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|    AMATEUR_RADIO    |    Ham radio for when Armageddon strikes    |    2,531 messages    |
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|    Message 337 of 2,531    |
|    Roy Witt to Ed Vance    |
|    Resurrected    |
|    11 Apr 14 14:46:01    |
      Greetings Ed!               EV>> The other photo shows that wire points towards the speaker, so I        EV>> figure the wire from the RF section has lost the Folded Dipole that        EV>> it once had.               RW>> As I explained above, the red twinlead wire and the red        RW>> 'skyryder' are antenna lead-in and wire wrapped iron core        RW>> antenna. Rather than run the vertical, I may plug the Skyryder        RW>> in and mount the antenna horizontally on the window, which        RW>> faces North-by-East. Maybe there's more out there than it        RW>> receives on that vertical telescoping antenna. Thanks for the        RW>> website URL, I can use the info they have there. But, I'm not        RW>> going to join, since $25 isn't my idea of really needing that        RW>> info.               EV> O.K., I sit corrected about that Red Twin-Lead cable.              You don't need to be corrected. You had it pretty close, considering that       you don't have one of these radios at hand to examine.               EV> I didn't investigate anything else on that web site and didn't know        EV> about their request for support was for more than Photos and        EV> Schematics of Old Radios.              Well, there are 3 schematics for that radio on that site. I'd like to have       a copy of them, but the radio has a schematic attached to the inside of       the back cover and it's readable, with a magnifying glass.               EV>> A UHF TV Station on Channel 32 came on the air, and I made a Folded        EV>> Dipole antenna out of some 300 Ohm Twin-Lead such as what is in the        EV>> back of your Hallicrafter Worldwide RX.               RW>> I've done that before. It works very well. But a log-perodic        RW>> would work much better for what I want...all UHF channels,        RW>> 14-69 at 40 miles (in Austin)...               EV>> The Tower was 3 1/2 Miles from our house so I calculated the length        EV>> of the antenna was 19 Centimeters, so I cut off enough Twin-Lead so        EV>> I could solder the two leads on each end to each other and cut one        EV>> wire in the center of the antenna to connected some 300 Ohm wire to        EV>> it, the other end went to a UHF TV Convertor we got.               RW>> If it was that close, a long wire would have worked just as        RW>> well. But at least you got some antenna mathematics and        RW>> building practice. BTW, that should have been 19 inches...I        RW>> have come up with a formula to make 1/4 wave GPs and        RW>> multiplying the answer by 4 gives me the a closer length to        RW>> build a full wavelength dipole; 2808/Freq in MHz = 1/4 wave...I        RW>> also use 2880 to give a 5% extra length to the GP radials...The        RW>> antennas I used to build went to the local San Diego HRO store        RW>> and sold out within a few days. They always displayed a flat        RW>> 1.2:1 SWR across the band they were designed for.               EV> I don't think I even had heard of a Log Periodic Antenna in the early        EV> to mid 1960's.              Ummmm. They were on every rooftop of houses with a TV set. Most of them       were dual banders, aka VHF and UHF...when I worked for Solar Turbines in       San Diego c1967, a younger friend and I built a few for our own use. He       was a tool & die apprentice, I was t&d journeyman at the time and he lived       two blocks down the street from me.               EV> But a Twin-Lead LPA would be OverKill for 3.5 miles.              No doubt, but it could be used to receive other stations within 25 miles.               EV> And it would be a bear to make and position by the TV Set.              There's a video on YouTube showing how to make one out of stripped RG59       coax (using the shield only) as the electrical 'boom' and #12 house wire       as the radials. It is only 58cm (22.6") long. The support boom is made out       of wood, 1" square, and all radials are wood screwed to the coax boom at a       specified spacing. Crude, but affective. The video shows the builder       holding the antenna pointing it out of the window, waving it about, the TV       HD signal fades and brightens as he finds the station's xmitter site.               EV> Also since it was the 2nd TV Station to be on a UHF Frequency in my        EV> area, (the 1st one stopped broadcasting in early 1960), I didn't need        EV> a broadband antenna back then, so the antenna worked O.K. for the        EV> only one that was in town on UHF back then.              