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