Hello:
I am looking words of advice on conducting an informal exercise to
evaluate performance of 75m mobile systems. I have done much reading
of rec.radio.amateur.antenna threads and have learned much from Cecil,
Reg, Keith, Roy, et al. The msg threads addressing how measurements
were taken during past shootouts have been very helpful but equipment
used in those events seem to be beyond my capabilities.

I am part of an ARES/RACES HF Mobile team. We are in the early stages
of assembling our team and have conducted a couple of field
exercises. I believe I adequately understand many of the issues
related to operating 75m mobile and have concluded (from assessing our
mobile configurations) that our systems are VERY compromised. As we
conduct our EmComm field exercises we take the opportunity to
experiment and make system adjustments that clearly improve
performance. Primarily we are using 100w mobile hf rigs with 75m
Hamsticks or Hustler resonators. We understand that the vehicle, the
antenna, the ground, etc comprise the "System". One important note
is that we are not focused on achieving DX communications. Our field
of operations is primarily Groundwave within a tri-county area in
Eastern Pa (many 600-700 ft ridges and valleys, heavily forrested),
perhaps 100 miles max. We do use and experiment with NVIS (using
restricted space configurations: tilted whip, Hamstick dipoles, etc)
however, this query is relative to Groundwave.

I would like to add an occassional field exercise expressly for the
purpose of measuring the performance of our systems (for improvement
and detecting problems). We currently have no equipment for this
purpose. One device I see advertised and would like some feedback on,
is the MFJ-802 Field Strength Meter.

- Would the MFJ-802 be an adequate measuring device for our use ? Any
caveats ?
- What test FIELD environment should we try to arrange (e.g. large
empty parking lot, or a rural open field) ?
- When testing each vehicle, what space should separate it from other
vehicles waiting to be tested ?
- Should the vehicle sit stationery, or be moving in a circle ?

Any suggestions offerred to assist with this effort will be sincerely
appreciated.

regards,
Dennis, K1DRW

k1drw wrote:
Any suggestions offerred to assist with this effort will be sincerely
appreciated.

Palomar manufactured a PFS-1 Field Strength Meter
for awhile. You might be able to find a used one.
It works very well in the absence of other strong
signals.

But you can take advantage of what is known already.
A 75m hamstick is 12 dB down from a good center-
loaded bugcatcher or screwdriver. That's at least
2 S-units and maybe more. Hustler systems are 8 dB
down, more than one S-unit. One S-unit can make or
break an emergency communications.

Anyone serious about 75m emergency communications
should replace those dummy loads (hamsticks) with a
real antennas. :-) A well-designed, well-installed
bugcatcher or screwdriver system is hard to beat
on 75m.

Here's my 75m mobile antenna guaranteed to beat
the socks off of a hamstick:

http://www.w5dxp.com/mobscrew.jpg

It is a High Sierra HS-1600 with the optional RV
bottom section. It has a top hat with eight radials
two feet above the coil. The top hat is at a
height of about 10.5 feet above the ground. Watch
out for trees.
--
73, Cecil http://www.w5dxp.com

On Feb 3, 7:24 am, "k1drw" wrote:


- Would the MFJ-802 be an adequate measuring device for our use ? Any
caveats ?

Almost any FS meter can be used as long as it's not overloaded and
saturated to a full peg reading on everything..
Also a distant receiver is ok as long as the signal is stable. Ground
wave is
usually pretty stable if you test quickly.

- What test FIELD environment should we try to arrange (e.g. large
empty parking lot, or a rural open field) ?

Doesn't matter, except I would use the same exact spot for every rig
tested. The only thing moving from field to lot, would effect the
ground
quality. The cdx of the ground doesn't really matter as long as each
rig is tested from the same spot. Improvement of the ground would
effect
all rigs equally.

- When testing each vehicle, what space should separate it from other
vehicles waiting to be tested ?

I would move and park each one in the same exact spot if I wanted
to be fairly accurate. Ground cdx could possibly change a few feet
away.
Or maybe not, but if I'm doing a test, I want things as equal as
possible.

- Should the vehicle sit stationery, or be moving in a circle ?

