Hi All,

Here's a challenge !

Having recently acquired a Yaesu FT-879 HF transceiver I'd like to use
it for portable operation from my camper van. Ideally to take
advantage of the improving HF conditions during my lunch hour at work.

So I originally thought about buying a Yaesu ATAS-120A, but then I
realised that I wasn't that interested in mobile operation. So I could
consider something a bit more efficient.

I have a 10m fishing pole and a G5RV doublet type antenna which I can
erect as an inverted V when space permits. However this is not quick
or easy to do in the parking lot at work, time taken for assembly and
disassembly eats into valuable operating time.

I then thought about one of the no tune broadband HF vertical antennas
such as the Diamond BB7V, Comet CHA250B and the Maldol MFB-300. These
have the advantage of no-tune operation and only requiring limited
radials (which you can't easily spread out in a car park).

Then it struck me ! I already have a good selection of basic
components to build a vertical antenna of my own.

1. 10m Fishing pole which mounts on the rear trailer hitch.
2. LDG Z-11 Pro
3. Campervan which works as a reasonably good counterpoise.

My design criteria are.

1. Operation on all bands from 3.5MHz to 52MHz (ideally broadband
operation using the Z-11). I would prefer to be able to quickly change
bands from inside the van, as operating time is limited and UK weather
is normally cold and wet.

2. Easy and quick to erect and take down single handed.

3. No radials - but with the option to roll some out if space permits.

4. As efficient as possible - Top hats and loading coils would be
considered but would need to be light weight and inconspicuous. I'm
not interested in gaining fractions of a percentage increase in
efficiency if it takes more than 5 min to erect the whole thing.

5. I would also like to use the same solution for backpack portable or
temporary installation on top of a building roof. But this is not the
main design criteria.

All this suggests using the 10m pole as a support for a vertical wire,
with some sort of matching network at the base (broadband impedance
transformer) fed against the van chassis and the Z-11 inside the van.

Suggestions for alternatives or best length of wire and transformer
ratio would be greatly appreciated.

UKM

wrote in message
ups.com...
Hi All,

Here's a challenge !

Having recently acquired a Yaesu FT-879 HF transceiver I'd like to use
it for portable operation from my camper van. Ideally to take
advantage of the improving HF conditions during my lunch hour at work.

So I originally thought about buying a Yaesu ATAS-120A, but then I
realised that I wasn't that interested in mobile operation. So I could
consider something a bit more efficient.

Suggestions for alternatives or best length of wire and transformer
ratio would be greatly appreciated.

UKM


See the Outbacker antennas http://www.outbackerantennas.com/products.html .
Some appear to meet your requirments.

One of our club's hams used one at Field Day last year and this. (Outbacker
8, I think) He did as well as the guys who had much bigger antennas. He
merely clamped it to a chain-link fence at head-level and he was on the air.
The mass of your camper van might be OK if you can't park adjacent to a
suitable fence or other structure.

Downsides: Not cheap; band changes require your attendance at the antenna
unless you switch among many of them. (You are quite wealthy, right? :-)

There are also vehicle-mount products known as "screwdriver antennas" but I
am not prepared to address them.

73,
"Sal"
(really KD6VKW)

On Jun 28, 7:42 am, "Sal M. Onella"
wrote:
wrote in message

ups.com...





Hi All,

Here's a challenge !

Having recently acquired a Yaesu FT-879 HF transceiver I'd like to use
it for portable operation from my camper van. Ideally to take
advantage of the improving HF conditions during my lunch hour at work.

So I originally thought about buying a Yaesu ATAS-120A, but then I
realised that I wasn't that interested in mobile operation. So I could
consider something a bit more efficient.

Suggestions for alternatives or best length of wire and transformer
ratio would be greatly appreciated.

UKM

See the Outbacker antennashttp://www.outbackerantennas.com/products.html.
Some appear to meet your requirments.

One of our club's hams used one at Field Day last year and this. (Outbacker
8, I think) He did as well as the guys who had much bigger antennas. He
merely clamped it to a chain-link fence at head-level and he was on the air.
The mass of your camper van might be OK if you can't park adjacent to a
suitable fence or other structure.

Downsides: Not cheap; band changes require your attendance at the antenna
unless you switch among many of them. (You are quite wealthy, right? :-)

There are also vehicle-mount products known as "screwdriver antennas" but I
am not prepared to address them.

73,
"Sal"
(really KD6VKW)- Hide quoted text -

- Show quoted text -

Hi Sal,

Thanks for this. I'm familiar with the outbacker range so I''l take a
look for some construction ideas.

