCC 3102
     
  2. W0LPQ

    W0LPQ Ham Member QRZ Page

    It won't ... without a VFO or crystal ... it will not function. Period.
     
  3. KE5YUM

    KE5YUM Ham Member QRZ Page

    I have not seen the rig, but I assume that the crystals are with the unit. With the 40 meter crystal installed, what should the transmitting frequency be?
     
  4. W9GB

    W9GB Ham Member QRZ Page

    When this radio was offered as a kit, Novice operators (1951 - 1973) were restricted to Crystal control and maximum power of 75 watts, (input to the transmitter's final amplifier stage) on 50 kc segments of the 80, 40 and 15 meter bands.

    The Heathkit DX-35 is a TRANSMITTER (Very common is 1950s/1960s), NOT a Transceiver.
    SO, What are you planning to use for a RECEIVER?

    You will need crystals or a VFO, such as the Heathkit VF-1.
    The crystal determines the ONE frequency that this transmitter can operate on.
    The Heathkit DX-35 has 3 crystal sockets (in rear) -- front switch determines which one you use.
    AF4K offers used crystals for sale
    http://www.af4k.com/crystals.htm

    Here are some photos!
    http://oak.cats.ohiou.edu/~postr/bapix/DX35.htm

    [​IMG]

    Scanned copy of manual
    http://pdf.textfiles.com/manuals/SCANNERS-F-R/Heathkit-dx-35.pdf

    http://www.utm.edu/staff/leeb/DX-35.pdf

    w9gb
     
    Last edited: Mar 12, 2010
  5. K9STH

    K9STH Ham Member QRZ Page

    Several things:

    First of all, Novice Class operators had 50 kHz segments on 80 meters and 40 meters. However, they had a 150 kHz segment on 15 meters and for most of that time 2 MHz on 2-meters.

    The Heath DX-35 does require either a crystal or external VFO. There are 3 crystal sockets located on the rear of the top of the chassis and an RCA phono jack for VFO input on the rear of the chassis. These are selected by a 4-position rotary switch. To access the crystals you have to remove the 4 inch by 3.5 inch "door" on the back of the cabinet. Because it was generally considered a "pain" to remove this door the door was often discarded and there is just a hole in the back of the cabinet.

    For 80 meter operation either an 80 meter fundamental crystal or else a 160 meter crystal operating on the 2nd harmonic could be used. For 40 meter operation either a 40 meter fundamental crystal or an 80 meter crystal operating on the 2nd harmonic could be used. For 20, 15, and 10 meters a 40 meter fundamental crystal is used on the 2nd, 3rd, and 4th harmonics.

    The Heath VF-1 VFO was sold to be used with the DX-35 transmitter and supposedly the voltage for the VFO was to be supplied by the transmitter. Unfortunately, using the internal power supply to operate the VFO is not a good idea. The VFO will "chirp" under almost all conditions. Also, the power transformer in the DX-35 is operating beyond its capabilities even when using the transmitter for CW, let alone when operating AM phone. Unfortunately, there are a lot of DX-35 transmitter around with "blown" power transformers. The later version, the DX-40, had a slightly heavier transformer but even those are operating on the "ragged edge" and that transformer is often bad in the DX-40 transmitters.

    You also have to be VERY careful when tuning the DX-35 transmitter. It is VERY easy to tune the transmitter to 20 meters when the intended operation is on either 40 meters or 15 meters. It also is very easy to tune the transmitter to 15 meters when 10 meter operation is desired.

    The moving vane meter on the DX-35 drives many people "crazy". It will "bang around" like mad. However, the meter is not damaged by all this activity! Also, the meter is hard to use when tuning for a "dip" in plate current as it tends to "bounce around". Frankly, the meter takes a "bit" of getting used to.

    Yes, I do have a DX-35 in my "boat anchor" collection. I also owned one for a very short period of time back in 1960. I acquired it in a trade deal and sold it off very shortly after obtaining it.

    Glen, K9STH
     
  6. KE5YUM

    KE5YUM Ham Member QRZ Page

    Thanks, all, for the responses.

    Yes, I understand that this is a transmitter only. Thanks especially for the info on tuning. I have a TS-520 that I operate almost daily, so I am familiar with the tuning.

    Perhaps we will QSO one day.

    Terry
    KE5YUM
     
  7. K9STH

    K9STH Ham Member QRZ Page

    Forgot to mention: The crystal/VFO selector switch on the DX-35 is mounted on the rear of the chassis, not the front panel. The position farthest clockwise switches to the VFO RCA jack input.

    The crystals from AF4K are in FT-243 holders (.486 inch spacing, .050 inch diameter pins). However, they are not true FT-243 types. Instead they are HC18/U sealed crystals installed inside the FT-243 holders. In most "boat anchor" transmitters, including the DX-35, the crystals work fine. But, it is not possible to change the frequency by grinding, polishing, putting pencil marks on the crystal, etc.

    Glen, K9STH
     
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