I would sit it still. You are not measuring pattern. Just efficiency.
Any improvement in effeciency will effect all angles or directions
equally. No point in moving around, and could in fact degrade the test
if the ground changes under the vehicle.
MK

"k1drw" wrote in message
oups.com...
Hello:
I am looking words of advice on conducting an informal exercise to
evaluate performance of 75m mobile systems. I have done much reading
of rec.radio.amateur.antenna threads and have learned much from Cecil,
Reg, Keith, Roy, et al. The msg threads addressing how measurements
were taken during past shootouts have been very helpful but equipment
used in those events seem to be beyond my capabilities.

I am part of an ARES/RACES HF Mobile team. We are in the early stages
of assembling our team and have conducted a couple of field
exercises. I believe I adequately understand many of the issues
related to operating 75m mobile and have concluded (from assessing our
mobile configurations) that our systems are VERY compromised. As we
conduct our EmComm field exercises we take the opportunity to
experiment and make system adjustments that clearly improve
performance. Primarily we are using 100w mobile hf rigs with 75m
Hamsticks or Hustler resonators. We understand that the vehicle, the
antenna, the ground, etc comprise the "System". One important note
is that we are not focused on achieving DX communications. Our field
of operations is primarily Groundwave within a tri-county area in
Eastern Pa (many 600-700 ft ridges and valleys, heavily forrested),
perhaps 100 miles max. We do use and experiment with NVIS (using
restricted space configurations: tilted whip, Hamstick dipoles, etc)
however, this query is relative to Groundwave.

I would like to add an occassional field exercise expressly for the
purpose of measuring the performance of our systems (for improvement
and detecting problems). We currently have no equipment for this
purpose. One device I see advertised and would like some feedback on,
is the MFJ-802 Field Strength Meter.

- Would the MFJ-802 be an adequate measuring device for our use ? Any
caveats ?
- What test FIELD environment should we try to arrange (e.g. large
empty parking lot, or a rural open field) ?
- When testing each vehicle, what space should separate it from other
vehicles waiting to be tested ?
- Should the vehicle sit stationery, or be moving in a circle ?

Any suggestions offerred to assist with this effort will be sincerely
appreciated.

regards,
Dennis, K1DRW


One thing I would do is get a portable antennna, maybe one of those 30+ft
fiberglass whips. Tried one of thes several years ago and could fairly
reliably talk from Charlotte NC to Atlanta Ga using a freq near the 40M
band. An antenna like this can be setup in just a few minutes. The antenna
we used broke down into sections about 4 ft long so its something you could
keep in the trunk of a sedan.

Jimmie

On 3 Feb 2007 05:24:08 -0800, "k1drw" wrote:

- Would the MFJ-802 be an adequate measuring device for our use ? Any
caveats ?

Hi Dennis,

Only that its purchase may be to lend the appearance of credibility
beyond the instrument's capacity to deliver it. This instrument, as
it should be, is dirt-simple to construct; and for your purposes
should have a digital readout. You can achieve the same thing by
using a DVM connected to the meter's terminals, but by that time you
could as easily build a detector box with DVM pin jacks and an antenna
connector.

- What test FIELD environment should we try to arrange (e.g. large
empty parking lot, or a rural open field) ?

As others point out, consistency in testing is paramount. All those
tested will suffer/benefit equally under same conditions.

- When testing each vehicle, what space should separate it from other
vehicles waiting to be tested ?

Where do you want to aim the signal? Think about it, you have an
array of antennas, one driven and the rest parasitic and parked
nearby. Does this remind you of something? Does spacing and
proximity count? Same admonition applies if you have the test group
near your detector antenna.

Think in terms of wavelength. Stay out of near fields.

- Should the vehicle sit stationery, or be moving in a circle ?

As long as you are as far away so as to not perceive the shift in
signal strength on the basis of path length variation. Is a 30 foot
turning radius tested 300 feet away going to matter? Terrain may have
some bearing here.

A dry run is encouraged.

73's
Richard Clark, KB7QHC

In article .com,
"k1drw" wrote:

Hello:
I am looking words of advice on conducting an informal exercise to
evaluate performance of 75m mobile systems. I have done much reading
of rec.radio.amateur.antenna threads and have learned much from Cecil,
Reg, Keith, Roy, et al. The msg threads addressing how measurements
were taken during past shootouts have been very helpful but equipment
used in those events seem to be beyond my capabilities.

