OK, I got a copy of RUFZ.zip but it appears corrupted. Can anyone point me
to a good source for the code ??? (contest)!!!!
********************************************************************
* W8CAR pems_st_dk@noeca.ohio.gov *
* Dan Kovatch *
* Antennas are the key - BUT an ALPHA sure doesn't hurt! *
********************************************************************
>From Larry Schimelpfenig <lschim@mailstorm.dot.gov> Fri Oct 6 17:51:39 1995
From: Larry Schimelpfenig <lschim@mailstorm.dot.gov> (Larry Schimelpfenig)
Subject: Slopers Fred Hopengarten
Message-ID: <Pine.SUN.3.91.951006123213.21674A-100000@mailstorm.dot.gov>
Bill, it's sad to note the losses that Steve suffered, while happy that
you and RJ lucked out.
In my travels around the country with the Coast Guard I have made
extensive use of slopers. Typically I used the top three guy wires on a
60 or 70 foot tower as slopers on 80. The tower usually had a two element
triband quad on top. The system played very well.
When I was running the MARS station here in Alexandria (K4CG) circa 78-82 I
had a quarter wave sloper on a 60 foot self supporting wind mill type tower
with a KT34XA at the top. This site used to be a Coast Guard
Communication Station, and still has ground screens running all over the
place. One is under this tower, and the sloper was a killer. Howie K4PQL
and I tried all sorts of configurations of wire supported by 100 to 120
foot towers to improve on the performance of that sloper. It was a waste
of time!
I also put a quarter wave sloper off the top of a 120 footer that
supported a 4 element Telrex 20 meter monobander. It also played
exceptionally well.
The only time I couldn't get a sloper to play was at my present qth.
After getting 55ft of tower with 8 feet of mast sticking out the top in
the air, I decided to put an 80 meter quarter slope up. Didn't matter how
much wire I used, it wouldn't resonate. As soon as I stuck the KT34XA at
the 55ft level and cut the sloper to a quarter wave it resonated. Or
maybe I would be safer to say the vswr in the cw part of the band dropped
to below 1.5:1! Putting the rotatable 40 meter dipole at the top of the
mast made no difference in the vswr curve on 80.
At my present qth, my gut feeling is that the N4KG reverse fed ground
plane outplays the sloper, but I can't make an a/b comparison because of
the interaction between the two when they are both on the tower.
I've seen a number of folks say they couldn't get a sloper to work. I've
had 8 slopers or sloper systems up at various locations and the only one
that didn't work didn't have a top hat.
de Larry K7SV - lschim@mailstorm.dot.gov
>From David O. Hachadorian" <74752.115@compuserve.com Fri Oct 6 17:48:46 1995
From: David O. Hachadorian" <74752.115@compuserve.com (David O. Hachadorian)
Subject: K6LL/6
Message-ID: <951006164846_74752.115_EHL125-1@CompuServe.COM>
If you hear K6LL on Saturday, it will be from Imperial County,
CA, NOT Arizona. We will be screwing around with an all-band
vertical over salt water (Salton Sea,) just to see how it works,
and to pass out a few CQP Q's until sundown.
Dave, K6LL
74752.115@compuserve.com
>From jreid@aloha.net (Jim Reid) Fri Oct 6 18:20:50 1995
From: jreid@aloha.net (Jim Reid) (Jim Reid)
Subject: Insurance
Message-ID: <199510061720.HAA01320@hookomo.aloha.net>
Aloha from Kauai, Bill,
Hope you don't have the same experience with insurance
companies as we have our here since Iniki wiped us out
three years ago. No insurance company will sell any
hurricane/wave wash coverage in Hawaii. The State of
Hawaii has established a "pool". Any home owner can
participate, as long as he has a "regular" home owners
policy; which of course, no mainland insurance company
will now sell on Kauai! So now, the only homeowners policies
available are from State of Hawaii insurance companies,
one of whom could not pay out all the damages for which
they were liable (if that is the correct term in the insurance
business when a policy holder has a loss.) So many,
many insured homes on Kauai were repaired by loans
from FEMA, the SBA, etc., as the insurance companies
had not enough money to cover the damages!
