MFJ-1622 counterpoise S Shape - Page 1
Forum section: electronics / rf-microwave

author: Pluscrafter
author_rank: Regular Contributor
timestamp: May 01, 2021, 12:31:35 pm
content: Can the counterpoise of thr MFJ-1622 layed down vertically on a wall of the balcony and how is the saftey?

author: coppercone2
author_rank: Super Contributor
timestamp: May 01, 2021, 06:51:50 pm
content: lmfao when I looked up that unit I started laughing imagining its off a balcony in the citylooks like a anti lunar laser designed by dr. evilfor the people that just wander in this thread and are too lazy to google

author: Pluscrafter
author_rank: Regular Contributor
timestamp: May 01, 2021, 09:03:15 pm
content: It is only for the night when nobody will see it. I also have a stealth dipole but that is only resonant in the 20m band and the problem is for compliance with the safetey distance to the antenna my siblings can't sit at their desks.

author: coppercone2
author_rank: Super Contributor
timestamp: May 01, 2021, 09:12:23 pm
content: i don't think it will look dangerous, just a little funnyhang a little flag on the end and no one will think anything of it

author: Pluscrafter
author_rank: Regular Contributor
timestamp: May 01, 2021, 10:07:42 pm
content: Problem is only if a counterpose in such a Shape and location will work as inntended as an RF ground or not and if there is any risk for other devices, because there is a PC in behind the balcony?

author: coppercone2
author_rank: Super Contributor
timestamp: May 02, 2021, 12:05:20 am
content: I don't think you can know unless you do field level tests with a meter and have a spec for the computer (is it put together properly with all the stuff tightened, is the power supply decent, etc.

author: coppercone2
author_rank: Super Contributor
timestamp: May 02, 2021, 12:50:12 am
content: A general measuring field intensity guide to various equipment for legal/safety reasons would be interesting to see (i.e. get by with several different methods with several different kinds of equipment, in some frequency band).

author: Pluscrafter
author_rank: Regular Contributor
timestamp: May 02, 2021, 12:51:54 am
content: The PC is an ACER Perdator G6-710 from 2016 and the cables are okish thighend. The max transmitting power is 50W

author: coppercone2
author_rank: Super Contributor
timestamp: May 02, 2021, 08:38:32 pm
content: Ok I think what you need to do to be safe is get a field strength meter and establish measurements around your antenna in a sphere shape (not just your level) as per the FCC regulations for safe field strength within close distance after you do anything weird with a counterpoise starting at low levels and observing all legal property rights (no trespassing).Most people will run a cable to the roof which is over a non occupied attic or set this up in their backyard so you have a unique and more difficult situation. The effects of modifying a ground plane are hard to predict (i.e. how much of a dipole it is) and probobly prediction is unacceptable for regulatory agencies when operating at license power levels.https://hamradioschool.com/rf-exposure-evaluating-your-station/Keep in mind the 'station' model that the goverment has in mind is a isolated shack in the back yard with an antenna nearby fed with a feedline at some distance away from things. (the ideal situation).https://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet65/oet65b.pdfLuckily you are operating at a low power, so it seems non issue, but you should obviously make sure there are no complaints, because interference is a problem if there are complaints, and there may be sub par equipment around that is effected (you can't exactly put pressure on someone to shield/replace janky equipment that malfunctions because of a weird thing you put up nearby, it would likely involve the land lord, if this is your situation)this is a common sense approach that may be relevant (particularly point 4)https://www.eham.net/article/5654it is still relevant towards determining if there is interference even in a private dwelling because it might take a while to notice if something has gone haywire (i.e. alarm system, home automation/control, garage doors, etc). Not to mention if you put 5W interference into someones crap, they might just get annoyed by a buzz or distortion, but if it totally fucks up a system someone is liable to fly off the handle and cause problems).For a computer you might want to do the following1) run a memory test program while doing intermittent transmissions ot see if causes errors2) listen to the computer to see if there are any acoustic signs of interference (messing with fan speeds, power control loops)3) do a packet transmission test or other methods to see if internet speed or connectivity is effected4) check bios readout to see if things are nominalKeep in mind it might do something strange like effect a dialup, DSL, satelite or cell phone connection, possibly, or something you do not have.

author: tkamiya
author_rank: Super Contributor
timestamp: May 02, 2021, 11:45:53 pm
content: Counterpoise aren't supposed to be resonant to any particular frequency, so it should work. Theoretically, there will be a high voltage point along the way, but if you are going to lay it down on some surface, impedance will be low enough that it won't matter. Safety wise, as long as you aren't running major power, I wouldn't worry about it.

author: A.Z.
author_rank: Super Contributor
timestamp: May 03, 2021, 07:54:48 am
content: Sounds like the server had an hiccup and my replies disappearedWhile the "S" shaped counterpoise will probably work, I believe that a better approach would be laying a metallic grid on the balcony floor (possibly covering the whole floor), the grid could then be covered with a proper size rubber mat and connected with a short run of "fat" wire to the ground connection of the antenna, such a setup will give you a better RF ground for the antenna, then you'll also want to run the feeding coax horizontally for some length and add it some good chokes (seeherefor some ideas) like for example these onestwo or three of those along the coax feeder should be enough to stop your coax from acting as part of the antenna and "persuade"the antenna to use the counterpoise (or the metal grid); then, by the way, since the antenna is just outside the balcony, the surroundings will be affected by its radiated RF (to work the antenna MUST radiate) , so using a field strength meter to check the RF levels will be a good idea