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  1. #91
    Join Date
    Jan 2004
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    5,169

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    Quote Originally Posted by ffiill View Post
    ...
    I have also gone back to a book I have on aerials and radio propogation which makes good reading if you are interested in this subject.
    www.hamuniverse.com/n4jaantennabook.html
    ...............

    For example from what I can gather whilst transmissions are better in daylight that is not necessarily true of reception.It would appear that a transmission at the right frequency sent up into the ionosphere in day light once it starts skipping can continue into a dark zone where ionisation is dissapating.
    So what this can mean I think is that if you are out mid Atlatic where local dawn is perhaps three hours later the GMT dawn Northwood will be transmitting at an optimum time for a good skipping signal out into the Atlantic even if its dark at the point of reception.
    Anyone not sure about the skipping/skimmimg wave just do a Captain Jack Sparrow in Davy Jones Locker-"skys the sea and seas the sky".So basically you are causing the radio signal to skip along in the ionoshpere the same as if you are skimming stones over the water.
    Thanks for the link. Full ham exam in a few weeks so will come in handy.

    Re the skip, Im regretting having a virtual tidy up now, deleted all the faxes recieved coming across Atlantic From memory they were not perfect but plenty good enough to see what was going on. That was with a degen 1103 attached to the car radio masthead FM antenna.

    Where are you recieving from at the moment? Your faxes are miles better than I can get. Through an Icom 7000, but surrounded by masts and offfice blocks twice the height of the mast so maybe no wonder.

    Dwd on 10.1Mhz comes in perfect mostly during the day but fades around sunset.

    Have you tried recieving psk31? A ham data mode, on 3.580, 7.035, 10.141 & 14.070. Fldigi will decode it, then you can watch hams saying hello to each other. For a few minutes til boredom kicks in

  2. #92
    Join Date
    Sep 2007
    Posts
    1,717

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    I am based in Glenmoriston which runs aprox.westwards of Loch Ness.
    I am completely surrounded by mountains-the skyline south of me is 30 degrees from the horizontal and to the rear of my house the first three hundred feet is nearly vertical granite.
    There is a small window between east and south east where the hills are about 8 miles way but which peak at 4000 foot in the Cairngorms.
    So I am assumning the only signal I am getting is reflected.
    We are assuming that we are getting a signal from the same transmitter.
    I am sure I read somewhere that Northwood uses a series of transmitters from Ascension Island northwards because Northwood itself is near Watford.
    My antenna is a horizontally strung 45 foot length of 1.5 mm dia.6 strand twisted insulated wire commonly used for wiring up ceiling spots.Feed line is 70 ohm low loss satellite coax. because I have a load of it!
    Also I use a low loss screened digital audio feed-a couple of s on e bay
    Today for a change I also tried the radios onboard whip.The whip showed a far poorer spectrum spike with progressive signal build up either end wheras the antenna has little either side of the spike.
    Radio is set local and narrow band ssb.
    The wind vector chart begins on the whip and swops over just about where I am in the Highlands ;the prognosis chart I received almost two hours after setting the system on auto running whilst I took my dog for a walk.
    Origional pic quality far better than this jpg conversion at 100kbs-1.4 mb per pic.and as I recall about 24x18 inches as transmitted.
    Last edited by ffiill; 06-04-12 at 16:51.

  3. #93
    Join Date
    Apr 2008
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    9,806

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    I can't match these yet, but today, after a year or so of messing about, I got this:



    Degen Short wave radio. laptop, Offenbach (DDH) weatherfax on 7878.1 Mhz. Software, demo version of JVComm32.

    Really messy, and hardly worth anything, but after months of trying to work out what all the jargon means, how the radio works, how the software works, and getting nothing but noise, I'm absolutely over the moon to see an Atlantic weather chart. I fiddled about, and got a much clearer image after this, but didn't manage to save it.

    Anyway, this isn't about me, it's just to say thanks to ed for providing the original info, and the other contributors. Cheers, lads.


  4. #94
    Join Date
    Aug 2010
    Posts
    72

    Default Was your laptop on mains

    Did you have your laptop or radio plugged into the mains when you collected this chart? It looks very like the charts I was collecting...look back to http://www.ybw.com/forums/showpost.p...8&postcount=56 and others.

