[OZAPRS] smart meters ?

[Ray Wells]

Gerard,

1. My preferred (simplest) method is a Q-section to a 4:1 balun. 
However, that method is non-adjustable, except by changing the Zo of the 
Q-section. A serious disadvantage is that an 1100 ohm Q-section requires 
2, 0.5mm wires spaced 2m apart - not very practical, to say the very 
least. There is enough vertical height to the antenna feedpoint to 
cascade two Q-sections, to perform the impedance match in two steps but 
I haven't done any math on that yet. I seem to remember some info on 
this in The Antenna Engineering Handbook by Jasik.

2. I have pondered over Delta matching but have not yet extended that to 
any practical application. I can't get my head around any phasing errors 
that might result from feeding the antenna away from the centre. EZNEC 
might be able to model that arrangement.

3. A grounded quarter-wave section (any Zo), with the 4:1 balun 'tapped 
up' from the grounded end (like the matching section of a J-pole) would 
be adjustable and has the advantage of providing direct grounding of the 
antenna to minimise precipitation static, etc.

5. An ATU mounted at the antenna feedpoint would provide a nice 
band-pass filter, in addition to any matching but, it needs a 
weatherproof enclosure and a cap capable of handling near 800V. I 'may' 
have something suitable ex some long pensioned off military gear.

6. Of course I could throw my hands in the air and stick with my 
existing dipole and balun. My knees would appreciate not having to climb 
the tower.

Ray vk2tv


On 12/12/10 10:38, Gerard Hill wrote:
> How will you match it, Ray? Delta match or T match perhaps?
> Maybe its discussed in Wells' article from 1943, but its hard to get 
> hold of without an IEEE subscription.
>
> Damien, I'm currently using an end-fed inverted L antenna for 30m 
> APRS. Originally it was designed as a 3/8λ for 160m like this one: 
> http://www.n8mr.com/topband.html
> I've shortened it to about 50m long so that its a 5/4λ on 40m and 7/4λ 
> on 30m. At 18m high, the horizontal length (32m) is less than an 80m 
> half wave dipole so it might fit your lot. Polarisation is mixed so 
> the vertically polarised local mobiles can be received as well as the 
> more distant stations via sky wave.
>
> Cheers ... Gerard, VK2IO
>
> On 12/12/2010 8:10 AM, Ray Wells wrote:
>> With EZNEC the various wires have to attach to a single segment that
>> contains the source. As I understand it, the NEC engine can't handle
>> multiple wires attached to the source, hence the single, centre segment.
>>
>> I haven't looked at fan dipoles in EZNEC yet, I'm too busy trying sort
>> out the Wells' Quadrant* for 30m.
>>
>> * Wells' Quadrant comprises two half-wave elements at right angles to
>> each other at the feed point. The resulting radiation pattern is
>> essentially omni-directional horizontal polarisation, within about
>> 1.5dB, according to EZNEC.
>>
>> Ray vk2tv
>>
>> On 12/12/10 07:53, Damien Gardner Jnr wrote:
>>> I'm thinking I got too technical.. either fan dipoles are completely
>>> flawed, or antenna modelling just doesn't work on them.. I finally
>>> finished putting the 20+10 dipoles in (lordy I re-learnt a lot of trig
>>> last night!), and it looks absolutely horrid for SWR.. yet everything
>>> I can find on the 'net suggests 1.5:1 on each band.. I might just
>>> build it and see ;)
>>>
>>> --DG
>>>
>>> On 12/12/2010, at 6:30 AM, Ray Wells wrote:
>>>
>>>> Gee, I didn't get that technical <grin>
>>>>
>>>> Ray vk2tv
>>>>
>>>> On 11/12/10 23:51, Damien Gardner Jnr wrote:
>>>>> Ewwww, ray was correct - swr on 30m would be 38 (609+j895) on 30m,
>>>>> due to the other band dipoles not being full wave etc on 30m.. Ok,
>>>>> will be a 40(+15)/20/10 dipole then ;) I had contemplated shoving 5m
>>>>> on the bottom, but it might look kinda rediculous in the middle..
>>>>>
>>>>> --DG
>>>>>
>>>>> On 11/12/2010 11:35 AM, Damien Gardner Jnr wrote:
>>>>>> ooh, really? I'm building one based from here
>>>>>> (http://www.hamuniverse.com/multidipole.html) - yard isn't big
>>>>>> enough for 40m of dipole for 80m band, so having already built the
>>>>>> centre (http://www.rendrag.net/wpg2?g2_itemId=11755), I thought I'd
>>>>>> just make the top band 40m, and add 30 in the middle.. Might shove
>>>>>> it through MMANA first to see what happens, before I finish cutting
>>>>>> and assembling that behemoth, and then pulling it up between the
>>>>>> masts..
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> DG
>>>>>>
>>>>>> On 11/12/2010, at 11:26 AM, Ray Wells wrote:
>>>>>>
>>>>>>> Previous experience of adding a 30m dipole to an existing
>>>>>>> 20/40/80m unit was not good. 30m doesn't have a harmonic
>>>>>>> relationship and it presented weird and wonderful reactance to the
>>>>>>> feedpoint. ymmv
>>>>>>>
>>>>>>> Ray vk2tv
>>>>>>>
>>>>>>> On 11/12/10 11:19, Damien Gardner Jnr wrote:
>>>>>>>> Lol, though monitors aren't allowed in bins, or even hard waste
>>>>>>>> roadside pickup :(
>>>>>>>>
>>>>>>>> I have to say I do like the dell service, where if you order a
>>>>>>>> computer with a monitor (can just be a laptop), they pickup the
>>>>>>>> old monitor for free and dispose of it :) Though they had a heart
>>>>>>>> attack when we asked if we could dispose of 60 21" sony's through
>>>>>>>> that :-p Actually, they had enough of a heart attack when we
>>>>>>>> asked about ordering 60 LCD's as 'spares' for our existing
>>>>>>>> machines.. ;)
>>>>>>>>
>>>>>>>> -_DG
>>>>>>>>
>>>>>>>> Off to build a 40/30/20/10m fan dipole this arvo after work, will
>>>>>>>> be interesting to see how much better that is than my TEV-1 
>>>>>>>> vertical!
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