I am part of an ARES/RACES HF Mobile team. We are in the early stages
of assembling our team and have conducted a couple of field
exercises. I believe I adequately understand many of the issues
related to operating 75m mobile and have concluded (from assessing our
mobile configurations) that our systems are VERY compromised. As we
conduct our EmComm field exercises we take the opportunity to
experiment and make system adjustments that clearly improve
performance. Primarily we are using 100w mobile hf rigs with 75m
Hamsticks or Hustler resonators. We understand that the vehicle, the
antenna, the ground, etc comprise the "System". One important note
is that we are not focused on achieving DX communications. Our field
of operations is primarily Groundwave within a tri-county area in
Eastern Pa (many 600-700 ft ridges and valleys, heavily forrested),
perhaps 100 miles max. We do use and experiment with NVIS (using
restricted space configurations: tilted whip, Hamstick dipoles, etc)
however, this query is relative to Groundwave.

I would like to add an occassional field exercise expressly for the
purpose of measuring the performance of our systems (for improvement
and detecting problems). We currently have no equipment for this
purpose. One device I see advertised and would like some feedback on,
is the MFJ-802 Field Strength Meter.

- Would the MFJ-802 be an adequate measuring device for our use ? Any
caveats ?
- What test FIELD environment should we try to arrange (e.g. large
empty parking lot, or a rural open field) ?
- When testing each vehicle, what space should separate it from other
vehicles waiting to be tested ?
- Should the vehicle sit stationery, or be moving in a circle ?

Any suggestions offerred to assist with this effort will be sincerely
appreciated.

regards,
Dennis, K1DRW


If you really want to get yourself a better antenna, you should look
at a Ballon Elevated Longwire, and use your Portable MF/HF Stations to
connect VHF/UHF Mobile Stations together in a network, to cover your
Service Area. Mobile MF/HF from vehicals is ALWAYS going to have a
compromised antenna, and VHF/UHF Mobiles and Handhelds are significantly
less powerhungry, and can cover large chunks of country, and report
back to a centrally located, designated High Point Elevated MF/HF
Portable Station, where antennas with less compromised parameters
can be employed, to communicate between local VHF/UHF Groups.
This approch isn't Rocket Science, and has been well thought out for
such purposes, by folks that design Comm's Systems to actually work.....

k1drw wrote:
Hello:
I am looking words of advice on conducting an informal exercise to
evaluate performance of 75m mobile systems. I have done much reading
of rec.radio.amateur.antenna threads and have learned much from Cecil,
Reg, Keith, Roy, et al. The msg threads addressing how measurements
were taken during past shootouts have been very helpful but equipment
used in those events seem to be beyond my capabilities.

I am part of an ARES/RACES HF Mobile team. We are in the early stages
of assembling our team and have conducted a couple of field
exercises. I believe I adequately understand many of the issues
related to operating 75m mobile and have concluded (from assessing our
mobile configurations) that our systems are VERY compromised. As we
conduct our EmComm field exercises we take the opportunity to
experiment and make system adjustments that clearly improve
performance. Primarily we are using 100w mobile hf rigs with 75m
Hamsticks or Hustler resonators. We understand that the vehicle, the
antenna, the ground, etc comprise the "System". One important note
is that we are not focused on achieving DX communications. Our field
of operations is primarily Groundwave within a tri-county area in
Eastern Pa (many 600-700 ft ridges and valleys, heavily forrested),
perhaps 100 miles max. We do use and experiment with NVIS (using
restricted space configurations: tilted whip, Hamstick dipoles, etc)
however, this query is relative to Groundwave.

I would like to add an occassional field exercise expressly for the
purpose of measuring the performance of our systems (for improvement
and detecting problems). We currently have no equipment for this
purpose. One device I see advertised and would like some feedback on,
is the MFJ-802 Field Strength Meter.

- Would the MFJ-802 be an adequate measuring device for our use ? Any
caveats ?
- What test FIELD environment should we try to arrange (e.g. large
empty parking lot, or a rural open field) ?
- When testing each vehicle, what space should separate it from other
vehicles waiting to be tested ?
- Should the vehicle sit stationery, or be moving in a circle ?

Any suggestions offerred to assist with this effort will be sincerely
appreciated.

regards,
Dennis, K1DRW


If the option is available to you, consider choosing a meter with an
external antenna connected through a coax connector. By placing a
calibrated attenuator between the antenna and the meter, you can readily
obtain resolution and repeatability approaching 1 dB. When coupled with
a DMM, as Richard Clark suggested, you will have very effective
instrumentation.

If you rely instead only on the meter dial, most likely calibrated in
volts, your measurements will be affected by circuit and meter
nonlinearities and the need to convert voltage readings into dB.

