"Tom Horne" wrote in message
news:j1aZi.80$Y32.72@trnddc04...
Hal Rosser wrote:
"Hal Rosser" wrote in message
...
"Tom Horne" wrote in message
news:Md4Zi.36$WN2.29@trnddc08...
Is it possible to ask questions here without triggering an arcane
debate about competing views of theory. I'm about to find out. I
asked earlier in another thread what measuring instruments I would need
to have the use of in order to compare the effective radiated power of
different antennas. As near as I can tell there was no answer.
Tom Horne, W3TDH
A Field strength meter can be used to compare relative output of
antennas.

Well, in addition to a field strength meter, some low low power source
hooked onto to your antenna may help so you don't have to drive all over
the country side. I used an MFJ antenna Analyzer, some string, and a tape
measure, to 'map-out' on a graph locations of equal field strength.
Just have to watch out for your body affecting the signal pattern.


Please guys
Without going to war with each other over the answer and leaving me not
knowing who to believe, is an MFJ analyzer a good choice in the under five
hundred dollar range? Would using one of the one watt HTs do for a signal
source or is that still to high.
--
Tom Horne

Tom,

A one watt HT will do fine, but the signal will still be too strong close in
to work with. You need to get the power down to perhaps one milliwatt or
less to plot the antenna pattern in a field or car park. You can make up an
attenuator to reduce the power from the HT. Just making up a patch lead
between the HT and the antenna with a 50 ohm, 1 watt resistor shorting the
core and outer will probably reduce the signal to something you can work
with while still giving the transmitter a load to work into. (You can make
up exactly 50 ohms using two 100 ohm, 1/2 watt resistors). Or make up a
simple single transistor 'bug' transmitter from a handful of components.
Plenty of designs available through Google No need to spend more than a
couple of dollars. The 9v battery is likely to be the most expensive bit.

Mike G0ULI

Please guys
Without going to war with each other over the answer and leaving me not
knowing who to believe, is an MFJ analyzer a good choice in the under
five hundred dollar range? Would using one of the one watt HTs do for a
signal source or is that still to high.
--
Tom Horne

Tom,

A one watt HT will do fine, but the signal will still be too strong close
in to work with. You need to get the power down to perhaps one milliwatt
or less to plot the antenna pattern in a field or car park. You can make
up an attenuator to reduce the power from the HT. Just making up a patch
lead between the HT and the antenna with a 50 ohm, 1 watt resistor
shorting the core and outer will probably reduce the signal to something
you can work with while still giving the transmitter a load to work into.
(You can make up exactly 50 ohms using two 100 ohm, 1/2 watt resistors).
Or make up a simple single transistor 'bug' transmitter from a handful of
components. Plenty of designs available through Google No need to spend
more than a couple of dollars. The 9v battery is likely to be the most
expensive bit.

Mike G0ULI

Mike's right - but if you don't have an MFJ 259 antenna analyzer yet, this
would be a good excuse to go ahead and get one. Its just great when working
with antennas.
You can get one for about half of your $500 budget.

"Hal Rosser" wrote in message
...


Please guys
Without going to war with each other over the answer and leaving me not
knowing who to believe, is an MFJ analyzer a good choice in the under
five hundred dollar range? Would using one of the one watt HTs do for a
signal source or is that still to high.
--
Tom Horne

Tom,

A one watt HT will do fine, but the signal will still be too strong close
in to work with. You need to get the power down to perhaps one milliwatt
or less to plot the antenna pattern in a field or car park. You can make
up an attenuator to reduce the power from the HT. Just making up a patch
lead between the HT and the antenna with a 50 ohm, 1 watt resistor
shorting the core and outer will probably reduce the signal to something
you can work with while still giving the transmitter a load to work into.
(You can make up exactly 50 ohms using two 100 ohm, 1/2 watt resistors).
Or make up a simple single transistor 'bug' transmitter from a handful of
components. Plenty of designs available through Google No need to spend
more than a couple of dollars. The 9v battery is likely to be the most
expensive bit.

Mike G0ULI

Mike's right - but if you don't have an MFJ 259 antenna analyzer yet, this
would be a good excuse to go ahead and get one. Its just great when
working with antennas.
You can get one for about half of your $500 budget.


Tom

It has just occurred to me that if you can make or get hold of a switched
attenuator to stick in between the antenna and the input socket of your
remote receiver, you can make very accurate measurements indeed. I am
thinking of the type with 8 or 10 switches. The first switch gives 1dB of
attenuation, the next 2dB, 4dB, 8dB, and so on. So long as you have some
sort of signal strength meter you can monitor on the receiver, you just
switch in enough attenuation to give the same meter reading at each test
location and record how much attenuation you have switched in at that point.
The more attenuation, the better the received signal. That will allow you to
determine relative signal strength to within 1dB which is going to be good
enough for your purposes. The attenuator can be used for all kinds of
projects, so it might be worth taking the time to build one irrespective of
what you end up using for a signal source. The usual Google search will turn
up construction details, just resistors and switches in a screened box with
some PCB offcuts or copper foil to provide internal screening between each
section.