Same thing with our automobiles. Mainland companies,
most of them anyway, have backed out. I am now
covered by Daiwa Insurance Co. Guess where
they are located!
Seems too bad the American mainland insurance companies
wish to pretend that Hawaii is a foreign country, as does the
DXCC. We feel just a bit abandoned. Maybe I should throw
my support to the Hawaiian Sovereignty Movement (not
sure I spelled thay right).
You cannot get insurance on antennas or towers even if
they are a structural part of your home out here!
73 and best of good fortune as you clean up and repair.
Jim, AH6NB
>From broz@csn.net (John Brosnahan) Fri Oct 6 18:48:34 1995
From: broz@csn.net (John Brosnahan) (John Brosnahan)
Subject: 91B info in response to W0UN
Message-ID: <199510061748.LAA16901@lynx.csn.net>
After I suggested that the 91B discussion be taken off line to save
reflector BW, I received 8 or 10 requests from interested parties that it be
kept on line. In the mean time Garry responded directly to me and with the
outpouring of interest I suggested that he cc: the reflector with his latest
comments, but unfortunately he isn't able to and asked me to repost his
message as well as my final comments, in order to satisfy the cravings for
91B info.
--John W0UN
-------------------------------------
(from NI6T)
Many thanks for your detailed response, to which I add only a few
comments.
You wrote:
>
>The demands placed on a generator by a rapidly varying current load
from a
>keyed or ssb modulated amplifier are especially difficult for a
generator
>since the time constant of the varying load is much faster than the
time
>constant of the response time of the mechanical governors on
generators.
>This can be helped by running oversize generators (where the mass of
the
>generator itself provides an additional flywheel effect) but this is
>difficult on an expedition.
Virtually impossible, in fact. The decision to purchase the 3kVA Robin
Diesel was made after many FAX exchanges between Mats and myself. I had
done rough calculations as to what the amp might require or
--alternatively--what we could expect from it for a given generator
capapcity. Naturally, cost and weight were issues. Mats was justifiably
concerned about moving generators across the reef. The Robin was a
beautiful unit, however, with a self-starter, and ran like a clock.
Diesel fuel is safer, of course, and there did not seem to be much of a
weight penalty: it was about the same size as the 3.3 kVA gasoline
unit. The battery for the self-starter became the means for putting a
third station on the air, after losing a crucial power supply
overboard. Mats spliced two battery cables, connecting his IC735 to the
raw DC output of the Robin; the battery provided the peak current
needed and he was QRV.
> It is also important to minimize the percentage
>change from min load to max load by running as much on the generator
as
>possible so that max load is near the capacity of the generator by
running
>lights and other gear even during the daytime to increase the current
drawn
>under "min load"--ie amp not keyed. This reduces the range over which
the
>governor needs to to work and makes sure that the generator is not
coasting
>during receive periods.
With only a 3kVA generator, adding more loads only served to deprive
the amp of steady-state power. In a situation like that, you are damned
either way.
>
>
>I was momentarily confused by "emitter" resistors in a vacuum tube amp
but I
>assume that transistor terminology has become pervasive and that you
mean
>the cathode resistors...
Har! Yes, that is exactly right. After 30 years of solid state
electronics, I have forgotten what a cathode is.
But the progressive failure of the cathode resistors
>doesn't explain the time delay that you noted between amp switching
and the
>appearance of power.
Maybe not, but the time delay did increase, so perhaps the increase in
cathode resistance influenced the control circuitry.
>
>
>Unbypassed cathode resistors do provide negative feedback (ie
degeneration)
>and result in more drive being required but in a grid driven amp with
lots
>of drive this is not a bug but a feature since you are throwing away
most of
>your drive power in the untuned grid resistor anyway.
I did not say it was a bug, and I am sure degeneration is used
precisely to prevent overdrive by lowering gain.