Good luck,

Chuck
NT3G



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"k1drw" wrote in news:1170509048.239078.207990
@a34g2000cwb.googlegroups.com:

Hello:
I am looking words of advice on conducting an informal exercise to
evaluate performance of 75m mobile systems. I have done much reading
of rec.radio.amateur.antenna threads and have learned much from Cecil,
Reg, Keith, Roy, et al. The msg threads addressing how measurements
were taken during past shootouts have been very helpful but equipment
used in those events seem to be beyond my capabilities.

I am aware that the traditional method of comparing mobile whips is by
some form of field strength measurement near to the transmitter antenna.
The measurement needs to be performed sufficiently far from the antena to
be in the "radiation far field" zone for meaningful results... but is
still potentially affected by the nearby environment (ground, structures
etc), and is a measurement of performance at near zero elevation.

I did some thinking on a more meaningful end-to-end test, and described a
technique at http://www.vk1od.net/lost/mobiletest/index.htm , which may
be of interest.


I am part of an ARES/RACES HF Mobile team. We are in the early stages
of assembling our team and have conducted a couple of field
exercises. I believe I adequately understand many of the issues
related to operating 75m mobile and have concluded (from assessing our
mobile configurations) that our systems are VERY compromised. As we
conduct our EmComm field exercises we take the opportunity to
experiment and make system adjustments that clearly improve
performance. Primarily we are using 100w mobile hf rigs with 75m
Hamsticks or Hustler resonators. We understand that the vehicle, the
antenna, the ground, etc comprise the "System". One important note
is that we are not focused on achieving DX communications. Our field
of operations is primarily Groundwave within a tri-county area in
Eastern Pa (many 600-700 ft ridges and valleys, heavily forrested),
perhaps 100 miles max. We do use and experiment with NVIS (using
restricted space configurations: tilted whip, Hamstick dipoles, etc)
however, this query is relative to Groundwave.

I would like to add an occassional field exercise expressly for the
purpose of measuring the performance of our systems (for improvement
and detecting problems). We currently have no equipment for this
purpose. One device I see advertised and would like some feedback on,
is the MFJ-802 Field Strength Meter.

As far as I can understand from its meagre online manual, it is an e-
field probe (at low frequencies), and uncalibrated.

I have peformed some field strength measurements using an untuned small
square loop, with balun and (50 ohm) crystal detector feeding a digital
multimeter. Knowing the Antenna Factor of the loop from NEC models (
http://www.vk1od.net/SmallUntunedSquareLoop/ssulNEC.htm ) and having a
measured the crystal detector DC output vs RF input, I was able to make
measurments of absolute field strength which reconciled with other
(albeit non-traceable) measurements and modelled expectations. I am
working on a development of this kit that uses a LCD panel meter / diode
detector / termination for a self contained portable field strength
meter. Another variation being considered is using a log detector IC (DC
- ~500MHz) for the termination / detector.

Anyway, it may be of interest.

As for calculating efficiency, won't you need to integrate the power flux
density over the hemisphere... a much bigger task than making FS
measurements on the ground at a hundred paces.

Owen

"k1drw" wrote in message
oups.com...
Hello:
I am looking words of advice on conducting an informal exercise to
evaluate performance of 75m mobile systems. I have done much reading
of rec.radio.amateur.antenna threads and have learned much from Cecil,
Reg, Keith, Roy, et al. The msg threads addressing how measurements
were taken during past shootouts have been very helpful but equipment
used in those events seem to be beyond my capabilities.

I am part of an ARES/RACES HF Mobile team. We are in the early stages
of assembling our team and have conducted a couple of field
exercises. I believe I adequately understand many of the issues
related to operating 75m mobile and have concluded (from assessing our
mobile configurations) that our systems are VERY compromised. As we
conduct our EmComm field exercises we take the opportunity to
experiment and make system adjustments that clearly improve
performance. Primarily we are using 100w mobile hf rigs with 75m
Hamsticks or Hustler resonators. We understand that the vehicle, the
antenna, the ground, etc comprise the "System". One important note
is that we are not focused on achieving DX communications. Our field
of operations is primarily Groundwave within a tri-county area in
Eastern Pa (many 600-700 ft ridges and valleys, heavily forrested),
perhaps 100 miles max. We do use and experiment with NVIS (using
restricted space configurations: tilted whip, Hamstick dipoles, etc)
however, this query is relative to Groundwave.

