Text 22587, 124 rader
Skriven 2006-01-15 11:53:16 av Roy Witt (1:1/22)
  Kommentar till text 22469 av Michiel van der Vlist (2:280/5555)
Ärende: Welding, brazing and soldering
======================================
15 Jan 06 10:00, Michiel van der Vlist wrote to Roy Witt:


 MvdV>>>>> One meter is long enough except for the reflector. That should
 MvdV>>>>> be 104 cm. I silver soldered an extra 4 cm to that rod. I used
 MvdV>>>>> a 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.
 MvdV> That is called the end effct.

Ok, same thing.

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

1.8-2.0, 3.5-4.0, 7.0-7.3, 10.1-10.5, 14.0-14.35, 18.068-18.168,
21.0-21.45, 24.89-24.99, 28.0-29.7, 50.0-54.0, 144-148, 222-225 (we lost
220-222 a few years ago), 420-450, 902-928, and 1240-1300...

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

Those above are off the DX map on my wall. There are even more in a
special frequency chart below the normal set. All in the SHF range.

 >>>> 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.

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

In California, the VHF and UHF bands are so crowded with repeaters, each
one is coordinated with RX/TX sub audible tone control. It's not uncommon
to have several repeaters on the same frequency.

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

There are frequency coordinating bodies within the Amateur community.
Southern California uses an agency nickmaned TAZMA and a UHF coordinating
body named SCCRBA (southern california coordinating repeater and base
association). Base meaning, remote base.

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

Yeup. That's what we ended up doing. But not before the bitch session
ended in the club meeting to authorize the expenditure.

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

Repeaters are required by FCC rules to ID themselves with a /R after the
call. i.e. K6RXT/R would be a repeater and if I used the repeater, I would
ID as usual (no /R).

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

Yes. Although they're usually required to have a remote system that allows
a control station to shut it down. Some do, some don't. The one I mention
above required that the trustee go to the site and pull the plug. My own,
had a remote receiver where I was able to do that with touch tones from my
base or mobile (a good use for the unused 220 band although mine was in
the 440 band).

 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.
 MvdV> Right.


Roy
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