I managed tom destroy the connector that goes into the rotator at the tower
end.
If anyone has one or two please let me know by email to me at
WK1W@ivanshapiro.com
Thanks 73
Ivan
WK1W
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
towertalk-request@contesting.com
Sent: Monday, October 17, 2016 2:48 PM
To: towertalk@contesting.com
Subject: TowerTalk Digest, Vol 166, Issue 53
Send TowerTalk mailing list submissions to
towertalk@contesting.com
To subscribe or unsubscribe via the World Wide Web, visit
http://lists.contesting.com/mailman/listinfo/towertalk
or, via email, send a message with subject or body 'help' to
towertalk-request@contesting.com
You can reach the person managing the list at
towertalk-owner@contesting.com
When replying, please edit your Subject line so it is more specific
than "Re: Contents of TowerTalk digest..."
Today's Topics:
1. Re: Voltage at ends of yogi parasitic elements? (john@kk9a.com)
2. Re: Voltage at ends of yogi parasitic elements? (Tom Osborne)
3. Re: Voltage at ends of yogi parasitic elements? (Steve, W3AHL)
4. 2-el array SWR question (160m) (Mike Smith VE9AA)
5. Re: Voltage at ends of yogi parasitic elements?
(Richard (Rick) Karlquist)
----------------------------------------------------------------------
Message: 1
Date: Mon, 17 Oct 2016 12:44:24 -0400
From: "john@kk9a.com" <john@kk9a.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Voltage at ends of yogi parasitic elements?
Message-ID: <9b6e307ba38029e2c9a4e4c0c25a98a4.squirrel@www11.qth.com>
Content-Type: text/plain;charset=utf-8
That is a good question. Years ago I thought of building an 80m vertical
with a relay on top to make it a 160m inverted L at my P40A home but I did
not know if even a vacuum relay would hold up and I knew that there would
be RF issues with the control wires running down the vertical. I had never
seen it done and did not want something likely to fail. If you are just
changing band segments most manufactures are using switchable loading
coils at the feed point.
GL
John KK9A
To: towertalk@contesting.com
Subject: [TowerTalk] Voltage at ends of yogi parasitic elements?
From: Rob Katz <rob.katz@thelegacycenter.com>
Date: Sun, 16 Oct 2016 23:09:11 -0400
I?m playing with some wire yagis, and I?d like to put relays at the ends
of the
parasitic wires to switch the director to a reflector (and vice versa).
If I?m
driving the antennas with a full 1.5 KW, what would be the maximum voltage
that
I can expect at the ends of the PARASITIC elements? Even a rough estimate
would be useful, I just need to get a sense of what kind of a relay I would
need to use.
73,
Rob K4OV
------------------------------
Message: 2
Date: Mon, 17 Oct 2016 10:10:44 -0700
From: Tom Osborne <w7why@frontier.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Voltage at ends of yogi parasitic elements?
Message-ID:
<CAG32hyO3CSZtPo-rxTYLFAsCLC+m_XLLQgPScFhdmiwOX_FR-w@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8
A friend here had a fixed 2-el quad on 80 and used a relay to switch the
parasitic element from reflector to director. He burned out some relays
before he finally got some high power vacuum relays. They seemed to work
OK. 73
Tom W7WHY
On Mon, Oct 17, 2016 at 9:44 AM, john@kk9a.com <john@kk9a.com> wrote:
> That is a good question. Years ago I thought of building an 80m vertical
> with a relay on top to make it a 160m inverted L at my P40A home but I did
> not know if even a vacuum relay would hold up and I knew that there would
> be RF issues with the control wires running down the vertical. I had never
> seen it done and did not want something likely to fail. If you are just
> changing band segments most manufactures are using switchable loading
> coils at the feed point.
>
> GL
> John KK9A
>
>
> To: towertalk@contesting.com
> Subject: [TowerTalk] Voltage at ends of yogi parasitic elements?
