Hi Andy, I operate 2 meters and 70 cm every day from here in Mount Pleasant. You really need 14 dBi of antenna gain on 2 meters and 17 dBi on 70 cm to reach 200 miles on phone if there is no propagation enhancement. A log-periodic will probably not have enough gain on any one of the bands it covers. Using DominoEx 4 (not critical for tuning) will get you farther, but there are not many people to talk to yet. Almost all 2 meter QSO's are on phone, with CW used when phone cannot make it. The biggest VHF contest of the year is the June VHF QSO Party, June 13 to June 15, because there is more chance for tropospheric ducting during the summer. This is the best time to find someone on the air. At other times, check the APRS propagation map at http://www.mountainlake.k12.mn.us/ham/aprs/path.cgi?map=na for propagation in your area. Even if you are not ready for the June contest, get up whatever you can and you will probably find activity. The calling frequency for 2 meter phone is 144.2 and for 70 CM phone it is 432.1.
Most 70cm QSO are coordinated on 2 meters first, so that the beam heading is already set, so align your 70 cm beam and 2 meter beam carefully in the same direction. You generally need 3 to 6 dB more gain on 70cm than you have on 2 meters, but the antennas are 1/3 the size of a 2 meter antenna, so if the boom lengths are equal, you should be OK. Check out my FM DXing presentation I made at the Southeastern VHF Society conference at Charlotte, NC, in April for other ideas. That link is also on my web page. If you want a medium gain antenna for 70 cm that you can easily homebrew, consider my SS5 skeleton-slot beam: http://home.comcast.net/~kh6ty/site/ and click on the SS5 link. Two or four of these stacked will give you enough gain to reach 200 miles or more if there is no ducting. When there is an opening, one of these antennas will get you 200 to 300 miles. For 2 meters, you can homebrew a cubical quad like the 12-element cubical quad that apparently was published in CQ Magazine. The dimentions are in the MMANA-GAL VHF ANT folder. You need MMANA-GAL http://mmhamsoft.amateur-radio.ca/mmana/ to display the beam dimensions. To work 2 meters and 70 cm with a common feedline, many people use a diplexer. You would probably want to have a separate feedline for 6 meters, and your transceiver may use a common antenna connector for 2 meters and 70 cm, but perhaps a different one (together with HF) for 6 meters. The best commercial antennas for 2 meters and 70 cm are probably the K1FO designs sold by Directive Systems: http://directivesystems.com/ Be sure to use low loss feedline for long runs, like hardline (the lowest loss), or RG-8, especially on 70 CM, unless your runs are very short, and at least RG-8 on 70 CM. WSJT is also a digital mode, and with 100 watts and a long yagi, you can also try EME on the rising moon using WSJT. The challenges for VHF/UHF DX are quite different from those on HF, but lots of fun in a different way. Signals, except during a 6 meter opening, are generally truly "weak signals"! You need all the antenna gain you can get, and will always wish for even more! I host a 2 meter DominoEX 8 net, using FM (and horizontally-polarized antennas) twice a week and we have had checkins by stations with long yagis from as far away as 200 miles. Everyone uses horizontally-polarized antennas. These opinions are based on my own rather recent excursions into VHF/UHF over the past two years- others may vary. 73, Skip KH6TY Andrew O'Brien wrote: > > > I am tempted to try get active on 6M-70cm for digital modes and CW > this summer. I am looking to avoid multiple runs of coax and thought > of a homebrewed log periodic for these bands, using one feedline . > Does anyone here use one, or have favorite software for log periodic > design? Is the range too great? Any commercial ones? > > Andy K3UK > > -- *Skip KH6TY* http://KH6TY.home.comcast.net
