So there is your answer.

L E Cebik (SK) did an excellent article on the Inverted-L called "Straightening out the Inverted L". You can get it from www.cebik.com for free if you sign up to the site. It will tell you everything you need to know.

Also modelling your antenna in EZNEC will show you the different azimuth patterns at varying elevations.

I notice that nobody has mentioned the SWR being affected by the co-ax getting pinched as it enters the vehicle due to the impedance of the co-ax being changed as the ratio of center to spacing of outer is massively reduced.

Talking of co-ax, with 1kW the amount of common mode and resultant RFI problems you'll have will be quite significant.

1) There are answers but they are usually not what the person asking wants to hear, ie that if you want good performance on lower frequencies you are going to have to get metal in the air and if you are using a vertical, it'll need radials unless its a vertical dipole. You cannot alter the laws of physics. Lets take a look at the end fed you're looking at. It is half an antenna. Where is the other half? If you don't lay out a radial system at the feedpoint, quite simply it is the outside of the braid of the co-ax you're feeding it with. What does that mean? RF in the shack and lots of RFI problems with you and/or your neighbours as your co-ax will be radiating a signal all the way back to the tuner.


As has been said, your best choices are to either add legs to your existing 80m dipole to create a fan dipole or to use ladderline to feed your 80m dipole turning it into a doublet. To create a fan dipole, you'd only need to add three more wires to give 80-40-20-15-10m as 15m is a third harmonic of 40m so the wire if cut for the bottom end of 40m would also work on 15m.

This will help.

http://www.karinya.net/g3txq/temp/angle_of_arrival_stats/aoa_dipole_elevations.png

 It shows that over the range of elevation from 0 to 35 degrees, a dipole half a wavelength high has a nice continual increase in gain and that one at 2 wavelengths high has two very nasty nulls up to -15dBi in that range at angles which are going to be very common for communications in the sub 6000 mile range. It demonstrats that if you are trying to talk to a station that is reached via an optimum take off angle/ angle of arrival of 15 degrees, a dipole at 2 wavelengths high is actually nearly 20dBi DOWN on a dipole 1/2 wavelength high.


Looking at that graph, 1/2 wavelength high is a good compromise. Yes it is down on 2 wavelengths high at the really low elevation angles but basically up to around 6000 miles an antenna 1/2 wavelength high is virtually as good and is better the closer you get. The dipole 2 wavelengths high is better from 6000-12000 miles.

Here is the forum articla I was looking for. It explains perfectly all about it in really easy to understand terminology. Please note that the graphs for the angle of arrival/takeoff angle for the various parts of the world are based on the UK but at the bottom is a graph for a dipole showing gain for various heights in wavelength for angles of arrival/takeoff angle for 0 to 35 degrees.

http://www.hamradiodeals.co.uk/forums/viewtopic.php?f=45&t=16602

Thanks to Steve G3TXQ for the information.

Not necessarily. The answer, as usual, is "it depends". In this case it depends on what you want to hear. For example, at a full wavelength high, it will be several dB down on one halfwave length high at take-off angles of 13-17 degrees OTTOMH. Whilst it is true that higher is better, there can be cases where you can be too high depending on what angles the signals are coming in to your QTH from a certain region.

We found during IOTA with the club tri-band beam at 60ft that it was simply too high on 15m band to work the EU from the UK. To work the EU we had to do it longpath. But it worked Oceana real well.

So what you need to do is to look at what the typical take off angles you need to reach who you want to hear and work for that height. Trouble is that what will be good for 20m could be way too high for 10m.

I went from TS480 to TS590. I still have a TS480. The 590 addresses all the shortfalls of the TS480 whilst keeping its best bits. It has far better close in strong signal handling and also a USB port for CAT and audio. It doesn't hear a lot more as in sensitivity but when you get on a crowded band, it really shines and the advantages of the roofing filters and IF DSP really show.

Here's a couple of things that instantly come to mind:

CW Tune. Its great to assign that to a PF button so pressing PF-A puts out a CW carrier for your ATU etc. On the TS480 it is fixed at 10W. On the TS590, you can press it then press PWR and alter the power it puts out.
In built ATU. The TS480 ATU will match roughly 3:1. The TS590 ATU will match 10:1 and I've verified that with an external SWR meter inline: Radio showing 1:1, external SWR meter still showing 10:1.
A and B DSP filter widths. On the TS480, you would have to set high and low cut then if you wanted to go back, adjust again. On the TS590 you can set high and low cut to one value, press the IF Fil button and then set another value - i.e set A to wide and B to narrow and then flick between them both with the press of a button.


I've never owned or used a TS2000 however we have a club TS850 fully filtered up which we've just replaced with a TS590 and it runs rings around the TS850.

Don't use the radios meter. You need to use a proper peak hold meter to measure SSB.

As above. You need to shorten the lengths by 4% if using insulated wire.

They add directivity. We use 3 phased 40m 1/4 wave verticals in our club for IOTA in a triangle shape. They are fed to a switch box so you can alter the directivity and they're great for nulling out noise. However they are a sod to set up. They need to be as parallel to each other as possible and getting a 50 Ohm match took 2hrs.

Why not just attach the fan dipole wires to the same feedpoint as the Alpha Delta? The RF would take the path of least resistance so it would just go down whatever wires it should be for the frequency you are on.

Ladderline would only make a difference if you had a high SWR but as it is a resonant dipole on each band, it won't.

How do you decide on a magmount? Simple....ignore them all. Drill a hole in the car and put in a proper body mount. Far better to have one small hole you can either leave filled with the mount, install a mobile phone/GPS/DAB antenna or a simple plug when you sell than have a 6" to 8" ring of scratched paint from a magmount or a bent body panel from a lip mount to straighten.

And not only will it perform better than using a magmount, they are cheaper to buy too.

Its not just the learning but operating. It is far easier to operate a radio with the settings you need and are likely to change accessible from a button or knob. I sold my FT950 because lots of stuff you use a lot was in menus. Want to change the NB level? Its in a menu. Want to change the DSP NR? Its in a menu. Want to change the power? Its in a menu. So to change the power on a FT950 you press the menu button, twist a knob to go through the menus until you get to the cryptic named one, which is always 50 items away from where the other stuff you use most of the time is, then use another knob to change the value and then press and hold the menu key to lock in the setting.  Then if you want to change the DSP NR setting, you repeat the aforementioned. To do that on the TS590 you press the PWR button on the front and twist a knob until its where you want it to be and thats it. If you then want to change the DSP NR you press and hold the NR button on the front and twist the knob until its where you want it to be.

Whilst it doesn't sound that bad as I write it, wait until you're doing it a few times in an hour.

 

I'd got shut of the old one before the QRM started to come in and I've not tried it on the replacement yet.