Hello all - I hope someone can help me figure this one out:

I just put up a 20 meter monoband today. Been working on it for
a week of nights, and got it in the air when I got off work today early.
I used the 234/f formula and cut it for around 14.100 mHz which
gave a length of 16 feet 7 inches. It was a a bear to hoist
up (my XYL helped me) - the base is only about 12 feet off the
ground (my only mounting option). I put up 4 identical-length
radials, 3 of which are quite close to 45 degrees, the 4th is is
only about 10 degrees down due to mounting issues. The coax
feed is about 40 feet (RG-58 - good quality). I wound a
4" form with 10 turns at the base of the antenna and another 10 turns
at the transmitter to try to keep the feed line 'out of the loop' (is this
wrong?)

I find it is REALLY broad - is this normal for a monoband? I
have only used trap verticals before. The SWR is 1.5:1 from
14.025 up to around 14.200 - very little change. It is actually
hitting resonance somewhere around 14.600 (using MFJ meter
when out of band). (See 'Problem' below)

Construction: Copper water pipe, 10' of which is 3/4" then 5' of
1/2" and finally a 1/4" section that is the 'tuning end'. For the radials,
I made a circle of 14-ga antenna wire around the 2x4 wood support
on brass hooks (one each side) that support the radials - diameter of the
radial 'circle'
is about 6" or so - not very large circle. Radials were cut exactly the
length of the antenna and are well insulated with ceramic eggs and poly
line, angles as stated above. Copper element is suported by 1.5"
ceramic stand-off insulators from the Oak + 2x4 treated wood support.

Problem: My TS-440s (AT) without the tuner only puts out
about 60 watts in CW and RTTY segments, and only hits
full power in the upper end of the SSB band UNLESS I use
the internal tuner - then I get a full power output in CW since
the transmitter is 'faked' into believing it is resonant. During my late
night (illegal 30 second) test, I get 110 watts at 14.600 with almost
no visible SWR - clearly the resonant frequency...

Questions:

Question 1: Are mono-band verticals always this broadbanded
or do I have something wrong? It does not seem to have much Q.
SWR only very slowly creeps up over the band... (I loaded at
power at 14.600 VERY FAST late at night - please don't give me
a ticket Mr. FCC! - and the SWR was almost unreadable it was
so low - the MFJ meter is right - that is my resonance point). My old
4BTV was 'sharp as a tack' in tuning... VERY high Q. Are mono-bands
less selective?

Question 2: Am I being overly concerned? I can use the Auto Tuner
in the TS-440 to make it happy without any problem... is this ok?

Question 3: I built this antenna to be good for my Oak Hills QRP rig -
I had hoped not to have a tuner in the loop - I use a Kenwood AT-180
when I'm not on the TS-440s - is the loss that significant? Again, am I
being
overly concerned, since the AT-180 very easily tunes out the difference?
Or should I tweak on this antenna until it is perfect for CW SWR?

Question 4: I understand the radials are a major part of the design - could
it
be that the 'formula' (234/f) was correct, but somehow my radials are a bit
off
and could make the difference without adjust the 16' 7" vertical length?

Question 5: Since I made the 'radial circle' about 6" diameter around the
base
of the antenna, but then connected the radials (cut exactly the length of
the
radiator, less the 'radial circle' of wire around the base, attached to the
brass
hooks used to support the radials) could this be de-tuning the antenna enuf
to
raise the frequency (seems it should LOWER in frequency if anything)?

If you 'wiser' hams advise, I'll certainly drop the antenna (after cutting
the radials
loose) and enlist my XYL to help again, and add a couple of inches of
copper to
the ends (and too the radials) and do it all agin... but it was not easy to
do in the
first place... (The antenna only weighs 25 pounds, but OMG lifting it up to
position
felt like it weighed 250 pounds!!)

How it performs: I found during on-the-air tests that SOME signals were
significantly
better over my 200' "random wire" and some were worse. Consensus was that
there
was almost no difference 'short haul' (coast to coast). Some signals are
not at all
audible on my 200' wire, but S7 on the vertical, for example... no DX today
so no
idea if the low angle is working or not...

But what about at QRP levels? With my AT-180 tuner? Just seems that I
should hit
my ideal SWR in the 14.060 range - rather than 14.600 despite the broad-band
performance.