I agree with Hal, the MFJ kit is jolly good for the price. It does what it
says on the box, just don't expect miracles.

Mike G0ULI

I agree with Hal, the MFJ kit is jolly good for the price. It does what
it says on the box, just don't expect miracles.
===================
Endorse that. Using the MFJ259B I have learned a lot about antennas and
matching units (ATUs) ,not just antenna gain ,but also antenna bandwidth
and (for HF freqs) dial settings for matching units.
Whereas the quality and uncertainty figures of the analyser might be
frowned upon by 'professionals', it an excellent device for any radio
amateur climbing the knowledge ladder.

Frank GM0CSZ / KN6WH

On 10 Nov, 04:17, Highland Ham
wrote:
I agree with Hal, the MFJ kit is jolly good for the price. It does what
it says on the box, just don't expect miracles.

===================
Endorse that. Using the MFJ259B I have learned a lot about antennas and
matching units (ATUs) ,not just antenna gain ,but also antenna bandwidth
and (for HF freqs) dial settings for matching units.
Whereas the quality and uncertainty figures of the analyser might be
frowned upon by 'professionals', it an excellent device for any radio
amateur climbing the knowledge ladder.

Frank GM0CSZ / KN6WH

Why not compare in the real world
Only the poster knows the conditions that he is likely to operate in
and it appears that it is in a very mixed environment.
In such a case I would compare antennas at home or some place
and move the frequency generator around to desired situations.
The generater can be a hand held or anything for that matter.
Now the real world does not care for "s" meters so one would
switch off the limitor in the radio and use a db counter at
the speaker.These results can be graphically recorded for direct
antenna comparison and for the record.
A sound DB counter can be obtained very cheaply
on E bay and the mechanics of comparison are in situations that
only the poster can determine. Lets face it , communication
is measured from what comes out of the speaker.
It is not rocket science!
Art

What's the easiest method of determining which antenna works the best
for a particular situation? Simplest answer is to try it and see
(experience). Then again, what happens when that 'situation'
changes? Hmm, try something else? Great answer, isn't it? Very
helpful, right?
There is no 'best' answer for all situations unless you do some very
comprehensive testing, with some very expensive equipment, done by
people who know what they are doing. That 'best' answer is still a
'maybe'.
So. A "Can you hear me now?" tends to work well. Accept the fact
that there are always going to be times when everybody isn't gonna
hear you. That's what relays are for (the 'INFO' line on a message
header?). For almost any range, but especially for VHF/UHF, higher is
usually better. Produces more usable range than the antenna design
(within reason!).
Everybody wants the 'best'! Very few, except in particular instances,
ever get it.
- 'Doc


(Don't you just hate answers like that?)

wrote:
What's the easiest method of determining which antenna works the best
for a particular situation? Simplest answer is to try it and see
(experience).

There is lots of experience on this newsgroup from
which to draw. Most of us can predict that someone
will not be satisfied with a CB whip and autotuner
on 75m, for instance.
--
73, Cecil http://www.w5dxp.com

"Cecil Moore" wrote in message
et...
wrote:
What's the easiest method of determining which antenna works the best
for a particular situation? Simplest answer is to try it and see
(experience).

There is lots of experience on this newsgroup from
which to draw. Most of us can predict that someone
will not be satisfied with a CB whip and autotuner
on 75m, for instance.
--
73, Cecil http://www.w5dxp.com


-----------


Hey! I heard that! G

I was kidding, you know.

Due to my certain lack of exposure to operating 75 meters mobile, I would
have thought that anything less than a full buck and a half of watts and
some horrendously large vertical
would have been a waste of time. I guess I have something left to learn
after all.

Problem is, outside of the R/C Flyers Net, I have no use for 75 meter phone.
Now that I'm retired, there is no reason to be mobile at 0600 these days.
I'll leave the mobile low banding for those with the need.

Ed, NM2K

It has just occurred to me that if you can make or get hold of a
switched attenuator to stick in between the antenna and the input socket
of your remote receiver, you can make very accurate measurements indeed.
I am thinking of the type with 8 or 10 switches. The first switch gives
1dB of attenuation, the next 2dB, 4dB, 8dB, and so on. So long as you
have some sort of signal strength meter you can monitor on the receiver,
you just switch in enough attenuation to give the same meter reading at
each test location and record how much attenuation you have switched in
at that point. The more attenuation, the better the received signal.
That will allow you to determine relative signal strength to within 1dB
which is going to be good enough for your purposes. The attenuator can
be used for all kinds of projects, so it might be worth taking the time
to build one irrespective of what you end up using for a signal source.
The usual Google search will turn up construction details, just
resistors and switches in a screened box with some PCB offcuts or copper
foil to provide internal screening between each section.

This is a bit of a challenge to make accurate to 1 dB at 144 or 440 MHz.
The leakage around the switches, etc, is difficult to deal with.

You're probably better off scrounging for a decent surplus/used step
attenuator made by someone like Weinschel or HP.