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Messages - W5LZ

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Antennas / Re: Double Bazooka antenna plans
« on: July 25, 2013, 06:46:30 AM »
Most of the 'playing' with a bazooka antenna was before 'eHam' or the other review sites were around so I can only go by what I've read and experienced.  Almost all of that 'testing' was done on 80 meters, that's where I hung out, and there were others there that used a bazooka type antenna too.  I have to say that this sort of 'testing' was subjective, not objective in nature.  I certainly didn't have the equipment and antenna range to do a really objective type of test.
Antenna comparison testing is very difficult to do objectively, there are just a huge number of variables involved in that and they can 'go' either way good/bad.  'On-the air' testing has got to be one of the most unreliable means of testing antennas.  What if there's no one listening, what if there's too many listening?  Anything around an antenna can affect how it behaves, so how can you have two antennas up at the same time, on the same band, and they not affect each other?  That doesn't mean that I doubt what you experience doing this sort of testing!  It does mean that it isn't exactly a 'take it to the bank' sort of test.  It's subjective.
If a particular type/style of antenna works for you then by all means use it. 
 - Paul

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Antennas / Re: RV HF antennas, whats the best?
« on: July 17, 2013, 05:39:39 PM »
Of the two choices you give, I'd pick the screwdriver antenna.  It's at least tunable, that 'marine' antenna isn't.
 - 'Doc

3
Antennas / Re: Double Bazooka antenna plans
« on: July 16, 2013, 05:19:54 AM »
In one of the early ARRL 'Antenna Compendium' series a very extensive series of tests were done on the bazooka antenna.    It wasn't 'on the air' type testing, but measurements done as on an antenna test range.  There were quite a few variations in the antennas tested covering feeding methods and I honestly don't remember what else.  My copy of that 'Compendium' (#2 I think?) has disappeared over the years so I can't cite it, rats.  The article was done by a well known author, can't remember his name though.  It would make for interesting reading...
 - Paul

4
Antennas / Re: Double Bazooka antenna plans
« on: July 14, 2013, 05:36:01 AM »
Here are some observations I've noticed about bazooka type antennas.
It's a 1/2 wave length antenna and will behave/radiate as any 1/2 wave length antenna will.  It will be
have the same radiation pattern and be affected by all the things any such antenna is affected by,
height above ground, whats around it etc.  The biggest difference is in how a bazooka antenna is fed.
It's fed through a tuned circuit, a lot like a 'beta' or 'delta' match.  That feeding method is why it has
such a 'wide' usable SWR range.
What type of coax cable used in the construction can make a huge difference in performance.  Coax with
a 'foam' type insulation will not handle the higher voltages present as well as a cable that uses a 'solid'
type of insulation.  So, RG-8X isn't a great type of cable to use for a bazooka antenna.  (A voltage increase
is always a product of impedance transformations.)  The old RG-8 type cable with solid inner insulation
tends to work better.
The old 'classic' bazooka with the open wire feed line type 'ends' uses those larger 'conductors' because of
end-effect, high voltage at the ends of a 1/2 wave antenna.  Makes for less arcing, corona discharge. 
Considering the intent of the original bazooka antenna, radar, which involves high power 'pulses', corona
discharge was a real problem.  With typical amateur use those large conductor 'ends' aren't really needed.
You can still use them, won't harm a thing if you do.
The type of coax used in it's construction will also determine the different lengths of various parts of a
bazooka antenna.  The overall length will stay pretty much a 1/2 wave length, but the lengths of those
center sections, the tuned circuits, will be affected by the velocity factor of the coax cable used.  Those
center section lengths (electrical 1/4 wave lengths) are affected by the velocity factor of the cable, making
them 'shorter' than the full length of 1/2 of that antenna.  That's why they are shorted toward the ends of
the antenna instead of just continuing to the ends, 'tunes' those center sections, right?
So why don't the 'numbers' work out exactly?  Because there are a lot of variations in coax cable, none of
it is ever exactly the same on the same spool, much less the same manufacturing 'batch'.  See how that
affects things?
Performance or efficiency is determined by what you are measuring with.  A bazooka antenna is not very
efficient away from it's design or center frequency.  A typical SWR meter is a terrible means of measuring
performance or efficiency.  At best, an SWR meter can only indicate how well impedance matching is done
which has very little to do with how well an antenna 'works', how it performs.  A dummy load is a very good
example of that, great SWR, lousy antenna.  If your main criteria is SWR then a bazooka antenna is a very
nice antenna to use.  If it serves your purpose well, then use one!  There still ain't no such thing as a free
lunch, but if the price isn't too steep, why not?
 - Paul

