W0BTU
| Joined: | Sat, Apr 4th 1998, 00:00 | Total Topics: | 0 | Roles: | N/A |
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Latest Topics
| Topic | Created | Posts | Views | Last Activity |
|---|---|---|---|---|
| Main page is blank when not logged in | Apr 7th 2012, 09:48 | 3 | 594 | on 7/4/12 |
| Discount for multiple subscriptions? | Mar 23rd 2012, 06:59 | 1 | 589 | on 23/3/12 |
| Rules violations on 60 meters | Mar 6th 2012, 03:03 | 6 | 1,401 | on 28/3/12 |
| January DIY QST | Dec 13th 2011, 03:22 | 1 | 818 | on 13/12/11 |
| Ethiopian jamming wiping out 40 meters | Oct 6th 2011, 04:37 | 2 | 1,339 | on 6/10/11 |
| How to access info in back issues of QEX and NCJ | Sep 2nd 2011, 19:37 | 10 | 1,954 | on 3/11/11 |
Latest Posts
| Topic | Author | Posted On |
|---|---|---|
| Dielectric Grease in Feed Line Connectors | KC2SVQ | on 2/2/13 |
| Absolutely. Silicone dielectric compound should be used inside any outdoor connector, especially on the center contacts. 73, Mike www.w0btu.com |
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| International Call sign Lookup? | wheels47130 | on 20/1/13 |
| http://www.qrz.com 73, Mike www.w0btu.com |
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| Ham-made TV Antennas work better | K4DUB | on 14/1/13 |
| I fully agree. We can certainly make our own antennas for OTA TV reception. I made my own from the plans at http://m4antenna.eastmasonvilleweather.com/Drawings/PDF%20Drawings.html . The antenna is indoors on a balcony overlooking my living room, and solved about all our OTA TV reception issues in this very rural area far from any TV stations. I used bare #14 copper wire and screwed it to a piece of 1.25" PVC pipe I had. There's an old broadband "TV-type" 300/75 (4:1) balun mounted at the feedpoint; and from there, about 12' of RG-6 coax goes down to the TV below. No preamp. Some of the following links are excellent sources of info about "DTV" antennas. Others, I'm probably doing somewhat of a disservice by posting them, but I don't have time to go back and weed out the inferior designs. The digitalhome.ca forums, frontiernet.com, and m4antenna were the best, IIRC. The "mclapp" fellow in the forums seems to be quite knowledgeable, and he's the guy who has the EZNEC files of "HDTV" antennas (which I did not examine) and lots of helpful info on his site. http://m4antenna.eastmasonvilleweather.com/Drawings/PDF%20Drawings.html http://www.youtube.com/watch?v=M8jsDxNgHn4 http://news.consumerreports.org/elec...v-antenna.html http://uhfhdtvantenna.blogspot.com/ http://www.digitalhome.ca/ota/superantenna/design.htm http://www.frontiernet.net/~mclapp/Antennas/Computer%20Models/ http://www.digitalhome.ca/forum/showthread.php?t=100137 http://www.frontiernet.net/~mclapp/Antennas/ http://www.digitalhome.ca/forum/showthread.php?t=81982 http://www.digitalhome.ca/forum/showthread.php?t=140206 http://www.tvantennaplans.com/ http://m4antenna.eastmasonvilleweather.com/index.html http://groups.google.com/group/rec.r...863ccbd4?hl=en 73, Mike www.w0btu.com |
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| Two new ham questions about antennas | KD0TYP | on 9/12/12 |
I think Zack was tired when he typed that. :-) "Balun" means BALanced to UNbalanced. A balun generally goes between a balanced line (or balanced antenna) and unbalanced coax. Depending on (1) the length of the antenna, (2) the length of the balanced line and (3) the impedance of that line, the impedance at the tuner and/or balun may be too high or too low to match on some bands. I agree with Zack about the G5RV and ZS6BKW. Or, you can build my version ("The W0BTU Antenna") which uses inexpensive 75 ohm coax and covers more bands than either one of those. See http://www.w0btu.com/g5rv_antenna.html#w0btu_antenna . It has a reasonable SWR on all HF bands between 80 and 10 meters except 30 and 60. There is a complete set of SWR curves for each band there. I used a ferrite-core broadband 1:1 current balun (choke) right at the junction of the window line and coax to keep RF off the outside of the coax shield. We used one of K9YC's designs using about 6 turns of the 75 ohm coax feedline (RG-6 or F-6 CATV coax) wound through 4 or 5 stacked Fair-Rite 2.4" diameter #31 ferrite cores. The 75 ohm coax can be any length needed from there to the tuner. If you build my version using 300 ohm twinlead instead of what we used, its length will have to be different. 73, Mike www.w0btu.com |
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| retransmission of frequency | n2nlm | on 5/11/12 |
| Doesn't Commcat, http://www.myqsx.net do something like that? 73, Mike www.w0btu.com |
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