"Ian Jackson" wrote in message
...
In message , Albert
writes

"Ian Jackson" wrote in message
...
In message , Andy
writes

"Ian Jackson" wrote in message
...
In message , atec77
writes
Andy wrote:
"Ian Jackson" wrote in
message ...
In message , Andy
writes


"Ian Jackson" wrote in
message
...
Andy, is your endfed wire the one in your other thread of the 8th
June (ie
the 80 Meter End Fed, fed with coax at the far end)? If so,
presumably the
tuner is at the shack end. Or are you feeding it from the shack
end.


In message , Andy
writes

--

Hi Ian,

Yes its the same. The tuner is at the shack end (house) and I'm
feeding the
antenna with 50 Ohm RG-58 C/U coax at the far end of the garden.
If
I
can
get it working well I will replace it with some RG-213 that I have
here. I
put it back up yesterday and started experimenting again.

The End Fed at the moment has 15 feet of 300 Ohm slotted ribbon
feeder. This
is all I had left spare. One side is connected to the wire antenna
and
the
other side left, not connected. The coax is connected to the 300
Ohm
at the
bottom and the braid side is now connected to the unconnected side
of
the
300 Ohm and also to the earth ground rod.
On 80 the receive is up 2-4 S points compared with the 40m coax
Centre
Fed
Dipole. I have not had chance to get any actual reports on 80 yet.
Maybe
this weekend.

73 Andy
OK, Andy. Noted.

I don't know if you will really improve things by using the 15 foot
of
300 ohm feeder. It's a sort of a zepp, but with one side of the
feeder
earthed. I would try disconnecting the earthed ('unconnected') side
from earth / coax braid. You can either leave it floating, or
connect
it to the coax inner. It will then be approximately a quarterwave
on
20m, fed in parallel with the long wire.

Don't read too much into the excellent SWR you're getting with the
tuner. That's what the TX sees, but the tuner can't affect the SWR
on
the aerial feeder. If the coax SWR is sky high (and it can be if
the
impedance at aerial feed point is high), the coax losses will be
much
more that you would get compared with when it is matched
correctly.
You only get away with it by using the lowest-loss you can find,
and
keeping the coax as short as possible.

I'm not surprised that 80m on the endfed is a bit better than the
40m
dipole. But what's 40m like on the endfed? That's when the feed
impedance (and coax SWR) will be very high, and where the RG-213
might
perform better noticeably better than the RG-58.

As I think I said before, although I am an advocate of simply using
coax (regardless), after all these years I am considering in
investing
in something like a SG230 remote tuner for the far end of the
coax.
-- Ian


Ian,
I'll have to do some experimenting with the 300 Ohm feeder and see
what
happens. The End Fed on 40m is very poor indeed. I would say
unusable
like it is.
The End Fed wire at the moment is resonate on 2. 682 MHz.
The funny thing is that when I cut the wire to bring the End Fed to
resonate on 80m, no matter how much wire I cut off it doesn't
really
move from the 2.682 MHz. I have tried this with and with out the
ribbon
feeder being in place and with coax connected direct and the braid
connected to the earth rod.
What would cause this?
I have no problem using the Analyser with my mobile and centre fed
dipoles.
73 Andy

adding a suitably cut wire counterpoise at +% for each band should
certainly assist things .

I rather think that Andy can't add counterpoises. A decent earthing
system
should work (although additional counterpoises certainly won't do any
harm).

Re the 2.682MHz resonance, this may be because the coax is completely
mismatched at lots of frequencies, and what you're seeing this is
more-or-less a spurious resonance of the coax itself. Do you still get
it
with the wire completely disconnected? Even with centre-fed dipoles,
you
often get some very unexpected resonances way off frequency
(especially
of
you are doing a wideband frequency sweep of the return loss / SWR).

As I said previously, persuading an approximate halfwave endfed (which
is
what you have on 40m) to work with a coax feed is certainly not ideal,
but
you can usually get it to work fairly well (with all the provisos
already
discussed). My setup here is almost twice the size of what you have,
so
the wire feed impedance will be low on 160m and I high on 80m and 40m.
80m
(corresponding to your 40m) is certainly lively enough. On 40m, the
performance does not seem to be unduly poor compared with the signal
reports swapped between others on the band.

So, Andy, I simply don't know why your 40m is so poor. Have you tried
(temporarily) reducing the length to around 33 feet, so that it is a
quarterwave on 40m? This should give a reasonable match for your coax
(at
least, nothing you can't tune out back in the shack). If this is more
lively than the 64 feet, maybe you can try two wires in parallel. This
can
be discussed later if the 33 feet shows promise. If a multiband (and
possibly compromise) aerial doesn't work well, it's a good idea to try
something simple which you know SHOULD work. The problem may lie
elsewhere.

Finally, can I ask you to follow the standard practice of bottom
posting!
Cheers...
--
Ian

I've have just connected the Analyser at the feed point on the End fed
wire.
The frequency is now at 2.898 MHz without coax being in line. I have
just
tried
to shorten the Antenna again to bring the frequency closer to the 80m
band,
but
it will not adjust from this frequency.

Ummmm...
Obviously something is wrong. It looks like your analyser is simply
telling lies. Could it have a spurious resonance at this frequency?

What's confusing me is that the End fed wire should be longer than a 1/4
wave on 80
and the frequency that it ended up on, that is now 2.898 would be
about right for the length.

A quarterwave on 80m is around 66 feet. Your 63 feet is actually a bit
on
the short side. Being only 20 feet up may pull the resonance a bit
lower,
but I doubt is could be anywhere as low as 2.898MHz.

So why won't that frequency change when I start
trimming the wire down in size?
It just isn't making any sense to me. The resonant frequency surely
should
change with the altered length.

If shortening the aerial doesn't change the frequency, I don't think
your
analyser is measuring the aerial. This is indeed a puzzle. As I
suggested
before, you could go from the sublime to the ridiculous, and try
something
like 33 feet, which should resonate at around 7MHz. If it sticks at
2.898MHz, something is seriously amiss.

--
Ian

MFJ Analyser ????

Isolate the transmission line (coax) from the antenna, ie; UGLY BALUN,
Line
Isolator

analyser may have copted a nose full of RF from the braid of feedline,
with such a mismatch

should build resonant antennas first, before inserting giant matcher, just
to see how much of your RF is dissipated in the match box. TX and RX

Unless I mis-read something, Andy says that he tried the analyser directly
on the antenna (at the antenna feedpoint) - so no coax was involved in
this particular test.

He seems to get a resonance at 2.898MHz, regardless of the length of the
antenna. Could this be because there is a strong (and permanent) RF signal
which is being picked up on the antenna, and is confusing the analyser?
--
Ian

Yes , could be a product of a Broadcast station ?
ok on the NO COAX, unless damage has been done.

tricky, will keep you off the streets, and out of the pubs Andy,
or perhaps in the pubs full as a boot if you do not get some answers soon
good luck