No doubt. And if that's all there was, it was all that you needed.               EV> I can't remember when the Local School System started their TV        EV> Station on Channel 15 around here. And it was several years later        EV> before another Commercial TV station came on the Air here, and then        EV> Everybody had TV Stations on UHF!              Same thing happened to the VHF station where I lived in Illinois. I forget       what channels they used, but it eventually went to UHF too. The earliest       and best station there was WREX (ch13) in Rockford, another in Daventport,       IA (ch6) and one in Madison, WS (forget its channel). Those were VHF and       about 30-40 air miles away. And of course, all of the Chicago stations       were about 90-100 miles away. WGN, WLS, etc.. but they required long, long       with many radial antennas.               EV> We've only have had two VHF stations, and both of them came on the        EV> Air way before any UHF stations did.               EV> I looked at the book I used back then to calculate the length of        EV> Twin-Lead I'd have to cut and one chart says TV Channel 32 back then        EV> was 578-584 Mc/s.              Which isn't the case today. The HD mode today doesn't use that much       spectrum. Part of that spectrum was for the video and part is for the FM       audio signal.               EV> I looked at another chart in the book to find the wavelength was        EV> about 52 Centimeters, Half of that is about 26 CM , or about 10.25        EV> Inches.              Which falls within the measurements given for the 582MHZ LPA...               EV> Tonight I looked at a ruler and that seems about the length that I        EV> recall the antenna being.               EV> My 19 CM guess earlier was way off the mark, wasn't it? .... ..              Yes, it should have been about 19 1/4 inches.               EV> I do the best I can with what I got, but when I really want to know        EV> something I go to the Books I have to get it down to the nitty        EV> gritty.              I keep a formula in my head that allows me to figure a 1/4 wave antenna.       Multiplying that by 4 and you get the full wave length.              2808/freq in MHz * 4 = a full wavelength.              2808/582 = 4.825 x 4 = 19.24"              Somebody asked me some years ago in the HAM echo where I got that 2808       number. Which had something to do with figuring the length of a dipole and       a number around 5600. It's been so long since I figured that, I have       forgotten what it was. Anyway, building 1/4 wave GPs that 2808 number       worked out very well, as each one of those antennas made for 450 MHz, had       less than 1.2:1 VSWR across the entire 10MHz of that band. As would be       expected, the 145Mhz and 220Mhz antennas worked just as well.               EV>> A neighbor across the street heard about the TV Channel 32 antenna        EV>> that I made and asked me to make one for them too, I had GOBS of        EV>> wire so I made one for them.               RW>> Believe it or not, that also works as a CB antenna, which is my        RW>> very first antenna fabrication. The next one was an all wire        RW>> ground plane, that was mounted outside my 'radio room' on the        RW>> second floor of our apartment, c1960?...               EV> I ran a wire around my radio room up near the ceiling, One Big Loop.        EV> I used it with the DX-40 on 20 Meters.              Not for transmitting I hope.               EV> -snip-               RW>>> That was illegal for a CBer to do, but we did the same thing.        RW>>> It sure beat looking through a pile of xtals and wasting time        RW>>> making the change.               EV>> Plus the switch box kept you from opening the case to change a Xtal.        EV>> -snip-               RW>> Actually, the 11mtr lunch box had a xtal socket on the outside        RW>> face of the radio, allowing xtal changes on the fly. It was a        RW>> cumbersome job of keeping track of those umpteen xtals, so we        RW>> fixed that.               EV> Oh, O.K., Thanks Roy!              Not only that, but the radio was xtal controlled xmit only. It had a       tunable receiver. That was nice for listening to off frequency radios.       My Golden Eagle had that too, but it could switch to a set of 23ch mixer       controlled receiver too.               R\%/itt - K5RXT               On Ward's exalted throne, he is still seated on nothing but his big arse.                            --- GoldED+/W32 1.1.5-31012       --- D'Bridge 3.99        * Origin: HAM Radio, aka Amateur Radio. 804? Over! (1:387/22)    |
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