In the meantime I've been doing further research and experimentation,
and have now found a good initial solution.

By using a vertical wire of a suitable magic length (7.2, 8.8 or
11.8m) supported by the fishing pole, I can get the LDG tuner to
provide a good match on all Amateur bands from 80m upto 6m as the
impedance presented to the tuner is just within it's (slightly
limited) matching range.

This has resulted in good signal strength reports on several bands,
even when using just 10watts ssb, so it's an excellent starting point
that I can work from.

The next stage is to improve the chassis bonding, play with some
impedance matching transformers and an optional counterpoise to try
and reduce the RF level inside the Van on 80m.

A linear loaded vertical possibly using multicore cable also shows
some promise. My initial measurements with an RF sweeper indicates
that it could add a useful secondary resonance at the low frequency
end, which may benefit the tuner.

A remote field strength meter is also in the plan, so that I can make
quantative measurements.

Once again thanks for the feedback.

UKM

wrote:
By using a vertical wire of a suitable magic length (7.2, 8.8 or
11.8m) supported by the fishing pole, I can get the LDG tuner to
provide a good match on all Amateur bands from 80m upto 6m as the
impedance presented to the tuner is just within it's (slightly
limited) matching range.

When a vertical monopole length is much longer than
5/8WL, the take-off-angle increases and much of the
radiated RF is lost into space on the higher
frequencies.

For instance, on 6m using the 7.2m monopole, the
take-off-angle is ~56 degrees.

7.2m is ~5/8WL on 12m, not good for 6m-10m.
8.8m is ~5/8WL on 15m, not good for 6m-12m.
11.8m is ~5/8WL on 17m, not good for 6m-15m.
--
73, Cecil http://www.w5dxp.com

On Jun 28, 12:44 pm, Cecil Moore wrote:
wrote:
By using a vertical wire of a suitable magic length (7.2, 8.8 or
11.8m) supported by the fishing pole, I can get the LDG tuner to
provide a good match on all Amateur bands from 80m upto 6m as the
impedance presented to the tuner is just within it's (slightly
limited) matching range.

When a vertical monopole length is much longer than
5/8WL, the take-off-angle increases and much of the
radiated RF is lost into space on the higher
frequencies.

For instance, on 6m using the 7.2m monopole, the
take-off-angle is ~56 degrees.

7.2m is ~5/8WL on 12m, not good for 6m-10m.
8.8m is ~5/8WL on 15m, not good for 6m-12m.
11.8m is ~5/8WL on 17m, not good for 6m-15m.
--
73, Cecil http://www.w5dxp.com

Hi Cecil,

Thanks for this, I must admit I hadn't considered the affect on
radiation angle.

I guess I'm prepared to trade this on 10m and 6m if it's going to
result in a reduction of less than say 10dB useful gain, just for ease
of operation. Epecially as both these bands tend to be either 'open'
or 'shut' with not much in-between. Just so I can get a feel for
this, what sort of magnitude are we talking about in terms of
elevation angle vs dB's

Alternatively could I coil a portion of the vertical to create
something aproximating to a 6m colinear which may help the situation
on the worst band without affecting the matching range too much on the
other bands.

Just to get this in proportion, If I've got sufficient space and time
(and the weather is good) I can roll out a ZS6BKW version of the G5RV
using the 10m pole as a support to create an inverted V (which works
very well as a general all rounder). The vertical is meant to be a
quick, cheap and cheerful, 'let's grab some QSO's' during the lunch
hour antenna, so any suggestions for alternatives which permit quick
band changing would be welcome.

Looks like I'll have to bite the bullet and start getting used to
modelling with NEC or similar.

UKM

On Jun 28, 3:32 pm, wrote:
On Jun 28, 12:44 pm, Cecil Moore wrote:





wrote:
By using a vertical wire of a suitable magic length (7.2, 8.8 or
11.8m) supported by the fishing pole, I can get the LDG tuner to
provide a good match on all Amateur bands from 80m upto 6m as the
impedance presented to the tuner is just within it's (slightly
limited) matching range.

When a vertical monopole length is much longer than
5/8WL, the take-off-angle increases and much of the
radiated RF is lost into space on the higher
frequencies.

For instance, on 6m using the 7.2m monopole, the
take-off-angle is ~56 degrees.

7.2m is ~5/8WL on 12m, not good for 6m-10m.
8.8m is ~5/8WL on 15m, not good for 6m-12m.
11.8m is ~5/8WL on 17m, not good for 6m-15m.
--
73, Cecil http://www.w5dxp.com

Hi Cecil,

Thanks for this, I must admit I hadn't considered the affect on
radiation angle.

