Best VHF UHF receive antenna?

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KE7RUX, Oct 1, 2019.

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  1. KF5FEI

    KF5FEI Ham Member QRZ Page

    Yep. We've had some openings on 2m off and on this summer, and I've talked through repeaters 100+ miles away with 25 watts, mobile. Height does make it a bit easier -- but since I work near the DFW TV transmitter sites, I can drive up to the fire station near there and have all the altitude I can stand.
     
  2. AI3V

    AI3V Ham Member QRZ Page

    Stay in your lane om, you are wrong on both accounts.

    There are almost no, none, zero, nada "line of sight" terrestrial paths.

    About the only true optical paths most hams will ever use is to a satellite, thats why you can hear the 1/2 watt to a quarter wavelength whip from a leo bird 1000 or more kilometers away, using nothing more than a uv5r and a rubber duck.

    And troposcatter is a 24/7 mode, with only slight dinural fluctuation, thinking a half watt and a rubber duck is even remotely equal to a killowatt and 4 or 8, 4.2 wavelength Yagi-Uda antennas is just silly

    Rege
     
  3. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    3V:

    "Line of sight", where VHF, and higher frequencies, is concerned, basically, follows a 4/3rds Earth curvature path and the higher the frequency the closer this becomes.

    Yes, there are other types of propagation that also play an important role. However, to say that there are virtually no terrestrial "line of site" paths is just not correct! How else do you explain "dead spots" caused by terrain, structures, etc.? Those are caused by physical objects appearing in the path blocking the r.f. signal.

    The higher the antenna, above the terrain, does reduce these blockages as well as increase the 4/3rds Earth curvature path. In addition, the higher the antenna the better the effective range due to other propagation means. There are certain propagation, such as true tropospheric ducting, where height has very little, if any, real effect. However, those are very specific circumstances. I have seen, especially in the very early 1960s, several examples of true tropospheric ducting where the duct was considerably less than a mile wide. This was on the 6-meter band.

    One could be driving down the highway when, suddenly, the band would go alive with stations. Then, not that far down the road, the band would go dead again. But, backing up a very short distance, the band would come alive again. These ducts could last for a few minutes and then for an hour, or more.

    If height didn't matter, then how can you explain that an antenna at, say, 20-feet above ground doesn't function as well as an antenna several hundred feet above ground where distance is involved?

    Glen, K9STH
     
  4. W4EAE

    W4EAE Subscriber QRZ Page

    'My lane' is my experience in my terrain with my various antennas.

    Come visit. I will happily demonstrate the validity of what I wrote. :)

    I can totally understand how what your are asserting about line of sight is applicable to your SPECIFIC AREA in the Appalachian mountains, but realize that most of us do live in such terrain.
     
  5. AI3V

    AI3V Ham Member QRZ Page

    Glen, you are used to selling a new radio to a police department that has a radio that works fine.

    I get that, I was in that biz myself for a while.

    But to think that vhf/uhf is sone sort of 4/3 earth coverage is 1940's thinking.

    My every day range on 2m ssb from Kingwood WVa, or Pittsburgh pa was well over 100 miles, pushing 200.

    There is no possible way to say these were los or even 4/3 paths.

    Again, this is obsolete thinking, based on wideband fm and 10-20 db noise figure frontends.

    Rege
     
  6. W6KCS

    W6KCS Ham Member QRZ Page

    That's impressive range and sounds like a lot of fun. But since the OP was referring to FM and that's what most folks are using, it's also reasonable to characterize most of their operation as non-tropo and more along the lines of LOS, 4/3K, occasional ridge diffraction, etc. I don't talk to many guys 100-200 miles away on FM, from the mobile OR base.

    But you are getting me interested in SSB with all of the long-range tropo scatter talk. it sounds like the kind of fun I had when I first started, on HF.
     
  7. W4EAE

    W4EAE Subscriber QRZ Page

    2m SSB can be remarkable. If you are really interested, invest in a directional antenna (I find this more valuable for noise suppresion than for gain) and an IC-9700. There is not current radio that is better for 2m SSB (and a lot of other things).

    The frequency of various different forms of tropo has a significant geographical and climate component. In central SC, I regularly reach FM repeaters which are over 100 miles away. One is ~150 miles away--but it sits atop the highest peak East of the Mississippi. This time of year in particular, two different repeaters which have the same frequencies as one of our local club repeaters (one 120 miles to the East, another 180 miles to the SW) can be heard in the mornings operating mobile if I do not set tone squelch. Tropo is also the reason that I can sometimes reach some repeaters in the foothills and southern Appalachians that have other mountains and hills completely blocking line of sight.
     
    W6KCS likes this.
  8. AI3V

    AI3V Ham Member QRZ Page

    Well, the troposphere dosn't give a hoot about what mode you use...

    On fm, using a simple colinear vertical, 10 feet tall, and a 80 watt amplifier, I could bring up at least one repeater on every 2m pair, some frequencys 2 or 3 (my Pittsburgh qth)

    Some were 75 miles or more away.

