Text 22366, 147 rader
Skriven 2006-01-13 17:11:18 av Roy Witt (1:1/22)
  Kommentar till text 22232 av Michiel van der Vlist (2:280/5555)
Ärende: Welding, brazing and soldering
======================================
13 Jan 06 11:17, Michiel van der Vlist wrote to Roy Witt:


 >>>> Yeup. 36 inches equals 3ft, 1m = 39 inches.

 MvdV>>> 36 inches is too short for most of the elements for a 2 m. beam.

 >> Yeup. But it's plenty long for a 220MHz or 440MHz beam...Most
 >> of what I worked when I built the Quagis was 440...

 MvdV> Ah, 220 is not an amateur band here. I have not done much on 440.

220 isn't much of one here, anymore. I havn't fired my tri-bander (Drake
UV3 - covers 2mtr, 220 and 440) up for awhile to check the activity in
Texas, but I suspect it's even less than the 440 activity I've found.

 MvdV>>> One meter is long enough except for the reflector. That should be
 MvdV>>> 104 cm. I silver soldered an extra 4 cm to that rod. I used a
 MvdV>>> pice taken from the last director.
 >> Maybe long enough, but the diameter doesn't suit the frequency.
 MvdV> How so? The 4 mm rods do fine for a 2m beam.

I think the term is called skin effect. I have yagi design software that
if you use 4mm wire and then change it to 6mm or 7mm, the elements are
automatically shortened. Not by much, but they are shortened.

 >> You could use shorter elements by increasing the diameter.

 MvdV> yes, they have to be a little bit shorter if they are thicker. But
 MvdV> just a little bit. also the bandwidth increases if the elements ar
 MvdV> thicker. Note that our 2 m band is only 144-146, half the bandwidth
 MvdV> of yours.

That short? Ours goes up to 148. Although, the use of a yagi like you
built would be useful in the same segment, as that's where the SSB band
usage is supposed to take place, below 144.900 I think, and FM simplex in
the middle of 146, as in 146.520.

 >> I used 3/8in (10mm) aluminum to build a pair of 3 element beams
 >> for the 2mtr repeater I was custodian of for a while.

 MvdV> Repeaters here do not use beams.

We used them because of the footprint they'd provide. We also had another
repeater sharing the same frequency, further north from SD county. Later
we switched to an antenna with 6 element folded dipoles for the same
coverage.

 MvdV> Also they invariably use the same antenna for receiving and
 MvdV> transmitting.

Yes, but the beams had seperate tuning devices on them. Being broadband
antennas, they worked satisfactorily, but not the best thing that could
have been used. Also, the price was a big factor among the older
generation who always griped when we spent money on the repeater.

 MvdV> That puts some constraints on the antenna. It must be very robust.

These were. I used 1 inch square tubing for the boom and 3/8 inch solid
aluminum rod for the radials. They were still in pristine condition when
we removed them from service. I forget how many years they were up there,
but I was long gone from the club when I was given one of them for my own
use.

 MvdV> The slightest bad connection anywhere will cause problems.

Yeup...although the connections were all soldered and the UHF connector
used was sealed from the weather. No problems with them ever.

 MvdV> I once had a loose tie wire scraping against a metal rain drain.
 MvdV> Gave a terrible cracking sound....

These were bolted to a special plate that I fabricated in my shop, so that
the beams could be pointed downhill from their 5700 foot perch to sea
level, some 20 miles away.

 >>>> It's non lead based, so the antenna won't know it's been painted.
 MvdV>>> It does not have to be conducting to absorb rf energy.
 >> Neither do trees...yet we tolerate them in our RF lives.
 MvdV> True. But we would avoid them if we could...

Especially at UHF...

 MvdV>>> them. But thereality is that ham radio is on the decline. It is
 MvdV>>> not going as fast as FidoNet, but it definitely is on the
 MvdV>>> decline. We have very little influx form the younger generation
 MvdV>>> here. There are so many other interesting toys for which they do
 MvdV>>> not have to go trough the effort of getting a license for. :-(
 >> That's true, plus in the US, there is Part 15 of the FCC rules
 >> that allow them to experiment with low power RF, so there's no
 >> longer a need to have a HAM license.
 MvdV> Even the licence free CB is near dead here....

I have a pair of Cobra 138 CB radios. One is in my Silverado. The truckers
in this country still use the frequencies and they're always a good source
of information about road conditions, etc. I've always had an attraction
to CB, as there are a lot more people out there on the road than on the
HAM bands. Although I've found truckers using 146.52 as their private
communications on the road too. With no license, I might add.

 >>>> I then became the repeater custodian until they got tired of
 >>>> maintaining it.
 MvdV>>> I was the custodian for the local 2 meter repeater PY3PYR for
 MvdV>>> over ten years. Then another group wanted to build a new repeater
 MvdV>>> and so I let go. I was tired of it anyway...
 >> I lent my call to the repeater and it had an audio ID'er,
 >> which said my call
 MvdV> Can't do that here.

That used to be the case here too. But the FCC has relaxed those rules.

 MvdV> If it is unmanned it needs a callsign of its own. One in the
 MvdV> special range for repeaters.

Those licenses have been phased out here...you can get a club license yet,
maybe a special operation license, but you won't get one for a repeater
anymore.

 MvdV>>> You can see a picture at: http://www.vlist.org/nera.jpg
 MvdV>>> The picture was taken last year in the reciever hall of the main
 MvdV>>> Dutch monitor station at Nederhorst de Berg. (NERA). Toy can see
 MvdV>>> some equipment in the background. The occasion was that it was
 MvdV>>> the last time our biannual meetings took place at that location.
 MvdV>>> The station is now disassembled and replaced by a series of
 MvdV>>> unmanned remote controlled station scattered over the country.
 >> That room looks like the control room and some of the labs in
 >> the Palomar Observatory on top of Mt Palomar in San Diego county.
 MvdV> All control rooms sort of look alike these days. 19 inch racks and
 MvdV> computer screens....

I think you're right there.

 >>>> What do you use for rod?
 MvdV>>> I mostly use the "universal" 2 mm electrodes. The ones with
 MvdV>>> cladding. The 2 mm is the core, with cladding they come to just
 MvdV>>> under 4 mm.
 >> So it's commercial grade welding rod...I was wondering if you
 >> might have invented a different way to weld.
 MvdV> These rods are not expensive. For the little welding I do, it is
 MvdV> not worth to experiment with a cheaper alternative.

Sounds about right. Don't fix what isn't broken.


Roy
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