> From: Rob Katz <rob.katz@thelegacycenter.com>
> Date: Sun, 16 Oct 2016 23:09:11 -0400
>
>
> I?m playing with some wire yagis, and I?d like to put relays at the ends
> of the
> parasitic wires to switch the director to a reflector (and vice versa).
> If I?m
> driving the antennas with a full 1.5 KW, what would be the maximum voltage
> that
> I can expect at the ends of the PARASITIC elements? Even a rough estimate
> would be useful, I just need to get a sense of what kind of a relay I
would
> need to use.
>
> 73,
> Rob K4OV
------------------------------
Message: 3
Date: Mon, 17 Oct 2016 14:11:43 -0400
From: "Steve, W3AHL" <w3ahl@att.net>
To: <towertalk@contesting.com>
Subject: Re: [TowerTalk] Voltage at ends of yogi parasitic elements?
Message-ID: <9C50DE2A5585451D922F6E571D77F947@AhlboT440S>
Content-Type: text/plain; charset="Windows-1252"
Rob,
As an upper limit, the voltage on the ends of the DE should be about 3700
volts RMS or 5200 volts peak. This is based upon a 40M wire Yagi EZNEC
model with a source power of 1500 watts, feed point voltage of 271.7 volts
and current of 5.54 amps. Assuming the power remains constant along the
length of the element the end segment of the model shows a current of 0.41
amps, which would require 3658 volts RMS for 1500 watts. That is the
average current along the entire length of that end segment in the model, so
it doesn?t represent the worst case at the very end, but it is close enough
for your purposes. Round up...!
In the ARRL Antenna Book, 22nd edition, page 3-14, figure 3.28, there is a
graph showing the voltage on the ends of elevated radials of a vertical.
For 4 radial configuration the voltage is 1800 volts RMS at the ends. For
12 radials the voltage is only 600 volts, since the power radiated by each
wire is less. Extrapolating for a single radial yields 5400 volts RMS.
For the parasitic elements of the 40M Yagi the center segment?s current is
only 2.55 amps, with 0.185 amps at the ends. If I insert a zero current
current source (acts as a voltmeter in EZNEC) near the end (2% from end) of
the reflector element, it shows the voltage 2140 vRMS or 3026 vPeak. Doing
the same for the DE yields 4058 vRMS or 5038 vPeak. Same caveat applies as
given in the first paragraph. Inserting the sources as voltmeters slightly
changes the antenna behavior, as would using a voltmeter to actually measure
it.
Good luck with whatever you decide to try!
Steve, W3AHL
------------------------------------
I?m playing with some wire yagis, and I?d like to put relays at the ends of
the parasitic wires to switch the director to a reflector (and vice versa).
If I?m driving the antennas with a full 1.5 KW, what would be the maximum
voltage that I can expect at the ends of the PARASITIC elements? Even a
rough estimate would be useful, I just need to get a sense of what kind of a
relay I would need to use.
73,
Rob K4OV
------------------------------
Message: 4
Date: Mon, 17 Oct 2016 15:47:00 -0300
From: "Mike Smith VE9AA" <ve9aa@nbnet.nb.ca>
To: <towertalk@contesting.com>
Cc: <topband@contesting.com>
Subject: [TowerTalk] 2-el array SWR question (160m)
Message-ID: <000001d228a6$d8fc20d0$8af46270$@nbnet.nb.ca>
Content-Type: text/plain; charset="iso-8859-1"
Today I installed 160m vertical #2 in what will soon become a Comtek PVS-2
(2el BS/EF) array for 160m. (vy recently I installed 3 Comtek (wire)
4-squares for 20, 40 &80m.
Spacing is about 134? for these two 1/4wl 160m antennas. (oriented
NNE/SSW-best I could do, given the property here)
With 3 of these wire (4-el) array?s now under my belt, I measured very
carefully today with some confidence and cut all my wires accordingly
thinking I was done.
