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   Home   Help Search  
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 21 
 on: Today at 12:05:20 PM 
Started by KD9FRQ - Last post by WB6BYU
Quote from: KD9FRQ

I am guessing that adding the simple knot in the line to keep it from slipping through the hole in the PVC spreader
and act an anchor will not be an issue.



I'd probably choose a figure-of-8 knot rather than a simple overhand knot for that purpose to avoid
weakening the wire.  Even better would be taking a turn of wire around the pipe so the stress on the
wire is spread out over a larger area, rather than putting all the pull on the knot.

But I'm always tying knots in my antenna wires:  usually one at the feedpoint for strain relief (separate
from the electrical connection) and a loop of some sort where the support rope attaches.  I use
stranded, insulated wire and treat it as rope in this regard.

Yes, the knots do affect the resonant frequency for a given length of wire - slightly.  A loop knot will
often act like a shorted stub of wire, providing some inductance, but not enough to replace the same
amount of wire run straight.  The effect depends on exactly where along the wire the knot is placed.
But generally the difference is smaller than the effects of height above ground, wire size, ground
conditions, coupling among the wires in a multi-band antenna, and other things that also affect the
resonant frequency in the real world, and the normal process of tuning a dipole will take them all into
account.  (The traditional formulas, including those on the license exam, are just approximations, and
can't be expected to give exact results over the range of dipoles that hams might build.)

 22 
 on: Today at 12:02:54 PM 
Started by WA9WIK - Last post by WA2ISE
I did a mod where I replaced the nicads with 8.4V LIion batteries from a camera.  I changed the charging jack on the battery pack to a 3 pin one that accepts a cable I connected to the LIion camera charger.  With this setup, the battery still sees its companion charger.   Works well.

 23 
 on: Today at 11:57:57 AM 
Started by KI7JKQ - Last post by WA2ISE
The gutter may act as a director or a reflector antenna element.  Depending how long and what band you use.   And if there are any joints, there may be poor electrical connections that might create harmonics.  And the downspout would also make things more "fun". 

 24 
 on: Today at 11:55:06 AM 
Started by K3STX - Last post by GW3OQK
Paul, I always use solid state rectifiers to maximise voltage and minimise drop on key-down. 420v dc off load seems low for that transformer voltage, I would have expected 500. What is the smoothing circuit you are using (LC?) and resistance of the transformer and choke?

I have an MO PA rig (5763, 807 equivalent) with 350v key down and only get 12 watts max out on 80m. I considered using a bridge rectifier to double the voltage, and maybe get 4 times the power, but as I have a 200 watt amp why bother.
73
Andrew

 25 
 on: Today at 11:41:38 AM 
Started by EI9GMB - Last post by K7KBN
The CQ from Florida shirt has an outline of California on it.   Grin

Beat me to it!! Grin

 26 
 on: Today at 11:35:50 AM 
Started by W2JJV - Last post by K7KBN
Quote
After school I was sent, eventually, to USS Kitty Hawk.  It was a great 3 years...
Was assigned to the RTTY Fleet Flash Net and did no code after RM school until becoming a .

Bummer!  Get trained but never get to use it.  On my first Westpac, CW was all we used most of the time because the TTY machines and the "ancillary" equipment seldom cooperated.  Got my "speed key qualifications" taken care of at Airpac, broke out the Vibroplex "Presentation" my uncle had given me when I went into the Navy, and so off into the sunset toward the Rising Sun...sounds strange that way!
I was wearing my RM2 crow when I left the Kitty Hawk, made RM1 in USNR and then had a chance to jump to WO1 - and jump I did.

 27 
 on: Today at 11:26:50 AM 
Started by N6YFM - Last post by K6AER
Any amplifier that can share multiple signals and have any kind of a decent IMD will have to be class "A" just like a cell phone amplifier. To share the needs of 2 signals at 1 KW each will cost north of $50,000. It would be much cheaper just to buy a couple of ACOM 600's.

SO2R is such a small segment of the Ham population their is almost no sales potential.

Every day on 20 and 40 meters I hear signals that are 100 watt and just above the noise floor. I wish more hams could afford amplifiers for it would make the HF experience much easier.

Most stations are antenna limited due to location and restrictions. Gone are the day of putting up a tower in the typical suburban lot.

I like the looks of the FLEX amplifier with the Green LED's. Maybe I should string some green LED lights around my tube amplifier. I could do that for about $4.00. Christmas lights are on sale.

 28 
 on: Today at 11:20:08 AM 
Started by AE5X - Last post by N2RJ
5A7A 2006

 29 
 on: Today at 11:19:56 AM 
Started by KI7JKQ - Last post by KI7JKQ
I have a small city lot with not a lot of options. No HOA, but very nice neighbors, and I want to be sensitive to their views. I have been trying out an Alpha Delta DX-ee inverted V with the apex at 16' feet as a temporary antenna on a rear deck (doesn't impair views), but I need to do something more permanent and higher.

The only option that doesn't involve modifying views is to use the property line on the side of my house. It is 3 feet away from the side of the house with 24" eaves, but I can use the house to stabilize a 40' mast and hoist the DX-ee without serious view blocking. The good part is that there is not another house on the other side of the fence so it is clear. The only issue I need advice on is a 34' aluminum gutter at a height of 16' along the roof line.

I was thinking of trying to put the inverted V above the gutter line, parallel to it along the property line. I assume that unless the two ends of the V are substantially higher the aluminum gutter will couple with the antenna and detune it. So how high do the lower ends of the antenna need to be to minimize the influence? With a 90 degree angle I can get the ends 6-10 feet above the gutter. Is that enough? Another option would be to put the mast in the corner of the property and slope the DX-ee along the same property line, but the gutters will still be an influence, perhaps worse, since the dipole will cross the gutter at a 45 degree angle within 1 foot of the aluminum.

I'm also wondering if it would be worth it to simply replace the gutter with a PVC gutter instead and make the issue go away, albeit with some expense.

Verticals would be difficult on this lot. There is very little room for radials, although a limited counterpoise might be possible. I've also thought about working an end fed wire just above ridge height, or even an inverted L, where I have about 72 feet of horizontal run.

Main questions is about the gutters, though. Any advice?

 30 
 on: Today at 11:13:44 AM 
Started by K3STX - Last post by K1ZJH
If he is using a screen dropping resistor, the value will have to be changed. The combined screen current will cause excessive voltage drop through the dropping resistor.

Looking the transformer spec's, I suspect you are bit light in current rating, however. 

Pete

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