    In my many and various tests I found mains (left on by mistake) could cause this and setting the 'slant control' also helped, however, your chart seems all neatly lined up, just very 'dirty'.

    I guess ensuring the radio is on narrow band tuning might help? Just been going back through my posts to see if I can find the moment I went from this kind of thing to a cleaner, readable chart.

  5. #95
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    Apr 2008
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    Quote Originally Posted by iainhu View Post
    Did you have your laptop or radio plugged into the mains when you collected this chart? It looks very like the charts I was collecting...look back to http://www.ybw.com/forums/showpost.p...8&postcount=56 and others.

    In my many and various tests I found mains (left on by mistake) could cause this and setting the 'slant control' also helped, however, your chart seems all neatly lined up, just very 'dirty'.

    I guess ensuring the radio is on narrow band tuning might help? Just been going back through my posts to see if I can find the moment I went from this kind of thing to a cleaner, readable chart.
    I'm learning with every attempt. First time I did have the laptop plugged in. I had a reasonably clear fax sound on the radio, but huge interference when I plugged in the mic lead from the radio. So, as Ed says, don't do it whilst charging.

    Then I read that you can use the fine tune dial on the Degen once the frequency is set. That affects whether the fax is translated as mainly black, or mainly white. I was fiddling with this whilst recording - hence the switch from white to black fax and back again.

    I haven't yet worked out why I can get faxes from Offenbach (Germany) but not yet from Northwood.

    Honestly, I don't care. Once I know I can do it, it's just a metter of time to get the best results, and I'm learning loads.

  6. #96
    Join Date
    Aug 2010
    Posts
    72

    Default A black art

    Yes it is all a bit of a black art. Look back as I struggled my way through to getting readable charts. However, having done so and being all set to use them trans Atlantic I could get *nothing* once on the boat...contrary to all predictions. Probably RF from the boat, so in the end it became a whole lot easier to use the sat-phone and download gribs, which worked fine, just failed to use my, I thought, new found skills to work!

  7. #97
    Join Date
    Jan 2004
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    5,169

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    Quote Originally Posted by Alcyone View Post

    Anyway, this isn't about me, it's just to say thanks to ed for providing the original info, and the other contributors. Cheers, lads.

    This one is fun as well, RTTY from DWD on 10.1MHz. On JVcom if you go into configuration/RTTY and enter these..

    mode:Whatever memory you want to save it as.
    Type:Baudot
    Baudrate:50
    shift:50
    PTC-11 type:baudot
    # of bits : 5
    centre frequency:400.

    you should get text weather from DWD in Germany. Strong signal usually.

  8. #98
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    Apr 2008
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    Apologies, Conachair, I missed your post. I'll try that. Many thanks.

  9. #99
    Join Date
    Sep 2007
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    What time were these faxes done at?-all mine are during the daymid morning and late afternoon is best.
    Just suprised how poor the quality is-I managed to get good quality within a few days of beginning to experiment.
    Several points-fine tune the signal whilst watching the image so as to get it as clean as possible.
    You can pick up a lot of spurious sound of the mains-I am in a rural area but can still get a lot of noise sometimes and find that internal batteries are better.
    When I was experimenting on the west coast I was getting a lot of interference on some frequencies-perhaps military jamming.
    Use a sheilded coax lead between radio and PC.
    Always tune down from reccomended frequency.
    Set to Upper side band?-if I dont use USB I get a lot of spurious noise.
    I am wondering if there are issues with Northwood of being too close.
    My signals are definitely ones bounced of ionosphere.
    Finally I did manage to pick one up on my long wire aerial if a little unclear from Boston -4000 plus miles away.

  10. #100
    Join Date
    Aug 2010
    Posts
    72

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    Some useful hints, thanks :-)

    For my part:
    1. I often did my reception in the evening, after dark, which is supposed to be better for signal reception so interesting to hear yours are in daylight
    2. I used a PC audio lead...not sure how much shielding that would have had
    3. I only ran both radio and laptop on battery except for one accidental use of mains which was very obvious
    4. I did all my recordings outside...not a hope inside!
    5. I did most of my recording with a retractable (16' I think) wire aerial stretched horizontally which helped 'a little'
    6. Yes, you need to tune low the get the upper side band
    7. Very impressed at you picking up Boston...makes me feel I should try that again!

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