I guess I'm prepared to trade this on 10m and 6m if it's going to
result in a reduction of less than say 10dB useful gain, just for ease
of operation. Epecially as both these bands tend to be either 'open'
or 'shut' with not much in-between. Just so I can get a feel for
this, what sort of magnitude are we talking about in terms of
elevation angle vs dB's

Alternatively could I coil a portion of the vertical to create
something aproximating to a 6m colinear which may help the situation
on the worst band without affecting the matching range too much on the
other bands.

Just to get this in proportion, If I've got sufficient space and time
(and the weather is good) I can roll out a ZS6BKW version of the G5RV
using the 10m pole as a support to create an inverted V (which works
very well as a general all rounder). The vertical is meant to be a
quick, cheap and cheerful, 'let's grab some QSO's' during the lunch
hour antenna, so any suggestions for alternatives which permit quick
band changing would be welcome.

Looks like I'll have to bite the bullet and start getting used to
modelling with NEC or similar.

UKM- Hide quoted text -

- Show quoted text -

Hi Again,

OK I just found this which answers most of my questions.

http://www.moonraker.com.au/techni/patterns.htm

Looks like some form of loading coil say 60% up may be the way to go.

As before suggestions welcolmed.

UKM

wrote:
OK I just found this which answers most of my questions.
http://www.moonraker.com.au/techni/patterns.htm
Looks like some form of loading coil say 60% up may be the way to go.

In general, loading coils are used on verticals that
are too short. Traps are used on verticals that are
too long. Traps are high-impedance parallel resonant
circuits that tend to block the flow of RF current
through them.

If you keep those previous lengths and install traps
for the higher bands, you should be in good shape.
--
73, Cecil, w5dxp.com

Here's a challenge !

Having recently acquired a Yaesu FT-879 HF transceiver I'd like to use
it for portable operation from my camper van. Ideally to take
advantage of the improving HF conditions during my lunch hour at work.

So I originally thought about buying a Yaesu ATAS-120A, but then I
realised that I wasn't that interested in mobile operation. So I could
consider something a bit more efficient.

See the Outbacker antennas http://www.outbackerantennas.com/products.html .
Some appear to meet your requirments.

One of our club's hams used one at Field Day last year and this. (Outbacker
8, I think) He did as well as the guys who had much bigger antennas. He
merely clamped it to a chain-link fence at head-level and he was on the air.
The mass of your camper van might be OK if you can't park adjacent to a
suitable fence or other structure.

Downsides: Not cheap; band changes require your attendance at the antenna
unless you switch among many of them. (You are quite wealthy, right? :-)

Based on the tests I've seen, the Outbacker is a bit more efficient
than Hamsticks (but not by much), and is probably less efficient than
all but the smallest of screwdriver-type antennas (including the ATAS).

If you're interested in a fairly traditional mobile-type antenna
(an inductively-loaded short radiator) with higher efficiency,
consider a bugcatcher - a lower mast, a large air-core center-loading
inductor, and a long whip on top (possibly with a capacity hat).
By winding the center coil properly (large-diameter wire or tubing,
turns spaced apart, with the right length/diameter ratio) you can get
a significantly higher Q in the coil (and thus lower losses) than
you'll get with a tightly-wound screwdriver coil or a helically-
wound Hamstick or Outbacker.

You may want one coil per band... although it's possible to work
multiple bands, with some additional loss, by using a jumper to short
out some of the coil turns on the higher-frequency bands. I've seen
some "dual-band" bugcatcher designs, in which the full coil is used to
load the antenna on 75 meters, and a series-resonant circuit shorts
out some of the turns on 40 meters.

Mount the antenna as high as possible on the van... ideally, so that
all of the antenna is up above the vehicle body.

Since you don't plan to actually operate while driving, you can use a
taller antenna than would be possible while mobile, and may not need
additional guying.

Another possibility is to simply throw up a random wire (perhaps an
inverted-L, suspended via thin rope from nearby trees... use the
vehicle body as a ground (perhaps with a counterpoise wire) and use a
wide-range antenna tuner. Any reasonably thin, flexible stranded wire
could be used... some specialist dealers such as The Wireman sell
antenna wires which are reportedly easy to coil without kinking.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Snip

Based on the tests I've seen, the Outbacker is a bit more efficient
than Hamsticks (but not by much), and is probably less efficient than
all but the smallest of screwdriver-type antennas (including the ATAS).