5
General discussion (QSO) / Re: How do I hookup rig and computer to run PSK31 ?
« on: July 13, 2013, 04:51:57 PM »
If your laptop has a sound card then just download a suitable PSK/RTTY program.  Interface the sound card's input to the radio's audio output, and the sound card's output to the mic input of the radio.  Use VOX for keying the radio.
 - Paul

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Antennas / Re: Double Bazooka antenna plans
« on: July 12, 2013, 05:04:44 AM »
In general, meaning that there are a lot of variable in that sort of comparison, I think it'd probably work out about even.  Both are 1/2 wave antennas so the difference in 'performance' isn't going to be that different.
I don't mind using a tuner and have for a long time.  I'm not too 'fixed' on having a 'perfect' antenna system, I've found that one that isn't exactly 'perfect' will do just as well in some cases.  That tuner can also make an antenna 'usable' on other bands, sort of, you know?  Tuners aren't a 'cure-all' but they can make things easier...
 - Paul

7
Antennas / Re: Double Bazooka antenna plans
« on: July 10, 2013, 06:45:22 AM »
I don't doubt your friend's findings, but you have to keep in mind that they are subjective, not objective in nature.  A bazooka antenna does have a wider 'apparent' usable band width, but only at the lessening of efficiency the further you get away from it's 'design'(resonant) frequency.  As the frequency range increases from it's design frequency the efficiency of the antenna lowers because of reactance present in the antenna because of it's method of being 'fed'.  Reactance doesn't radiate anything, it contributes to a 'dead' loss in radiation.  The means of measuring SWR, a typical SWR meter can't distinguish between 'R' and 'X' (which combined equals impedance).  The SWR meter 'sees' a combination of 'R' and 'X' that it 'thinks' equals 50 ohms impedance, but doesn't mean 'R=50' and 'X=0' at all.
Why does it seem like an improvement over his wire dipole?  Because of how he's measuring things, using an SWR meter.  Those things are just not very 'accurate' in measuring radiation efficiency, just impedance matching.
 - 'Doc

8
Antennas / Re: 40 and 80 meter wire dipoles... How far apart?
« on: July 06, 2013, 09:47:16 PM »
I don't see any reason it wouldn't work.  If you could mount them 90 degrees from each other (an 'X') it would minimize any interaction.  There will be some, but it shouldn't be all that objectionable.
 - Paul

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Antennas / Re: Tilt-over Vertical Antenna I am working on
« on: July 03, 2013, 06:43:41 AM »
Brass toilet bowl float??  That's my guess.  What will the total height of the thing be?
 - Paul

10
Digital Modes / Re: Digital Ham Radio
« on: July 01, 2013, 05:24:59 AM »
I think I've tried most of the 'digital' modes at one time or another.  I have PSK and SSTV capability now but don't use either very often.  The digital voice modes I have very little interest in at all, just none in common amateur use around here.  Doubt if there will be in the fore$eeable future.
 - Paul

11
Antennas / Re: Antenna options for those living in apartments
« on: July 01, 2013, 05:20:14 AM »
I would think the simplest solution would be to use an antenna that doesn't require an RF ground (one that doesn't use ground/dirt as it's 'other half').  A safety ground (lightning) is a completely different 'animal'.  If possible, it's a good idea to safety ground any antenna.  And/or place a ground point device in the feed line before it enters your building.
Safety grounding is NOT a simple thingy.  Usually, it also isn't cheap if it's done right.  A 'spark-gap' type device is NOT a very good safety grounding device for antennas.  It isn't fast enough and only 'grounds' one half of the antenna, usually.
 - Paul

12
General discussion (QSO) / Re: Raspberry Pi and Amateur Radio
« on: June 30, 2013, 10:14:05 AM »
I've never even heard of it before.  But, if it will do what you want it to do, isn't a huge pain in some part of your anatomy, then why not?
I'm not fond of being on the 'cutting edge' anymore, too many painful 'cuts', you know?  So, if/when you get the thing to do just what -I- want it to do, then tell me about it!  How do you tell what I want it to do?  How would I know?  ;)
 - Paul

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