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The place to talk about specific radios, equipment and accessories. Do you prefer the latest generation of rigs and antennas or do you like the classics? Discuss it here!
Never seen a plant pot antenna to comment, I have seen decoupling sleeves made from plant pots,
its good to hear you are interested building homebrew antennas looking for info & asking questions,
keep it up, there is much to learn.
I would give you a pass just because you are interested enough to build something radio related if I was in charge
W8JI
"An antenna with a poor ground using few radials cannot have a support mast grounded to the radial common point (at least it shouldn't if designed properly) There is no exception to this!
Thanks for all your help. I spent the majority of today securing my mast, some concrete and a wall bracket made sure of that!
Insulating the antenna from it and I used a new length of Coax. I followed the guide and created a choke of five coils as close as possible to the 259 socket.
Right away I could tell I had it right! The swr changes ever so slightly as soon as I raised it off the ground and predictably changed as I adjusted the length of the antenna.
I settled for an SWR of 1.1 on Channel 19 midband and this went to 1.2 on UK FM. Full power gives me 1.3.
At the same time I attached the 2 meter antenna on the mast mid way up and 'for now' I'm happy to leave it up as is for as long as it lasts! I don't think I could get it any better.
All the advice you gave was perfect and my understanding of antennas has increased!
Happy to be of help GDog,
Best of luck with the foundation test .
W8JI
"An antenna with a poor ground using few radials cannot have a support mast grounded to the radial common point (at least it shouldn't if designed properly) There is no exception to this!
The important thing to remember is that ground plane horizontal elements are trying to simulate a really large surface area. Your antenna on a boat a few inches above salty water will give it the almost perfect ground plane. The concept of 'planes' in both RF and audio rely on a large surface area and a mirroring effect. If the surface area is smaller than it should be, performance is always compromised. A car roof with central antenna is really quite a poor ground plane, but while performance is reduced, it's a compromise that works. A biscuit tin will often allow an antenna to be tuned, but it's no guarantee the antenna actually works that well. 3 or four quarter wave radials produce a 'sort of' ground plane effect, but the perfect donut shape of the polar performance has gaps in it distorting the pattern, but electrically making a workable match. Clearly though antennas where we have wavelengths of many metres are going to be compromised. The degree often being significant. Slapping a vertical with no radials on a staff pole means the pole itself has to become part of the antenna - so it's often a sort of vertical unsymmetrical dipole. You have the correct length going up, and a random bit of metal going down. However, the metal is still doing something. You now need to consider the antenna and the support as 'the antenna system'. If you change this, performance will change too. You cannot see performance, so seeing a low VSWR on a meter means electrically you have max power out, minimum power reflected - but how the antenna system actually squirts that into the ether can be amazingly poor. Over the years, we've kind of drifted into low VSWR meaning job done - the quest is over, we have 1:1. Year ago, many people had field strength meters, so you could walk in a constant distance circle around your antenna and it read exactly the same through a full 360 degrees - or, as usually happened, you had a dirty great gap in the circle - and it would always be in just the wrong place - where everyone you want to talk to, lives!
You have a poor meter, evidenced by the differing readings on different powers, so you are just guessing on what is going on. See if you can borrow one of the fairly cheap meters that can tell you where your antenna is resonant. You may have a good VSWR match, but if you discover the actual thing resonates way, way from your operating frequency, you might realise all is not well.
Thanks for taking the time to explain that. Could you please go a little further in terms of how to use the field strength meter properly? Other tha holding the SWR meter near the source and watching the needle move on transmit (which I have seen on youtube)
I have looked on the Internet and either I've not searched for the right thing or very little information on the correct use and instructions in my meter mention nothing about how to correctly use the Field Strength functionality.
I think it would go some way in filling in the holes in my knowledge while covering a good portion of the subject of good antenna installation that may help others.
Since my original post I have learned more and yes you are absolutely correct that a Good VSWR isn't everything! Also my equipment is on the cheap it's true.
