|[AMRadio] new antenna and matchbox a bust.|
wa9nqw at nconnect.net
Tue Jan 30 09:45:53 EST 2007
The germanium were all that was available at the time that had a relatively
low forward voltage drop. I think that modern shotkey diodes may work as a
> From: Brett gazdzinski <brett.gazdzinski at verizonbusiness.com>
> Reply-To: Discussion of AM Radio in the Amateur Service
> <amradio at mailman.qth.net>
> Date: Tue, 30 Jan 2007 08:38:10 -0500
> To: "'Discussion of AM Radio in the Amateur Service'"
> <amradio at mailman.qth.net>
> Subject: RE: [AMRadio] new antenna and matchbox a bust.
> Well, that's a thought!
> I would be kind of reluctant to change things as
> the antenna seems to be working quite well on 80 and 40,
> but I must keep this in mind, instead of using end insulators
> and rope, just tie the rope onto the wire and pull it through
> and partway down the trees.
> I think the wireman sells insulated antenna wire that
> should hold up well in the sun.
> As it is, I have thick strong rope, and #14 solid copperweld
> and both have a high breaking strength and that allows me
> to pull the antenna quite tight.
> There is a difference when running high power though,
> many here seem to be running moderate power, which will
> work with mfj antenna tuners and various baluns and feedlines,
> traps, etc, but some of that stuff may not work with
> higher powers and high swr's.
> I would worry about setting fire to the trees
> running the wire right on them, depending on the voltage/
> current points, insulation rubbing through, wet or dry
> wood, etc....
> Even though I turn things down, I still seem to blow out
> the ham gear designed for 2000 watts, the swan peak reading
> watt meter bit the dust, as did the diodes used to
> read SWR in the heathkit antenna tuner.
> I replaced the diodes (with 1N34a) but the meter needs
> calibration now. A giant pain in the butt to get at the
> parts and adjustments.
> I wonder if I could use a better diode type, higher
> voltage and current to withstand the spikes.
> Does anyone know why germanium diodes (1N34a) seem to
> be used in all the SWR bridge circuits?
> What advantage does germanium have?
> I have lots of insulated wire
>> First, Nice QSO Sunday night.
>> Second, my antenna is a full 80m dipole supported at 75ft by
>> two pinetrees
>> that are <50ft apart, that means that there is a LOT of
>> Dangle there(around
>> 35 ft or so I think). I just pulled the support lines over
>> the trees, and the
>> ends of the dipole actually drape over the top and down the
>> back of each
>> tree. Its insulated #12AWG stranded wire, fed with cheap
>> brown 300 ohm twin lead,
>> that drops down to a choke balun inside the attic (15 turns
>> at 4.5 inch
>> diameter). This is definitely NOT an optimal setup. BUT I
>> do get out, and I've
>> been heard as pretty far off on AM, and work the North East
>> with No Problems.
>> (I run a Valiant at about 120watts output). I can load it
>> up on any band
>> except 160, using my el-cheapo MFJunk tuner. (160 causes
>> quite a light show)...
>> The biggest problem I have with it is that the pines are
>> always dropping
>> branches after storms and sometimes they pull down the
>> antenna or part of it
>> with them.
>> SO if there is a significant vertical portion to your dipole,
>> don't sweat
>> it. It will just add some vertical polarization, and change
>> the pattern, but
>> using trees will skew that anyway.
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