What do you recommend I do at this point? I have the whole weekend to
either play with the
new antenna or quit obsessing over it :-)

Thanks for replies and putting up with my long-winded posting. Please
either post here
or at my email address of

many thanks,

Dave WB7AWK

Zommbee wrote:

What do you recommend I do at this point? I have the whole weekend to
either play with the
new antenna or quit obsessing over it :-)

Sounds fine to me.. A monoband on 20m will seem fairly broadbanded.
Ground losses can add to this, but you are stuck at your height, so
it's
not worth worrying about. All you could do as far as that is add more
radials.
You are almost a 1/4 wave up, so things could be worse I guess..
As far as the match, 1:5.1 is fine as long as your radio is happy with
it.
That's the only thing that matters. Trimming the antenna will not help
performance unless the radio requires it to put out full power. If you
are
putting out full power, "most rigs should at only 1:5.1", thats good
enough.
If not, you might want to consider tweaking the lengths a bit. Most
likely
you could just add an inch or two to the radials only, if you wanted to

avoid pulling it all down. That should be enough to dial it in. You
won't
lose too much using a tuner, but if you are running QRP, I'd avoid it.
There is no real need to use a tuner with that antenna. I never use a
tuner
if I don't need it.. Which is about 98% of the time.. I have a big
tuner,
but the only thing that really sees any use is the wattmeter that's in
it. :/
MK

"Zommbee" wrote in
:

Hello all - I hope someone can help me figure this one out:
....

Dave,

I guess that you are hoping that with radials sloped down at 45 deg, you
should approach a 50 ohm feedpoint at resonance.

My experience is that sloping the radials tunes them high, in other
words, they need to be a little longer than were they are 90 deg to the
vertical element. Try clipping a short length of wire (say a couple of
feet) to the ends of the radial, just hanging down, and see what it does
to the feedpoint impedance. You can slide them away from the end to
lessen the effect. The outcome might just give you a hint of what needs
to be done. Remember, measure twice, cut once!

Re the tuner loss, they should be very low for the VSWR you have
discussed. Nevertheless, if you planned to have an antenna that shouldn't
need a tuner, I can understand why you might want to pursue the reasons
why or why not. It is an excuse for learning or frustration, depending on
your point of view.

As a matter of principle, I avoid using tuners like the '440's, they are
the achilles heel of those radios when the relays become unreliable.

BTW, one of the techniques for obtaining a match to 50 ohm feedline from
a groundplane antenna is to tune it a little high, and shunt the
feedpoint with an inductor or s/c stub. I drafted some notes on the topic
at http://www.vk1od.net/QWVmatch/QWVmatch.htm . This is probably not the
answer to your problem, since your 45 deg radials should lift the
feedpoint Z close enough to 50 ohms and closer than VSWR=1.5 that you are
observing right now.

Owen

Your bandwidth is correct for a 20 meter ground plane. At 14 MHz,
covering the entire band is not a problem.

To drop the resonant frequency down to what you want, you have three
choices:

1. Add length to the vertical section.

2. Add length to all the radials equally.

3. Insert a small coil in series with the base of the vertical
section. Start with about one turn, one inch in diameter.

Since you say this thing is hard to get up and down, I would recommend
either 2 or 3. Either one will do, but my personal preference is for
the coil *IF* you can insert it in series easily. If not, go for the
radials.

It's good that you have the SWR analyzer. It will save a lot of hair
pulling.

GL!

73, Bill W6WRT

On Fri, 22 Dec 2006 20:34:19 -0800, "Zommbee"
wrote:

.... excerpted...

What I'd do, is alligator-clip small lengths of wire to the tip end of
each radial to see if lengthening them just so does what you want.

On an L-wire I had up recently, I tuned it by rolling and unrolling
the tip-end of the single counterpoise.

bob
k5qwg

I just put up a 20 meter monoband today. Been working on it for
a week of nights, and got it in the air when I got off work today early.
I used the 234/f formula and cut it for around 14.100 mHz which
gave a length of 16 feet 7 inches. [snip]


Thanks for all the replies. I added about a foot to all 4 radials and now
the antenna has an unreadable SWR (1.0+something small) from 14.005
to 14.200, where it barely starts to wiggle the needle! I had no idea a
mono-band vertical was SO BROAD! Now most medium distance
stations (1500 - 2500 miles and up) are easily 2 S-units above my 200'
wire. Seems to be working quite well!