This 160m antenna is all wire and configured as an inverted L, same as the
original (ant#1). Two raised radials only 90? apart (not 180?) around
6-10? off the ground in the woods (varies with what trees I could find for
supports and they zig zag a little bit at the far ends for around 15? due to
property line constraints). They ?Gull-Wing? a very little bit at the PVC
hub where the vertical itself and coax and 2 raised radials all meet.
When I checked the SWR on the new antenna (#2) with my AA-230pro I was a
little surprised to find out my math wasn?t quite as good as I have enjoyed
on my 3 previous arrays.
SWR was ~1.5:1 or so at 1770kHz?.not quite what I had calculated. (by the
3rd array I thought I was getting pretty good at the math and had it
virtually bang on freq and flat as a board on the desired frequency)
My original vertical?s (#1) SWR remained virtually unchanged, pretty much
flat at 1835kHz?The original (#1) has a mile(1.6km) of in&on ground
radials?..Antenna #2 just has the 2 raised radials??I don?t have the PVS-2
relay box situated or two coax or control line(s) run to the center
yet?.more work for the coming days.
So my first question is, once I am feeding them with the PVS-2 box, will the
resonant frequency of both rise or is simply the proximity to one another
what causes the SWR to rise in these arrays?
It?s probably pretty easy at this point to tweak the just-installed
vertical?s (#2) SWR to dip precisely @ 1835 like the other one by adjust
some of wire lengths (either radials or the vertical itself), but I?d rather
get it right the first time, rather than trying to add wire later !
My 2nd question is I know (now!-oops) this type of array is supposed to be
fed with two equal 50 Ohm cables, but I only have 75 Ohm on hand. How bad
do you think the SWR will be affected? (I just don?t have the $$ right now
for a big spool of 50 Ohm coax, so will use what I have on hand.
I should mention there is a LOT of clutter 50?-150? to the north of this
160m 1/4wl vertical (three 4-squares, other wire antennas, etc.) so maybe
this
has affected the SWR and my Casio calculator is not actually broken?)
Thanks for any advice from the collective.
Mike VE9AA
Mike, Coreen & Corey
Keswick Ridge, NB
------------------------------
Message: 5
Date: Mon, 17 Oct 2016 11:47:49 -0700
From: "Richard (Rick) Karlquist" <richard@karlquist.com>
To: "john@kk9a.com" <john@kk9a.com>, towertalk@contesting.com
Subject: Re: [TowerTalk] Voltage at ends of yogi parasitic elements?
Message-ID: <6e9f2e55-5118-e746-bf08-a33a91361b6d@karlquist.com>
Content-Type: text/plain; charset=utf-8; format=flowed
On 10/17/2016 9:44 AM, john@kk9a.com wrote:
> That is a good question. Years ago I thought of building an 80m vertical
> with a relay on top to make it a 160m inverted L at my P40A home but I did
> not know if even a vacuum relay would hold up and I knew that there would
> be RF issues with the control wires running down the vertical. I had never
> seen it done and did not want something likely to fail. If you are just
> changing band segments most manufactures are using switchable loading
> coils at the feed point.
>
> GL
> John KK9A
>
For many years, I have had an insulator with a relay across it at
the 60 foot point of my 90 foot vertical. At first I tried vacuum
relays, with ratings up to 8000V. All worked for 6 months or so
and then failed. Then I figured out a simple way to modify a
big contactor to increase the contact spacing to 1/2 inch or so
as described here:
QST, May 2009, page 66
This relay has given many years of trouble free service.
It is likely that it has many 1000's of volts across it on
80 meters at 1500W. It just works.
I also use MJN series relays at the center of my 80 meter
inverted vee to switch in various mica capacitors to tune it
across the band. Again, it works perfectly. In that case
I didn't need to modify the MJN relays because the voltage
was within their 1000V rating.
Rick N6RK
------------------------------
Subject: Digest Footer
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
------------------------------
End of TowerTalk Digest, Vol 166, Issue 53
******************************************
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|