Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KC9PNN, Feb 23, 2015.
satire in public can't be a personal tirade.
are there no kids on your lawn?
Re portable or temporary operation: yes, try to find a location as high as possible and get above trees. But if you can't, there is no reason you can't support a VHF beam from a tree:
Take a look at the DK7ZB designs. Fairly easy to build: http://www.qsl.net/dk7zb/start1.htm
I've been in this situation a lot before. I wanted to try 2m SSB and didn't have money or much space. I used some steel tubing that I had found as a mast; it was just tall enough to get the antenna above the houses. Some rope and spikes in the ground held it up. As for the antenna, I built the quick 2-element quad in the ARRL Handbook. It required a small piece of wood and some stiff wire. I used 12AWG solid conductor wire for the two elements. I hooked up the FT-817 up to it and was able to communicated effectively throughout Southern California with it. Yes, it won't go much further, but it was great start and got me interested in the band. Later on, I made a longer boom and added some straight elements to it to make a quagi. 2m is small enough that your antenna elements don't need to be beefy.
One summer I used stacked 4 element yagis at 30 ft and an old Kenwood TS 700 sp, 10 watt transceiver....Did I want more? You bet. Did I make lots of contacts ? You bet. Sometimes we just use what we have. The 2 meter SSB folks are happy to make contacts no matter what you are using, they love working weak signals.
The Quagi (thanks to Wayne Overbeck, N6NB) is an easy design, and an easy to match antenna. But it does occupy more "volume" when portable than a simple Yagi, especially at 2 Meters.
Okay, use a push up mast but I'm not sure where you'll find an adequate tri-pod to insert that mast pipe into and be stable. As far LMR-400UF (Ultra Flexible) coaxial cable would be one product to use for it's Losses compared to RG-213/U. I suggest 1/2" Heliax coaxial cable because of it's Losses are much lower per 100 feet at 144 MHz. For all of the so-called Old Timers that have been operating 2 m SSB, where is your resourceful methods top acquire USED Heliax feedline and connectors? I've been on 2 m SSB since 1971 and did much horse trading to acquire USED Heliax from Commercial Tower, Radio Paging, Cellular / Nextel Companies and fellow hams. Generally Heliax is good for 30 to 40 years if it's been installed correctly and some Public Safety contracts require to have the feedline changed out every 20 years.
For USED 7/8" Heliax cable I would not pay more than $1 Per Foot, USED 7/8" RF connectors $15 each and for USED 1/2" Heliax Cable $.50 Per Foot, USED 1/2" RF connectors $5 each. Well granted Heliax is a little bit more difficult to work with than conventional LMR-400UF or RG-213/U and it will not rotate around a rotor / mast pipe, this is where you would use LMR-400UF or RG-213/U as short pigtail to the antenna(s) but lets say you have stacked antennas, well then you'll need a 2 or 4 Port 50 OHM RF Power Divider and these have Type "N" UG-21 RF connectors on them so you might as well learn how to make all of your connections with "N" connectors, first because they are constant 50 OHM connections and if you have to ADD adaptors, each adaptor will ADD .1 dB into the overall insertion Loss. Besides Height being a major concern so are Feedline Losses.
As far as mounting a 2 m beam atenna into a Tree ... I would recommend this approach since Trees are considered Foilage and at VHF, i.e. 144 to 148 MHz Trees can cause -2 to -6 dB RF Path Losses and UHF at 420 to 450 MHz can cause -2 to -10 dB RF Path Losses which is sometimes very hard to overcome no matter what you try so it's better steer away from using Trees.
Using a Kenwood TR-9130 25 W PEP RF Output with a good Yagi beam antenna at 25' good feedline should provide contacts between 250 and 300 air miles away.
For short term portable or FD use, look at the "Cheap Yagi" construction. They are easy to build (and expand) and while not normally meant for permanent installation, can be perfect for occasional outdoor and field day use. Just Google; there are plans ranging from 6 M through 23 cm. Easy to build, and as described, "cheap." But more importantly, effective. Maybe not as good as a commercial Yagi, but close enough for portable/Field Day use.
I do agree, that at least LMR-400 or similar cable would be a good choice, and antenna height is still "the higher the better," but in your portable /Field Day situations, safety is of tantamount importance. Don't install an antenna because of of a attitude "we think we can," make sure it's "we CAN do it." And have a few extra hands around in case some things don't go quite as planned.
I built a 2 element beam out of a stick I found in the yard, a scrap chunk of 12/3 house wire and a coathanger. Works pretty well around the Front Range. It's not about S-units, it's about intelligible communication, and if everybody in the QSO is comfortable, who cares?
I think we should put forth a more positive, try-it-out, experimenter attitude when trying to attract people to weak signal! The allocations are quiet except for contest weekends and special events. Plenty of room.
Different band, but years ago, I built a 6 meter log-yagi that I broke down for field use. Everything fit on top of my minivan. I would suggest gathering a few older large TV antennas & be building a log yagi. Short the rear element for a reflector & 3 driven elements, then a couple/few director elements (Shorted). Fold it up & go. Use screws & wing nuts lightly snugged to replace the rivets. Fold & go, spread & talk. You will need to figure the impedance (300 ohm I think) & make some form of balun for it. Best part is that most of the hardware is already there. If you have access to an antenna analyzer, it will be simple.