Thanks for all the assitance

Dave WB7AWK

ORIGINAL MESSAGE:

On Sat, 23 Dec 2006 13:58:32 -0800, "Zommbee"
wrote:

I had no idea a
mono-band vertical was SO BROAD!

------------ REPLY FOLLOWS ------------

It's not broad because it's a mono band vertical. It's broad because
of the relatively high frequency, relatively narrow bandwidth and it
being *not* inductively loaded. Try the identical design cut for 80
meters which is a much lower frequency and a larger band (500 KHz) and
you will be singing a different song. :-)

Have fun!

73, Bill W6WRT

Zommbee wrote:
I just put up a 20 meter monoband today. Been working on it for
a week of nights, and got it in the air when I got off work today early.
I used the 234/f formula and cut it for around 14.100 mHz which
gave a length of 16 feet 7 inches. [snip]


Thanks for all the replies. I added about a foot to all 4 radials and now
the antenna has an unreadable SWR (1.0+something small) from 14.005
to 14.200, where it barely starts to wiggle the needle! I had no idea a
mono-band vertical was SO BROAD! Now most medium distance
stations (1500 - 2500 miles and up) are easily 2 S-units above my 200'
wire. Seems to be working quite well!

Thanks for all the assitance

Dave WB7AWK



And thank you for doing much of my work for me! I was planning to put up
such an antenna (20 M ground plane vertical)a few weeks ago. Your post,
and the replies to it, will allow me to erect and tune mine quite a bit
faster.

Thanks for the Xmas present!

73's

Steve
W1KF

Hi Steve,

Tried to email you but it bounced. Here's my reply I wrote:

Hi Steve,

You're welcome! I'm having a blast with the new antenna - I've only used
trap verticals in the past, and they are SO sharp that you have to pick a
band segment and live with high SWR elsewhere forever. Since I run QRP on 20
a lot, I wanted it to be as efficient as possible. I have been tweaking some
more and now the SWR at 14.025 is not measurable on my meter, and only 1.3:1
at the far end of SSB! Using my MFJ-259 antenna meter, I was able to tweak
the down-angle of the radials for a precise 52 ohm match at the transmitter.
So now I think every microwatt possible will make it into the air!

I was very surprised to find that I could make up for the slightly short
vertical element (about 2 inches off I'm guessing) by tuning the 4 radials.

It took a LOT more wire than I expected - over a foot on each. But the MFJ
meter says it's dead-on resonant at 14.025 at 52 Ohms, so obviously tuning
the radials is very important. The vertical element was a BEAR to get up so
I was dreading getting it back down - it's copper water pipe and I had to
fish it around tree branches to get it in the clear. And the weight vs.
leverage (only 25 pounds 'dead weight') made it seem like it weighed at
least 100 pounds!

It's only about 12-14 feet up (haven't measured) and the radials get close
to the ground (5 feet or so) with the proper 'droop' - but it clearly runs
circles around my 200' random wire with tuner - most signals are

2-3 S-Units better on the vertical (some signals though still come in better
on the wire, so I have both tuned for where I'm operating in case I need to
switch).

Now to build a high-performance (!!) inverted vee for 40-meter QRP work.

Good luck in your project - if I can help in any way, drop me an email.

If you want pix or diagrams of how I built mine, just let me know.

73

Dave WB7AWK

"Steve Reinhardt" wrote in message
...
Zommbee wrote:
I just put up a 20 meter monoband today. Been working on it for
a week of nights, and got it in the air when I got off work today early.
I used the 234/f formula and cut it for around 14.100 mHz which
gave a length of 16 feet 7 inches. [snip]


Thanks for all the replies. I added about a foot to all 4 radials and
now
the antenna has an unreadable SWR (1.0+something small) from 14.005
to 14.200, where it barely starts to wiggle the needle! I had no idea a
mono-band vertical was SO BROAD! Now most medium distance
stations (1500 - 2500 miles and up) are easily 2 S-units above my 200'
wire. Seems to be working quite well!

Thanks for all the assitance

Dave WB7AWK

And thank you for doing much of my work for me! I was planning to put up
such an antenna (20 M ground plane vertical)a few weeks ago. Your post,
and the replies to it, will allow me to erect and tune mine quite a bit
faster.

Thanks for the Xmas present!

73's

Steve
W1KF