Thinking of toying with my antron 99 tomorrow -

my idea is to top coil the antron by winding half of an old gr5v (or as much as required) all the way up the top section to try make it more resonant on 20m (i've got a spare top section which is why i've chose this way as to not ruin the antron if i choose to revert back)

Q1. does anyone have any experience in doing the same / similar?

Q2. Does anyone have any measurements of what sort of length i would need to wind onto the top section?

Q3. or am i just waisting my time

i'm quite open to main roads and neighbours so i'm trying to keep a clean look (basic) antenna i've tried a half size g5 but i attracts too much noise at my QTH

thanks for any feedback

You do of course realise that you are trying to use an 11m vertical on 20m? I know that the A99 is quite widebanded, but I think you are stretching it somewhat.

The spare top section that you have, is that part of the original aerial or the Fire-up?

Why do you get noise with the G5? Did you have one leg attached to the house? You probably don't get much noise with the A99 because it is deaf.

Isn't there some sort of matching network built into the base of the Antron? If so, shifting the frequency by so much wont be as simple as adding electrical length to the whip.

Steve G3TXQ

Details of the matching section is here http://xoomer.virgilio.it/ham-radio-manuals/a99.pdf

Yes you're wasting your time. Its a half wave antenna so you need to make it a half wave long for 20m unless you intend taking the base apart to bypass the matching section. You're not going to do that coiling wire onto the top section.

Its hard to beat a simple dipole on 20m. Build one with the wire you were going to use on a A99 and use the pole supporting the A99 to support the center of the dipole and configure it as an inverted V.

no i'm trying to modify an 11m antenna for 20m i appreciate it in standard form is an 11m antenna like wise a length of wire in standard form is just a length of wire not an antenna

the spare top section is from when i upgraded to a firestick which with a longer length coil supposedly turns a 11m 1/2 wave into a 5/8 wave which is where my theory comes if i increase the coil further will it become resonant fourth down the frequency?

that's the part i'm trying to figure steve would the matching network be able to match the antenna to the feed if i increase the antenna ;length down to 20m, was just curios if anyone had experience, i know lots have just gutted the antron and used it as a fibreglass p[ole with a so239 attached but i'm wanting to swap and change top sections as required if it does work as i intend

cheers

Turns out it has a perfect SWR on 18mhz with the top section coiled with a G5 so back to the drawing board all though I never messed with the tuning rings

A perfect SWR (assuming you mean 1:1) is not the holy grail.

Do you have access to an analyser?

A couple of things.

You didn't answer my questions.

I have a dummy load, it gives me a perfect SWR, from 1.8, to 20, then it goes to about 1.05 on my analyser, at about 28.480.

I never answered the why I have noise with a G5 because that wasn't what my post was about, my post was about converting a Antron (because I already have one to play with) so I have a simple clean looking antenna without wires strung up all over due to my house location, my garden runs parallel to old folks bungalows with all sorts of telecoms inc 2 broadband location cabinets etc... , I wanted a feedback backed with technical reasons on why it will work not a "you do realise it's an 11m antenna" answer. I do know that SWR vs resonance is an whole other ball game but I don't have a Antenna analyser to prove either or so I will go the old fashion route of build it try it build it again

Cheers anyway

Hi . Here is a suggestion ! why not use the A99 on ten metres by moving the tuning rings to get a match on 28.5Mhz and then use the top of the mounting pole as the centre of an inverted V dipole as suggested by Alistair ? If the mounting pole is tall enough it could be an inverted V for 40metres and you can then add traps for 20 metres ....hey presto you have 3 Hf bands without a tuner HTH

What some people think is a waste of time, others will enjoy.

I'd say keep playing around mate it's all part of the hobby.

Cheers Paul

Yes play about with it ........ I'd try making it a 'inverted L' shape by doubling its length ( plus a bit for error) add the wire to the top then trim it back to match it in.
Seen this on a mods web site for a modification to a silver rod style vertical but can't find it again sorry

You'll need to reconstruct the matching coil at the base before you even attempt any thing else (extra turns, different tapping point), more trouble than it's worth IMHO.