Summary of three (equipment) methods of transmitting on 630m

Discussion in 'The Low Bands - 630/2200 Meters - VLF' started by AE5X, Nov 24, 2017.

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  1. AE5X

    AE5X Ham Member QRZ Page

    KB4QAA and N5CEY like this.
  2. K7JEM

    K7JEM Ham Member QRZ Page

    I am thinking that someone could post a conversion process for surplus FDM channel modems, like the Granger DTL7300 series. These are basically a full duplex synthesized SSB transceiver on a card. They cover the frequency range of around 12 to 2500KHz on 4KHz channel steps. The steps could be changed if needed. But the cards are very high quality, sharp filtered SSB, at a low level for TX, and requiring a somewhat high level for RX. Amplifiers and filters could be located on a separate interface board. The boards are available fairly cheaply, since they have pretty much been replaced by digital systems in most applications. You can purchase an individual board for around $60 or less. Here are a couple of links:

    http://teamequip.com/granger-associ...5-2795-11-model-4-channel-modem-board-t72636/

    https://www.ebay.com/itm/GRANGER-DT...914364?hash=item2a94ca54bc:g:Xp0AAOSw5dNWtW8l
     
  3. WA3ETD

    WA3ETD Ham Member QRZ Page

    I would have concern about transmitting with an "open" rig as there is
    no specific LPF for 630m. Most likely it would use the 160m filter, which may
    exhibit bizarre characteristics. Note that the 2nd harmonic of 475 kHz is right
    in the AM broadcast band...caution! I'd use an external 5-pole LPF if doing this!

    John WA3ETD
     
    KB4QAA likes this.
  4. KA4KOE

    KA4KOE Ham Member QRZ Page

    What about a MOPA type rig using vacuum tubes??
     
  5. NO3M

    NO3M XML Subscriber QRZ Page

    630M Hartley power oscillator:
    http://no3m.net/wp-content/uploads/2015/08/630m-hartley-4.jpg

    630M MOPA (89-802-811):
    http://no3m.net/vintage/630m-mopa/

    630M MOPA (89-42-802) + PP 814 amp. I get on the air with this one almost every night:
    http://no3m.net/wp-content/uploads/2017/07/DSCF7162.jpg
    http://no3m.net/vintage/push-pull-814-rack-transmitter/

    MOPA using UV201 and UV202 by WA1ZMS:
    http://w4dex.com/500khz/wd2xsh31.htm
     
  6. KA4KOE

    KA4KOE Ham Member QRZ Page

    I could retune one of my tube theremin's oscillators and it would resonate on 630m, if not with a lot of power.
     
  7. WA4ILH

    WA4ILH Subscriber QRZ Page

    Very interesting! does anyone know if a Kenwood TS-440 or TS-480 can be modified to transmit below 500 KHz?
    Tom WA4ILH
     
  8. N0NB

    N0NB Subscriber QRZ Page

    Threw away scads of those things almost a decade ago when we scrapped the analog microwave. I didn't see much of a use for them at the time. Oh well...

    A preamp would most likely be required as I doubt they were good for anything below -60 dBm.
     
  9. K8JD

    K8JD Ham Member QRZ Page

    Receivers and Antennas
    My TS440 doesn't put out power below 1700 KHz, probably doesn't have a bandpass filter switched in the transmitter side there. Receives fine on the LF beacon band down to 200 kHz.

    My best antenna for receiving the low freqs is my 160M dipole, 2nd best (kind of poor) is my 40 M fullwave loop, the several other HF antennas up here really suck on low freqs. :D
    I also have a two wire inverted L for short wave listening with a tunable preamp that works on low freq but it is near a neighboring house and picks up TERRIBLE noise . I only can hear airport beacons up to about 70 miles in the daylight hours.
     

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