It got a bit quiet.
I have learned a lot about antennas & matching with this primitive
lash up.

http://dixienc.us/28FtVert/28FtVertical.htm

Too primitive for the Gurus but other students such as I may find it
interesting.

de W8CCW John
John Ferrell W8CCW

John, I like your radial plugs... Good creativity...
Strapping the antenna to the wood shed will not affect the tuning...
So what are you guys going to measure? Gain/impedence/current drop
across the inductor/?
Are you going to elevated radials?
There are a few easy ways to make capacitors... Early on they lined
mason jars with foil inside and out... Not tuneable but can be
swithced in and out to provide the bulk of the capacity and then a
small variable cap in parallel for tuning...
(I only thought of the banks of mason jars the instant I typed this...
I don't know what the capacity would be but they will take a heck of a
lot of voltage before arcing.. I will have to do that at home and
measure)
Anyway, you can stack up two or more 8X10 copper PCB and put Saran wrap
between them Won't take a lot of voltage but may be OK for 100
watts... You can order thin sheets of Teflon to insulate the copper
sheets... This will make a high voltage insulator for a capacity
pile... You can adjust the capacity by sliding the plates across each
other... Another way to tune would be a hinge so the plates are like
butterfly wings...
I vaguely remember someone, somewhere, published an article about ahigh
power tuner he built with the capacitor being two copper sheets
separated by thin glass... He used a threaded rod and a gear motor to
slide the plates back and forth... Had limit switches, automatic motor
reversing, yadda, yadda... TOo much work for a quick-n-dirty
experimentor like me...

Another way would be two aluminum tubes that just fit inside each other
with Teflon insulator... Sliding these in and out like a trombone will
change the tuning... I have actually done this.. Keeping the internal
spacing even is difficult and the insulator seems to want to bunch
up... Probably a pile of plates is better...

On 15 Aug 2006 04:39:27 -0700, "Denny" wrote:

Another way would be two aluminum tubes that just fit inside each other
with Teflon insulator... Sliding these in and out like a trombone will
change the tuning... I have actually done this.. Keeping the internal
spacing even is difficult and the insulator seems to want to bunch
up... Probably a pile of plates is better...


I know the spacing will be wider, but can two pipes with a PVC pipe
between make a usable capacitor? i.e. 1/4 od metal pipe inside 1/2 od
pvc, inside 3/4 id metal pipe. (numbers are fictitious, but you get
the idea.)

Buck
N4pgw

--
73 for now
Buck
N4PGW

"Buck" wrote in message
...
On 15 Aug 2006 04:39:27 -0700, "Denny" wrote:

Another way would be two aluminum tubes that just fit inside each other
with Teflon insulator... Sliding these in and out like a trombone will
change the tuning... I have actually done this.. Keeping the internal
spacing even is difficult and the insulator seems to want to bunch
up... Probably a pile of plates is better...


I know the spacing will be wider, but can two pipes with a PVC pipe
between make a usable capacitor? i.e. 1/4 od metal pipe inside 1/2 od
pvc, inside 3/4 id metal pipe. (numbers are fictitious, but you get
the idea.)

Buck
N4pgw
PVC is not a great dielectric. Polystyrene, polyethylene or teflon are far
better.

Dale W4OP

On Tue, 15 Aug 2006 01:36:27 GMT, John Ferrell wrote:
It got a bit quiet.
I have learned a lot about antennas & matching with this primitive
lash up.

http://dixienc.us/28FtVert/28FtVertical.htm

Please re-size your JPEG's. You are formatting them as 740x550, but you
are forcing folks to download images that are 2048x1536 -- approx. 8
times larger than neccc.

Not everyone is on fiber, cable, or DSL. (Even on caable, it was a slow
load.)

Thanks
Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
*** Killfiling google posts: http//jonz.net/ng.htm

Thank you Jonesy!
I knew that if I displayed my ignorance some one would teach me
something.

I just needed someone to explain the problem in terms I understand.

de W8CCW John

On 15 Aug 2006 15:19:55 GMT, Allodoxaphobia
wrote:

On Tue, 15 Aug 2006 01:36:27 GMT, John Ferrell wrote:
It got a bit quiet.
I have learned a lot about antennas & matching with this primitive
lash up.

http://dixienc.us/28FtVert/28FtVertical.htm

Please re-size your JPEG's. You are formatting them as 740x550, but you
are forcing folks to download images that are 2048x1536 -- approx. 8
times larger than neccc.

Not everyone is on fiber, cable, or DSL. (Even on caable, it was a slow
load.)

Thanks
Jonesy
John Ferrell W8CCW

The purpose of the whole thing is just a series of lab projects to
better understand what I think I know. I went into this thinking that
I could match up 160M with just a larger coil, it is not so! The TLW
software, EZNEC and G4FGQ's programs are very clear on that subject.

I work in a frenzy for a while on given parts of the antenna and then
sit back and digest what I have done.

I will first scrounge around a bit on the capacitors and see what I
may have stashed away before I spend too much effort fabricating
anything. There is a pretty good chance I can get away with some low
voltage stuff if I limit my testing to the MFJ 269 Analyzer. That is
probably the way to go. Also, there is no real reason to run 100 watts
to test.

I have not tried the Mason jars since I was about 12 years old but it
did not work out well then. I think the glass is too thick!

I think any performance measurements are well beyond my resources.
So far I have not used more than three radials but that has been
enough to convince me that an emergency antenna is easy to assemble.

de W8CCW John

On 15 Aug 2006 04:39:27 -0700, "Denny" wrote:

John, I like your radial plugs... Good creativity...
Strapping the antenna to the wood shed will not affect the tuning...
So what are you guys going to measure? Gain/impedence/current drop
across the inductor/?
Are you going to elevated radials?
There are a few easy ways to make capacitors... Early on they lined
mason jars with foil inside and out... Not tuneable but can be
John Ferrell W8CCW

OK John,
Well if you are sticking to the MFJ analyzer then the saran wrap will
work fine as the insulator...
And scrounging up metal isn't that hard.. PCB, or aluminum from a rain
gutter company, even Reynolds wrap, etc..
Yup, I thought about the thickness of the glass reducing capacity, but
if you have enough jars?!? Fun to think about... Someone needs to do
it and post the pics...
Check the yard sales.. Maybe you will be lucky and find an old AM radio
with the dual gang 365 MMF variable caps... That will work like
gangbusters... Back in the 60's I built more than one transmitter with
those caps and a pair of 1625's...
Keep us posted...
cheers ... denny/k8do

Hmmm!
I probably have a few of those in the junk box(es).

I am not doing anything new but I am getting some details through my
thick skull.

On 16 Aug 2006 04:42:52 -0700, "Denny" wrote:

OK John,
Well if you are sticking to the MFJ analyzer then the saran wrap will
work fine as the insulator...
And scrounging up metal isn't that hard.. PCB, or aluminum from a rain
gutter company, even Reynolds wrap, etc..
Yup, I thought about the thickness of the glass reducing capacity, but
if you have enough jars?!? Fun to think about... Someone needs to do
it and post the pics...
Check the yard sales.. Maybe you will be lucky and find an old AM radio
with the dual gang 365 MMF variable caps... That will work like
gangbusters... Back in the 60's I built more than one transmitter with
those caps and a pair of 1625's...
Keep us posted...
cheers ... denny/k8do
John Ferrell W8CCW