Print

[HZ1MW]

Hello my friends
Hope you are in good health

I have a mobile station in my car
The radio I used is Icom 7100
with MAT-TUNER MAT-40
with Icom whip antenna AH-2B

After reading the tuner's instruction manual it was mentioned that it supports tuning from 6-40 m with the whip antenna
The antenna also works at 6-40 m
But the tuner did not do the tuner on the 40m range,
On a scale of 20 and above it works great.
I tried to add some coils between the antenna and the tuner, but it didn't work.
Try coil length 4.5m and 5.5m 6.5m it didn't work,
If you connect a long wire to the tuner, it works great.
Note: I grounded the radio and tuner perfectly
Are there any suggested solutions?

Sorry for the long post, but I wanted to clarify the problem

I wish you a good time , HZ1MW 73

[WA2EIO]

Although you have grounded everything well, try using a 'counterpoise;' a wire at the base of the antenna about 10 Meters long also connected to ground might help, (like radials on a permanently mounted vertical) although now the antenna will not be as 'portable' as it was.

[WA2EIO]

Sorry, I just re-read your question, and I did not realize that you were using the antenna mounted on a car, so the counterpoise idea will not help.
 
Since this is a mobile installation, try using braided cable jumpers at the hinge points of the trunk, hood, and doors to be sure you have a good, continuous bond.    K0BG's web site may offer you more help:
http://www.k0bg.com/bonding.html

[LA9XNA]

The problem is most likely that you don't have enough counterpoise for your antenna.

[K6AER]

Moore information is needed for help with your tuning problem.


How far is the tuner to the whip antenna?

What is the length of the jumper from the antenna to the tuner?

Where is the tuner installed on the Vehicle?

Where is the antenna installed on the vehicle?

Most likely the whip antenna is to short for 40 meter operation on your vehicle. If you add 4 feet of wire to the top of the antenna whip will the antenna tuner give you a match?

[WA3SKN]

From page 4 of their manual...
"mAT-40 is a long-wire antenna tuner. The recommended length of the antenna is 12 meters, and
the antenna of this length has the best tuning performance and transceiver efficiency. The
minimum length of the antenna supported by the tuner is 2.5 meters. If the length of the antenna is
less than 2.5 meters, good tuning can't be guaranteed at low frequencies. Short antennas have low
transmission efficiency, even if they can be tuned, but it will make communication difficult,
especially the whip antenna, which is generally used in close-range communications."

Is your whip antenna 40 feet long?

-Mike.

[WB6BYU]

Welcome to eHam!

Is the tuner connected directly to the base of the
antenna, or through a length of coax?

The whip is 2.5m tall, which is the minimum length
for your tuner.  A small variation may shift it out
of the matchable range.

Using coax cable between the whip and the tuner
will change the impedance, and may cause the
antenna not to match.  Also, make sure that the
tuner is well grounded to the car body.

Some other things you can try:

1.  A ferrite 4 : 1 step-down transformer between
the tuner and the antenna may give an impedance
that the tuner can match.

2.  A shunt coil across the antenna feedpoint (from
the tuner output to ground) may also help.  4 or 5
turns of wire, 4 cm in diameter, might be a good
starting point for experimenting.

3.  If the antenna is mounted on the back of the
car, I have extended similar antennas using
50-100 cm of wire connected to the top of the
whip and tied to the front of the car with rope.
In one case, I used two loading wires running to
each front corner of the car, which helped to
reduce whip movement at highway speeds.

[HZ1MW]

Thank you to everyone who interacted with me, the antenna length is 2.5 meters,
the tuner is in the back of the car,
the wire feeding the antenna is 1.2 meters long,
the antenna is installed on the base of the spare tire,
I made a 70 cm iron base and installed the antenna on it,
 the height of the antenna below the ground is 1.7  meters, and the height of the antenna above the ground is 4.2 meters.
Honestly, I make qso to the United States, Spain, and Indonesia at a range of 20 meters and 15 meters, and the results are amazing. As for at a scale of 40 meters, I spoke to Japan, but I separated the whip antenna and used  Long wire 12 meters long .

[WB6BYU]

...I made a 70 cm iron base and installed the antenna on it...

Did you make sure that the antenna is properly insulated
from the bracket and car frame?

...As for at a scale of 40 meters, I spoke to Japan, but I separated the whip antenna and used  Long wire 12 meters long...

