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My thoughts on MF and LF.

Discussion in 'The Low Bands - 630/2200 Meters - VLF' started by WA4ILH, Nov 9, 2017.

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  1. WA4ILH

    WA4ILH Subscriber QRZ Page

    I wonder why they decommissioned that program. I know that the locals didn't like it and thouight that it was hazardous to their health.
    Tom WA4ILH
     
  2. K8JD

    K8JD Ham Member QRZ Page

    Interesting low end AM BC station
    The VLF bands are interesting. A favorite AM station near here is on 540 KHz and has great propagation characteristics.[/QUOTE]
    s.[/QUOTE]
    There is a station, CIAO, near Toronto on 530 kHz that runs 1 KW in daylight and 250W at night, It has a good signal in the day time and still able to recover audio at night, from about 250 miles away. I'm in a Detroit suburb.
    There are two licenses showing info, not sure what is current, one shows a non directional antenna with a 697 ft tower, the other shows three tower directional east with 280 ft tall towers.
    Google Earth image from 2014 shows the one tall tower on the site.
     
    Last edited: Nov 20, 2017
  3. G3YRO

    G3YRO Ham Member QRZ Page

    When Commercial Radio stations were first being set up here in the UK, the IBA were paranoid about not giving them excessively good coverage.

    So they adjusted the transmitter power to give the required Field Strength on the edges of their official coverage area for which they were licensed.

    The station I first worked for was in Portsmouth (on the south coast), and the site chosen for the AM transmitter on 1170 kHz was on a salt marsh.

    I guess the ground conductivity was so good that when they were setting the transmitter up they had to turn the power right down to just 150 watts !

    I'd love to know about different ground conductivity here in England . . .

    One thing I HAVE noticed since being active on 160m Mobile again, is that working stations 3- 400 miles away, once I get within a mile or so of my current home QTH, signals are always stronger . . . so guess that means I have a good location!

    Roger G3YRO
     
  4. WA4ILH

    WA4ILH Subscriber QRZ Page

    I can recall being at the beach (Virginia Beach) with a small portable AM radio. I was listening to a station which was kind of weak. I walked down to the surfline and the signal came up considerably. Just out of curiosity, I took a few steps into the water and started tuning around. This was early morning. I could hear stations on just about every frequency. Some day, I may repeat that process when I have a better radio and more time. No, I am not going to buy a boat!
    Tom WA4ILH
     
  5. KE4EST

    KE4EST Premium Subscriber QRZ Page

    Link is showing dead here.
     
  6. KB4QAA

    KB4QAA XML Subscriber QRZ Page

    Yup. Oh well....
     
  7. KB4QAA

    KB4QAA XML Subscriber QRZ Page

    Well the end of the Cold War meant there was little need for an extremely expensive comms program for ballistic missile submarines [that are no longer on high alert].
     
    Last edited: Dec 6, 2017
  8. AE5X

    AE5X Ham Member QRZ Page

    Actually, it was less about the end of the Cold War and more to do with better satellite technology/data speeds.

    Submarines, ballistic missile and fast attacks, had/have two antenna for VLF - a "football" and a floating wire. The football is a many-turned loop inside a football shaped housing that can be raised a few feet above the sail that houses the periscopes, snorkel and other protrusions. It always sucked as a receiving antenna and never outperforms the floating wire.

    Receiving on the floating wire requires subs to operate at a specific depth, be on a conducive-to-comms heading (often arrived at by trial & error) and have a calm sea state. Rough seas generate noise in the receiver. Receiving a VLF broadcast takes a long, long time. Receiving the same broadcast via satellite takes seconds. Also, a QSL can be sent (and that's what it's called by those onboard even though most aren't hams) via satellite but subs can't transmit VLF.

    My two best friends onboard USS Barb (SSN-596) deploying the floating wire (photo by me!) 1987-ish:

    [​IMG][​IMG]

    73,

    John AE5X
     
    WD4IGX and WA2FXM like this.
  9. K9STH

    K9STH Ham Member Staff Member QRZ Page

    Good old TACAMO!

    That was one of the projects, when I was with the Collins Radio Company, over which I had administration oversight. The other 2 major projects were the LR-104 (designed for use in the C-5A) and Sandia Base (Nuclear Regulatory Commission) thin films. All 3 projects were "over budget and behind schedule" when I went to work at Collins in 1967 and when I left, 2-years later, in 1969! There wasn't much that I could do as an administrator except to try to get engineering and production on the same page to get down the costs and to step up production!

    One major problem was reeling in the 5-mile long trailing wire antenna on the aircraft. Often, the wire would bind and then have to be cut off for the aircraft to land. There was a hatchet kept by the retraction reel to use when the wire got caught to cut away the wire. There are hundreds of miles of antenna wire at the bottom of the Gulf of Mexico that were cut free from TACAMO aircraft.

    Collins had a 35 mm slide program (this was long before computer presentations) in which one of the slides had Heckle and Jeckle (cartoon crows) sitting on a fence post. One was saying to the other, "Here comes that damned wire again" meaning the TACAMO antenna.

    The VFL / ELF systems are still in use today although there are other, much higher frequency, systems in use as well.

    Glen, K9STH
     
  10. KB4QAA

    KB4QAA XML Subscriber QRZ Page

    The ELF program was discontinued as we have been discussing.
     

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