Any change in plate
>efficiency one way or the other is so small as to be a
wash--especially in
>view of the requirement to add some series resistance in the plate
lead to
>limit the energy dissipated inside the tube during an arc over.
Typically
>this plate resitor will be on the order of 50 ohms and a cathode bias
>resistor will be about 1/5 of this value. With only a few watts
disipation
>required in the cathode resistor this is pretty insignificant compared
to
>the 2 kilowatts of anode input power.
Good point.
>
>But I must disagree with you on the statement of slightly compromised
IMD
>statement when using catode resistors. (Snip)
The Eimac
>design uses 11 ohms for the 4CX600J and the ETO 91B uses 12 ohms for
the
>Svetlana 4CX800, which is a pretty close match to Eimac's design.
Actually, one always would expect degenerative feedback to reduce
distortion, but I was actually looking at the published numbers in the
Svetlana 4CX1600B data sheet--using 24 ohms and an apparently large
conduction angle. I do understand that IMD numbers are misleading, due
to to sensitivity of the cusps to operating point.I learned long
ago--in an undergrad electronics lab project--that
amplifiers--especially tetrode amplifiers---have so many interactive
parameters as to make such comparisons quite difficult. My "test amp"
then was my own homebrew pair of 6146's.
>I have to admit that I am a homebrew fan as well and I am building a
number
>of single band 8877 amps. I chose the 8877 since I had a lot of pulls
left
>over from atmospheric radar projects. If I were to go out and buy new
tubes
>I would choose the Svetlana tubes at this point due to their price
>differential. I feel that they are good tubes at a bargain price.
Eimac
>tubes in general are also good tubes but are becomming prohibitively
>expensive for ham use, unfortunately.
>
That price differential is providing a feast for George Badger, W6TC,
and Svetlana. The 4CX800A is priced virtually at the Eimac 3-500Z and
the retail price for a 4CX1600B is only about $385! And I am told these
prices are much more than what they can be had for in Russia! Ehrhorn
is no fool: he has really created some gross margin by dropping his
manufacturing and parts costs!
DXpeditioning, contesting, my newsletter and DXing have kept me from
diving into this amp, and I do not have your resources, but I have
accumulated most of the parts, and am eagerly anticipating the joy of
building the beast--something I wanted to do as a kid. The local flea
markets have been productive. Wish I had a sheet-metal shop, but I do
have access to help. I could use a 50 ohm 100W globar--the resistors I
have are larger. Got any kicking around?
>
>I will try to work closely with the Heard group to insure reliable
operation
>of the 91Bs. My support is available both before the expedition and
during
>it. I feel pretty knowledgeable about the amps but obviously not as
>knowledgeable as the designers at ETO.
I am glad that you are there as a resource for the Heard Herd.One feels
pretty helpless when the amp craps out in the middle of nowhere. I do
feel, however, that for most DXpeditions, it probably makes sense to
bring a moderate-size amp. 500W is a great improvement over 100 watts,
and such an amp is certainly more manageable in terms of carrying,
shipping and powering. That was the lesson I took home for next time.
>
Garry, NI6T
-----------------------------
response of W0UN
Garry, after my comment about the lengthy discussion and taking it off-line
from the reflector, I received a number of comments about how our discussion
was one of the more infomative ones in recent months and please don't take
it off the reflector. Since I think we have wound down a bit at this point
and since I think your most recent comments were sent directly to me you may
way to cc: the reflector just to bring this to a close with all of the lurkers.
Been an enjoyable discussion and you raised a number of interesting
technical issues that got the juices flowing and got the old books down from
the shelf. The cathode bias resistor is more complex in its effect than I
had recalled but it was nice to review all of my old books (and not find
much, in fact only one reference) and then give Eimac a call. Been a while
since I have talked to the factory.
I will continue to try and help ETO with the Alpha 91B issues and at a loss
to figure out what is involved with the delayed output issue. WIll check
the schematics in more detail for some clue.
73 and thanks for the interesting discussion.
John W0UN
BTW if you cc: your latest note to the reflector then I will cc: this one
so that the lurkers know that it has quieted down with amicable results. HI
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