    One of the more notable tv stations I could receive was uhf 44/45 out of Alliance Ohio, about 86 miles away, another non line of sight path.

    I was located in the Brighton Heights rea of pittsburgh, about halfway up a hill, a VERY average qth.

    Get some antenna gain, get that skyhook above local objects, and run a modest amount of power, and you will find your vhf range well beyond 4/3.

    When I lived in Kingwood WVa, I had a lt23s transverter on 1296 mhz, and a single "looper" yagi.

    I would run nightly skeds with Wa3tts in pittsbugh, s7 signals, 24/7 about 80 miles or so.

    I also had a 10watt 6m rig, and a 3 el yagi, I would work a fellow in Harpers Ferry WVa nightly (104 miles)

    Again, I had a very average qth, and none of these paths were anywhere near los.

    Not even close.

    Rege
     
    W6KCS likes this.
  9. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    3V:

    You are absolutely correct in that the propagation, that you are seeing on 2-meters, is not line of sight / 4/3rds path. There are other propagation factors, tropospheric is one of the most common, involved. Depending on frequency, conditions, even time of day, seasons, etc., tropospheric propagation can exist for just tens of miles out to a thousand miles or more. However, the higher the frequency the less that tropospheric propagation plays a role. But, ducting is just one of the tropospheric propagations.

    For example, an 896 MHz system. Occasionally, there are short term conditions, tropospheric ducting is a major condition, in which ranges beyond line of sight / 4/3rds Earth curvature happen. But, most of the time the range just does not exceed the 4/3rds limits with vertically polarized antennas.

    You said that line of sight propagation does not exist. That is wrong! Terrain, as well as other physical obstacles, does block the signal especially as you go higher in frequency. You are comparing apples to oranges! Other forms of propagation definitely can extend the range and the polarization of the signal also plays an important role. Most of the time, a vertically polarized signal does not have anywhere near the range of a horizontally polarized signal whereas a horizontally polarized signal is much more likely to be enhanced by various tropospheric propagation. That was discovered, decades ago, and that is why weak signal VHF operation utilizes horizontally polarized antennas.

    The 4/3rds Earth curvature technology may be from the 1940s. However, it is still a VERY viable technology. I have run into too many instances where "modern", computer generated, antenna plots have severely overestimated coverage of, especially 450 MHz, 800 MHz, and 896 MHz systems (and, in some cases, even 150 MHz systems) where field measurements were undertaken. Then, when a 4/3rds Earth curvature plot was undertaken, taking into consideration line of sight where terrain is concerned, the plot has been within at least 95%, even up to as much as 98%, concurring with the field measurements. But, these systems used vertically polarized antennas and not horizontally polarized antennas.

    As for bringing up some repeaters 75-miles away with a 20-foot antenna: The whole idea of a repeater is to have the antenna as high above the terrain as possible. You were NOT working another station that far away, on a regular basis, over "normal" terrain, that also had an antenna only 20-feet above ground unless one, the other, or both stations were located on relatively high points with lower terrain in between if the antennas were vertically polarized. With horizontally polarized antennas, which are not used all that often for FM, then tropospheric propagation comes into play and such would be much more likely to happen such could happen on a regular basis.

    If line of sight propagation does not exist, then, explain to me why terrain / obstacles can definitely block the signal into those areas obscured by the situation and that can happen with vertical, horizontal, any angle between, and even circular polarization. You are just lumping all propagation means into a single concept. Line of sight is just one of the propagation means affecting a signal. There definitely can be, especially with polarization other than vertical, several propagations that are affecting a single signal all at the same time. Line of sight can be eliminated but the other forms still get the signal through.

    There is one form of propagation where vertical antennas have a definite advantage over horizontal antennas. Below around 3 MHz, true ground wave propagation results in ranges, using vertical antennas, that far exceeds that available using horizontal antennas. As the frequency increases above around 3 MHz (although it can, on occasion, make it to the 80-meter / 75-meter band), the true ground wave propagation decreases to the point of being just a few wavelengths from the antenna. For all practical purposes, true ground wave is very limited to almost being, basically, non existent with horizontally polarized antennas.

    However, ground wave is completely different from line of sight. Ground wave is just another one of the types of propagation.

    You seem to keep ignoring that line of sight is just one form of propagation. You keep saying that it does not exist because you can communicate way beyond what a 4/3rds propagation allows. I agree, wholeheartedly, that you can definitely communicate beyond that restriction. However, line of sight drops out of the equation but other forms of propagation then take over.

    Glen, K9STH
     
    W6KCS likes this.
  10. KF5FEI

    KF5FEI Ham Member QRZ Page

    Several springs or so ago, we had a hella tropo opening on 2m -- we were conversing with locals via their repeater in Mobile AL from Dallas / Fort Worth.

    We kept hearing them on our local repeater frequency during the morning commute -- one of us stopped and did a quick Google, and discovered their repeater did not require a tone. We all turned our tone off and 3 or 4 of us, including the wife, were able to key their repeater and have a conversation. Sadly, we only had about a 10-15 minute window.
     

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