If you're interested in a fairly traditional mobile-type antenna
(an inductively-loaded short radiator) with higher efficiency,
consider a bugcatcher - a lower mast, a large air-core center-loading
inductor, and a long whip on top (possibly with a capacity hat).
By winding the center coil properly (large-diameter wire or tubing,
turns spaced apart, with the right length/diameter ratio) you can get
a significantly higher Q in the coil (and thus lower losses) than
you'll get with a tightly-wound screwdriver coil or a helically-
wound Hamstick or Outbacker.

You may want one coil per band... although it's possible to work
multiple bands, with some additional loss, by using a jumper to short
out some of the coil turns on the higher-frequency bands. I've seen
some "dual-band" bugcatcher designs, in which the full coil is used to
load the antenna on 75 meters, and a series-resonant circuit shorts
out some of the turns on 40 meters.

Mount the antenna as high as possible on the van... ideally, so that
all of the antenna is up above the vehicle body.

Since you don't plan to actually operate while driving, you can use a
taller antenna than would be possible while mobile, and may not need
additional guying.

Another possibility is to simply throw up a random wire (perhaps an
inverted-L, suspended via thin rope from nearby trees... use the
vehicle body as a ground (perhaps with a counterpoise wire) and use a
wide-range antenna tuner. Any reasonably thin, flexible stranded wire
could be used... some specialist dealers such as The Wireman sell
antenna wires which are reportedly easy to coil without kinking.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!- Hide quoted text -

- Show quoted text -

OK this is getting interesting now !

Thanks for all your suggestions, I respect your judgement as I realise
what a wealth of experience I'm tapping into.

I had discounted random wires hanging from trees, as I wanted the
whole thing to be attached to the van. The G5RV is relatively easy to
deploy when I have the space, but I'm trying to operate from a
standard car park bay, without drawing too much attention to myself by
having lots of wires running across other bays which people are trying
to park in. Likewise I didn't want to use critical matching components
or high-Q tuned circuits which may require adjustments every time I
moved location or it started to rain (actually I should have said
stopped raining, as that is less frequent).

As I already have a Z-11 I thought I could use it as an autocoupler at
the base of the antenna. It's capable of doing this but it doesn't
have quite as wide a matching range as say the SGC range. LDG 6 to
1000 ohms vs SGC 0.3 to 3000 ohms (from memory) So providing I don't
use a coax feed to the antenna base and the impedance stays within the
6 -1000 ohm boundaries, so I don't need an additional 4:1 balun, then
the losses should be down to acceptable levels.

I realise that I could simply create a muliband trapped vertical, say
using coax based traps to reduce the size and weight. However I wish
to maximise the full length of the 10m pole as much as possible.
Bearing in mind that the lowest 2m or so of the pole would be below
the van roof, so I can only really use the remaining 8m or so, which I
need to optimise as much as possible.

The existing 7.2m wire works OK but it would benefit from a bit more
inductive loading to reduce the capacitive reactance at 3.5MHz to be
within the tuning limits of the Z-11. The other problem as indcated by
Cecil is the length being greater than 5/8 wave at 10m and 6m
resulting in a poor angle of radiation.

I thought that by adding a 3m phasing section in the form of a coil at
1.5m down from the top of the mast with approx 2.7m below, the phasing
section this would approximate to a 1/4 over 1/2 wave collinear for
6m, and add some loading at 3.5MHz. My thinking is that this would use
the length of the pole to it's best advantage on the 6m band and
reduce the radiation angle to acceptable limits on 10m.

I could play with overall lengths of wire (say 8.8m or 11.8m and the
length and size of the phasing coil to optimise the 6m gain and
impedance range on each of the bands if this was worth doing. But as I
said before I'm not agonising over the last dB of performance as I
would on the microwave bands. I believe it's a law of diminishing
returns, you need a lot of optimisation to gain a few dB but in most
cases an S point difference goes practically unnoticed. Especially
when the environment surrounding the vehicle will have a significant
effect on the overall radiation efficiency.

I had thought about the ATAS-120 but having 80m is useful for inter-UK
contacts and I would think that I could at least match the performance
of an ATAS on the higher bands and beat it on the lower ones. Has
anyone seen efficency figures for the ATAS ?

Another thought which struck me was that I could wind a counterpoise
coil on the bottom 2m of the pole which would be below the roof of the
van. This would be close coupled into the van body as well as other
nearby objects such as fences ect. but it may improve things slightly
by adding an additional counterpoise element. Something like the W2IK
IK-STIC design.

Keep the suggestions coming !

UKM