Text 22469, 101 rader
Skriven 2006-01-15 10:00:02 av Michiel van der Vlist (2:280/5555)
  Kommentar till text 22366 av Roy Witt (1:1/22)
Ärende: Welding, brazing and soldering
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 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.

That is called the end effct.

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

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

 > That short? Ours goes up to 148.

I know. same for othar bands. You have far more bandwidth that us. 3.5-3.8,
7-7.1 (Soon to be changed to 7.7.2, but that's still less than yours) 50-52,
430-440.

There is probaly more, but these are the ones that come to mind.

 >>> 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.

Over here these things are coordinated. One won't get the license for a
repeater if there is such a conflict.

Especially in the 2 meter band, there is a shortage of repeater channels. Only
16 channels 12.5 kHz wide. we simply can not allow everyone to set up repeaters
at will. So there is lisencing and frequency coordination.

 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.

We did not have that problem. We bought a commercial grade antenna paid for by
voluntary donations from the users. We had regular meetings where we sold
bumper stickers.

 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.

I hope they will never do that here, as with the shortage of frequencies that
would certainly result in a mess.

 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.

So you are allowed to run unmanned transmitters on a regular license?

 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.

Right.

Cheers, Michiel

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