I would like to add an occassional field exercise expressly for the
purpose of measuring the performance of our systems (for improvement
and detecting problems). We currently have no equipment for this
purpose. One device I see advertised and would like some feedback on,
is the MFJ-802 Field Strength Meter.

- Would the MFJ-802 be an adequate measuring device for our use ? Any
caveats ?
- What test FIELD environment should we try to arrange (e.g. large
empty parking lot, or a rural open field) ?
- When testing each vehicle, what space should separate it from other
vehicles waiting to be tested ?
- Should the vehicle sit stationery, or be moving in a circle ?

Any suggestions offerred to assist with this effort will be sincerely
appreciated.

regards,
Dennis, K1DRW

If you are actually looking for EmComm antennas (as well as the test
equipment, I would strongly urge you to look at the screwdriver. In
addition to blowing the socks off the hamstick/Hustler, it has a flexibility
that is amazing. For example, if you are looking at fixed and
fixed-portable operation, the screwdriver can be used as BOTH a mobile
system OR a FIXED antenna. Simply make a "half-dipole" arrangement with a
random length of wire, a rope and the usual insulator. Remove the whip,
and, using a 3/8" X 24 TPI bolt, attach one end of this one-pole(?) antenna
to the top of the screwdriver and sling the other end (rope) into a nearby
tree. You can then tinker with NVIS, high-angle slopers, height of the
wire, or the mobile whip to get whatever configuration that works at the
time PLUS quickly QSY to ALL frequencies of interest. Of course, the longer
the wire, the better it works on the lower frequencies and you will lose the
higher ones. But you can make more 'poles to put in your kit to account for
this and/or place the whip in a variety of positions. LOTS of ways to play
with this. The screwdriver is definitely the way to go!

73

Jerry
K4KWH

"k1drw" wrote in message
oups.com...
Hello:
I am looking words of advice on conducting an informal exercise to
evaluate performance of 75m mobile systems. I have done much reading
of rec.radio.amateur.antenna threads and have learned much from Cecil,
Reg, Keith, Roy, et al. The msg threads addressing how measurements
were taken during past shootouts have been very helpful but equipment
used in those events seem to be beyond my capabilities.

I am part of an ARES/RACES HF Mobile team. We are in the early stages
of assembling our team and have conducted a couple of field
exercises. I believe I adequately understand many of the issues
related to operating 75m mobile and have concluded (from assessing our
mobile configurations) that our systems are VERY compromised. As we
conduct our EmComm field exercises we take the opportunity to
experiment and make system adjustments that clearly improve
performance. Primarily we are using 100w mobile hf rigs with 75m
Hamsticks or Hustler resonators. We understand that the vehicle, the
antenna, the ground, etc comprise the "System". One important note
is that we are not focused on achieving DX communications. Our field
of operations is primarily Groundwave within a tri-county area in
Eastern Pa (many 600-700 ft ridges and valleys, heavily forrested),
perhaps 100 miles max. We do use and experiment with NVIS (using
restricted space configurations: tilted whip, Hamstick dipoles, etc)
however, this query is relative to Groundwave.

I would like to add an occassional field exercise expressly for the
purpose of measuring the performance of our systems (for improvement
and detecting problems). We currently have no equipment for this
purpose. One device I see advertised and would like some feedback on,
is the MFJ-802 Field Strength Meter.

- Would the MFJ-802 be an adequate measuring device for our use ? Any
caveats ?
- What test FIELD environment should we try to arrange (e.g. large
empty parking lot, or a rural open field) ?
- When testing each vehicle, what space should separate it from other
vehicles waiting to be tested ?
- Should the vehicle sit stationery, or be moving in a circle ?

Any suggestions offerred to assist with this effort will be sincerely
appreciated.

I have done quantitative signal strength measurements professionally, but
you don't need any expensive gear to get some decent comparitive
measurements during your field exercise.

I would recommend a level-shift technique to determine the relative merits
of your systems under test. Doing this only requires a fixed transmitter
and a mobile receiver with an S-meter and a variable attenuator. Also,
having an independent coordination link is a real plus. Local repeater?

At each of several remote locations, have your transmitter site key up.
Next, insert attenuation as required to reduce the S-meter to some chosen
low S-meter reading using one of your antennas. Repeat for each antenna.
The antenna that required the MOST attenuation is the one pulling in the
strongest signal.

I zipped through the foregoing. If you want a more detailed treatment, let
me know.