The extension wire from the tuner is part of the
effective whip length, which should make it easier
for the tuner to match it.  That makes me think
there may be a fault somewhere.

One test that may help analyze the problem would
be to see how short of a wire antenna you can match
with the tuner.  If you can match a 2.5m wire, but
not a 2.5m whip, then we would suspect a problem
with the whip mount.

[HZ1MW]

...I made a 70 cm iron base and installed the antenna on it...

Did you make sure that the antenna is properly insulated
from the bracket and car frame?

...As for at a scale of 40 meters, I spoke to Japan, but I separated the whip antenna and used  Long wire 12 meters long...

The extension wire from the tuner is part of the
effective whip length, which should make it easier
for the tuner to match it.  That makes me think
there may be a fault somewhere.

One test that may help analyze the problem would
be to see how short of a wire antenna you can match
with the tuner.  If you can match a 2.5m wire, but
not a 2.5m whip, then we would suspect a problem
with the whip mount.








Yes, the antenna is isolated from any other part and is not touched by anything,
As for the test, I will do it and tell you the results, thank you, because it did not cross my mind

[HZ1MW]

I connected a 2.5 meter wire to the tuner
I tried it on a range of 40 meters and the result was very good, as the swr did not exceed 1:2.5 and on the other scales 1:1

I also did another experiment, where the wire reached 2.5 meters between the tuner and the antenna, and it worked on all bands except for the 40 and 6 band

I separated the antenna from the base, the same results before connecting the 2.5-meter wire

[WB6BYU]

If you connect your wire antenna to the steel whip, instead of
directly do the tuner, does it still tune up properly?

If you disconnect the feed wire from the base of the antenna
so that it is the only antenna connected, can the tuner match
it on the higher bands?


It sounds like the tuner is working properly, although relay-
switched tuners can have a problem with one relay that
can allow them to match some antennas / bands but not
others.

The most likely source of the problem appears to be the
antenna mount or the feedwire from the tuner to the whip,
this is part of the antenna, and will have very high voltages
on it, especially on 40m.  The wire provided with the kit
appears to have high voltage insulation, but is only 90 cm
long, so I assume you have added some other wire to make
the connection.

It is quite possible that this wire is arcing over to the car
body or some other metal when the voltage gets high enough,
but not at lower voltage.  Can you try using the antenna at
lower power and see if the SWR is better?

Or can you post a photo of how the wire is routed from the
tuner to the whip antenna?  I am not an expert on the AH-2B,
but someone else here on eHam may be able to see a problem.

[W9IQ]

Mohammed,

You should not use the AH-2B when the tip is in the "antenna catch element" as it shorts out the whip.

With the tip free and the antenna cable removed from the tuner, use your ohmmeter to confirm continuity between the wire end and the whip. Then confirm that there is no continuity between the wire end and the tuner ground connection.

Take care with the routing of the wire from the antenna to the tuner. This is a simple, unshielded wire that should be kept away from all metal. Use as short and as direct of a wire as possible. Cut off the excess - do not coil it and do not put a choke on it.

You may require some ferrite on the control cable between the tuner and the radio. Snap-on type 31 beads work well if you can put a few turns though the bead(s). A toroid version of type 31 can also be used. If you happen to have type 43 ferrite, that is a reasonable second choice.

Finally, take care when testing the tuner with other antennas near the same frequency. The tuner may memorize the settings for a given frequency and simply use those settings when the antenna is changed. You may need to reset the memories or force the tuner to retune.

- Glenn W9IQ

[WA8NVW]

As Glenn W9IQ just pointed out, the connection between tuner output and base of the antenna whip MUST be a very short unshielded wire.  If you use coax, the parallel capacitance of several feet of cable severely detunes the antenna. 
 
QUICK FIX: 1)  Shorten the piece of coax to maximum 3 feet (1 meter).
2)  Peel off the outer plastic jacket and remove the shield braid for all but one foot closest to the tuner output. 
3)  You should now have only the center conductor and its plastic dielectric remaining, nothing else. 
If transmitting above 20 W, the RF voltage on this wire and the whip will be VERY high. 
RF burns are very painful, so keep everyone's hands away from the antenna base!

[HZ1MW]

I thank you all from the bottom of my heart for your response
The word "thank you" is not enough to thank you

I have not been able to try your proposed solutions for the past two days due to the work conditions.
I will try it as soon as possible and give you the results.
Also, your suggestions gave me some ideas, and I will present the results to you shortly.

I wish you happy times 73