Posted: 10/21/2008 11:34:05 AM EDT
| Does anyone know if is possible to use NVIS in the 2 meter band?? |
Unless you have terrain issues 100mi should be doable on 2m with very good antennas and moderate tower height. Depending on your exact situation as far as terrain and other conditions, sometimes you will do better on 6m and sometimes you might do better on 220 or 440. Is it one 100mi path or a bunch of people spread out over a 100mi area that you need to cover? There are also these amazing things called repeaters. |
there is no "predictable" skip with 2m. there is no way to make that work. NVIS on 80m SSB would be good. you can, with enough power, elevation, and gain communicate between two locations 100 miles apart using 2m. the elevation is the problem, and is made worse if there are hills/mountains in the middle. the radio horizon for VHF, in miles, is approximately the square root of (the antenna height in feet times 2)...  doing the math... you need the horizon at 1/2 of 100 miles, and reversing the terms above to (50^2)/2 gives about 1250 feet combined height my guess it that you need approximately 200W, a 13 element yagi (or perhaps a stacked pair), and a location as high up as possible. that last part is the tricky part. ar-jedi |
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Where we are at we have a local club that has a repeater on a "large hill" or small mountain. Transmission on 2m in my personal experience with a 2m ht VX6R and ext. ant. is aprox. 60-65 miles one way. We have had people on the local net as far away as 250 miles but they were on base units with unknown ant. height. We use this same ant. for the local weather spotters... just more info. Might look at this as a viable means to an end. |
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Man... i was testing 2 vx-170's with a buddy the other day and we barely got 2 miles down the road, was very frustrating. Needless to say better antennas were ordered and will be here friday for testing, i certainly hope it improves, i'd hope to get atleast 5 miles Strangly i can key a repeater that may be as far away as 30-40 miles, not quite sure on it's exact location I just don't get it at all help? |
Not unusual at all to get that kind of range for handhelds over average terrain, especially VHF/2m handhelds used from inside vehicles.
5 miles with handhelds with any kind of reliability is going to require good vehicle mounted antennas or fixed station antennas. Unless you're on an overwater path, hilltop to hilltop, etc etc.
Nothing at all "strange" about that. It's (antenna) location is probably several hundred feet up in elevation and with a large high performance antenna.
What part don't you get? |
the repeater has a far better antenna attached to it, and the antenna is likely high up. you'll see a difference with better antennas attached to your HTs, as well. ar-jedi ETA: 50 seconds. 
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Because the other handheld 2 miles away has dirt blocking the signal. It's also a lower performing receiver attached to a low performance antenna. The antenna 30 miles away is on a very tall tower so you have a clear line of sight to it. It's likely a very high performance receiver and using a very high performance antenna. For your HT to HT case, if you climbed up on a ladder you'd probably get another 1/2 mile or a little more of range. Climb up on the roof of your house and you'd probably get another couple miles. Climb up 100' on a tower... Height is king at VHF and higher frequencies. You can work contacts at hundreds or thousands of miles away with an HT if you get high enough (like in orbit). |
k thanks for the quick feedback i'll let you guys know what the outcome is of the new ht antennas i got 2 different types to try, 2 of each. |
a Yagi is a type of directional antenna, consisting of a radiating element (sometimes called the driven element), one or more reflectors (behind the radiating element), and one or more directors (in front of the radiating element). compared to the length of the radiating element, the lengths of the reflector(s) and director(s) vary a bit, with the former a tad longer and the latter a tad shorter. en.wikipedia.org/wiki/Yagi_antenna 
more elements = more forward gain.  the more reflectors and directors you add, the more the RF is concentrated in the direction of interest. moreover, this added gain works both ways; your radio receives much better in the direction the antenna is pointing. but, with those additional elements comes ... more weight, more wind load, more cost, narrower beam means more directional accuracy needed, etc etc etc. and when it falls down you are left with an impressive collection of bent aluminum. --- note that a Yagi, like a dipole, can be oriented horizontally or vertically, leading to horizontal or vertical polarization of the resultant electromagnetic wave. for both technical reasons and by convention, 2m FM is vertically polarized and 2m SSB is horizontally polarized. there is evidence which shows horizontal polarization is better suited for 2m "DX" work. that said, nothing keeps you from using typical 2m FM radios and horizontal polarization for your point-to-point application. ar-jedi |