George,
Thanks for taking the time reply.. and yes you understand.. like I told
another respondee its about technical excellence and understanding ! Ya gotta
understand why your doing something.
My core was a FT114-75 and using the rule of 4 I wound 24 turns center tapped
for the secondary and 8 turns for the primary (50 to 450 feed transformer) and
yes the ration is the same so maybe not too far off after all. I have a large
assortment of ferrites here but just didnt have the correct one for this (I
would like to have had some of the ones that W8JI used) but am waiting to get
enought to meet the minimum order requirements of the vendors.
My gut is telling me however that the termination is not correct and I did not
have time to sweep the SWR of the
antenna yesterday or today. Part of my problem is that there is so much crap
on the web that there is a fair amount of wrong and half right info out there.
I would like to have measured the surge Z but when I tried I got a lot of BCST
interference that disturbed both the MFG and AEA analyzers. Consequently I am
not real sure what Z
to wind the termination transformer to.
Again thanks for the reply .. and thanks to all of the others who have replied
Jim
----- Original Message -----
From: w4buw@aol.com
To: wa3mej@comcast.net
Sent: Saturday, December 3, 2011 8:32:04 AM
Subject: Re: Topband: Beverage up but maybe has problems comments requested
Guess I still don't understand, as the impedance ratio is still the same, 9:1,
and hence the turns ratio is still the same also, 3:1,,,, I think what you are
driving at is to rather than making the turns one and three, to make it say,
three and nine, or four and twelve... this gets more turns on the core, and can
reduce variations due to physical location on the core...
Often this problem takes care of itself due to the turns ratio being an odd
number....like lets say, matching 50 ohm line to say 900 ohm load...
900/50=18, and sq rt of 18 is about 4.2... well, kinda hard to get 4.2 turns,
but can get 42 to 10, and that could drop to 21 to 5 for the same ratio...
think you can follow the math OK,, and see how often the odd impedance matches
often require the turns ratio that would meet the rule of 4 in terms of
multiple turns for both primary and secondary.
I really enjoy working with antennas, as that was my major interest in
College... got my BSEE from Clemson in '62, now retired for 12 years, and
really never did work in my field of interest. Started out with Fllorida Power
& Light as a protective relay engineer, then to DuPont in Textile Fibres making
type 6 and type 6-6 nylon, and my last 30+ years with GE, mostly in Quality
Assurance Management. Hard to realize I will be 73 soon, and retired for 12
years now... Have enjoyed ham radio since age 12-13 when assigned W4BUW.
Have fun with the antenna work... I am a firm believerr in the antenna being
the most important element in the station, in that it is there that you get
reciprocity of gain, both in receive and transmit. Transmission line loss is
often a big factor, moreson at the higher frequencies.... I enjoyed 160M work
but am not on that band now... got my DXCC there, and that was my goal...
Let me know how the toroid works out. If you have an MFJ antenna analyzer, a
neat check is to take a non-inductive carbon resistor and place it as the
antenna load, then check the SWR at the desired freq to see how the turns ratio
came out.... one other factor I'm sure you know is to get the correct core
material, so that it does not reach saturation, usually not a problem at the
lower frequencies... If you are building a library, Amidon has a good pub, and
of course there are several good ones, Sevik comes to mind...
73 & GL on the antenna work!!! de George, W4BUW
-----Original Message-----
From: wa3mej <wa3mej@comcast.net>
To: w4buw <w4buw@aol.com>
Sent: Sat, Dec 3, 2011 1:07 am
Subject: Re: Topband: Beverage up but maybe has problems comments requested
The rule of 4 is basically to ensure there is enough inductance I think (geeze
its been a long time since I studied this) but you multiply by 4 and get
1800/200. This is done with broadband tranformers but I thought
it was also for conventional transformers.. evidently not
----- Original Message -----
From: w4buw@aol.com
To: wa3mej@comcast.net
Sent: Saturday, December 3, 2011 12:03:09 AM
Subject: Re: Topband: Beverage up but maybe has problems comments requested
Not familiar with any rule of 4, or what it means... if you are looking at a 50
ohm transmission line, and a 450 ohm drive impedance for the Beverage, then
450/50=9. Turns ration then would be the square root of 9, which is 3, or 3:1
turns ratio. Just plain olde math... 73, George, W4BUW
-----Original Message-----
From: wa3mej < wa3mej@comcast.net >
To: topband < topband@contesting.com >
Sent: Fri, Dec 2, 2011 10:31 pm
Subject: Topband: Beverage up but maybe has problems comments requested
OK the Beverage is up, transformers installed, and coax hooked up. Let me
refresh everyone’ memory - I put up a 490 ft window line beverage which
turns out to be headed 30deg magnetic (best I could do on short notice) and it
has a termination transformer as opposed to the open/short termination.
I have noticed several things:
1. I am not impressed with the front to back. I don’t think it is all it
should be but I have not measured it.
2. Although I did work YN2CC last night I have not heard but one station
from Europe .
3. There appears to be some discrimination off the side of the antenna. The
8’s, 9’s etc are down as much as 20db.
Having said all of this I started rereading all of the literature and think I
may have discovered a problem with my transformers. I noticed that some
calculated the transformers based directly on the impedance of the line/ surge
z. By this I mean they calculated the transformer turns based directly on say
50 ohms for the primary and 450 ohms for the secondary.
When I designed my transformers I used the rule of 4 like is done with broad
band transformers so that the turns would be calculated on 200 ohms for the
primary and 1800 ohms for the secondary. DID I ERR?????? This might be why
there is no front to back like there should be and maybe even the why I can’t
seem to hear the Europeans.
Luckily changing the transformers is an easy task.
Comments please !
Jim WA3MEJ
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
-----Original Message-----
From: wa3mej < wa3mej@comcast.net >
To: topband < topband@contesting.com >
Sent: Fri, Dec 2, 2011 10:31 pm
Subject: Topband: Beverage up but maybe has problems comments requested
OK the Beverage is up, transformers installed, and coax hooked up. Let me
refresh everyone’ memory - I put up a 490 ft window line beverage which
turns out to be headed 30deg magnetic (best I could do on short notice) and it
has a termination transformer as opposed to the open/short termination.
I have noticed several things:
1. I am not impressed with the front to back. I don’t think it is all it
should be but I have not measured it.
2. Although I did work YN2CC last night I have not heard but one station
from Europe .
3. There appears to be some discrimination off the side of the antenna. The
8’s, 9’s etc are down as much as 20db.
Having said all of this I started rereading all of the literature and think I
may have discovered a problem with my transformers. I noticed that some
calculated the transformers based directly on the impedance of the line/ surge
z. By this I mean they calculated the transformer turns based directly on say
50 ohms for the primary and 450 ohms for the secondary.
When I designed my transformers I used the rule of 4 like is done with broad
band transformers so that the turns would be calculated on 200 ohms for the
primary and 1800 ohms for the secondary. DID I ERR?????? This might be why
there is no front to back like there should be and maybe even the why I can’t
seem to hear the Europeans.
Luckily changing the transformers is an easy task.
Comments please !
Jim WA3MEJ
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
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